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ОглавлениеActinopterygii I
Lower Ray-finned Fishes
POLYPTERIFORMES : POLYPTERIDAE—Bichirs
DIVERSITY: 1 family, 2 genera, 12 species
REPRESENTATIVE GENERA: Erpetoichthys ( = Calamoichthys), Polypterus
DISTRIBUTION: Africa
HABITAT: Freshwater; tropical; demersal over soft bottoms
REMARKS: Bichirs are thought to be the sister group of all other actinopterygians, exhibiting many unique characters. All bichirs have lungs, an intestinal spiral valve, a skeleton of mostly cartilage, and a uniquely divided dorsal fin. Pelvic fins are present in most species but absent in one (Erpetoichthys calabaricus). Bichirs are carnivorous and feed on other fishes, mollusks, and crustaceans. They are restricted to Africa, are known to reach lengths of up to 90 cm, and are often seen in the aquarium trade.
REFERENCES: Britz and Johnson, 2003; Daget et al., 2001; Gayet et al., 2002; Gosse, 1984, 1988.
POLYPTERIFORM CHARACTERISTICS:
1) five to eighteen dorsal finlets, each with a single spine and one or more soft rays
2) four gill arches
3) spiracles large
4) two gular plates
5) branchiostegal rays absent
6) ganoid scales
7) maxilla fused to skull
ILLUSTRATED SPECIMEN:
Polypterus palmas, CU 87580, 126 mm TL
ACIPENSERIFORMES—Sturgeons and Paddlefishes
The sturgeons and paddlefishes are an ancient lineage of fishes that evolved in the Permian over 250 million years ago. They and the Polypteriformes have a complex mixture of traits not seen in other ray-finned fishes including a heterocercal tail, skeleton of mostly cartilage, and spiral valve in the intestine. In addition, the Acipenseriformes have a well-developed rostrum, lack an opercle, have a reduced or absent preopercle, and lack branchiostegal rays. The group includes two families, six genera, and 28 extant species. Living acipenseriforms are restricted to the Northern Hemisphere where they inhabit coastal areas and large river systems (Bemis et al., 1997).
REFERENCES: Bemis et al., 1997; Chen and Arratia, 1994; Grande and Bemis, 1996
ACIPENSERIFORMES : ACIPENSERIDAE—Sturgeons
DIVERSITY: 4 genera, 26 species
REPRESENTATIVE GENERA: Acipenser, Huso, Pseudoscaphirhynchus, Scaphirhynchus
DISTRIBUTION: Northern Hemisphere temperate (except Greenland)
HABITAT: Anadromous or freshwater; temperate; demersal to benthic on soft bottoms
REMARKS: Five rows of bony scutes along the body distinguish sturgeons from all other fishes. These large freshwater/anadromous fishes inhabit lakes, slow-moving rivers, and coastal areas and feed on mollusks, crustaceans, insect larvae, and occasionally plants. The long-lived species of the genus Huso are some of the largest freshwater fishes in the world, reaching 8 m TL and over 1,500 kg, and are the source of what is considered the world’s finest caviar. As a result of the caviar fishery and habitat destruction, nearly all sturgeons are vulnerable to extinction and at least 16 species are listed as critically endangered by the IUCN (2013).
REFERENCES: Bemis et al., 1997; Birstein et al., 2002; Boschung and Mayden, 2004; Choudhury and Dick, 1998; Grande and Bemis, 1996; Hilton et al., 2011; Hochleithner and Gessner, 2001; IUCN, 2013.
ACIPENSERID CHARACTERISTICS:
1) five rows of bony scutes along body
2) four oral barbells
3) caudal fin heterocercal
4) gular plates absent
5) teeth absent in adults
6) pectoral fin with soft rays fused into an anterior spine-like element
7) skeleton largely composed of cartilage
ILLUSTRATED SPECIMEN:
Acipenser medirostris, SIO 62–155, 960 mm TL (lateral and dorsal views).
