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Introducing the Indonesian Islands

The islands of Indonesia spread in a wide arc, more than 5,000 kilometers long, from mainland Southeast Asia to Papua New Guinea. Dotted with volcanoes, covered with thick tropical vegetation and bright green rice fields, and surrounded by coral reefs, the Indonesian archipelago is one of the world's most beautiful places.

The most reliable figure offered for the number of islands in Indonesia is 17, 508, including rocks and sandbanks exposed by the tides. Some 6,000 of these are important enough to have names, and perhaps 1,000 are inhabited.

Indonesia is the largest archipelagic nation in the world, with at least 80,000 kilometers of coastline. Some estimates run as high as 200,000 kilometers, but even the lower figure makes Indonesia's coastline longer than that of any other nation. The territorial waters of Indonesia include 3.1 million square kilometers of tropical seas.

Indonesia is the world's fourth-largest country, with 204 million inhabitants. Most are Muslims, but there are significant Christian and Hindu minorities. Racially the majority of Indonesians are Malayo-Polynesian, with Chinese and Papuan minorities. The capital and largest city is Jakarta.

The Indonesian language is a variant of Malay, which, in this nation of hundreds of languages, has long served as the lingua franca of trade.

Seafaring Empires

Indonesians refer to their country as tanah air kita—"our land and water"—and have always considered the seas as an integral part of their country. The ancestors of the great majority of Indonesians—the Austronesians—arrived in the archipelago by boat. The invention of the outriggered canoe some 5,000 years ago was as essential a development to seafarers as the wheel was to land-locked people.

Many of Indonesia's 17, 508 islands are graced with beautiful, palm-lined beaches. This is the south coast of Bali.

Spreading first from the Asian mainland to Taiwan, and then— about 3,000 B.C.—through the Philippines and into the larger islands of western Indonesia, the Austronesians brought with them rice and domesticated animals, and thrived on the rich volcanic soil of the Sunda Islands.

But seafaring skills were not forgotten. Starting in the 4th century, Indonesians from south Kalimantan (Borneo) sailed across the Indian Ocean to settle in uninhabited Madagascar, just off the coast of Africa.

The first great Indonesian empire, the Buddhist Srivijaya, was a maritime empire based around the port of Palembang in southeast Sumatra. The Srivijaya controlled the Straits of Malacca, the key to the crucial China-India trade route, from the 7th to the 13th centuries.

Influences from the Asian subcontinent continued to reach the archipelago, which became increasingly Indianized in culture and religion.

From A.D. 1294 to the 15th century, most of western Indonesia was controlled by the powerful East Java kingdom of Majapahit, the most famous of the archipelago's ancient kingdoms. Majapahit is thought to have exacted tribute from islands as far away as New Guinea.

A fisherman tries his luck off the dock at Ampenan, Lombok.

Islam and the Europeans

Beginning in the mid-13th century, Indonesian traders and rulers began converting to Islam, for both political and religious reasons. The biggest boost to Islamization of the archipelago came with the conversion of the ruler of Malacca, which sat in a very strategic position on the strait between Sumatra and peninsular Malaysia.

Most of these conversions were peaceful—the Sufi doctrine offering a theologically smooth transition for the Hinduized kingdoms—but Majapahit, past its prime, fell by force to the neighboring Islamic kingdom of Demak in the early 16th century.

This was also about the time the Portuguese, seeking spices, arrived in the archipelago, conquering Malacca in 1511. Soon after, the Spanish and English also sought Indonesia's valuable spices, but it was a century later that Holland, newly independent of the Holy Roman Empire, ruled from Spain, succeeded in controlling the market in cloves, nutmeg and pepper. During much of the 17th and 18th centuries, the Dutch East India Company held a virtual monopoly.

The company went broke in 1799, and in the 19th century, the Dutch concentrated their colonial efforts on Java, leading to a huge increase in the population of this island.

During World War II, the Japanese quickly swept through the Dutch Indies, evicting the colonialists in 1942. At the end of the war, Indonesian nationalist leaders declared independence—on August 17, 1945—but it took four more years to oust the Dutch. Irian Jaya, the western part of New Guinea, was transferred to Indonesia in the 1960s; the former Portuguese colony of East Timor was annexed in 1976.

Lush Islands

The "Ring of Fire" runs through Sumatra, Java, the Lesser Sundas, and then up through the Moluccas. These islands are marked by jagged volcanoes, and the rich, black soil that produces the great rice crops of Java and Bali. Some of the islands—for example, Timor, Seram and Biak—are formed of uplifted coral limestone. Here the soil is poor, and some areas—particularly parts of Timor—exhibit dry grassland that is more reminiscent of Australia than the tropics.

Two seasons of wind sweep through Indonesia each year. The northwest monsoon, usually starting (depending on the area) between late October and late November and ending between March and April, brings rain and wind. The southeast monsoon, with wind but much less rain, begins around late April to late May, and ends in early September. The pancaroba—between monsoons—brings generally calm seas and good weather, and falls just about everywhere in the archipelago in October and April.

The worst of the rainy season in most of Indonesia is in the months of December and January. The weather in the eastern province of Maluku is the most out of step with the rest of the country, and the worst comes in July and August. Some islands— such as Bali—have mountains that block the rains, creating a dry rain shadow in their lee.

DIVING IN INDONESIA

Fantastic Diving, but Kafkaesque Transport

Indonesia is the least known of the world's best dive locations. The introduction of scuba gear and the beginning of dive operations here are barely a decade old, and new locations are still being explored and opened, albeit slowly.

It will be many years before diving in Indonesia reaches its full potential, which has both great advantages and serious drawbacks. Experienced divers will be excited by the possibility of diving clear, rich waters without being surrounded by hordes of human beings. It is still very possible to dive areas where no one has yet gone underwater. This will be a refreshing change from sites like the Caribbean, Hawaii, the Great Barrier Reef, the Maldives and the popular spots in the Pacific Islands.

In all of the huge Indonesian archipelago, containing 10-20 percent of the world's coral reefs, there are few locations with dive services, and a handful of year-round live-aboard boats.

The diving is excellent, inexpensive (averaging around $75 a day for two dives) and uncrowded. This does not come without a cost, however: flights can be unceremoniously cancelled, the quality of guides is variable, and the weather is sometimes fickle.

Live-aboards are the obvious solution to diving in Indonesia, with its thousands of islands and huge area. Some of the boats are luxurious and expensive but take you to the top dive locations in Indonesia. A few are more basic.

Indonesia's Dive Sites

The sites listed below are the main ones in Indonesia, with compressors, equipment and other facilities for diving. They appear here in the order they appear in this book, roughly west to east across the archipelago.

West Java. The Pulau-Pulau Seribu—"Thousand Islands"— dive area is quite close to the capital of Indonesia, Jakarta, and many efficient dive clubs provide all the necessary transportation and services to these islands. There is some interesting diving here, but in general coral and fish life is quite limited, and the visibility poor. The clubs will also take you diving off the islands around the famous Krakatau volcano, and off the Ujung Kulon Nature Reserve on the tip of southwest Java.

Although it makes a heroic effort to connect the archipelago's far-flung islands, Merpati Airlines is often the bane of travelers to Indonesia. Above is one of the airline's rugged Twin Otters in Karubaga, Irian Jaya.

A diver in the waters off Bali peers into a large barrel sponge, Xestospongia testudinaria.

Beautiful Bali cattle wander the rocky beach at Tulamben, Bali, one of the most popular dive sites in Indonesia. These placid animals are a domesticated form of the wild cow or banteng.

If your plans will take you through Jakarta, these dives might be worthwhile, but the diving is much better at points east. If you are coming all the way to Indonesia expressly to dive, your destination should not be Java.

Sumatra. Just an hour's ferry ride from Singapore, north Bintan Island has opened for diving. Visibility is limited, but there's a wealth of life to see, especially at night. On the opposite side of the island, offshore Padang and the Mentawai Islands promise great diversity—shipwrecks and fringing reefs to wall dives. And much of it is still relatively unexplored.

Bali. Bali has more tourist services than anywhere else in Indonesia. It is a beautiful island, and the diving is excellent. There are many different sites here, from the clear water and steep walls of Menjangan to the famous Tulamben wreck to the 4-knot currents and cold water of Nusa Penida. The visibility is usually very good, and the fish and coral life are excellent. One caveat: almost 1 million tourists a year visited Bali at last count, and here is one of the few places where you might find a crowd.

Live-aboards and chartered boats from Bali can also take divers to the islands south of Sulawesi, the Lesser Sundas, and the dive sites in the Banda Sea.

Lombok. The only diving available on this island, just a cheap ferry ride or short flight from Bali, is on the Gilis, three tiny islands off Lombok's west coast. Gili Trawangan and Gili Air have quite good reefs, but even these are far from Indonesia's best. But the Gili islands have fine white beaches and a get-away-from-it-all kind of appeal, and the diving is just offshore. You can find luxury accommodations in Senggigi beach on the mainland, an hour's ride from the islands. The dive businesses are all based there. With prior arrangements for pickup, it's better to rough it at the small places on the beach in the Gilis, with the young frisbee-tossers and sunbathers.

Komodo Island. The waters between Komodo Island (home of the fabled "dragon," a large monitor lizard) and Labuhanbajo, Flores are speckled with small islands ringed with coral. It is also swept by fierce currents. There are several places in Labuhanbajo which sometimes offer day trips for diving.

For the best locations, try the inexpensive live-aboards the Komodo Plus I and II. These ships do not offer luxury, but their charts show all the best locations in this world-class area, all pioneered by the outfit.

Maumere, Flores. Early in the decade, Maumere Bay was hit by a triple whammy: earthquake, tsunami, and a cyclone. Many of the reefs were devastated, but there are still good locations. Life is returning to the area, and this process of recovery can be very interesting from a diving perspective. Diving services are now very limited, but the essentials are there.

Sumba. It's no piece of cake to get there, but the south coast of Sumba offers a top location, dubbed Magic Mountain. It's an undersea mound, teeming with large fishes. The resort on land has been bought by the internationally acclaimed Oberoi chain.

Kupang, West Timor, and Roti and Alor. This area provides the closest diving for North Australia-based divers. The marine life is plentiful, and the operators are very good, experienced and enthusiastic. The only drawback to Kupang is the visibility, which is poor to just fair by Indonesian standards: 6-12 meters. Roti is better.

For the best diving, the operators have pioneered Alor Island, where a couple of dozen spots, along with some in the Banda Sea, top our best-of-the-best in Indonesia list. Currents can be strong, but for hard core divers, Alor gets our highest recommendation. Now the live-aboards Komodo Plus I and 77 also visit Alor.

Sulawesi. The steep coral walls ringing the islands off Manado are some of the very best in the world. The visibility is very good, and the variety of marine life is superb. Some of the dive operators could use more reliable dive boats, and English-speaking dive masters with international certification. Bangka Island offers excellent spots, without the crowds at Bunaken. A new dive center, quiet and luxurious, offers very good diving from just north of Bitung, on the other side of the peninsula from Manado. The waters of the Lembeh Strait are very rich, and hold interesting wrecks.

The Serenade and its daughter ship Arlena, both operated by Murex, and the live-aboard operated by Liburan Adventure Diving Tours, all run out of Manado to the Sangihe-Talaud Islands. The Spermonde archipelago off Ujung Pandang, Selayar island just off the southwest peninsula, the Tukang Besi archipelago off the southeast tip, and the Togian islands tucked away in the Gulf of Tomini in central Sulawesi all offer exciting exploratory diving opportunities.

East Kalimantan. Manta rays and a salt-water inland lake are the top drawing cards here. World-famous Borneo Divers, the folks who pioneered Sipandan diving, started operations in Sangalaki. After a period of suspended operations, they are planning to reopen their dive business with a new Indonesian partner. Another dive outfit, based on nearby Derawan Island, also offers diving on Sangalaki, and this has evolved into a well-run operation.

A school of pennant butterfly-fish, Heniochus diphreutes. Swarms of these beautiful butterflyfish are a common sight on Indonesian reefs.

Ambon. Dive operations in Ambon and the Lease Islands are smoothing out. Operators now have adequate boats, with all the essentials. The diving here is very good and there will be no crowds at all. But the quality of dive personnel varies greatly. New sites here are still waiting to be discovered.

Our favorite live-aboard, the wooden Pindito, operates out of Ambon. Most of the year, it covers the Banda Sea. When the weather gets bad there, it runs dive cruises to Irian Jaya. The Pindito has pioneered most of the best dive spots in the Banda Sea and they know the area well. With the deepest seas in Indonesia and islands jutting up from abyssal depths, this is truly spectacular diving, second to none.

Unfortunately, the Pindito is quite expensive, and markets chiefly to Europe. Other live-aboards that make Banda Sea runs can be found in Bali.

Banda Islands. The Banda Islands are a tiny group rising incongruously out of the middle of the wide Banda Sea—the Hawaii of Indonesia. Some of the dive sites here are fantastic, and large pelagics are commonly seen. There's not always someone around with formal dive training, although recently a European divemaster has taken up residence in Banda. The real problem is getting to these beautiful islands, however. They are really out of the way, and the bottleneck is the final leg on a small plane from Ambon.

Irian Jaya. Abundant reef life and little-explored ship and aircraft wrecks make diving in the Raja Ampat islands and Cenderawasih Bay on the north coast of Irian Jaya exciting adventures. A new hotel on the tip of Biak Island also offers diving in the Padaido group.

Exploratory dives

In addition to the few locations in Indonesia where compressors, tanks, weights and guides are available, dozens of others have been prospected, and await investment to be opened. To this list, add hundreds of sites—a few "discovered" but most unexplored—accessible only by the live-aboards.

You can also simply charter a large enough boat, and head off to a location of your own choosing. The problem, of course, is finding a compressor. This may be possible in Bali, however, which would open up locations such as the Kangean Islands, Taka Bonerate and the Bonerate group. This is territory for real explorers, and if you have the time, patience, and self-sufficiency, this could provide a once-in-a-lifetime experience.

Scuba Guides: Variable

The quality of dive services and guides in Indonesia is, to be polite, "variable." Most of these guides have spent more time underwater than their customers, accumulating thousands of dives, and are excellent scuba divers. But this does not make them good guides. They usually fall short in emergency training and organization.

It best to dive with the fore-knowledge that you probably can not expect any help from your guide. Many guides may even have had some theoretical training in emergency procedures. But we have only rarely seen a first-aid kit on any of the local dive boats, let alone oxygen. Do not expect your guide to rescue you if you get into trouble.

This is not much of a problem for well-trained, experienced divers, particularly those who are traveling as a group. In fact, if you fall into this category, Indonesia is going to be a paradise for diving—no crowds, virgin reefs, and a lot of underwater time for your buck.

Beginners, on the other hand, are advised to use extreme caution—especially those who take a resort course after arrival here. Instructors' command of English is usually incomplete, and safety procedures are sometimes neglected. Being "certified" in Indonesia does not make you a competent diver. If a resort course here is your only diving experience, stick to the easy locations, and be very particular in choosing an operator and guide.

In all cases be extremely wary of rental gear. This equipment is very expensive to buy with Indonesian rupiah, and operators use it to within an inch of its life. If maintenance were regularly scheduled and carried out properly, this wouldn't be a problem. But spare parts are expensive and very hard to get here, and training in repair and diagnostics of dive equipment is basically non-existent.

In most places, dive guides and assistants will ready your gear for you, but we suggest you do this yourself. If you are in the habit of just looking at the pressure gauge to make sure you have a good fill, you better change your way of thinking in Indonesia. Test everything—regulator, gauges, BC valves and straps. You should infer from this advice that we highly recommend you bring your own gear.

Indonesia is not the place to push your limits as a diver. We discourage dives below 30 meters, especially if decompression stops are required. Take your dive tables (better yet, a computer) and follow them scrupulously. Don't even think about a decompression chambers being available—except perhaps in Bali and Manado, they are too far away.

Dive-tour operators, particularly in Europe, are reluctant to send their clients to Indonesia because of the poor training of local guides. This situation will be remedied only when more dive guides receive adequate instruction in dive planning, emergency procedures and language skills.

Transportation: Kafkaesque

Marine tourism in Indonesia is also stalled by the archipelago's transportation infrastructure. Bali, Java and Sulawesi are easy to get to, but particularly at the height of the tourist seasons, July-August and December-January, travel to Maumere, Banda, and other points in eastern Indonesia can be an exercise in frustration. Delays, overbooked flights, and broken computers will make a mess of your schedule. The guilty airport is Ujung Pandang in South Sulawesi. This is the main hub to eastern Indonesia, but too few planes fly there to and from Bali.

Since most of the Indonesian dive sites are the steep outer walls of fringing reefs, access is usually just a matter of a short ride by out-board-powered canoe. This is the fringing reef off Bunaken Island in northern Sulawesi.

Tulamben in Bali is famous for the World War II Liberty shipwreck, lying just 30 meters from the beach. This dive location is also noted for its remarkable diversity of marine life.

The scene at the ticket counters of the Indonesian government airlines—Garuda and Merpati—often produces a strange mix of Kafkaesque angst and hilarity.

It's not always this bad. Things are better in the off-peak months, and even during the middle of the tourist rush, only perhaps 25 percent of the confirmed passengers have problems. The basic problem is that Merpati—the main internal carrier—has too few airplanes, lacks organization, and owns a computer reservation system that is, in fact, often worse than useless.

Start with the obvious—it can't hurt. Ask the travel agent with whom you made your original booking if the company has a local correspondent Many have agents in Bali who can re-check confirmations. Even before you arrive, try to obtain something tangible from this agent and/or Merpati airlines, such as a fax or telex showing your confirmed dates. As soon as you get to Bali, re-check your bookings.

As soon as you make it to your destination, confirm your return booking. The dive resorts and many hotels are quite efficient at doing this—they will usually ask you for your plane details right away—but still make sure that it's been done.

If you do all this, it's likely-but not guaranteed—that things will work out as planned. But, just in case, keep some flexibility in your schedule in case there is a day or two of delay. If you have to sit in Bali for a day or two, there are plenty of good day-trips for diving. Unless you are traveling in a large group, go to the airport and try to get on your desired flight, even if you have been told that it's full. We've been on many of these over-booked flights where half or more of the seats are empty.

If you don't get a seat on the plane, forget about lodging an official complaint, getting mad, or punching somebody. If you throw a fit, you will provide a great deal of entertainment to the people waiting around the counter, but such unsavory behavior will inevitably lead to more delays. Sometimes—but not always—it might help to offer to pay "something extra" to get on your flight. It is not unknown that even someone with a confirmed reservation has been "bumped" due to a shady deal.

Still Worth It, Though

Are all these potential hassles worth it? You bet. Chances are you won't have problems. We just wanted to warn you—not scare you away. Remember: the diving is great out there. If you can schedule your visit from April through June, or September through early November, planes will be less crowded and everything will be much easier.

When planning your visit, don't try to visit too many places. If you have a week, go just to one place. Otherwise, you can spend much of your precious vacation time contending with the difficulties mentioned above.

REEF ECOLOGY

Coral Growth and the Formation of Reefs

Diving over a tropical coral reef has been compared to stepping into a time machine. You find yourself in a strange place, millions of years out of sync with the land. The reef is a reminder of a time when all the life on earth existed in shallow, tropical seas, the original soup of creation.

The myriad fish and invertebrates that shelter among and encrust the rugged surfaces provided by the clumps, shelves and branches of coral are overwhelming in their numbers, shapes and colors. Nowhere else is there such a diversity of animal forms.

Clear tropical seawater is nutrient poor, an aquatic desert. The strange and varied forms of the members of coral reef communities allow each to fill a niche in a complex nutrient cycle, beginning with the fixing of nutrients by the photosynthesis of algae, and working up to the barracuda that snatches an aging fish from the school. The ammonia and feces secreted by the predator are cycled right back into the reef ecosystem.

Over 240 million years, when scleractinian coral reefs first formed, this community has made a remarkable geological impact. The stony coral skeletons become overgrown and compacted into rock, eventually building up a prodigious thickness of limestone. When forced upward by the buckling of the earth's crust, this old reef rock forms islands.

Distribution of Coral Reefs

Reef-building corals require large amounts of sunlight, and thus are only found in the tropics, and even there only in shallow water. The effective limit of coral growth is usually given as 100 meters, although in Indonesia coral usually stops at 60-70 meters. Corals, even stony corals, are found as deep as 6,000 meters, but these grow slowly and do not form the diverse communities of tropical coral reefs.

The Indo-Pacific region, centered around the islands of Indonesia, harbors most of the world's coral reefs. Of the total area covered by coral reefs, 55 percent is in southeastern continental Asia, Indonesia, the Philippines, North Australia and the Pacific islands; 30 percent is in the Indian Ocean and the Red Sea; 14 percent is in the Caribbean; and 1 percent is in the North Atlantic. In variety, central Indonesia is the richest in the world: 80 genera, 450 species.

The presence of large gorgonians, crinoids and schools of planktivores like these anthias indicates plankton-rich waters, which can provide a spectacular concentration of marine life. Mike's Point, Bunaken Island, Sulawesi.

Reef-building corals grow only in water from 18° C (65°F) to 33°C (91°F). And the extremes of this range can only be tolerated for very short periods.

This explains why reefs are generally found only on the eastern coasts of large continents. The wind patterns caused by the rotation of the earth create currents that bring an upwelling of cold water (14° C [57°F]) from the depths at least part of the year to the western coasts of the Americas, Europe and Africa. Thus the Indian Ocean side of Africa has extensive reefs, and the Atlantic side almost none.

No cold currents flow through Indonesia, but even temporary rises in sea temperatures can devastate reefs. In 1983 sea temperatures around the Pulau Seribu islands off western Java rose to 33°C (91°F), killing much of the shallow reef coral there. Most has now recovered.

Turbid waters, those carrying a great deal of suspended sediment, deter reef formation. This is a very important in South and Southeast Asia, where rivers dump 70 percent of all sediments delivered to the ocean worldwide. (The Ganges is the champion, carrying almost 1.7 billion tons a year to the Bay of Bengal.) In Indonesia, the larger rivers in Kalimantan and Sumatra produce enough sediment to discourage reef formation a significant distance from their mouths, although even here some rich reefs have formed.

The Biology of Corals

True reef-building or hermatypic corals are animals grouped in the phylum Cnidaria, order Scleractinia. They all have an indispensable symbiotic relationship with dinoflagellate algae called zooxanthellae. (see "Zooxanthellae and Corals," opposite.) These algae are essential for respiration and nutrient uptake, and the vigorous deposition of calcium.

Coral skeletons are made of aragonite, a very soluble form of calcium carbonate. The material is secreted as a way of disposing of excess ionic calcium.

Grazing and predation of fish and invertebrates causes portions of the coral skeletons to die, and these are immediately encrusted with algae, sponges, soft corals, or any of a myriad forms of small invertebrates. Over time, these too are grazed, silted over by coral sand, or out-competed by other organisms, and their remains become part of another compacted layer.

The lithification of coral rock is not well understood, but a fine-grained carbonate cement seems to form in the pores of the old coral, turning it into dense coral rock. This is thought perhaps to result from bacterial action.

The buildup of limestone on the reef is not a simple process of accumulation. It is a cycle just like the nutrient cycle. Scientists studying a 7-hectare reef in the Caribbean measured an annual production of 206 tons of calcium carbonate; they also measured an annual loss of 123 tons. The greatest part of this erosion was produced by boring sponges, and the rest by grazing fishes and echinoderms.

Not all the limestone produced is created by corals, either. In some areas, particularly where there is very strong wave action, calcareous algaes are the primary producers of carbonate, forming algal ridges at the outer edge of the reef.

Coral Reef Architecture

Coral reefs are generally defined as falling into three main types: fringing reefs, barrier reefs and atolls. In a sense, these types also form a historical progression. As a fringing reef grows outward, a boat channel forms behind. As the reef widens, the boat channel becomes a lagoon, and the fringing reef graduates to a barrier reef. If the fringing reef began around an island, and the island subsequently sinks or the sea level rises, the final result is an atoll, a near circular reef surrounding a central lagoon.

Zooxanthellae and Corals

Reef-building corals have evolved an indispensable, symbiotic relationship with a type of yellow-brown algae called zooxanthellae, which is "farmed" in the tissues of the coral polyp. The relationship is mutually beneficial: the coral receives oxygen and nutrients, and the algae receives carbon dioxide and "fertilizer" in the form of animal waste.

The presence of zooxanthellae is so important to the health of the coral that scientists speculate the symbiotic algae must have been present in the polyp tissue almost throughout modern coral's 50-100 million years of evolution.

The zooxanthellae alga has been dubbed Symbiodinium microadriaticum, part of a "supergenus" of marine dino-flagellate algas, but recent research suggests there are more than one species. These algas are dinoflagellates, which have whip-like processes giving them some limited ability to move. This is probably how the cells initially enter the corals, although once they are there they divide vegetatively, and take on a simpler structural form.

Corals are not the only reef animals to have zooxanthellae. Sea anemones and other cnidarians host the algae, as do some molluscs, most famously the giant clams (Tridacna). Because zooxanthellae is a yellow-brown algae, and the host tissues are generally colorless—to pass the greatest amount of light to the algae—zooxanthellae-containing animals are usually a dull color: beige, brown, olive green. There are exceptions, however, including some of the giant anemones and Tridacna clams, which can be richly hued. As a general rule, however, the most brightly colored invertebrates—such as some of the soft corals—do not harbor zooxanthellae.

Coral nutrition

Corals derive their food energy from three sources: plankton captured by their tentacles, organic nutrients absorbed directly from the water, and organic compounds provided by the zooxanthellae. For the reef-building corals, the latter is by far the most important.

In the presence of sunlight, the zooxanthellae produce oxygen and photosynthetically fix nutrients—glycerol, glucose and amino acids—which are "leaked" to the surrounding tissues of the coral polyp. The raw materials for this process are the waste products of the coral animal: carbon dioxide, ammonia, nitrates and phosphates. It is a very efficient, almost self-sustaining partnership.

— David Pickell

On the steep walls of Indonesian reefs, normally deep-dwelling species can be seen at relatively shallow depths. This is a male square-spot anthias, Pseudanthias pleurotaenia.

These are not the only forms, and scientists studying reef topography offer many more types. For example, bank reefs, reefs that grow up more or less in patches in open water where the depths are relatively shallow, are an important type in the Coral Sea off Australia. These reefs often form at the edge of undersea plates, and appear when geologic activity causes an uplifting of the bottom. If the bottom is pushed up high enough that sunlight can reach it, a bank reef will form.

Fringing reefs. Most of the reefs a diver will be exploring in Indonesia are fringing reefs, coral formations that grow right up to the edge of an island. These reefs can take many forms. The steep coral walls for which Indonesian diving is famous are fringing reefs, with sometimes just a few meters of reef flat, and a reef edge that has an almost vertical slope.

Walls, or drop-offs, fascinate divers because these are where deeper dwelling animals come closest to the surface. Some of the deep-dwelling dwarf angel-fish (Centropyge spp.), damsels, and anthias (e.g., Pseudanthias pleurotaenia) can be found at comfortable depths only along steep drop-offs.

Generally, a fringing reef consists of a reef edge of stout corals, which absorb the brunt of the waves and current; a reef flat, a shallow area exposed at the lowest spring tide; and perhaps a boat channel or back reef, deeper than the reef flat and quite calm.

The reef edge, and the fore-reef area towards the open sea, are the most rewarding areas for the diver. Here the current is strong, bringing plankton and fresh water from the open sea. Here also is where divers will see larger reef fish, and occasional pelagic visitors to the reef. Sometimes the reef edge is indistinct, marked by pinnacles or other formations. And sometimes the area just back of the reef edge will not immediately become part of the reef flat, but instead, protected from the full force of the current, will be rich in more delicate corals and animals.

The reef flat is shallow, and usually light brown with sediment. This is an area of coral sand and detritus, with small boulders of hardy massive corals and clusters of branching Acropora coral, growing in pools. Usually there are fewer than a handful of very hardy coral species on the reef flat.

Most divers will walk or wade across this area (wearing a pair of dive boots, of course) without even looking down. Here there are echinoderms—particularly brittle stars, which sometimes occur in great numbers—small fish, a variety of molluscs and soft algaes. Sometimes there will be meadows of the calcareous alga Halimeda.

The back reef or boat channel is a deeper area, between the reef flat and the shore. Although often deep enough for swimming, the coral growth here is poor because of sediment run-off from the shore. Resistant Pontes, Acropora or Goniastrea grow in the boat channel in patches. Further inland, there may be beds of turtle grass, a rich habitat for juvenile fishes and many crustaceans.

Barrier reefs. The most famous barrier reefs are the Great Barrier Reef off Queensland, Australia, which is 2,000 kilometers long and 150 kilometers wide, and the large barrier reef off the coasts of New Caledonia in Melanesia. A barrier reef is a fringing reef where the back reef or boat channel has become a large lagoon. In the case of the Great Barrier Reef, this "lagoon" is in places 100 kilometers wide.

Trepang drying on a dock in Pagimana, Sulawesi

Trepang Fishing

The lowly sea cucumber, a lumbering, inoffensive detritus feeder, hardly looks like something you would want to touch, much less eat. But this homely animal is the target of small-scale fishermen all over Indonesia, and for many it serves as a major source of cash income.

Plucked from the shallow reefs of Indonesia, the sea cucumbers are dried, cleaned and sold in small lots to local businessmen, who ship them to Ujung Pandang, the center of the trade. There they are graded, and sold to the Asian market where this trepang becomes the key ingredient in a Chinese soup.

Most of the collectors are young boys. Wearing homemade goggles made of circles of glass fitted with pitch into carved sections of bamboo, the trepang collectors scan the shallows for their foot-long quarry.

Although the animals are not dangerous, they have a tendency to eject their Cuvierian tubules— long, sticky white strands—when disturbed. Collectors invariably get this goo, designed to immobilize a predator, all over their hands.

Some 30 species—generally Holothuria—are collected. The inferior, small black ones are sold to the Chinese market, where they fetch up to $2.40 a kilo for the wholesalers in Ujung Pandang. The real prize, however, is H. aculeata, fat and whitish when dried. These are saved for the more lucrative Hong Kong market, where they sell for up to $17/kilo wholesale.

Trepang, a Malay word, is also called bêchede-mer, a pseudo-French word derived from an old English word, derived from the Portuguese bicho do mar, "sea worm." The original Latin, however, is more evocative: "little sea beast."

— David Pickell

Biak Fish Bomb Industry

Fish bombing and dynamite fishing are unfortunately widespread in Indonesia. The practice began in earnest after World War II, as wartime construction brought dynamite to Indonesia, the Philippines, and the Pacific Islands. In Indonesia, a flourishing cottage industry has developed to remove the cordite from Surplus Allied shells—dumped in the sea at war's end—and distribute it to markets across the archipelago for fish bombs.

Fish bombing is a simple process. A likely spot is located and staked out by a fisherman. A small bomb, usually powder packed into a beer bottle, is stuffed into a cored papaya and thrown over board. After the explosion, the stunned and killed fish are scooped up with nets as fast as possible. The papaya helps the bomb sink and muffles the blast; one doesn't want any unsolicited "helpers" when the fish start floating upward.

To a fisherman, who works a long, hard day to bring a few fish to market, the appeal of bombing is obvious. Unfortunately, the impact on the reef is disastrous. Not all the dead fish float, of course, and method is very wasteful. But the most damage is caused by the destruction of the coral by the blast. Fish will essentially reproduce to fill the environment. Coral is the environment.

Flourinshing Cottage Industry

According to a report by Stephen Nash of the World Wildlife Fund for Nature, an old Allied ammo dump in the Padaido Islands has been the source of a cottage industry supplying the fish bombs used in Biak and the Cenderawasih Bay, and may supply powder to markets as far away as western Indonesia. The report was written several years ago, and at the time the supply of easily-found shells was running out. But the author feared that scuba gear, brought to Biak to equip collectors of tropical marine fish, would make accessible new supplies of bombs.

The Padaido islanders are masters of the very delicate art of live bomb recovery. The shells are found by dragging the sandy bottom with a piece of iron tied to a rope. When it is felt to hit something hard, a diver puts on goggles and dives to the bottom—18 meters—ties the bomb to the rope, and returns to the surface. Then the bomb is hauled up. Once on land, the bomb is carefully opened, and the priming mixture and cordite are extracted for packaging and sale.

The trickiest part of building the fish bombs is constructing the fuse, which is made of the flat, malleable aluminum from a tube of toothpaste. Priming mixture is "diluted" with crushed matchheads and the aluminum sheet is rolled around it like a cigaret. The aluminum makes the fuse waterproof; heat and combustion gases keep the water from rushing in the open end. Different lengths of this waterproof fuse are used depending on how deep the fisherman wants the bomb to go before exploding.

The fuse is attached to a standard beer bottle—or a large ale bottle, or a small medicine bottle—with coconut husk rope and pitch. The whole package is stuffed into a papaya, and thrown over board. According to the report, fish bombers off the south coast of Biak near the airport time their bombs with the noisy arrival of the Garuda flight, which effectively masks the explosion.

Today, the supply of cordite and gun-powder has for the most part disappeared. Unfortunately, the clever fishermen have now discovered how to make bombs using ingredients found in widely available chemical fertilizers.

— David Pickell

A barrier reef that forms around an island is sometimes called an "almost atoll." There can be multiple barrier reefs, extending outward like ripples, and the large lagoon behind a barrier reef can harbor small patch reefs and sandy cay reefs.

Atolls. Some 425 of these characteristic circular reefs, with a large central lagoon, have been recorded throughout the tropics. The vast majority (more than 300) are in the Indo-Pacific. The largest is Kwajalein in the Marshall Islands, which forms an oval 120 by 32 kilometers.

The largest atoll in Indonesia—and the third-largest in the world, just 20 percent smaller than Kwajalein—is Taka Bone Rate, in the Flores Sea south of Sulawesi. Taka Bone Rate (called Tijger in older texts) stretches 72 by 36 kilometers, covers 2,220 square kilometers, and includes 22 sandy islands. "Taka,"probably a Bugis word, is a generic term used throughout Indonesia for atoll or bank reef.