ACIPENSERIFORMES : POLYODONTIDAE—Paddlefishes
DIVERSITY: 2 genera, 2 species
REPRESENTATIVE GENERA: Polyodon, Psephurus
DISTRIBUTION: Mississippi River and Yangtze River basins
HABITAT: Freshwater but can tolerate some salinity; temperate; pelagic in slow-moving rivers
REMARKS: Paddlefishes are large (up to 3 m in length, with reports of much larger specimens), riverine species characterized by a long spatula-like snout. Although similar in appearance to its Chinese counterpart, the American Paddlefish is planktivorous with a non-protrusible mouth and numerous, long gill rakers, while the Chinese Paddlefish eats other fishes, has a protrusible mouth, and fewer, shorter gill rakers. Both species, however, use their paddles for electroreception in murky river waters (Wilkens et al., 2002). As a result of habitat destruction, pollution, and overfishing, the Chinese Paddlefish is critically endangered and may be extinct (IUCN, 2013; Zhang et al., 2009).
REFERENCES: Boschung and Mayden, 2004; Grande and Bemis, 1991, 1996; Inoue et al., 2003; IUCN, 2013; Wilkens et al., 2002; Zhang et al., 2009.
POLYODONTID CHARACTERISTICS:
1) snout long, flat, paddle-like
2) body essentially naked, with few scales
3) spiracle above and behind eye
4) caudal fin heterocercal
5) gill cover extended posteriorly
6) snout and gill cover with conspicuous electrosensory pores
ILLUSTRATED SPECIMEN:
Polyodon spathula, TU 37062–7, 882 mm TL (lateral and dorsal views)
HOLOSTEI—Gars and Bowfins
The Holostei includes the gars, with seven extant species, and the single extant species of bowfin. This group was recognized in early classifications of fishes (e.g., Patterson, 1973), but for a number of years, the Holostei was thought to be a paraphyletic group, with the bowfin more closely related to the teleost fishes. However, a recent exhaustive study of extant and fossil species by Grande (2010) provides morphological support (e.g., presence of a paired vomer) for the monophyly of the Holostei, in agreement with several analyses of molecular data (Inoue et al., 2003; Meyer and Zardoya, 2003). The Holostei is the sister group of the Teleostei; together they are called the Neopterygii.
LEPISOSTEIFORMES : LEPISOSTEIDAE—Gars
DIVERSITY: 1 family, 2 genera, 7 species
REPRESENTATIVE GENERA: Atractosteus, Lepisosteus
DISTRIBUTION: North America and Cuba
HABITAT: Freshwater to coastal marine; tropical to temperate; pelagic in rivers, lakes, and estuaries
REMARKS: Gars are elongate, toothy fishes that live predominantly in freshwater or brackish water and feed on other fishes, some benthic invertebrates, and waterfowl. Several small, toothed bones (including the infraorbitals) form the upper jaw. Gars use their lung-like gas bladders to supplement respiration (Graham, 1997) and are known to spend time in a stationary position near the surface. Opisthocoelous vertebrae (anterior end convex, posterior end concave) are unique to this group, one genus of the Blenniidae, and some reptiles.
REFERENCES: Boschung and Mayden, 2004; Graham, 1997; Grande, 2010; Wiley, 1976; Wiley, in Carpenter, 2003.
LEPISOSTEIFORM CHARACTERISTICS:
1) elongate jaws with fanglike teeth
2) bony, ganoid scales in oblique rows
3) row of median scales along the first ray of the dorsal, anal, and caudal fins
4) body elongate, with the dorsal and anal fins located posteriorly
5) pectoral fins low on body, pelvic fins abdominal
6) cheek with numerous bony plates
7) three branchiostegal rays
ILLUSTRATED SPECIMEN:
Atractosteus spatula, TU 124963, 666 mm TL (lateral and dorsal views)
AMIIFORMES : AMIIDAE—Bowfins
DIVERSITY: 1 family, 1 genus, 1 species
REPRESENTATIVE GENUS: Amia
DISTRIBUTION: Eastern North America
HABITAT: Freshwater in streams, rivers, and swamps; temperate; demersal over soft bottoms
REMARKS: The Bowfin, Amia calva, is the only living representative of the Amiidae and Amiiformes. It is restricted to eastern North America, though fossil forms are known worldwide (Grande and Bemis, 1999). It inhabits still or slow-moving freshwaters and can swim by either undulating its long dorsal fin or utilizing its strong tail. The Bowfin is predatory and feeds on other fishes, reptiles, amphibians, birds, snails, and crayfishes. It is among the many groups of air-breathing fishes and utilizes its lung-like gas bladder to supplement respiration (Graham, 1997). Males construct a nest where they defend eggs and young after they hatch.