The lagoon of an atoll, because it is so thoroughly cut off from the open ocean, forms a unique environment, and is often much richer in life than the lagoon side of, say, a small barrier reef. The level of organic matter in the water inside the atoll's lagoon is considerably higher than outside, allowing it to support as much as 10 times the biomass as the outer reef edge. And, because it is not adjacent to a large land mass, problems caused by run-off and turbidity are eliminated.

The richness of the lagoon water is thought to be the result of deep ocean water percolating through the walls of the basement structure of the reef, bringing with it nutrients that previously had been locked away in geological storage.

The Formation of Reefs

Darwin's theory. British naturalist Charles Darwin first published his theory of coral reef formation in 1842, and it is still the dominant theory today. Darwin, in The Structure and Distribution of Coral Reefs, suggested that a fringing reef around the edges of an island would gradually grow outward, leaving a lagoon in its wake, and evolving into a barrier reef. If the island, over geological time, subsided, then what would be left would be an atoll:

"Now, as the island sinks down, either a few feet at a time or quite insensibly, we may safely infer from what we know of the conditions favourable to the growth of coral, that the living masses bathed by the surf on the margin of the reef, will soon regain the surface...

"Let the island continue sinking, and the coral-reef will continue growing up its own foundation, whilst the water gains inch by inch on the land, until the last and highest pinnacle is covered, and there remains a perfect atoll." (See diagram at right.)

This, like natural selection, was pure speculation on Darwin's part. Atoll-formation was a phenomenon of history, and not something that he could "prove" with 19th century technologies. In fact, it was not until the 1951, when the U.S. Geologic Survey drilled Enewetak Atoll in the Marshalls to 1,340 meters, that Darwin's theory was confirmed: deep down, below the layer of coral in the atoll lagoons, the core samples revealed the volcanic rock of a former island.

In the clear waters of Indonesian reefs, ultraviolet radiation can penetrate several meters underwater. Pigments made up of amino acids, called S-320, shield the delicate growing tips of shallow-water corals such as this Acropora sp.

Step 1. A fringing reef forms around an island.

Step 2. The island sinks, and the fringing reef grows into a barrier reef.

Step 3. The island sinks below the surface, and only an atoll remains. (After Darwin, 1842)

Step 1. Limestone is exposed by geological forces.

Step 2. Rainfall erodes exposed limestone.

Step 3. Water level rises, and eroded limestone is colonized by coral. (After Purdy, 1974)

However, this still did not explain the mechanism for Darwin's subsistence of the island. We now know, for example, that the Ice Ages, by locking up much of the earth's water into ice, brought about large changes in the level of the earth's oceans. At the peak of the last Ice Age, 18,000 years ago, the sea level stood almost 130 meters lower than it does today. In some cases it has probably been the rising of the oceans and not the sinking of the island that has created atolls.

Karstic saucers. Darwin's is not the only theory of reef formation, and there are some areas where geological evidence does not accord well with his speculations. A newer explanation has been offered, called the karstic saucer theory. "Karst" is the name given to the formations caused by the action of rainwater on exposed limestone—caves, sinkholes and underground channels. (The name comes from the type region around the Dinaric Alps, near the Adriatic coast of Yugoslavia.)

The emperor angelfish, Pomacanthus imperator.

This theory proposes that an area of exposed limestone, acted upon by the weak carbonic acid produced by rainfall, would take the shapes Darwin's theory attributes to reef growth. When the water level subsequently rose, corals would colonize the already shaped and eroded limestone. (See illustration at left.)

One of the great appeals of this theory to scientists is that it can be tested in the laboratory. Weak acid applied to a flat-topped block of calcareous rock will tend to erode it into the shape of a saucer, the acid acting to a greater degree in the center than at the edges. It also better explains some of the structures, like blue holes, found in Caribbean reefs.

Products from the Sea

Indonesians have always been sea-farers, and for an archipelagic nation, the ocean is still its greatest resource. Fish provides the main source of protein to Indonesia's 204 million people. The waters off Indonesia are thought to be able to support a fishing industry of 5 million tons a year, with actual catches just 20 percent of this.

Commercially valuable sea products also provide some cash to people living on sandy islands with little or no resources, save perhaps copra from coconuts. Ujung Pandang, the capital of South Sulawesi, is the Indonesian leader in the export of sea products, shipping several thousand tons a year. These include pearl oysters, mother-of-pearl or Trochus shells, other shells and dried sea cucumbers. The sea cucumbers, or trepang, are used in Chinese soup. (See 'Trepang Fishing," page 27.)

Although collecting these animals provides necessary income to the islanders, over-harvesting by itinerant Bugis and Bajo fishermen has all but wiped out certain species in some areas. Particularly hard-hit are the giant clams (Tridacna). The meat is canned and then sold at considerable prices in East Asia. These clams used to grow in huge "fields" in the reefs of eastern Indonesia. You can now dive in the same areas and not see a single one.

Triton shells (Charonia tritonis), helmet conchs (Casts cornuta) and turban shells (Turbo marmoratus), which are sold as trinkets, have also disappeared from some areas.

Future of Coral Reefs

Although Indonesia has some of the most untouched coral reefs in the world, even in the remote parts of the archipelago, where industrialization has not yet reached, the reefs are not free of danger. According to officials of the World Wide Fund for Nature (WWF) in Irian Jaya, the Indonesian half of the island of New Guinea, it is predominantly the reefs, and not the great forests of that island, that are most at risk.

Like forests, reefs are subject to succession. A diverse, well-populated reef does not just spring from the sandy bottom. Once a reef is wiped out, unprotected wave action and current may prevent regrowth from taking place.

In the more developed areas of Indonesia, dredging of channels, harvesting of coral for construction materials, and filling of estuarial waters has had a devastating impact on the reefs. The Bay of Ambon, in the central Moluccas, once had a reef that moved naturalist Alfred Russel Wallace to write: "There is perhaps no spot in the world richer in marine productions, corals, shells and fishes, than the harbour of Amboyna." During the post-war building boom, the coral was dragged up for building material in Ambon town. Today, the bay is a wasteland.

Giant clams like this Tridacna gigas were once common on Indonesian reefs. But a market for the canned meat in Asia, and the use of giant clam shells in making terazzo in Surabaya, Java have decimated the population in many areas.

A gorgonian goby (Bryaninops sp.) on an antipatharian wire coral. This little animal is no more than 4 centimeters long. Many fishes rely on invetebrates for food, shelter, and protection, but few are as particular as the gorgonian gobies. Some species of Bryaninops live and lay their eggs on only a single species of gorgonian or antipatharian.

Also damaging is the continuing practice of fish bombing, in which small charges are thrown overboard to stun fish so they can be easily captured for market. (See 'The Biak Fish Bomb Industry," page 28). The bombs don't just kill the fish. They create lifeless craters in the reef, deserts where all the coral and the life it supported have been destroyed. In some places this practice has reduced all the nearshore reef to barren rubble. Fishing for aquarium specimens and groupers for the live seafood trade using sodium cyanide is just as damaging.

In the long run, however, the greatest damage to reefs will probably be a result of bad land use: poor farming practices, including overgrazing, public works projects that expose the thin tropical soil to erosion, and deforestation through timbering.

These practices increase runoff and erosion, loading rivers up with silt, which is then carried out to sea. Silt chokes off coral growth, and leads to eutrophication, a great increase in nutrients in the water. This, in turn, causes an algae bloom, which robs the water of oxygen and can form a lethal mat over the coral.

Divers in Indonesia also have a responsibility to keep the country's reefs, many of which truly are in pristine condition, in a continued state of health. This means taking no souvenirs, developing good diving habits so as not to break off or damage fragile corals, and not harassing animals. In some areas, careless placement of dive boat anchors has already caused damage.

In many areas the guides are not educated in reef conservation. I have been served fresh giant clam after a dive by a guide who took the animal while diving on an Indonesian reef that was a protected marine reserve. He couldn't at first understand why we were upset. As visitors—and customers—divers are in an excellent position to help dive operators develop good conservation habits. I think we owe it to the people and reefs of Indonesia to do at least this much.

— David Pickell

MARINE LIFE

The Varied Inhabitants of Indonesia's Reefs

The waters surrounding the islands of Indonesia form the richest marine habitat on earth. Indonesia lies at the epicenter of species diversity for the entire tropical Indo-Pacific region, which stretches from Madagascar and the Comoros islands in the west to the easternmost of the Pacific islands—a vast 12,000-mile sweep through the Indian and Pacific Oceans.

Perhaps 3,000 species of fish, and several hundred species of coral populate the reefs off the larger Indonesian islands. A 19th century Dutch ichthyologist cataloged 780 species of marine fish just in Ambon Bay alone, almost as many as can be found in all the rivers, lakes and seas of Europe. (Alas, this reef has been destroyed, dredged after World War II to provide building materials for booming Ambon town). Even the healthiest Caribbean reef has just 10-20 percent of the species diversity of a comparable Indonesian reef.

The islands that now make up Indonesia are likely to have been the genetic "source" of Indo-Pacific marine life. This region has remained tropical for 100 million years, exposed to the strong sunlight that makes tropical waters so much richer than temperate waters, giving the animals a long time to diversify.

Although ocean currents distribute fish widely, the further across the Pacific one goes from Indonesia, the fewer species will be found. For example, 123 species of damselfish are found in Indonesia.* (see note at right.) In the Philippines, 118. In Papua New Guinea, 100. In Fiji, 60. In the Society Islands, 30. In the Galapagos, just 18. The entire Caribbean holds just 16 species.

One million years ago the Ice Ages began, periodically tying up much of the earth's water in ice. This lowered sea levels by as much as 130 meters, reducing the tropical Atlantic to a small refuge in the south Caribbean, decimating the animal population. The Indo-Pacific never suffered such an extinction.

But volcanism and continental drift caused similar disruptions in Indonesia, and it is probably because the islands provide such a wide variety of habitats— deep sea trenches, rocky shores, sand and mud flats, sea grass beds, mangrove swamps and, of course, coral reefs—that the fauna here is so diverse.

While muddy turtle grass beds, mangrove swamps and estuarial waters are of immense interest to the biologist, divers usually find little in these shallow, turbid waters to hold their attention. When divers talk about tropical water diving, they mean coral reefs.

A long-nosed hawkfish, Oxycirrhites typus, sitting among the lacy antipatharians encrusting a wreck, just off Molas beach near Manado, Sulawesi.

A Compendium of Reef Life

There are so many species present on the Indonesian reefs that even specialists can not give an exact tally of their numbers here. With this in mind, the aim of this chapter is to provide an introduction to the major groups of animals that will be seen when diving on Indonesian reefs. No attempt at comprehensive coverage is made.

Algae

Although people often mistakenly think of many of the reef animals—corals, gorgonians, sea "anemones"—as plants, what is perhaps most striking about the coral reef is the apparent lack of plant life. Other rich coastal marine environments, for example the kelp forests off California or the sea-grass beds and man-grove swamps off some of the Indonesian islands, are obviously based on the photosynthetic production of oxygen and nutrient-fixing by algae or higher plants.

Turtle grass, Thalassia sp., is one of the very few true marine plants. Although not found on reefs, back-reef areas may have beds of turtle grass, which nourish crustaceans and juvenile fishes as well as the dugong.

The marine algas Udotea (top) and Halimeda can both be occasionally found on the reef. Udotea is only lightly calicified, but the calcium carbonate disks of Halimeda are in some areas a major component of the reef substrate.

On the reef, however, despite its teeming life, plants seem absent. In fact, plants are the primary producers on the reef, just like every other environment. Most of the algae found on the reef grows as a short "turf," a fine carpet of hairs that is a mix of dozens or hundreds of species of brown, red and green algaes. While diving, look closely at an area of bare coral rock and you will probably see a fine carpet of "hairs" growing on it.

The algal turf grows at a prodigious rate, but a herd of grazers—tangs, parrotfish, damselfish, sea urchins, snails and many others—keeps it clipped short. If an area of reef were caged off to prevent the entry of herbivores, the turf would quickly sprout into a thicket. The farmerfish damsel (Stegastes lividus) does just this, by force of personality keeping out all intruders from his own luxurious green patch of hair algae.

Some reef algaes, the so-called coralline algaes, are calcified, providing them with protection both from grazers and physical damage by surge. These appear as small pink "trees," or flat, encrusting pink or lavender growths on old chunks of coral. Some of the coralline algaes grow in areas of very high wave action, indeed preferring areas that are too turbulent for even corals to survive.

On reefs facing the open ocean, it is a ridge of coralline red algae that receives the full force of the crashing ocean waves, dissipates their energy, and allows less robust organisms including corals to thrive. Other varieties of coralline algae grow deep on the reef, below the level at which reef-building corals can survive, where they contribute significantly to reef growth and sand production.

One recognizable green macro-alga that can sometimes be seen on shallower reefs is Halimeda, a heavily calcified alga made up of chains of green disks, each the size of a small button. These disks are calcium carbonate, like coral, and in some areas Halimeda rubble is a major component of the reef substrate.

Sometimes an inshore reef will merge with shallow beds of turtle grass, one of the very few true marine plants. These grassy beds provide an environment for seahorses, pipefish, damselfish, wrasses, and the young of some reef fishes, including butterfly-fish, as well as small crustaceans, mollusks and worms. The sea grass also provides forage for the rare dugong (Dugong dugon), or sea cow, which ranges across Indonesian waters.

Plankton

The diver will rarely see plankton, and if he or she does, it will usually be apparent as a cloudiness of the water, or an irritating backscatter in photographs. But plankton is an important link in the reef food chain. Reef areas rich in plankton will be characterized by an abundance of filter-feeders, animals that have evolved methods of sifting or snaring plankton from the current—including soft corals, mussels and oysters, anemones, crinoids, gorgonians and sponges.

Plankton consists of both "plants"—phytoplankton—and "animals"—zooplankton, and the larger zooplankters are predatory on the diatoms and algae of the phytoplankton. The plankton also contains some temporary members, the meroplankton, which consists of the larval stages of fish and invertebrates. As these grow, they settle out of the plankton stream to become part of the swimming nekton (fish, jellyfish) or the crawling or fixed benthos, or bottom dwellers (sea urchins, gorgonians).

Sapphire damsels, Pomacentrus pavo, take shelter in the sponge Cribrochalina. Halmahera, Maluku.

Sponges

Indonesian reef sponges vary in size from tiny to huge, from the small patches of color provided by encrusting sponges (family Clionidae) to the meter-high barrel sponges (Xestospongia). All sponges are members of the phylum Porifera, "the hole-bearers," and their porous, "spongy" nature is crucial to their mode of feeding. Sponges are the archetypal filter-feeders, straining plankters from the water through myriad microscopic pores.

A cross-section of a sponge shows a very sophisticated system for moving water. Small intake pores lead to an internal system of tiny canals and chambers lined with cells bearing whip-like processes. Beating constantly, these cells create a current through the sponge that moves its own volume of water every 4-20 seconds. Even a relatively small sponge can circulate as much as 5,000 liters a day. The chimney or barrel shape of many larger sponges helps increase surface area and the water flow through the animal.

Sponges are notoriously difficult to identify. Colors vary and even the shape or size of a sponge does not necessarily mark its species; sometimes shape is just a response to local conditions. Scientists would call this new form an "ecomorph."

Scientists rely on detailed examination of the internal "skeleton" to identify sponges. Sponges are made of a proteinaceous secretion called spongin. This fibrous net forms the useful part of the bath sponges (Spongia and Hippospongia) harvested in the Mediterranean and Caribbean. Many sponges also contain spicules of silica or calcium carbonate, or both, bound together with spongin.

There are an estimated 830 species of sponges in Indonesia. The giant barrel sponges are most impressive to divers, but the smaller tube sponges and vase sponges also create colorful and aesthetically pleasing forms.

Marine dinoflagellate plankters, top to bottom: Gymnodinium, Gonyaulax, Peridinium, Ceratium.

Like many invertebrates, sponges can grow to a remarkable age. Experiments with commercial farming of bath sponges in the Caribbean have led researchers to estimate that larger specimens are at least 50 years old, and maybe much older.

Reef sponges create an environment that is exploited by a variety of other creatures. Small crabs and shrimps and even fish hide in the tubes and cavities. Crinoids perch on upright sponges to filter plankton from the current. And sea cucumbers and other detritus feeders graze on the organic material that collects on the sponge's surfaces.

Corals and their relatives

Corals, soft corals, sea anemones, gorgonians, hydroids, jellyfish and the other members of the phylum Cnidaria (formerly Coelenterata) cause a great deal of confusion for the diver trying to identify the teeming mass of branched and tentacled life he sees attached to the reef. Taxonomists identify these animals by their stinging cells, nematocysts, and simple coelenteron, from the Greek koilos, "hollow," and enteron, "gut." All have the form of a polyp at some stage in their lives. Other than these shared characteristics, the form of these animals varies widely.

Aristotle considered them an intermediate form between plants and animals, and they were first placed by taxonomists in a group called Zoophyta, "animal-plants." Only in 1723 were corals properly identified as animals, and Jean Andre Peyssonel, the naturalist who proposed this to the French Academy of Sciences, was laughed at and quit science in disgrace.

Phylum Cnidaria is usually divided into four classes: Hydrozoa, hydroids and fire corals; Anthozoa, corals and anemones; Cubozoa, box jellies; Scyphozoa, jellyfish. Anthozoa, in turn, is split into three sub-classes: Alcyonaria (Octocorallia), containing the soft corals and gorgonians; and Zoantharia (Hexacorallia), containing the stony corals and anemones; and Ceriantipatharia, including the black corals and cerianthids, or tube anemones.

The Stony Corals

The stony or hard corals are the reef-builders. They are in the order Scleractinia, and are sometimes called scleractinian or "true" corals. The skeletons these animals secrete range in shape from the massive, smooth boulders of Pontes and stout-branched Pocillipora that take a pounding at the reef edge to the finely foliated needle coral Seriatopora histrix.

These corals are colonies, comprised of thousands of individual coral animals, or polyps. Each polyp, upon close examination, will be seen to have much the same shape as a sea anemone, with tentacles ringing a central mouth. What makes the stony coral polyp distinctive, and so ecologically important, is that it deposits calcium carbonate around its lower part, forming a skeletal cup. The skeleton is essentially formed of repeated casts of the tiny polyp.

The presence of whip coral gorgonians often indicates very clean water and plenty of plankton. This is Ctenocella (formerly Ellisellaj. Bunaken group, Sulawesi.

Most reef-building corals are nocturnal. During the day, the polyps are retracted, drawn down into the skeletal cup. At night, these corals are transformed from dead-looking lumps of rock into miniature forests thick with polyps, which expand to feast on the abundant night plankton. Tiny plankters are snared by the polyp's tentacles, which are armed with stinging nematocysts. Although they feed on plankton, the vast majority of the nutrition of reef-building corals is provided by the symbiotic zooxanthellae in their tissues. (See sidebar, "Zooxanthellae and Corals," page 25.)

Corals, like other reef animals, also spawn at night, releasing pink clouds of sperm and eggs. To increase the chances of fertilization, corals of the same species tend to coordinate the release of their eggs and sperm. Many reef animals spawn around the time of the full moon, when tidal currents are strongest, to ensure wide dispersal of the larvae. On the Great Barrier Reef of Australia the majority of corals spawn 4-5 days after the November full moon. Some corals in Indonesia spawn at this time too, but the full pattern of coral spawning has not yet been determined here.

According to travel brochure cliches, corals are supposed to be "kaleidoscopic" with color. Divers, of course, know that at least for the reef-building corals, this is not at all the case. Most shallow water corals are a dull brown color, a consequence of the pigments in their zooxanthellae. Still, some are blessed with subtle pastel tints. In particular, the growing tips of Acropora can be colored with a pinkish or purplish pigment, a group of amino acids called S-320 which serves as an ultraviolet filter to protect the still-young polyps.

A detail of the eponymous vesicles of the bubble, or grape coral, Plerogyra sinuosa. These sacs, called acrorhagi, possess stinging nematocysts. During the day they are inflated with water and protect the polyp tentacles. At night they shrivel, and the polyps are extended to snare plankton. The acrorhagi also discourage other corals from over-growing Plerogyra, blocking its sunlight and supply of plankton.

The shape of stony corals, rather than their color, is their most salient characteristic. The form the coral will take is strongly influenced by wave action and currents, and even the same species may take different forms under different conditions. A specimen of the distinctive pal-mate Caribbean elkhorn coral (Acropora palmata) placed in a research ecosystem at the Smithsonian Institute in Washington, D.C. sent up new growth in the bushy form of A prolifera. This, it would seem, further complicates the already difficult project of stony coral identification.

Massive forms. In general, massive, boulder-like forms grow in shallow water where light is plentiful, and along the reef edge where the current is strong. These include the common Monastrea, Pocillopora, and Pontes. In the shallow, often turbid water of the back reef, the more robust branching forms (Acropora) can out-compete the massive forms, which are more vulnerable to siltation.

Massive corals sometimes form "micro-atolls" in relatively calm backreefs and reef flats. These are flat-topped forms in which the center has been killed by excessive siltation or regular exposure by low tides. The sides continue to grow outward, demonstrating Darwin's theory in miniature.

Goniopora is an unusual massive coral that extends its polyps during the day. These are also usually large, reaching 20-30 centimeters in length. The effect is of a round stone, covered with little brown flowers.

Branching forms. Deeper in the reef, or in protected parts of the shallows, the diver will encounter finely branched and "leafy" forms. These more delicate structures cannot withstand strong wave action, and the added surface area of their shapes serves to better expose their zooxanthellae to the diminished sunlight of deeper waters.

The most common is the fast-growing and ubiquitous Acropora. This genus (there are some 100 species) takes a variety of forms, ranging from branching thickets to table-like formations. The tables are considered to be a defense mechanism, as the Acropora quickly grows outward, shading any other corals that might try to overgrow it.

Another branching coral often recognized by divers is the needle coral Seriatopora hystrix, sending up delicate, pointed branches of cream, blue or pink. Seriatopora is usually found in quiet, rather shallow water.

Smaller corals. Some of the smaller coral colonies have distinct, interesting shapes. These corals are not primary reef builders, but colonize already established areas of the reef.

The mushroom corals (family Fungiidae) are common in Indonesia. These form carbonate skeletons that are flat and oval-shaped, perhaps 15-30 centimeters inches long, with fine, radial structures reminiscent of the "gills" of a mushroom. The skeletons are not attached to the reef, and particularly on drop-off reefs, are often knocked upside down by currents. These corals are capable of limited movement, and can usually right themselves eventually. The long-tentacled Heliofungia actiniformis is often mistaken for a sea anemone.

The flower corals (Euphyllia) are not as common as Fungia, but can be quite beautiful. They form a maze of flat plates that stick up vertically 10-20 centimeters and cover an area 50 centimeters or even much more in diameter. These corals have long, colorful tentacles, which they extend during the day. Euphyllia tolerates turbid water, and can be found growing on patch reefs in back reef channels.

The very bright orange polyps of the coral Tubastrea (or the similar Dendrophyllia) can be seen in small clusters, usually in low-light areas such as deep on the reef or under overhangs. These finger-sized polyps can easily be mistaken for anemones. They are true scleractinian corals, however, and secrete a very fragile internal skeleton. Tubastrea contains no zooxanthellae and receives all its nutrition by capturing plankton. At night, you can watch the polyps feeding by using your light to attract the plankton within reach of the polyps' tentacles. (If your light is very bright, shade it so the polyps won't retract.)

Anemones

Despite their soft and fleshy appearance, sea anemones (order Actinaria) are more closely related to stony corals than soft corals. The giant anemones commonly encountered in Indonesia contain symbiotic algae and are most abundant in relatively shallow areas. They can be seen growing in sand, or tucked into the coral rock in the shallows or at the lip of drop-off reefs.

Like the corals, color and even shape varies widely in the giant anemones, and they are often very difficult to identify. In Indonesia, one can find the long-tentacled Heteractis, the short-tentacled carpet anemone, Stichodactyla, and the unusual Entacmaea quadricolor, with bulbous-tipped tentacles. These anemones are large, sometimes growing to half a meter or more in diameter, although what at first seems to be one anemone is sometimes a group of several.

Discovering New Species

For the diving scientist, Indonesian waters are the most exciting in the world. Not only can "new" species be found on just about every dive, but so much of the behavior of these animals is still unknown that underwater observations are full of surprises.

Scuba has radically changed the way scientists study marine animals. No longer is it necessary to collect everything to study in an aquarium, an artificial environment that often produces artificial behavior, or to collect species the old way—netting, trapping, or even poison. A diver can collect very selectively, and make observations without interfering with the animals' ways of life.

Innumerable small crustaceans and other benthic creatures living in the cracks and crevices of Indonesian reefs go undescribed by science. Even among the best-known reef animals—the fishes—new discoveries are made regularly.

The Grandfather of Ichthyology

To find new species of fish, a good eye and thorough knowledge of the literature serves one better than an academic degree. The grandfather of Indonesian ichthyology was Pieter Bleeker, a Dutch army doctor with a keen interest in fishes. He arrived in Jakarta in 1842, and over the following 30 years produced some 500 papers that became the foundation of his famous, nine-volume Atlas Ichthyologique (1862-78).

Unlike many 19th century scientists, who were for the most part simple taxonomists, Bleeker had a very modern understanding of the inter-relationship of species. His work is highly respected by today's scientists.

Finding New Species

Bleeker's work was so good that species described 100 years ago are still waiting to be "re-discovered." It is amazing how many deep-water fishes were collected in those days and never seen again. But scientists tend to concentrate on these, and the intertidal areas are often overlooked. A knowledgeable diver, with sharp powers of observation, has a very good chance of finding an unknown animal on just about any dive in Indonesia.

The red-headed wrasse, Halichoeres rubricephalus, is sexually dichromic (male at top). This beautiful wrasse was discovered by Kuiter in 1986 in Maumere Bay. Common there, it has not been seen anywhere else.

I have been visiting the Flores Sao Resort on a regular basis since 1986, photographing and observing the animal life of Maumere Bay. Despite my many dives in these waters, new species turn up on every trip. Often a "new" species looks very similar to a well-known one, and thus has been overlooked. But in other cases the new species is so spectacular one wonders how it could possibly have ever gone unnoticed.

I started underwater photography 20 years ago, and even among my first dives with a camera, I photographed things that I have never seen since. I always take the picture first, and try to sort out the story later. The underwater world is so diverse you may never see it again.

— Rudie Kuiter

Giant anemones are easy to spot because they nearly always host a pair, or small group of clownfish (Amphiprion and Premnas). (See "Clownfishes and their Sea Anemone Hosts," page

46.) These fish are not the only animals to take advantage of the security of the anemone's stinging tentacles. Porcelain crabs (Neopetrolisthes) and shrimps are also anemone commensals.

Corallimorphs. These animals (order Corallimorpharia) have some of the characteristics of anemones, and others of corals. In fact, however, they look like small anemones. They are mostly colonial, and consist of flat disks, 2-4 inches in diameter, with a smooth, napped or tentacled surface. One genus, Discosonia, is particularly colorful, overgrowing rocks with its bright blue, purple or red disks.

Soft corals and gorgonians

These animals (subclass Alcyonaria) are among the loveliest of the cnidarians. In the clean, plankton-rich waters of Indonesia, soft corals and gorgonians— sea whips or sea fans—are common. Some contain zooxanthellae, but many frequent the deeper parts of the reef, where they filter plankton from the water. Semi-precious pink "coral" is a gorgonian (Corallium), harvested from deep waters off Japan and in the Mediterranean.

Soft corals. Soft corals, as the name suggests, lack the hard limestone skeletons of their reef-building relatives. Instead, the numerous polyps that make up the colony are supported by a fleshy central "body"; in some cases strengthened by spicules, spines of silica or calcium.

Soft corals (order Alcyonacea) have few obvious defense mechanisms, and might seem to be vulnerable to attack by predators and parasites, or to fouling by overgrowth. The animals avoid these problems by secreting various bioactive substances, a kind of chemical defense. Substantial efforts are being made by biochemists and pharmaceutical companies to identify compounds in soft corals—and also sponges—that may have properties useful in medicine. Since many of these compounds have evolved to prevent alien growths, they are receiving attention as potential anti-cancer drugs.

A very common group of soft corals in Indonesia are the leather corals (Lobophyturn, Sarcophyton and Sinularia) so-named because of their color and texture. These corals grow as wrinkled lobes in well-lit, shallow areas of reef. Because of their symbiotic zooxanthellae, they are a dull brown, sometimes with a slightly green or yellow tinge. When their white polyps are extended for feeding they are easy to identify as soft corals, but when their polyps are retracted they could be mistaken for sponges. The leather corals, however, have a much smoother surface than sponges.

Perhaps the most beautiful of the soft corals is Dendronephthya, a soft coral with fuzzy branches of vivid pink, white, orange, red, red-and-white, and a variety of other colors. The main "stem" is normally translucent and contains numerous white spicules, which offer some structural support. Most of the color comes from the polyps, which also contain sharp spicules to deter browsing by fishes. Dendronephthya grows deeper on the reef and in areas of low light, and always where currents can provide it with abundant plankton.

Xenia, particularly common in Indonesia, has perhaps the largest individual polyps of any soft coral, each 6-8 centimeters long. The white (also tan, or light blue) polyps grow in clusters, and the tentacles at the end of each are feathery. These continually open and close, like numerous grasping hands. In Xenia one can easily count eight tentacles, which is one feature that distinguishes soft corals (Octocorallia) from hard corals and anemones (Zoantharia) which have six, or multiples of six, tentacles.

Gorgonians. Gorgonians (order Gorgonaceae) have a strong, horny skeleton, which gives strength and support without sacrificing flexibility. They tend to grow on the deeper parts of the reef, away from strong wave action. They live by filter feeding, and to maximize the water flow across their surfaces always grow at right angles to the prevailing current. Where the tidal current flows along the reef, gorgonians grow with their long axis vertical. Sometimes, however, particularly on some of the big walls in Indonesia, large sea fans can be seen growing horizontally out from the reef wall, to take advantage of the current upwelling.

There" are many species of these animals. Some have a twig-like structure, like a branch from a delicate tree. Many are brightly colored. The sea fans (Melithaeidae and Plexauridae) are flat nets, growing in some cases to three meters across. The skeleton of a sea fan is coated with a kind of "rind," which is sometimes a delicate shade. When you see a big gorgonian it is worth spending a few moments looking closely at its surface because they often host an assortment of small symbiotic animals.

Sea pens. These animals (order Pennatulacea) are filter-feeders related to the gorgonians. Their common name comes from their resemblance to the old-fashioned quill pen. Although common in Indonesia, they are not really reef dwellers, and will usually only be seen by night divers who venture out over mud or sand bottoms. Sea pens, sometimes growing in large fields, rotate gently back and forth with the current, their "feathers" sifting plankton from the current.

Closeup of the lovely soft coral Dendronephthya. In this photograph the strengthening spicules are clearly visible in the animals ' transparent tissue.

The poisonous sea wasp, Chironex. This animal has been responsible for human fatalities in Australian waters.

Black corals. Black coral (subclass Ceriantipatharia, order Antipatharia) looks to the diver like a gorgonian, although it is more closely related to the stony corals and anemones. On deeper dives in Indonesia, one can see wire corals (Cirrhipathes) and black coral bushes (Antipathes).

The polished skeleton of the latter, particularly the thicker branches, is the precious black coral. Black coral is scarce, and its export from Indonesia and import into many other countries is prohibited by laws.

Cerianthids. In some areas, particularly with sandy bottoms, one can find cerianthids (subclass Ceriantipatharia, order Ceriantharia) or tube anemones. These are quite different from true anemones. Cerianthids have fine tentacles arranged in two concentric bands, and a tube— made of fibers created by special nematocysts—into which they can retract if disturbed.

A pair of Chromodoris willani, perhaps mating. All nudibranchs are hermaphrodites, although they require a partner to produce viable off-spring. Bunaken group, Sulawesi.

Fire coral and hydroids

All cnidarians have stinging cells on their tentacles with which they can defend themselves and immobilize their prey. In most cases, however, these are rather weak and are usually not capable of penetrating human skin. One group, class Hydrozoa, which includes the fire corals and their relatives, has members capable of inflicting very painful stings. The notorious Portuguese-man of-war (Physalia physalis) is a hydrozoan, and not, despite its appearance, a jellyfish. Fortunately for divers this animal is more of an open ocean dweller.

Stinging hydroids. A far greater nuisance to divers in Indonesia are the hydroids Aglaophenia and Lytocarpus. Despite their delicate, fern-like appearance, these colonial animals can deliver a burning sting that raises a welt on bare skin. They are fairly common on many Indonesian reefs, and their presence prompts divers to wear Lycra or thin neoprene suits even in the warmest of conditions. The stinging hydroids are sometimes called sea ferns, or sea nettles.

Fire corals. Somewhat less virulent are the fire corals of the genus Millepora, but as their name suggests they too should be treated with respect. These hydrozoans are members of a group called hydrocorals for their superficial resemblance to the true corals. Hydrocorals secrete a limestone skeleton, and form colonies that are usually a dull-yellow brown in color (Millepora) although some species (Distichopora, Stylaster) can be brightly colored.

The unusual blue coral (Heliopora coerulea), is a fire coral which has a skeleton that when dried displays a light blue tint. It is taxonomically distinct, however and has been placed in class Anthozoa with the octocorals.

Some hydrocorals are important reef-builders, particularly M. platyphylla, which can be found growing with massive scleractinian corals at the pounding edge of the reef.

Jellyfish

These familiar animals (class Scyphozoa) are characterized by a dominant medusa stage. Like all cnidarians they form a polyp for part of their lives, but for the jellyfish, this is just temporary. Occasionally, large jellyfish can be seen while diving in Indonesia, particularly in areas of rich plankton. These can be quite beautiful to observe. More bothersome are the cubomedusae, or sea-wasps, tiny jellyfish that can have an irritating sting. Members of the genus Chironex have even been responsible for human fatalities in Australia. Because they tend to inhabit the surface layer during the day, they are more of a bother for snorkelers. The lights of night divers, however, can often attract an unwelcome swarm of these creatures.