REFERENCES: Boschung and Mayden, 2004; Graham, 1997; Grande and Bemis, 1998, 1999.
AMIIFORM CHARACTERISTICS:
1) body cylindrical, with long dorsal fin
2) single gular plate
3) caudal fin heterocercal
4) ten to thirteen flattened branchiostegal rays
5) maxilla included in gape
6) males with prominent ocellus near upper base of caudal fin
ILLUSTRATED SPECIMEN:
Amia calva, SIO 69–491, 138 mm TL
INSET: Head of Amia calva, SIO uncatalogued (ventral view)
TELEOSTEI—Teleosts
The Teleostei has long been recognized as a monophyletic group. Its composition, distinctive features, and relationships have been discussed at length by a variety of authors (e.g., Arratia, 1997, 1999, 2001; de Pinna, 1996; Fujita, 1990; Gosline, 1971; Greenwood et al., 1966; McAllister, 1968; Nelson et al., 2010; Patterson and Johnson, 1995; Wiley and Johnson, 2010; Winterbottom, 1974a). Most extant members have a somewhat to highly mobile premaxilla that is free from the skull, unpaired basibranchial tooth plates, a unique caudal-fin skeleton with elongate uroneurals (modified neural spines), and a number of other features. The extraordinary diversification of the teleosts has been attributed, in part, to a genome duplication event that occurred early in their evolution (Hoegg et al., 2004; Hurley et al., 2007; Meyer and Van de Peer, 2005; Santini et al., 2009). The diversity of the Teleostei is immense, including approximately 96% of all living “fish” species (Nelson, 2006). Several recent studies (e.g., Betancur et al., 2013; Faircloth et al., 2013; Inoue et al., 2001; Ishiguro et al., 2003; Near et al., 2012, 2013) have hypothesized the relationships among the major lineages of teleosts based on molecular data.
Hypothesized phylogenetic relationships of the early lineages of the Teleostei. The traditional hypothesis (left), based on morphology (Nelson, 2006) and supported by Inoue et al. (2003), differs from the recent molecularly based hypothesis (right) of Faircloth et al. (2013) and Chen et al. (2014) in the placement of the Osteoglossomorpha and Elopomorpha.
OSTEOGLOSSOMORPHA—Bonytongues and Mooneyes
The bonytongues and relatives are a broadly distributed early lineage of ray-finned fishes with a substantial fossil record. Their evolution predates the breakup of Gondwana, with extant representatives found in freshwaters of North America, South America, Africa, Asia, and Australia. At least one group, the Notopteridae or Old World knifefishes, also occurs in brackish waters. They are characterized by several internal features (Hilton, 2003; Li and Wilson, 1996; Wiley and Johnson, 2010; Wilson and Murray, 2008) including a unique “shearing bite” between the basihyal and lateral pterygoquadrate teeth (Greenwood et al., 1966). Most species in the group provide parental care to eggs, and in some cases, young (Britz, 2004). Two lineages are recognized within the Osteoglossomorpha: the Osteoglossiformes, with four families (Mormyridae, or elephantfishes, Notopteridae, or Old World knifefishes, Osteoglossidae, or bonytongues, and Gymnarchidae, or African knifefishes), and the Hiodontiformes, with a single family (Hiodontidae, or mooneyes).