Worms

Although the word conjures up a dull, and faintly repulsive animal to many people, the worms found on the reefs of Indonesia show a diversity of form and color that often astounds the observer.

There are many different sorts of worms, but most likely to be seen by divers on Indonesian reefs are those in the following phyla: the flatworms (phylum Platyhelminthes); the ribbon-worms (phylum Nemertina); the tongueworms (phylum Echiura); and the segmented worms (phylum Annelida).

Flatworms. Flatworms often have the strikingly beautiful colors divers associate with nudibranchs (which are molluscs). The species seen on Indonesian reefs rarely grow longer than 10 centimeters, and feed on sessile animals such as tunicates and sponges. Flatworms move by gliding over the bottom, or by muscular undulations. This latter waving action is characteristic, and mimicked by the juveniles of several species of fish. This mimicry and the bright colors suggest the presence of a noxious chemical to deter predators.

Ribbonworms. These animals are longer than flatworms, and not as showy. Many are white, with dark stripes or bands. They tend to live under rocks and corals or in the sand, and are most likely to be seen by divers at night. Some can grow to astonishing sizes, as much as several meters. They feed on molluscs and other worms.

Tongueworms. The tongue-worm Bonellia can be seen on reef slopes. However, it hides its sac-like body in a crevice, with only a forked proboscis protruding, is easily overlooked. These animals have an unusual sex life. All the fully formed Bonellia are females; if a larva settles into an area where there are no worms, it becomes a female. If there are already Bonellia established in the area, the larva passes into the body of an adult, becoming a dwarf male, which lives like a parasite on the female "host."

Two do rid nudibranchs, Notodoris citrina (top) and Nem-broth a sp. Nudibranchs tend to be very prey-specific. Nembrotha, as is shown here, feeds only on hydroids. Notodoris was photographed in Halma-hera, Maluku; Nembrotha in Flores.

Segmented worms. The segmented worms are the most abundant and diverse of all the groups of reef worms. Divers are familiar with the feathery feeding parts of the tiny Christmas tree worms (Spirobranchus) which extend from lumps of living coral. The body of the worm is hidden in a tube within a Pontes coral head. The similar, but larger fanworm, or feather duster worm (Protula, Sabellastarte), secretes a tube of flexible parchment to protect its soft body. From its tube, it periodically extends a crown of colorful "feathers" to collect plankton. These worms make good subjects for macrophotography, but any sudden movement will cause them to withdraw their crowns.

The triton shell, Charonia tritonis. This gastropod preys on crown-of-thorns starfish.

The helmet conch, Casis cornuta. Indonesians call this kirn a kepala kambing, the "goat's head shell."

Some of the segmented worms have evolved unusual reproductive strategies, perhaps the most famous being that of the palola worms, (Palola siciliensis). Called nyale in parts of Indonesia, these worms spend their lives in coral crevices, but one night a year, their tail parts metamorphose into a sexual form, containing either eggs or sperm.

These sexual forms, called epitokes, break off and swarm to the surface. The timing of the event is set by the moon, and in parts of Indonesia, most notably western Sumba and southern Lombok, the appearance of the epitokes is an important event in the ritual or cultural calender. It is also a great culinary event, as the rich-tasting epitokes are highly prized for eating.

Molluscs

Molluscs are one of the largest and most familiar groups of invertebrate animals, and thousands of species live in Indonesian waters. The phylum is organized into either five or eight classes, the main ones found on Indonesian reefs being: Gastropoda (univalves—single shells), including snails, cowries and conches, as well as the shellless sea slugs; Pelecypoda (bivalves—two-part shell), including clams, oysters and mussels; and the Cephalopoda, including octopi, squid and cuttlefish. Despite their differences, animals in these three groups all possess a soft, fleshy body (mollusc means "soft") and most— octopi and nudibranchs are exceptions—have the ability to produce a calcareous shell.

Nudibranchs and snails

Gastropods are abundant on Indonesian reefs, but they are easily overlooked because most are small, many are nocturnal, and some are very well camouflaged. Nevertheless the diver who develops the habit of carefully scrutinizing the reef surface will soon find many of these delightful creatures.

Nudibranchs. Nudibranchs, the "naked gilled" sea slugs, are the most interesting to the diver. Like common garden slugs, they are snail-like animals that have lost their shells. Nudibranchs are often strikingly colored.

In some species the coloration is clearly cryptic, allowing them to blend in with their chosen prey. Nudibranchs are carnivorous, and most are very prey specific, feeding for example only on particular types of soft coral or sponges. Since these prey animals are often very colorful, so are the nudibranchs.

In other species, it seems certain that coloration serves as a warning to would-be predators that the animals are foul-tasting or poisonous. Nudibranchs are known to produce some very concentrated toxins. Some even have nematocysts, which they obtain from their cnidarian prey and concentrate in the outer layers of their own skin.

Most nudibranchs are small, although a few mainly nocturnal forms grow to 20 centimeters or more in length. One of the largest and certainly the most spectacular nudibranch found in Indonesia is the Spanish dancer, Hexabranchus sanguineus, a beautiful, crimson-colored animal. This nudibranch only wanders out at night, and if it is found and gently picked up, it will begin its "dance." The wild undulations of its body and surrounding skirt are thought to serve as part of a warning display. Like many nudibranchs, Spanish dancers lay their eggs in huge numbers, in spiral ribbons that can look like flowers.

Tridacna gigas is the largest of the seven species of giant clams. It can be distinguished by its size and the pebbly texture of its mantle. Scientists believe these to be among the longest-lived animals, some surviving as long as 200 years. A speciman as large as the one pictured here is probably well over 50 years old.

Rock shells. The rock shells or murex (Murex spp.) feed heavily on small bivalve molluscs such as oysters. This is not an easy task, because the bivalves clamp their shells shut when attacked. A murex shell overcomes this resistance by chipping away at the edge of the oyster with its sharp radula or mouthpart, and then pokes its proboscis into this opening to feed on the fleshy tissues within. Another species, with similar tastes in prey, is the drill (Thais). This small gastropod literally drills a hole through the oyster's shell. The large number of bivalve shells with neat holes drilled in them that are washed up on Indonesian beaches testifies to the efficiency of this feeding method.

Tritons. The triton shell (Charonia tritonis) is famous as a predator of the troublesome crown-of-thorns starfish, which has devastated Australian reefs. This large shell (to more than 30 cm.) is a popular souvenir, and over-harvesting has been blamed for population explosions of the crown-of-thorns. The helmet conch (Casis cornuta) is another large, predatory gastropod found in Indonesia. Because of collectors, both the triton and helmet conch are endangered in parts of Indonesia.

Cone shells. Cone shells (Conus spp.) are even more rapacious predators. Their radulas are modified as barbs, with which they stab their victims. They then immobilize their prey by injecting a neurotoxic poison. Most cone shells eat worms, although a few are piscivorous. The poison of some of the fish-eating Conus species is powerful enough to kill a human, so treat them with respect.

A predatory gastropod prying open a bivalve.

Cowries. Cowries (Cypraea spp.) are common, small (most just a few cm.) gastropods with a smooth shell that is completely covered by the animal's fleshy mantle. Both the shells and mantles can be beautifully marked, often with very different patterns. The cowries are omnivorous, feeding on algae as well as a variety of sedentary animals such as soft corals.

Clownfish and their Sea Anemone Hosts

There is perhaps no sight more charming than a pair of bright clownfishes nestled in one of the colorful giant reef anemones. Although known to possess powerful stinging cells, the anemones clearly don't harm the clownfishes, which look downright snug tucked into the soft tentacles of their host.

The colorful magnificent anemone, one of the largest clown-fish anemones.

The relationship between the fish and the actinian is commensal; the anemonefishes clearly benefit, receiving protection for themselves and their offspring. They even pluck at the tentacles and oral disk of the anemone, eating the organic material that has collected there.

The benefit to the anemone is less clear. The constant prodding, cleaning and stimulation provided by the fishes certainly seems enjoyable, but this maybe just to us. Anemonefishes are never found without anemones; anemones, however, are sometimes found without the fish.

A Delicate Operation

It had been thought that clown-fishes were somehow immune to the anemone's stinging nematocysts. Close observations, however, have shown this not to be the case. The fish, through a series of brief—and careful— encounters with the actinian, picks up a substance in its mucous that the anemone recognizes as its own. The nematocysts don't fire when touched by the fish for the same reason one tentacle doesn't sting another.

Some cold-hearted experimenters tested this theory by scraping the mucous off a clown-fish and placing it back with its anemone. The hapless fish was immediately and unceremoniously stung.

Juvenile Clark's anemone-fish, in the distinctive bulb-tentacled anemone. 15 meters, Bunaken Island, Sulawesi.

Clownfishes are protandrous hermaphrodites; that is, all mature as males, and then a few sex-reverse to females. A typical anemone will contain a pair of clownfish, and perhaps a few young ones.

The largest fish in the group is the female. If she should die, the reigning male sex-reverses, and the dominant juvenile becomes the functional male. Juveniles sharing an anemone with an adult pair are hormonally stunted, and remain small.

Although clownfish are the only fishes to require an anemone host, other small damsels will opportunistically occupy anemones as juveniles, especially various species of Dascyllus.

Young Clark's anemonefish, Amphiprion clarkii, in the distinctive sand anemone, Heteractis aurora.

The spine-cheek anemone-fish, in the bulb-tentacled anemone. The spine-cheeked anemonefish varies from red to almost black.

A pair of Amphiprion ocellaris, in Haddon's anemone. This is not a known association in the wild.

Sea Anemones

Some of the giant reef anemones can reach a meter in diameter. All have zooxanthellae, and are thus found in relatively shallow water. They derive most of their nutrition from the algae, but also consume plankton and any other small animal unlucky enough to blunder into their tentacles.

Anemones can live to a ripe old age. In the 19th century, British naturalist John Dalyell kept a coldwater Actinia sp. anemone for 66 years. Over this period, it produced 750 young (by budding), 150 of these after the age of 50. The anemone eventually outlived the scientist.

Some 10 species of Indonesian anemones, in three families, host clownfish. The systematics of this group was in some confusion until Dr. Daphne Fautin reorganized it in 1981.

Cryptodendrum adhaesivum. Lies flat; very short tentacles. Hosts only Clark's anemonefish.

Entacmaea quadricolor. The bubble anemone. (See photo at left.) Hosts 11 species.

Macrodactyla doreensis. Very long, widely spaced tentacles. Usually dull color, buries column in sand. Hosts 2 species.

Heteractis aurora. Dull color, buries column in sand. Distinctive tentacle shape (see top photo above.) Hosts 7 species.

H. crispa. Long, thin, almost pointed tentacles that often seem tangled. Hosts 11 species.

H. magnifica. Brightly colored column, blunt tentacles. Often photographed. (See small photo opposite.) Hosts 10 species.

H. malu. Buries column in sand, fairly short tentacles, limited range. Hosts only Clark's.

Stichodactyla haddoni. Haddon's carpet anemone. Short-tentacles. Grey, with white radial stripes. Hosts 6 species.

S. gigantea. Bludru anemone. Longer tentacles, larger than Haddon's. Hosts 6 species.

S. mertensii. Merten's anemone. Colorful; largest carpet anemone, to lm across. (See bottom photo above.) Hosts 10 species.

— David Pickell

One of the piscivorous cone shells (Conus sp.) devouring a small goby. Most cone shells eat worms, but the relatively few fish-eating species are very dangerous.

The octopus has highly developed eyes and a very sophisticated nervous system. It is thus considered "intelligent," and people find it hard to believe that it is a mollusc. The white color of this specimen suggests exhaustion, and perhaps the photographer was a bit overzealous in getting this shot.

Trochus. Top shells (Trochus spp.) are relatively large (6-8 cm.), and conical. Before the advent of plastics they were widely collected for the manufacture of buttons. Removing the grubby outer layer of shell reveals the lustrous nacre, or mother-of-pearl beneath. Until the invention of Bakelite, and the many plastics that followed, shell nacre for buttons was an important business in Indonesia. Today they are still collected, most to be used in souvenirs and to supply the small market for "real" buttons.

Clams and Oysters

The bivalves include such familiar forms as clams, oysters, mussels and scallops. All have two articulated shell halves that can be closed with a large muscle. It is this muscle that makes bivalves so prized as seafood. With a very few exceptions, bivalves cannot move, like gastropods, and thus most have adapted to filter-feeding. They draw water in through one tube or "siphon" and pass it out through another. This stream of water passes through the animal's gills, which serve the dual purpose of respiration and filtering out food particles.

All bivalves must hold their shell halves at least slightly ajar to maintain water circulation through their bodies. But when danger threatens they are clamped shut. Some Indonesian bivalves gain further protection by boring into corals and reef rock, so that predators cannot reach them. The boring is achieved by a combination of chemical action and rasping with the two shell haves. Eventually, reef bivalves become so encrusted with sponges, coralline algae, bryozoans and cnidarians that they are barely visible.

Giant clams. The giant reef clams, Tridacna spp., have a different means of feeding. Like reef-building corals, Tridacna clams harbor zooxanthellae in their fleshy mantles, and can thus "manufacture" most—or perhaps all—of their own food. Like corals, they require lots of light, and tend to be found in the shallows. They grow with the hinge of their shells down, and their rippled gape facing the sun.

There are seven species of Tridacna, of which the giant clam, T. gigas, is the most dramatic. These animals can reach a meter and a half in diameter. An animal that big could be a century old. Although smaller than T gigas, T squamosa has a beautiful ruffled shell. The fleshy mantles of Tridacna clams are beautiful, varying in color from brown to yellow to green to blue, with contrasting spots or mottling.

Tridacna clams are a great delicacy in Asia, particularly in Taiwan, and their shells are made into terrazzo in factories in Surabaya. Over-harvesting has greatly reduced their numbers throughout Indonesia. Shallow reefs in Eastern Indonesia that used to support literally fields of giant clams have been stripped in just the past few years. There is fear that the population in many areas is no longer at a self-sustaining level.

Recently, however, researchers at the Micronesian Mariculture Demonstration Center in Palau, headed by Gerald Heslinga, have discovered a method of "farming" giant clams by inoculating the veliger larvae with zooxanthellae. Once the symbiotic algae is in place, the clams need only a good supply of sea-water and plenty of light to thrive. The farming operation requires little room, and the clams reach 10 centimeters across in just two years. Because of the commercial potential for these clams, a number of pilot farms have recently been established in the Pacific region.

The thorny oyster ("Spondylus sp.) is often so encrusted with sponges, algae, tunicates and other organisms that only when it is agape with its bright mantle showing (as here) can it be seen. Halmahera, Maluku.

Oysters. A number of oysters can be found on the reef, in many cases so well camouflaged with encrusting growths that they are at first invisible. The cock's comb oyster (Lopha cristagalli) has a distinctive sharp, zig-zag opening, and is often covered by encrusting sponges.

The colorful mantle of the thorny oyster (Spondylus spp.) stands out, although its rough shell is usually overgrown with algae, sponges, and small cnidarians.

In many parts of Indonesia, Japanese operators seed pearl oysters (Pinctata) and hang them in the shallows to grow pearls. The oysters are purchased from local collecters, and the "seed" comes from a freshwater mussel found in the Mississippi basin. Security on these "farms" is high, and divers are unwelcome.

Cephalopods

These animals, despite their close relationship to the snails and clams, are active, "intelligent" predators with highly developed eyes and sophisticated behaviors. The octopus has eight suckered arms, while squid and cuttlefish have an additional two grasping tentacles. Both octopi and squids have a hard, chitinous beak. The nautilus—of which only one genus is extant— differs markedly from the other cephalopods. It has 90 arms, without suckers, and a well-developed shell. Unlike other cephalopods, the nautilus has very primitive eyes, lacking a lens and open to the water.

Octopi. These familiar animals can be found on the reef, although they normally hide in small caves or crevices. They have no internal skeleton so are able to squeeze into surprisingly small spaces.

Chromatophores on their skin give octopi remarkable abilities to change color, which they do either to blend in with their surroundings or to display emotion. Some species can also change their surface texture, from smooth to lumpy and back, producing very believable imitations of shells, and even lionfish.

Octopuses are particularly fond of eating crabs and other crustaceans, and a pile of shells often marks a hole where one is resident. Normally an octopus crawls rather slowly across the reef, but it can also swim by contractions of its legs, much like an umbrella opening and closing. If disturbed, it can produce a short burst of speed by squirting water out of its large gill cavity through a muscular siphon.

Beware of the common, small blue-ringed octopi (Hapalochlaena) which can be found under rocks on the reef flats in Indonesia. Do not pick one up. They possess a very virulent poison.

Squid. Squid are free-swimming animals, usually seen in groups in shallow lagoon areas or along the reef edge. They have perfected the mode of jet-propelled movement. While stationary they maintain position with gentle undulations of their lateral fins. Movement, either forward or backward, is achieved by the highly maneuverable water jet. Like the octopus, squids can change their coloration, adopting a sparkling array of brilliant colors and patterns.

Squid have a rudimentary internal "shell," actually a noncalcareous strengthening device called a pen. It is of a clear, flexible substance that looks and feels like a piece of plastic.