OSTEOGLOSSIFORMES—Bonytongues
DIVERSITY: 4 families, 28 genera, 234 species
REPRESENTATIVE GENERA: Arapaima, Chitala, Gymnarchus, Mormyrus, Pantodon
DISTRIBUTION: Circumtropical
HABITAT: Freshwater, rarely brackish, rivers, streams and still waters; tropical; near surface and over soft bottoms
REMARKS: The bonytongues exhibit remarkable variety in form among and within the four included families. The Osteoglossidae can have long dorsal and anal fins and attain a length of more than 2.5 m (Arapaima gigas) or have short dorsal and anal fins with a maximum length of 10 cm (Pantodon buchholzi). The long pectoral fins of P. buchholzi (Freshwater Butterflyfish) allow it to glide over the surface up to 2 m. The Notopteridae have an extremely long anal fin, but a short or absent dorsal fin, and the pelvic fins may be present or absent. The Mormyridae have moderately long dorsal and anal fins, considerable variation in the snout and lower jaw, and in some cases, electric organs. The monotypic Gymnarchidae (Gymnarchus niloticus) has no anal, pelvic, or caudal fins, but also has electric organs. Air breathing has been documented in all four families (Graham, 1997).
REFERENCES: Graham, 1997; Hilton, 2003; Li and Wilson, 1996; Li et al., 1997; Wilson and Murray, 2008; Zhang, 2006.
OSTEOGLOSSIFORM CHARACTERISTICS:
1) glossohyal (tongue bone) usually with teeth
2) pelvic fins abdominal or (rarely) absent
3) premaxilla fixed to skull
4) branched caudal-fin rays usually fewer than 16
5) three to seventeen branchiostegal rays
6) six (or fewer) hypurals
ILLUSTRATED SPECIMENS:
A) Arapaima gigas, SIO 76–343, 809 mm SL (Osteoglossidae—bonytongues)
B) Gnathonemus petersii, SIO 64–228, 118 mm SL (Mormyridae—elephantfishes)
C) Xenomystus nigri, SIO 64–228, 132 mm SL (Notopteridae—featherfin knifefishes)
D) Gymnarchus niloticus, SIO 64–228, 165 mm SL (Gymnarchidae—Aba or African Knifefish)
HIODONTIFORMES : HIODONTIDAE—Mooneyes
DIVERSITY: 1 family, 1 genus, 2 species
REPRESENTATIVE GENUS: Hiodon
DISTRIBUTION: North America
HABITAT: Freshwater; temperate; pelagic in slow-moving rivers and lakes
REMARKS: Mooneyes characteristically have large eyes, their diameter greater than the length of the snout, and silvery or golden bodies. Unlike similar families, in mooneyes the single dorsal fin is located well posterior to the origin of the abdominal pelvic fins. Mooneyes migrate either upstream or to lake shallows in order to spawn. These fishes are visual predators and feed near the surface at night and during low light, primarily on insects, crustaceans, small fishes, frogs, and small mammals. The anal fin is sexually dimorphic, with males having thickened anterior rays.
REFERENCES: Boschung and Mayden, 2004; Britz, 2004; Greenwood, 1970a; Hilton, 2003; Li and Wilson, 1994; Li et al., 1997.
HIODONTIFORM CHARACTERISTICS:
1) single, short-based dorsal fin situated relatively far posteriorly
2) anal-fin base much longer than dorsal-fin base
3) subopercle with a small spine
4) seven to ten branchiostegal rays
5) pelvic fins with seven rays
6) eyes large
ILLUSTRATED SPECIMEN:
Hiodon tergisus, SIO 74–131, 99 mm SL
ELOPOMORPHA
This large group of morphologically diverse fishes is united in sharing a distinctive larval type, the leptocephalus. These ribbon-shaped larvae have small heads and elongate bodies that in some may be as long as 2 m (Böhlke, 1989). At metamorphosis, they shrink in size and take up the general form of their respective lineages. In addition, elopomorphs have numerous branchiostegal rays (15 or more) and teeth on the parasphenoid. The group includes over 850 species classified in five orders, 24 families, and 156 genera. The largest of these orders is the Anguilliformes or true eels, with nearly 800 species. While the monophyly of the Elopomorpha has been questioned by some, recent molecular data and morphological evidence support its monophyly (Chen et al., 2014; Forey, 1973; Forey et al., 1996; Inoue et al., 2004; Obermiller and Pfeiler, 2003; Wiley and Johnson, 2010).
Hypothesized phylogenetic relationships of the Elopomorpha after Chen et al. (2014); that study placed the Saccopharyngiformes within the Anguilliformes.
ELOPIFORMES—Tenpounders and Tarpons
Members of Elopiformes have an elongate body, abdominal pelvic fins, long jaws with toothed premaxillae and maxillae in the gape, wide gill openings, a single gular plate, cycloid scales, and numerous (23–35) branchiostagal rays. Like those of the Albuliformes, their leptocephali have a well-developed, forked caudal fin. This group includes two families, the well-known tarpons (Megalopidae) and the tenpounders (Elopidae).
ELOPIFORMES : ELOPIDAE—Tenpounders and Ladyfishes
DIVERSITY: 1 genus, 7 species
REPRESENTATIVE GENUS: Elops
DISTRIBUTION: Atlantic, Indian and Pacific oceans
HABITAT: Primarily marine but occasionally in brackish estuaries and freshwater; tropical to subtropical; coastal pelagic
REMARKS: Tenpounders are elongate, silvery fishes with a large, terminal mouth and a deeply forked caudal fin. These predatory fishes reach lengths of approximately 1 m and feed primarily on small fishes and some crustaceans. Unlike the closely related tarpons, tenpounders do not breathe air but do possess a large pseudobranch. There are currently only seven described species of tenpounders, but there are likely more undescribed, cryptic species in the Indo-Pacific and elsewhere (McBride et al., 2010). Tenpounders are generally not targeted commercially but are considered a good sport fish.
REFERENCES: McBride et al., 2010; Smith, in Carpenter, 2003; Whitehead, 1962.
ELOPID CHARACTERISTICS:
1) body elongate and somewhat rounded in cross section
2) last ray of single dorsal fin not elongate
3) mouth terminal, large, extending past eye
4) pelvic fins abdominal
5) caudal fin deeply forked
6) single gular plate
7) scales small, approximately 100 in lateral line
ILLUSTRATED SPECIMEN:
Elops affinis, SIO 64–326, 172 mm SL
ELOPIFORMES : MEGALOPIDAE—Tarpons
DIVERSITY: 1 genus, 2 species
REPRESENTATIVE GENUS: Megalops
DISTRIBUTION: Atlantic and Indo-West Pacific oceans
HABITAT: Primarily marine but occasionally in brackish estuaries and freshwater; tropical to subtropical; coastal pelagic
REMARKS: The tarpons are large, silvery fishes with large scales, a slightly superior mouth, and a deeply forked caudal fin. They grow to well over 2 m in length and are predatory, feeding primarily on fishes and invertebrates. They are able to respire via air gulped at the surface and passed into the physostomous gas bladder (Graham, 1997). There are two known species, one in the Atlantic and a second in the Indo-West Pacific. They are very popular sport fishes.
REFERENCES: Ault, 2008; Forey et al., 1996; Graham, 1997; Greenwood, 1970b; Seymour et al., 2008; Smith, in Carpenter, 2003; Wade, 1962.
MEGALOPID CHARACTERISTICS:
1) body elongate, laterally compressed
2) last ray of single dorsal fin elongate
3) mouth terminal to superior, large, extending past eye
4) pelvic fins abdominal
5) caudal fin deeply forked
6) single gular plate
7) scales large, less than 50 in lateral line
ILLUSTRATED SPECIMEN:
Megalops atlantica, SIO 78–124, 270 mm SL
ALBULIFORMES—Bonefishes
This group includes two families, the Albulidae (covered below) and the Pterothrissidae, two genera, and about 13 species. They are silvery fishes with a forked caudal fin in adults as well as in their leptocephalus larvae (also found in the Elopiformes) and are distinctive in a few osteological features (Forey et al., 1996; Wiley and Johnson, 2010).
REFERENCES: Forey et al., 1996; Wiley and Johnson, 2010.