Although you will never see one on the reef, the largest cephalopods by far are the giant squids (Architecteuthis), which can reach a length of 18 meters. These animals frequent very deep water, and little is known of their habits. They are the preferred prey of the sperm whale.

Cuttlefish. Cuttlefish (Sepia) superficially resemble squid, but can be distinguished by their generally larger size and more robust shape. Unlike squid, which often travel in large groups, lone cuttlefish can often be seen foraging on the reef slope, and are the most frequently encountered cephalopods.

Like the other cephalopods, cuttlefish can squirt out a blob of ink if threatened. The shape of this blob, roughly the size of the animal that ejected it, and its strong smell, distracts the would-be predator while the cuttlefish jets away. In earlier times, this ink was used for writing, as is suggested by the cuttlefish's genus name, Sepia.

Instead of the squid's flexible pen, cuttlefish have a "cuttle-bone," a calcareous structure perhaps most familiar for its use as a dietary supplement for cage birds. Although it provides some stiffness, the most important use of the porous "bone" is for buoyancy control, balancing the animal's vertical movements across the reef face.

Nautilus. These animals, with their distinctive spiralled shell, are the most unusual of the living cephalopods. The chambered shell serves as a form of buoyancy control, like the cuttlefish bone, but much more sophisticated. This control is necessary as the animals undergo a considerable daily vertical migration. During the daylight hours, the nautilus stay at 1,000-1,500 meters, and only rise into relatively shallow water at night. Only very rarely are they found in depths a sport diver could reach. In this way they avoid predators, and perhaps also are able to more easily find their food—carrion and, particularly, the molts of crustaceans.

A mantis shrimp, Odontodactylus scyllaris. These animals are fierce predators, using their modified front claws to seize or bludgeon prey in the manner of their namesake, the praying mantis. Odontodactylus is the most colorful and one of the larger mantis shrimps — it is said to be able to smash a four-inch crab with one strike. Some divers call these animals "thumb-splitters" and with good reason. Do not try to touch one! Tulamben, Bali.

There are several species, but the most common on Indonesian reefs is the pearly nautilus (Nautilus pompilius).

A dispute developed between these two prawn gobies, Mahidolia mystacina, when the yellow goby and its shrimp wandered into the grey goby's territory. When the grey fish came out of its burrow, the sand started to fly. Both of these gobies are females. Tulamben, Bali.

Crustaceans

The jointed-foot animals— Arthropoda—is the single most successful phylum of animals. On land, the insects and spiders dominate; in the water, the sub-phylum Crustacea is king, with almost 40,000 species. Crustaceans—crabs, shrimp and lobsters—are very abundant on Indonesian coral reefs, but many keep themselves well-hidden, particularly during the day. They are most likely to be seen by night divers.

The largest commonly seen crustaceans are the spiny lobsters, Panulirus. By day spiny lobsters hide in caves and crevices, often in small groups, with only their long antennae protruding. But at night they venture out of their retreats in search of food. If surprised out in the open, spiny lobsters can swim backwards with great speed using powerful flicks of their tail.

These lobsters, of course, make very fine eating, but visiting divers should resist the temptation of trying to catch a lobster for the table. Removal of animals from a dive site is short-sighted, and lobster catching is quite a skilled operation. An unpracticed diver who attempts it is likely to be left only with painful cuts and a handful of antennae.

Shrimps

On night dives large shrimps can sometimes be spotted out in the open where their reflective eyes catch the light and stand out as two bright red spots. But even by day the careful observer should be able to spot several species of small shrimp.

Commensals. A variety of sometimes colorful shrimp associate with anemones, coral and echinoderms for protection, making them easy to spot. The tiny bumble-bee shrimps (Gnathophyllum) associate with sea urchins. Various species of Periclimenes, some quite colorful, associate with anemones, gorgonians, and echinoderms. One,

P. imperator, lives in the folds of the Spanish dancer nudibranch.

Cleaner shrimps. Also easy to see are the cleaner shrimps, protected from predation by the services they offer. These cleaners pick parasites and bits of dead tissue from fish, and can all be recognized by long, white antennae.

The candy shrimps (Lysmata) axe beautiful red striped or spotted cleaners. The coral shrimps (Stenopus) live in pairs in small caves or holes extending their large white antennae to attract the attention of passing fish.

The common banded coral shrimp, Stenopus hispidus, has well-developed front claws, and is sometimes called the boxer shrimp. Various species of Periclimenes also serve as cleaners.

Cleaner shrimp often set up a "station," that fish visit repeatedly. It is quite a sight to watch a tiny shrimp crawl into the mouth and gills of a grouper or large angelfish. If approached slowly enough cleaner shrimps will climb onto a diver's outstretched hand, to see if it too needs cleaning, or even into his mouth.

Pistol shrimp. These animals (Alpheus and Synalpheus) have well-developed pincers, one much larger than the other. By some means that is not well understood, the pistol or snapping shrimp is able to create an audible clicking sound with its large claw.

Some of the blind or near-blind pistol shrimp have developed interesting relationships with small gobies. In lagoons and on sandy patches around the reef you can see these small fish sitting up on their fins outside a small burrow. Next to the fish will be one or more pistol shrimps. The shrimps rely on the gobies, with which they keep in contact by their long antennae, to warn them of the approach of any danger. The gobies benefit from this relationship by having a safe burrow dug for them.

Crabs

Many species of crabs live on Indonesian reefs, but they are not always easy to find. Crabs would soon be eaten by strong-jawed fish such as wrasses if they ventured out boldly by day. Many species are therefore only seen at night when they come out under the cover of darkness to feed. If you look closely at a well-protected coral thicket, however, you will likely see a few small crabs safely wedged in.

Hermit crabs. These familiar, and comical creatures use the discarded shells of gastropods as portable refuges. Some of these small animals are very colorful, particularly Aniculus and the demon hermit crabs, Trizopagurus. A few species of hermit crabs go one stage further, carrying small sea anemones on their shells as additional discouragement to potential predators.

The large terrestrial coconut or robber crab (Birgus latro), a delicacy in the Moluccas and other parts of Indonesia, is actually a hermit crab that abandons its shell when it reaches adulthood. Small land hermit crabs (Coenobita) are common along the high tide line on some Indonesian beaches.

Decorator crabs. These are types of spider crabs that protect themselves by sticking live sponges, gorgonians or other material onto their fuzzy or spiny backs as camouflage. Small decorator crabs may be spotted at any time on sea fans or black coral trees. But look out for the large nocturnal species that carry massive chunks of soft coral or sponge on their backs, held on with their last pair of legs.

The small and colorful boxer crab, Lybia tesselata, grasps a pair of tiny sea anemones in its claws which it then uses for both defense, and to collect food.

Porcelain crabs. The porcelain crabs (Neopetrolisthes), so-named for their smooth, colorful shells, are sometimes called "half-crabs," for they are structurally similar to prawns and lobsters. They are commensals on the giant anemones where, protected from predators, they strain plankton from the water with mouthparts that have been modified for filter-feeding.

Echinoderms

Everyone is familiar with the common starfish or sea star. But starfishes are only one of five groups that together form the Echinodermata, "hedgehog-skinned" animals. The others are the sea urchins, the brittle stars, the feather stars and the sea cucumbers. Most echinoderms have a skeleton of spiny plates— most developed in the sea urchins, and least developed in the sea cucumbers—and five-sided symmetry.

Starfish. The five-sided symmetry of the echinoderms is clearly displayed in the starfishes. Most Indonesian species have five arms, although some individuals may have one arm more or less. The common cobalt-blue starfish Linckia laevigata is particularly variable in this regard. Some of the larger starfishes may have a great number of arms.

Starfishes are predators, feeding on a wide variety of bottom-dwelling animals, or detritivores. A feeding starfish envelops its prey with its arms, then actually pushes part of its stomach out through its mouth over the victim, digesting it externally. Starfishes are able to hang on to even actively struggling prey with their myriad tube feet, tiny suckers that cover the under-sides of their arms. The gripping power of these animals is considerable, and over time they can even overpower the strong muscle of a bivalve. The tube feet are also used for locomotion.

Some starfish have very thick arms, particularly the pincushion starfish (Culcita spp.) common on Indonesian reefs. These animals can inflate their bodies to the point where they become almost spherical. Culcita normally have tiny symbiotic shrimps living on their lower surfaces.

The most notorious starfish in Indonesian waters is the crown-of-thorns, Acanthaster plancii, which is found throughout the tropical Indian and Pacific Oceans. This animal feeds exclusively on coral polyps.

Normally the crown-of-thorns, large, multi-armed and bristly, occurs in very low numbers on coral reefs—divers usually see perhaps one per dive. But population densities have occasionally reached plague proportions, and at these times whole reefs can be destroyed. Some of the greatest damage has been on the Great Barrier Reef of Australia and on the reefs of southern Japan, but Acanthaster outbreaks have occurred throughout its range, including Indonesia.

These plagues have been the subject of a long and heated debate by reef scientists. Some argue that over-fishing, over-harvesting of predators like the triton conch, and agricultural runoff have contributed to the disastrous outbreaks. Huge coral heads, hundreds of years old, have been destroyed by the ravages of the starfish. These scientists argue that control measures are necessary, and advocate the removal of Acanthaster whenever seen by divers. (Note: The crown-of-thorns is spiny, and some people have a toxic reaction to its thorns. Do not touch one unprotected.)

Another opinion suggests that the outbreaks are a natural phenomenon, and point to core samples taken on the Great Barrier reef that show periodic accumulations of Acanthaster spines. These scientists say the outbreaks remove dominant coral species, and may be necessary to increase the species diversity of tropical reefs. They note that the reefs have recovered relatively rapidly from the outbreaks, and suggest removal of crown-of-thorns would in the long run be counter-productive.

Brittle stars. Brittle stars are quite similar in appearance to starfish, but have thin, flexible arms. These arms are easily bro ken off, hence the name. While starfish move mainly by the action of the tiny tube feet on the underside of their arms, brittle stars move by movements of the whole arm.

Many brittle stars have spines on their arms which are very sharp and can give the unwary diver a nasty sting. Despite these spiny defences and their unappetizing appearance, brittle stars are preyed upon by several species of fish, and thus tend to remain well-hidden.

On the shallow reef flats one can sometimes find literal "fields" of brittle stars, their bodies flat on the bottom and their arms wriggling in the water, filtering plankton and debris. On deeper areas of the reef, these animals are less bold, and extend just an arm or two from the safety of their crevices.

Serpent stars are brittle stars smooth arms, and often very striking colors. These animals can sometimes be seen with their arms coiled in tight loops around gorgonians.

Basket stars are the most highly developed filter-feeding brittle stars. They only come out to feed at night, when they extend their branched arms to capture planktonic animals drifting past. Basket stars are beautiful creatures to watch, and they are particularly common on Indonesian reefs, where they can grow to over a meter across.

Crinoids. The crinoids or feather stars are survivors of the sea lilies, animals that once were among the most common in the seas. Although there are still some stalked crinoids extant, those seen on Indonesian reefs are unstalked. They perch on the edge of sponges or gorgonians with a set of small clasping legs, and deploy their delicate arms— of which they have 30 or more—to strain plankton from the water, Feather stars can also walk on these long arms, and if dislodged may swim with them in a beautiful but rather inefficient manner.

Many species of shrimps act as cleaners. This is a Leandrites sp. at work on the mouth of a coral grouper, Cephalopholis miniata.

The charming little boxer crab, Lybia tesselata. The boxer crab clutches two tiny sea anemones, which it uses for defense, and even to immobilize small prey. The sea anemones (Triactis producta) are so important to this crab that the only time it releases them is when it sheds its integument. And then, observers say, it seems very nervous until it picks them up again. You easily can find these crabs under coral rocks on the drop-off at Tulamben, Bali from about 3-12 meters depth. Take care not to break up living corals, however. Ambon, Maluku.

Food filtered from the current by the fine hairs on the crinoid's arms are passed down a channel to the central mouth. Crinoids sit "upside-down" compared to the starfish, and the mouth is on top the animal.

Some feather stars are nocturnal and hide by day in reef crevices. As night falls they come out of hiding and climb up onto prominent blocks of coral or other high points where they are exposed to the strongest current flow. Crinoids are particularly abundant in plankton-rich areas.

Sea urchins. Sea urchins are important and abundant grazers on Indonesian coral reefs. Even the spiniest of urchins may be attacked if they venture out into the open by day, so they tend to confine their activities to the night. By day they wedge themselves into crevices or hollows to avoid the attentions of predatory fish. Sea urchins have a very sophisticated feeding apparatus which they use to scrape at the reef, removing not only algae but also quantities of coral rock. In fact, some small species actually excavate their own daytime hiding places out of the soft coral rock by the constant scraping of their jaws and spines.

On shallow, quiet reefs in Indonesia one can often see the black, long-spined urchin Diadema, so-named for the cluster of glistening "jewels" set into its upper body. This urchin has very long and brittle spines, and stepping on one would be a real disaster. In harbors and other disturbed areas of reef, very large numbers of these animals can be found. Shrimpfish and urchin clingfish hide among their spines.

The rarely seen slate pencil urchin (Heterocentrotus mamillatus) is a distinctive species, with thick, pink spines. No longer used as chalk, the unfortunate animals' attractive spines are in some areas now being made into wind chimes.

The bodies of most sea urchins seem roughly spherical, but in fact they are made up of five radial segments, in typical echinoderm fashion. Sea urchins develop a calcareous skeleton or test, which contains the feeding apparatus, the intestines, and the gonads. Prior to reproduction the gonads expand to fill the whole shell, and it is this rich substance that make sea urchins so attractive to hungry fish despite their spiny defenses.

The ripe gonads of the sea urchin Hemicentrotus pulcherrimus are prized in Japan for sushi; the taste of this uni is strong, but delicious.

Sea cucumbers. Though at first they look just like loose sacks, or large worms, sea cucumbers (class Holothuria) are constructed with the same five-sided symmetry typical of the echinoderms. Because they are so elongate, they have a "head" and a "tail," unlike the starfish or urchins. The head of a sea cucumber is not, however, particularly well developed, consisting of little more than a ring of tentacles around the mouth. Sea cucumbers are an important trade item in Indonesia. (See "Trepang Fishing," page 27.)

Most species are detritus feeders, the tentacles being used to pick up sand and pass it into the mouth. Organic matter is digested and the undigested remains are passed out through the anus. Sea cucumbers have to eat a lot of sand in order to obtain enough food, so they often leave a continuous trail of sandy feces behind them. A few species are filter feeders. They hide their bodies in reef crevices and hold their tentacles up in to the water current to feed. The tentacles are rapidly withdrawn if disturbed.

Sea cucumbers appear as elongated and somewhat flaccid forms lying among coral rubble or sea grass, moving slowly in a worm-like way by contractions of their bodies. These are usually black or dull-colored. A few species, such as the sea apple (Pseudocolochirus), are very colorful, however.

Many sea cucumbers are active by day. Since they are not attacked by predatory fish it would seem that they must have some efficient means of defense. Some species can discharge sticky white threads if molested, and most tropical sea cucumbers contain toxins.

Tunicates

The tunicates or sea squirts are an entirely marine group of animals, and are unfamiliar to many people. Despite their unimpressive appearance, they are chordates, and—technically—are more closely related to human beings than to any of the invertebrates listed above. They have a notochord, a primitive backbone, only in their larval form. Once they settle out of the plankton and become sessile filter-feeders, the backbone is unceremoniously shed. (So much for the vaunted evolutionary superiority of "higher order" forms.)

The tunicates seen on Indonesian reefs are all in the class Ascidiacea, a name derived from the ancient Greek word for leather bottle. They are rather like little bottles, with (usually) two openings rather than just one. Water is drawn in through the uppermost of these siphons, filtered through a basket-like arrangement internally, and then passed out through the lower siphon. Peer into the opening of a large tunicate and you may be able to make out the fine sieving apparatus within. Many tunicates have stout spikes projecting from the inner wall of their siphons, to thwart small fish or other unwanted intruders.

One of the most common and conspicuous tunicates on Indonesian reefs is the beautiful white, purple and yellow Polycarpa aurata. These creatures are about the size of a man's thumb, and have a tough leathery outer coating, or tunic. Polycarpa is a solitary and very distinctive animal and easy to identify underwater. But many tunicates are colonial, and can easily be mistaken for sponges. If the siphons of a sea-squirt are touched (gently so as not to harm the animal) they will squeeze shut. Sponges do not react to touch. If a tunicate is lifted out of the sea this same contraction will cause water to be squirted out of its siphon—hence the common name sea squirt.

A cluster of tunicates, Rhopalaea crassa. Water enters through the uppermost opening, is filtered of plankton and nutrients, and then passed out the lower opening. Bunaken group, Sulawesi.

The blue ribbon eel, Rhinomuraena quaesita, is one of the most attractive moray eels. Young eels are black, and don't turn electric blue until they reach a bit over a half-meter in length. Bunaken group, Sulawesi.

Most colonial tunicates are overlooked because they tend to be tucked away in dark corners. An exception are the marblesized, white-and-green grape ascidians, Diademnum molle, a common compound tunicate on shallow reefs in Indonesia. Diademnid tunicates have a single large inhalent opening, and many small exhalent openings around their globular tunics.