ALBULIFORMES : ALBULIDAE—Bonefishes
DIVERSITY: 1 genus, 11+ species
REPRESENTATIVE GENUS: Albula
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally in freshwater; tropical to warm temperate; coastal, demersal over soft bottoms
REMARKS: Bonefishes are coastal fishes characterized by their single dorsal fin, deeply forked caudal fin, and inferior mouth. As indicated by their mouth position, these fishes feed on or near the bottom, on crustaceans and other small invertebrates, as well as fishes. Reaching a maximum size of over 1 m, bonefishes are highly regarded as sport fishes, but are rarely eaten and generally not targeted commercially. Recent researchers have used molecular and morphological characters to determine the presence of several cryptic species (e.g., Hidaka et al., 2008; Pfeiler et al., 2008).
REFERENCES: Ault, 2008; Hidaka et al., 2008; Pfeiler et al., 2008; Smith, in Carpenter, 2003.
ALBULID CHARACTERISTICS:
1) body elongate
2) mouth inferior, small, not extending past eye
3) tail deeply forked
4) single gular plate
5) six to sixteen branchiostegal rays
6) scales small
ILLUSTRATED SPECIMEN:
Albula sp., SIO 62–213, 159 mm SL
NOTACANTHIFORMES—Spiny Eels and Halosaurs
DIVERSITY: 2 families, 6 genera, 27 species
REPRESENTATIVE GENERA: Aldrovandia, Halosaurus, Lipogenys, Notacanthus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; lower continental shelf to abyssal plain, demersal over soft bottoms
REMARKS: Spiny eels (Notacanthidae) and halosaurs (Halosauridae) are elongate, deepsea fishes that, in addition to the features below, are characterized by a large connective tissue nodule intercalated between the pterygoid arch and the maxilla. Their long anal fin extends nearly half the body length and includes numerous spines. Spiny eels and halosaurs associate with the benthos and feed on small invertebrates (e.g., crustaceans, echinoderms, polychaetes) and detritus. These fishes can regenerate their long tails when broken or injured. The leptocephalus larvae of some notacanthids are known to reach an amazing length of 2 m (Böhlke, 1989).
REFERENCES: Böhlke, 1989; Crabtree et al., 1985; Forey et al., 1996; Smith, in Carpenter, 2003; Sulak et al., 1984.
NOTACANTHIFORM CHARACTERISTICS:
1) tail elongate, tapering posteriorly to a point; caudal fin absent
2) mouth small, inferior, not extending past eye
3) pelvic fins abdominal, connected along ventral midline with a membrane
4) maxilla toothed, in gape, with a posteriorly directed spine
5) base of anal fin extremely long
ILLUSTRATED SPECIMENS:
A) Notacanthus chemnitzii, SIO 87–84, 385 mm TL (Notacanthidae—spiny eels)
B) Aldrovandia phalacra, SIO 68–463, 189.5 mm TL (Halosauridae—halosaurs; tail broken)
ANGUILLIFORMES—Eels
Historically, the true eels have been called the Apodes because they lack pelvic fins and a pelvic girdle. The pectoral fins and caudal fin may be present or absent. Scales are absent in most eels, but if present they are cycloid and imbedded. The gill openings of eels are narrow and gill rakers are absent. Eel leptocephali have a rounded caudal fin that is contiguous with the dorsal and anal fins. The Anguilliformes includes 15 families, 141 genera, and nearly 800 species. They are found in all major aquatic habitats of the world. Protoanguilla palau, recently described from deep reefs of Palau, represents a new genus and unique family of eels, the Protoanguillidae, that is hypothesized to be the sister group of all other eels (Johnson et al., 2012).
REFERENCES: Böhlke, 1989; Johnson et al., 2012; Robins, 1989; Santini, Kong et al., 2013.
ANGUILLIFORMES : ANGUILLIDAE—Freshwater Eels
DIVERSITY: 1 genus, 18 species
REPRESENTATIVE GENUS: Anguilla
DISTRIBUTION: Atlantic, Indian, and Pacific oceans, and all continents except Antarctica
HABITAT: Marine and freshwater; tropical to temperate; catadromous; demersal to benthic in lakes, rivers, and estuaries, benthopelagic in open ocean
REMARKS: Though referred to as freshwater eels, the species in the Anguillidae are generally catadromous. While they live most of their adult lives in freshwater, they spawn in open ocean, far from land (Tsukamoto et al., 2011). Freshwater eels are also semelparous, meaning they die soon after spawning. Recent studies have shown that they are related to a group of deep-sea marine eels, the Nemichthyidae and Serrivomeridae (Inoue et al., 2010). Anguillids are generalized predators and feed on other fishes and benthic invertebrates. Freshwater eels are commercially important food fishes and several species support a large aquaculture enterprise.