Their green color comes from a symbiotic algae living within its tissues, much like the zooxanthellae of stony corals. The relationship between this tunicate and its algae is one of mutual dependency, neither party being able to survive alone. Diadem-num larvae even carry samples of the algae with them to ensure that the relationship is continued in the next generation.

The Fishes

Corals and other invertebrate animals can provide a lifetime of interest for a diver in Indonesia, but the fish are what really grabs one's attention. On most reefs, brightly colored and beautifully patterned fish are everywhere, darting among the corals or lying sedately in mid-water. It would be impossible in the space available here to offer a complete description of the thousands of fish species found on Indonesian reefs, so all that will be attempted is a brief survey. Consult "Further Readings" page 321 for more complete resources.

Elasmobranchs

Sharks and rays are elasmobranchs, and differ from true bony fishes by having a cartilaginous skeleton, only parts of which are calcified (e.g., the jaws of a shark). Gill structure—elasmobranch means "plate-gilled"— and other physical features differ between bony fish and sharks and rays, which are considered a more primitive form.

Sharks. There are many species of sharks in Indonesian waters, but those most commonly seen by divers are the reef white-tip shark (Triaenodon obesus), the gray reef shark (Carcharhinus amblyrhynchos), and the reef black-tip shark (C. melanopterus).

The reef white-tip shark grows to 1.7 meters, and is a thin, gray fish with white tips to its dorsal and tail fins. This is the most commonly seen shark on the Indonesian reefs. This small shark can be often be found hiding under overhangs.

The gray reef shark grows up to 2.3 meters, and has a very dark trailing edge to its tail. Although this animal is known to be aggressive in some areas, it is not considered dangerous in Indonesia.

The reef black-tip shark grows to 1.8 meters, and is pale gray or brown with distinct black tips on all its fins. This shark sometimes comes up into very shallow water on reef fiats and in lagoons to look for food.

The largest fish extant is the whale shark (Rhincodon typus), a harmless animal that strains krill and small fish from the water. Growing to more than 12 meters in length (although specimens of 5-7 meters are more common), the whale shark is not a reef fish, although it can be found seasonally off some reefs in Indonesia.

The only really dangerous sharks a diver might encounter on an Indonesian reef are the tiger shark (Galeocerdo cuvieri), a large—up to 5.5 meters—scavenger that sometimes comes up onto the reefs at night or in the late afternoon/These sharks, however, are very rarely seen.

Rays. Structurally, rays are essentially flattened sharks. The stingrays have one or two stout spines at the base of their tail, which are their main means of defence. They will not normally be used against divers, although you should always take care to avoid stingrays while walking in shallow water.

Stingrays are bottomfish, and have strong teeth which they use to crush shellfish. In areas where stingrays are common you may see large craters in the bottom, caused by their feeding activities. Perhaps the most common stingrays in Indonesia are two species of blue-spotted stingray: Taeniura lymma, which frequents coral rich areas, and Dasyatis kuhlii, which lives in sandy areas of disturbed reef, or between patch reefs. A much larger animal is the grey reef ray (Taeniura melanospilos).

Not all rays are bottom-dwellers. The spotted eagle ray (Aetobatis narinari) cruises the reef edge looking for crustaceans. Eagle rays can reach 2.3 meters across.

The largest ray, however, is the manta (Manta birostris). Like the whale shark, mantas are essentially open water fish, but they are regularly seen by divers in Indonesia. The manta ray, growing up to 6.7 meters across and weighing 1,400 kilos, is a planktivore. Both whale sharks and mantas occur only seasonally in different parts of the country, as they migrate to the areas where the plankton is thickest.

Because they are found in areas dense with plankton, mantas tend to be seen at times when visibility is relatively low. This, however, is a small inconvenience when weighed against the pleasure of swimming with such magnificent creatures.

Sometimes seen in the same places that attract mantas are the smaller, but very similar devil rays (Mobula). These animals travel in groups and sometimes large schools.

Bony Fishes

Eels. The moray eels (family Muraenidae) are common both in folklore and on the Indonesian reef. Although not as dangerous as Hollywood would have us believe, they have sharp teeth and should not be provoked. The largest species, the giant moray (Gymnothorax javanicus), can reach more than two meters in length, and weigh 35 kilos. Many morays are nocturnal hunters, resting in holes by day and prowling the reef by night. They feed on dozing fish which they detect by smell.

The ornate ghost pipefish, Solenostomus paradoxus. This strange animal is a relative of the seahorses and pipefishes, however in Solenostomus the female broods the eggs. The coloration and growths are cryptic. This juvenile stands out here against the brilliant red crinoids, only because it has moved from a neighboring white crinoid or antipatharian. Tulamben, Bali.

A school of shrimpfishes, Centriscus scutatus. The shrimpfishes always swim with their noses pointed downward, in the process of evolution their dorsal, tail and anal fins have migrated to a position on the side fo the body, where they can produce lateral motion while the animal is oriented vertically,

A very beautiful eel, related to the morays but more delicately built, is the blue ribbon eel (Rhinomuraena quaesita). The adult coloration of this animal is electric blue and yellow, and adult females turn bright yellow. Juveniles are black.

Several species of the unusual garden eels (a subfamily of the conger eels) can be found on sandy bottoms in Indonesia. They live in burrows in often large groups, and the sight of all their thin bodies waving in the current gives them their common name. They have small mouths, and pluck plankton from the current. If you swim over the "garden" the eels will slip back down into their burrows, disappearing in a wave before you.

Although garden eels are usually found in deeper water, particularly the sandy channels between reefs, they can sometimes be seen in very shallow Sand patches on the reef. There is a colony of garden eels in shallow water on the approach to the popular wreck at Tulamben, Bali.

Seahorses and pipefish. These fishes (family Syngnathidae) are generally slow-moving and secretive, and are not often easy to find. They are planktivores, and can be found in sea grass beds and estuaries as well as in coral reefs. In tact; their fins are poorly developed, and they shun areas of high current or surge. Seahorses (Hippocampus) can be highly camouflaged, some exactly matching a single species of gorgonian.

The master of camouflage, however, is the ghost pipefish (Solenostomus cyanopterus), an animal whose shape and color precisely duplicate a blade of turtlegrass, A strikingly colored relative is the ornate ghost pipefish, S. paradoxus.

Pipefish are long and thin, and superficially appear quite different from seahorses. In fact, structurally they are quite similar, the pipefish just being a stretched-out version. The male incubates the eggs in a pouch on its stomach, and the young are born "live."

The large trumpetfish (Aulostomus chinensis) looks like a pipefish on steroids (these can be a half-meter or longer) and feeds on small fish. It has the curious habit of hiding behind larger fishes until it comes within range of its prey. One color morph is bright yellow.

Scorpionfish. The most commonly seen of this family (Scorpaenidae) are the lionfishes (Pterois and Dendrochirus). During the day these lavishly colored fish can be seen perching on coral heads. Perhaps because of their poisonous fin rays, they are relatively unperturbed by the presence of divers.

Lionfishes feed mainly at night on shrimps and small fishes. They use their elaborate fins to shepherd their prey into a suitable position, whereupon they shoot forward and inhale it whole into their large mouths.

Scorpionfish are less commonly seen, chiefly because they are so well camouflagued. Covered with folds and flaps of skin, they blend right in with the algae and other growths.

The scorpionfishes and lion-fishes have a row of poisonous spines along their backs. So, despite their usually benign behavior these fish should be treated with some respect. More than one underwater photographer has been stuck by a lionfish while trying to encourage it into position for that perfect photograph. Lionfish poison is not strong enough to kill an adult, but it will certainly give you many hours of acute pain.

Some victims have required hospitalization. The best treatment is to immerse the affected part in very hot water, as heat breaks down the venom.

Much more dangerous is the stonefish (Synanceia verrucosa), which carries a toxin responsible for several well-publicized deaths. These animals are masters of disguise, and encrusting algae and bryozoans actually grow onto their skin. When a small fish or crustacean absently wanders within range, it is engulfed by the animal's formidable mouth.

Groupers. The groupers (family Serranidae), are a common family on Indonesian reefs, ranging in size from more than a meter to the tiny dottybacks or pseudochromids, colorful plank-tivores no larger than a man's little finger.

Most of the larger groupers are plainly marked, but some, most notably the bright red and blue-spotted coral grouper (Cephalopholis miniata) and the flagtail grouper (C. urodeta) dire exceptions. One of the largest fish on the reef is the giant grouper (Ephinephelus lanceolatus), which can reach 2 meters and weigh 400 kilos.

The fairy basselets or anthias (subfamily Anthiinae) are also groupers. Anthias, which hover in large schools around coral heads and soft coral colonies, picking plankton from the water, are very beautiful, and staples of underwater photography. Their names—the peach fairy basslet (Pseudanthias diaspar), the purple queen (P. pascalus and P. tuka) and the square spot anthias (P. pleurotaenia)—hint at their lovely colors.

Anthias are protogynous hermaphrodites, meaning that the fish all mature as females, and then a few undergo a terminal sex-change to male. These terminal males exhibit distinct, and very striking colors.

The dottybacks (Pseudochromidae), also among the real jewels of the reef, are small, secretive fishes that hide in caves and under ledges.

Another unique member of the grouper family is the comet (Calloplesiops altivelis). This small fish has long, black fins covered with a multitude of white spots. Because of the ocelli on the fins, and the fish's movements, it is thought to be a Batesian mimic of the juvenile spotted moray eel (Gymnothorax meleagris). A Batesian mimic uses its resemblence to a known dangerous animal to discourage predation.

Ciguatera Poisoning

Ciguatera is a toxin produced by a tiny dinoflagellate alga, Gambierdiscus toxicus. The alga itself is harmless enough, living around rocks, sea-grass and filamentatious algae. The quantities of poison in each organism are minute.

But the dinoflagellates are eaten along with the algae in which they live by herbivorous fish and invertebrates. These herbivores are then eaten by larger, carnivorous fishes, and these are in turn are eaten by even larger, and more voracious predators. Since the ciguatera is not broken down, it concentrates in the tissues of these higher order predators.

A human being who eats a ciguatoxicfishwill experience numbness in hands and feet, disorientation, weakness, vomiting, diarrhea, shortness of breath and even cardiac arrest. The poison is very serious. People have died from ciguatera and there is no available cure.

The greatest danger comes from fish at the highest levels of the food chain: snappers, groupers, large jacks, barracuda, some trigger-fish and moray eels. For reasons not well understood, certain species are morefrequentlyciguatoxic than others: particularly the red snapper (Lutjanus bohar), and also the giant moray (Gymnothorax javanicus), the saddleback grouper (Plectropomus laevis) and the giant grouper (Epinephelus lanceolatus).

Open-water fish (tuna, mackerel, etc.) are not part of the same food chain and are not affected, but any large, predatory reef fish is a candidate.

— David Pickell

Hawkfish. Hawkfishes (family Cirrhitidae) get their name from their predatory habits. These small fish (6-10 cm.) perch on coral heads or sponges—anything that gives them a good lookout—and when a small crustacean or fish comes within range, they swoop down on it like a hawk. Because they are so sedentary, they make very easy photo subjects. Some species are also quite colorful— particularly the large Forster's hawkfish (Paracirrhites forsteri)— and the long-nosed hawkfish (Oxycirrhitus typus) has an interesting, pointed "beak."

Jacks. The jacks or trevallies (family Carangidae) are often seen patrolling the upper reef slope in small groups. They are among the most active predators on the reef. Jacks are always on the lookout for a meal, and groups regularly interrupt their steady cruising with powerful bursts of speed as they chase unwary smaller reef fish. Sometimes a few jacks will make a sortie into a lagoon in search of prey. If they find and attack a school of fish the sea surface erupts as the hunted fish desperately try to escape, sometimes throwing themselves onto the beach in the attempt.

Snappers and sweetlips. Snappers (Lutjanus) are common predatory fish around deeper reefs, and are an important food fish. The red snapper (Lutjanus bohar), although delicious, is in some areas one of the most frequently ciguatoxic fishes (see "Ciguatera Poisoning," at left.)

Perhaps the most commonly seen reef fish in Indonesia is the yellow-backed fusilier (Caesio teres), a streamlined, 20-30 centimeter fish marked with bright blue and yellow. These planktivores, related to snappers, travel in large aggregations that provide a measure of protection against predators such as jacks.

Sweetlips (Plectorhinchus) are medium-sized, strikingly marked fish related to the snappers. They are common in Indonesia, where they can often be seen in mixed schools. The juveniles are especially attractive, with bold stripes and dots of white against a brown or black background.

Batfishes. The batfishes (Platax) are common inhabitants of Indonesian reefs, As adults, these animals take the shape of a large, silvery platter, as much as half a meter in length, with two or three broad black vertical bands. Traveling about the reef in small groups, they have a reputation for being very "intelligent," and seem to regard divers with curiosity.

There are three species commonly seen in Indonesia, the orbiculate (Platax orbicularis), the round-faced (P. Hera) and the pinnate (P. pinnatus). As adults, orbiculate and round-faced bat-fish are almost impossible to distinguish. The pinnate batfish can be recognized by its long snout.

As juveniles, the fish are very different in shape, with greatly elongated dorsal and ventral fins. Juvenile orbiculate batfish are mottled brown and have a transparent tail, which—together with their habit of floating on their sides in the shallows—allows them to match a dead leaf. Juvenile round-faced batfish are black and white and have long fins.

The most beautiful as a juvenile is P. pinnatus, which has a band of electric orange all around its body and fins. This juvenile, sometimes called the orange-rimmed batfish, is thought to mimic a toxic flatworm.

Butterflyfishes. The butterflyfishes (family Chaetodontidae) are beautiful, delicate looking fish that feed on small benthic animals. Some species feed heavily on coral polyps. They have laterally compressed bodies, and snouts and teeth adapted to their particular feeding habits, enabling them to pick up their preferred prey deftly. In particularly, the long-nosed butterflyfishes (Forcipiger) have long, thin mouths perfect for snatching small animals from cracks and crevices in the reef. These bright yellow fish will be seen hovering under overhangs in the reef, sometimes even upside down.

Some species, occur singly or in pairs, e.g. Forcipiger. Others are schooling fish. The black, white, and yellow pyramid butterfly fish (Hemitaurichthys polylepsis), for example, occurs in massive aggregations along the walls in Manado and other parts of eastern Indonesia, Common schooling butterflyfish include the bannerfish (Heniochus), the most distinctive of which is the pennant bannerfish (Heniochus diphreutes), which has a very elongated dorsal fin and bright yellow, white and black markings,

Angelfish. The angelfishes (family Pomacanthidae) probably make it onto more postcards than any fish other than the Moorish idol. They browse the reef for sponges, algae and occasional small crustaceans. Adult angelfish, some of which can reach 30 centimeters, are truly magnificent animals.

The twinspot lionfish, Dendrochirus biocellatus, is one of the most attractive of the dwarf lionfishes. It is much smaller than Pterois sp., growing to just 8 centimeters. Halmahera, Maluku.

In Indonesia, one can often see emperor angelfish (Pomacanthus imperator), with thin, horizontal stripes of blue and yellow; blue-girdled angelfish (P. [Euxiphipops] navarchus), with a deep blue "girdle" against bright orange; and regal angelfish (Pygoplites diacanthus), the most shy of the bunch, with vertical stripes of yellow, white and blue.

All Pomacanthus species have very similar juvenile coloring, a series of thin white or light blue stripes against a dark blue background. Two fish with dramatically different adult coloration, for example the blue-girdled and emperor angelfish, look so similar as juveniles that only an expert could tell them apart.

Damselfish. These small, ubiquitous fish (family Pomacentridae) are members of one of the largest groups of tropical reef fish. In addition to the reef itself, they occur along rocky shores, algal flats, and even in silt-choked harbors. The damselfish feed on plankton and algae, some even setting up small territories from which they aggressively keep all herbivores away, "farming" the algal turf that then grows on the coral rock.

The black and white three-striped damselfish (Dascyllus aruanus), the blue devil (Chrysiptera cyanea), and the blue damsels (Pomacentrus) are common among the coral heads and rubble of the shallow reef. The pugnacious black farmer fish (Stegastes lividus) also defends its patch of algae in the shallows.

Deeper on the reef, the planktivorous blue-green chromis (Chromis viridis) is common, occurring in large schools like anthias, which it superficially resembles. Along rich drop-offs, the pugnacious yellow Golden sergeant (Amblygliphidodon aureus) is often seen. A single good Indonesian reef can host more than 100 species.

Favorites among divers are the anemonefish (Amphiprion and Premnas biaculaeatus). These beautiful and plucky little fish will even nip a diver to defend their anemone home. (See "Clownfish and their Sea Anemone Hosts," page 46.)

Wrasses. The wrasses (family Labridae) are a large and successful family on the coral reefs. Most are small, elongated fishes, with a distinct swimming style that depends more on the pectoral fins than the tail. Many are colorful, and inhabit the shallow parts of the reef and reef flats, although some (such as the hog-fishes) are characteristic of the deep reef.

Wrasses undergo sometimes dramatic color changes as they pass from juveniles to adults. Many of these predators on worms and small crustaceans bury in the sand at night to sleep, or dive into the sand to escape predators.

Most familiar to divers is the blue-streak cleaner wrasse (Labroides dimidiatus), which set up stations to clean small parasites and pockets of decay from the skin, mouth and gills of larger reef fish. Some wrasse act as cleaners only when young (for example, the colorful lyretail hogfish, Bodianus anthoides).

The largest of the family is the Napoleon wrasse (Cheilinus undulatus), which can reach 1.8 meters. This is one of the largest fish a diver will see on many dives. These stately animals, also called the humphead wrasse, have a prominent forehead and formidable-looking snout and cruise the outer edge of the reef in loose groups, with one large male and a few smaller females.

The Napoleon wrasse, or humphead wrasse, Cheilinus undulatus, is the largest wrasse and—at up to two meters — often the largest fish of any kind one will see on a given dive. This predator on crustaceans, gastropods, fishes and echinoderms is usually a solitary rover, but sometimes a pair or a small "squad" will be seen. Australians call this fish the Maori wrasse.

Parrotfish, The parrotfishes (family Scaridae) are among the most important herbivores on the reef. They get their name from their bright colors, curious flapping "flight" (much like wrasses), and their strong, birdlike beaks, which they use to scrape algae and other living matter from rocky surfaces. In so doing they inevitably take in great quantities of coral rock. This is ground down by powerful sets of teeth in the throat so that the organic material can be more easily digested, The waste product of the feeding activities of parrotfish is coral sand—a major component of Indonesian beaches especially on the offshore islands.

Parrotfishes are protogynous hermaphrodites that undergo a series of color changes with age and sexual status. Primary phase parrotfish—whether males or females—are exceedingly difficult to identify, all being relatively drab grey or rust-colored. The terminal males are striking, however, usually green with bright markings, particularly around the cheeks and eyes, In most species the primary phase is made up of mixed males and females (diandric); in others the primary phase is all females (monandric).

One notable exception to this pattern is the bumphead parrot-fish (Bolbometopon muricatum). All bumphead parrotfish (males, females and juveniles) are a dull green in color. Although parrot-fish have popularly been considered coral-eaters, they are chiefly herbivores, scraping the reef surface to extract the algal turf, not to eat coral polyps. The bumphead parrotfish is an exception, and feeds for the most part on living coral. They are massive beasts which grow to over a meter in length and travel along the reef in groups looking for all the world like squadrons of army tanks, leaving clouds of coral sand in their wakes. Sometimes their crunching can be heard Underwater.

They should not to be confused with the Napoleon wrasse (see above), a superficially similar fish. The bumphead parrot-fish has a more rounded head.

At night, parrotfish secrete a transparent cocoon of mucus in which to- sleep. At first glance such a fragile structure would seem to offer little protection against predators, but at night, most predators hunt with their sense of smell not their eyes, and the cocoon is an effective defense against this.

Barracudas. These familiar fish (family Sphyraenidae) are one of the most important predators on the reef but their reputation for ferociousness is exaggerated. Despite their formidable teeth in Indonesia they are not known to attack divers. Smaller species of barracuda often gather in school during the day, sometimes numbering many hundreds of individuals In contrast, large barracudas (which may grow up to1.7meters)tend to be solitary. Such giants may be quite old, so are less likely to be seen near heavily populated areas where there is lot of fishing pressure.

The bumphead parrotfish, Bolbometopon muriaticum. This, the largest parrotfish, is also one of the few true coral feeders. With its impressive fused "beak" it can crunch on corals like they were pretzels. It is sometimes confused with the Napoleon wrasse, but a comparison of this photo with the one on the previous page should make clear the physical differences: between them.

Blennies. These little fishes (family Blenniidae) often go unnoticed by divers They are most abundant in the shallows, and can:also be found on back-reefs and in murky estuarial waters. Most are not very colorful. Some have interesting "faces," although these are only really visible to the macro lens.

The mimic blenny (Aspidontus taeniatus) mimics the color and even the movements of the blue-streak cleaner wrasse Labroides dimidiatus. However, instead of cleaning parasites from the larger fish the mimic blenny bites off a tender chunk of scales and flesh, and then beats a hasty retreat.

Dartfishes. One group the diver will notice, because of their striking colors and their habit of hovering in small groups above the coral sand, are. the firefishes (Nemateleotris: spp particularly N. magnifica, a beautiful fish with a greatly, elongated dorsal fin which it flicks in nervous little movements.

Gobies. These fish (family Gobiidar) are small usually dull-colored, and often remain hidden In crevices and the branches of coral. There are many hundreds of species and perhaps 100 genera in the Indo-Pacific: making them the single most successful family on the coral reefs. Identifying these fishes is very difficult, and there are probably hundreds still undescribed.

Although not reef-dwellers, the curious mudskippers (Periophthalmus), which can be found In Indonesia on the brackish mudflats around mangrove swamps are also gobies As long as their gills and skin remain wet, these small brown fish can hop about on land.

Related to the gobies are the little dragonets. These are found in weed area and sea grass beds as well as the reef itself. Perhaps the most spectacular is the mandarinfish (Synchiropus splendens), with a pattern that could have come off a bright paisley silk tie.

Surgeonfish. The surgeon-fishes and tangs (family Acanthuridae) are a particularly important group of herbivores. They are sometimes seen in singly, in shallow Water over coral flats. Since single grazei are often chased by damselfishes protecting their territories, surgeonfishes sometimes form large feeding aggregations.

Despite their apparently destructive feeding habits, herbivorous fish are of immense value to the coral reef community, By breaking clown hard-to-digest plant material they make the nutrients in it available to other animals. Furthermore, by limiting the growth of plants they may actually enhance that of corals. Without grazing, the plants would grow to such an extent that they would soon cover the reel making new coral settlement virtually impossible.

The surgeonfish family includes some of the most exquisitely patterned and colored of all reef fishes. But one feature that is common to all is that they all have one or two pairs of scalpel-like blades on the Sides of their tails. These give the family its name and can inflict serious cuts if the fish are handled carelessly.

The orangespine unicornfish (Naso lituratus) with its bright orange spots warning of its spines; the hepatus tang (Paracanthurus hepatus) with its electric blue and black body, and the clown surgeonfish (Acanihurus lineatus), oraiige-and-blue striped, are just a few examples.

Moorish idol and Rabbit-fishes. The Moorish idol (Zanclus cornutus) and the rabbitfishes (Siganus) are close relatives of the surgeoniishes. The Moorish idol is for many people the quintessential reef fish; with its bright, contrasting yellow, white and black color, prominent snout, and long, thin dorsal fin, it is indeed an elegant-looking animal. They are fairly common grazers, and can be found all the way from the east coast of Africa to the west coast of Central America.

The rabbitfishes look much like surgeonfish or Moorish idols, although with the exception of the foxface (Siganus volpinus) and the coral rabbitfish (S. corallinus), not as brightly colored. They have no "scalpels," but they do have a strong venom in the short spines of their fins, and should not be handled.

Tuna and Mackerels. Although one or two members of the family Scombridae patrol reefs—particularly the dogtooth tuna (Gymnosarda unicolor)— most are true pelagics, living in the open sea, and will only occasionally be seen on the outer reef edge. When traveling by boat between islands or to offshore dive sites it is not unusual to see big schools of tuna splashing at the surface, often with attendant flocks of seabirds overhead. These schools are usually composed of slapjack tuna, although there are several other species found in Indonesia.

A school of pyramid butterfly-fishes, Hemitaurichthys polylepsis. These plankton feeders gather in large groups around the lip of drop-off reefs in eastern Indonesia. The Bunaken group, Sulawesi,

Indonesian flashlight fishes, Anomalops katoptron, top, is the more common of the two. Photoblepheron palpebratus tends to be found in smaller groups in rather deep caves, Both species are easy to see in TuIamben Ban: Anomalops on the wreck, and Photoblepheran on the wall. Both grow to about 10 centimeters long.

Skipjack (Katsu won is pelam is) grow to just under a meter in length, and are plump and streamlined, with a characteristic series of about five black lines on their bellies. They will not be seen on the reef itself, however, although there will be plenty In the fish market.

Triggerfish. Triggers (family Balistidae) are common fish at moderate depths on the reefs, where they hunt spiny crustaceans and echinoderms. Shaped like a compressed football and often exquisitely marked, they use powerful jaws to dispatch their hard-shelled prey. Large schools of the black triggerfish (Odonus niger), which is actually more blue in color, can be seen hovering off the reef walls, swimming with characteristic undulations of their fins. This fish is sometimes called the red-toothed trigger, although you have to look very closely to see that its teeth are, indeed, red.

Some distinctively marked triggers include the Picasso trigger (Rhinecanthus aculeatus), so-named for its cubist markings, and the undulate trigger (Pseudo-balistes fuscus), covered with wavy markings. The largest trigger you will see on the Indonesian reefs is the Titan triggerfish (Balistoides viridescens), a loopy-eyed and sometimes aggressive animal that grows to more than 60 centimeters.

The most dramatic of the family is the clown triggerfish (Balistoides conspicullum), with its bright orange snout, blue body, and white-spotted belly. The clown trigger is very territorial, and will patrol the same area of reef. When threatened, a clown trigger will wedge its body head-first into a crack in the coral wall, and extend its dorsal spine. The first spine, once raised, is locked in place by the second, making it impossible to pull the fish out of his hole. A diver who knows what he is doing can reach in and gently push back the second spine, unlocking the fin. He can then extract the irritated fish.

Puffers. The curious puffer-fishes (family Tetraodontidae) are solitary omnivores, often seen wandering about the reef in their slow, almost clumsy way and plucking at algae, crustaceans, molluscs, worms and sponges. When threatened they inflate themselves with large quantities of water, which either locks them into a coral crevice, or makes it impossible for a predator to swallow them. In addition to this protection, the skin and most of the internal organs of puffers contain a deadly poison. This poison is absent from the flesh, which in Japan is the highly prized fugu.

A common putter on Indonesian reefs is the dog-faced or black-spotted puffer (Arothron nigropunctatus), which exhibits a great deal of color variability, from the usual dull brown to bright yellow; always with many small black spots.

The related porcupinefishes (family Diodontidae) possess the same defenses as the puffers, with the addition of numerous spines, which become erect when the animal is inflated. The common porcupinefish (Diodon hystrix) is often seen. Boxfishes (family Ostraciontidae) are similar to puffers, except their protection comes in the form of a hard, roughly cubical external covering.

Nocturnal fish. At night the schools of clay active species break up and the fish take refuge In holes in the reef. They are replaced by nocturnal species such as the cardinalfishes (family Apogonidae), bigeyes (family Priacanthidae), and squirrelfishes or soldierfishes (family Holocentridae), which feast on the abundant night plankton.

One of the most interesting families of fish to come out at night are the flashlight fishes (family Anomalopidae). These delightful littleblack fish have special organs under their eyes which contain million of light-producing bacteria. The fish are able to cover and uncover these organs to produce characteristic flashes of blue-green light. The function of these lights is not fully undertood but they are probably udrd to communicate, to see by, and perhaps to confuse predators,

Two species of flashlight fish are found in Indonesia. The most often seen is Anomalops kataptron, a 6-8 centimeter fish that forages for plankton in shallow reef waters, often in large schools. (Anomalops also occurs in a much larger—27 centimeters—deepwater form that lives in up to 400 meters of water.) Photoblepharon palpebratus is rare and tends to occur in relatively small groups in deep caves.

Marine Reptiles

Sea turtles. One of the most delightful experiences a diver can have swimming with turtles, and in Indonesia such encounters are quite common. Six species of marine turtles are found in Indonesian waters, but the two most likely to be seen by divers are the tiawksbill turtle (Eretmochelys imbricata and the green turtle Chelonia mydas).

They are not always easy to distinguish underwater, althoug the hawksbill has a distinct beak and the trailing edge of its shell is jagged. The hawksbill is also generally smaller, and is tortoiseshell brown (instead of olive green) although such relatively minor color difference are very hard to determine underwater. A third species that may be seen by divers is the loggerhead (Caretta caretta), which is much like the green turtle, except it has a massive head.

The green turtle feeds almost entirely on sea grass, while the hawksbill and loggerhead are both largely carnivorous. The shell of the hawksbill is covered with large horn-like scales, the source of "tortoiseshell." Tortois shell products—and even stuffed and varnished hawksbill turtles—are offered in Indonesian markets, although import into most Western countries is strictly prohibited.

A bluestreak cleaner wrasse, Labroides dimidiatus picks at the eye of a bright terminal male purple queen, Pseunthias tuka. The little cleaners provide an essential service and are never molested by their "costomers." Manado, Sulawesi.

Traditional whaling still takes place in two villages east of Flores. These men, from Lamaierat Lembata are flensing a sperm whale they caught with a hand-hurled spear from their small wooden boat The men catch no more than 15-20 small whales a year, although the) will also harpoon whale sharks, marlin or any other large fish they come across,

Marine turtles spend nearly all their lives at sea but their eggs have to be laid on land. At certain secluded beaches females regular:, emerge at night to deposit their eggs above the high water mark.

Sea snakes. Most sea snakes (family Hydrophiidae) never come onto land at all, even giving birth at sea. There are some 60 species of sea snakes in the world, over half of which are found in Indonesia. They tend to be patchily distributed very common In some areas and absent form others, As reptiles; they must come up for air although they have a very large lung and can stay under for many hours.

Sea snakes can be seen underwater poking their small heads into cracks and crevices, searching for small fish and crustaceans. The head of a sea snake is often difficult to distinguish from the tail as both are blunt, although the head is always smaller, and the tail is laterally flattened to aid in swimming.

Sea snakes are equipped with extremely toxic venom which can be delivered through two short fangs on the upper jaw. The venom is used to subdue prey such as spiny fish or moray eels, which could cause the snake considerable damage if not killed very quickly. Since fish are quite resistant to most toxins, it is not surprising that sea snake venom is so strong.

Sea snakes are rarely aggressive towards divers, however, and unprovoked attacks are virtually unknown. They are sometimes inquisitive however, and may inspect a diver.

The grey-and-black banded colubrine or amphibious sea snake (Laticauida colubrina) is common in Indonesia This animal—collected in huge numbers in the Philippines for its skin—It is an inoffensive creature, and slow to anger. Guides often catch the animals for their clients to pose with We don't suggest you try this, however.

The yellow -bellied sea snake (Pelamis platurus) is the most numerous reptile on earth. This colorful animal is so completely adapted to anaquatic life that if washed ashore, it will die. It cannot even crawl back to the water.

Crocodiles. One marine reptile that is truly dangerous is the salt water crocodile (Crocodylus porosus). These monsters can grow to many meters in length, although real giants are very rare these days. Fortunately for divers they usually live in murky estuarine areas, not on coral reefs. Saltwater crocodiles are found in Irian Jaya, and in scattered locations in Maluku.

Marine Mammals

While common enough in Indonesian waters, sea mammals are rarely seen while diving, and swimming with whales or dolphins is a rare occasion indeed for a diver.

Dolphins. Schools of dolphins are a frequent sight while traveling out to dive sites by boat. Sometimes their "whistling" can be heard during a dive (a sound that is sometimes uncannily like a leaking air cylinder) but they will normally stay well beyond the range of visibility. The best way to see them underwater is to snorkel from the dive boat when a school is encountered in deep water. Usually they will move away, but you could get lucky.

There are several dolphin species in Indonesia and identifying them at sea is a far from easy task. Common species here include the spinner dolphin (Stenella longirostris), so-called because of its characteristic high, spinning jumps; the common dolphin (Delphinus delphis), which has a black-tipped snout, and a crisscross pattern on its flanks; and the spotted dolphin, with a pattern of fine spots on its sides.

Whales. Several species of large whales also occur in Indonesia, some arriving seasonally from polar regions, others being year-round residents. Like dolphins they are best watched from a boat rather than the water. Some whales breed in Indonesian waters, so it is very important not to harass them by chasing them in boats.

Most of the species seen are plankton-eating baleen whales which have vertical spouts and a small, but distinct, dorsal fin. They might be distinguished on the basis of size, but this requires some experience. The blue whale (Balaenoptera musculus) is known in Indonesian waters, as are several smaller but very similar species, including the fin whale (B. physalus) and minke whale (B. acutorostrata). The humpback, (Megaptera novaeangliae), is easier to identify.

The sperm whale (Physeter catodon), of Moby Dick fame, is a very different animal. These are toothed whales, which feed on giant squid and fish snatched from great depths. The sperm whale has a characteristic forward pointing spume and hump-like ridges rather than a dorsal fin on its back. Pygmy and dwarf sperm whales (Kogis) also inhabit Indonesian waters.

Dugong. It is very unlikely that a diver will see this rare animal. The dugong or sea cow (Dugong dugon) is a slow-moving animal, up to 2.5 meters long, that looks like a walrus without the tusks. There are only three other members of order Sirenia, manatees from Florida, the Amazon basin and West Africa.

The dugong is the only herbivorous marine mammal, and is strictly aquatic. The animals can eat 10 percent of their body weight a day in sea grasses, and are found mainly in sheltered bays where these plants grow.

Dugongs are threatened throughout their range, because they are slow-moving, easy targets for hunters—their tusks are used for cigaret holders—and because they take so long to reproduce. Calving takes place only once every 3-7 years, and dugongs take 15 years to mature.

— Charles Anderson and

David Pickett