REFERENCES: Inoue et al., 2010; Smith, 1989; Tesch, 1977; Tsukamoto et al., 2011.
ANGUILLID CHARACTERISTICS:
1) lower jaw projecting beyond upper jaw
2) pectoral fins well developed
3) scales small, embedded in skin
4) teeth small, in bands
5) trunk lateral-line canal complete
ILLUSTRATED SPECIMEN:
Anguilla japonica, SIO 85–138, 356 mm TL
ANGUILLIFORMES : MURAENIDAE—Moray Eels
DIVERSITY: 15 genera, 198 species
REPRESENTATIVE GENERA: Echidna, Gymnothorax, Muraena, Uropterygius
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally freshwater; tropical to temperate; continental shelf to upper continental slope, benthic on or in coral and rocky reefs, as well as soft bottoms
REMARKS: Unlike most eels, morays can be quite colorful with distinctive markings. They range in size from ∼20 cm to 3.75 m in total length, and are among the world’s largest eels. In addition to their laterally compressed head and body, morays have a characteristic raised-head profile behind the eyes. These eels are both predators and scavengers and eat living or recently dead fishes or crustaceans. Piscivorous species are characterized by long, needle-like teeth and highly mobile pharyngeal jaws (Mehta and Wainwright, 2008), while species specializing on crustaceans may have molariform teeth. Care should be taken when eating large morays as they are responsible for many cases of ciguatera poisoning. The phylogenetic relationships of morays were hypothesized by Tang and Fielitz (2013) based on molecular data.
REFERENCES: Böhlke et al., 1989; Böhlke and McCosker, 2001; Böhlke and McCosker, in Carpenter and Niem, 1999; Mehta and Wainwright, 2008; Smith, 2012; Tang and Fielitz, 2013.
MURAENID CHARACTERISTICS:
1) pectoral fins absent
2) posterior nostril high on head
3) head and body laterally compressed for entire length
4) gill opening reduced to small round hole or slit
5) scales absent
6) trunk lateral-line canal absent
ILLUSTRATED SPECIMENS:
A) Uropterygius versutus, SIO 59–7, 289 mm TL
B) Gymnothorax moringa, SIO 71–275, 377 mm TL
C) Enchelycore octaviana, SIO 65–33, radiograph
ANGUILLIFORMES : OPHICHTHIDAE—Snake Eels and Worm Eels
DIVERSITY: 52 genera, 318 species
REPRESENTATIVE GENERA: Muraenichthys, Myrichthys, Ophichthus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally in freshwater; tropical to temperate; continental shelf to continental slope, usually benthic on or in soft bottoms, with some species occuring in midwaters of the mesopelagic
REMARKS: The Ophichthidae is a large family of eels with considerable morphological diversity. For example, the pectoral, dorsal, anal, and caudal fins can be either present or absent, and the origin of the dorsal fin, when present, can be over the pectoral fin or well posterior. The unusual basket-like structure formed by the branchiostegal rays often involves rays that are detached from any other bone. Some species in the Ophichthinae use their hard, pointed tails to burrow backward, and their burrowing lifestyle implies that the bulk of their diet is likely benthic invertebrates. They are abundant in certain areas, caught by hook-and-line, and occasionally consumed by humans.
REFERENCES: Böhlke and McCosker, in Carpenter and Niem, 1999; McCosker, 1977, 2010; McCosker et al., 1989; McCosker and Rosenblatt, 1998.
OPHICHTHID CHARACTERISTICS:
1) posterior (excurrent) nostril on upper lip (usually) or inside mouth
2) tail usually hard, pointed; caudal fin absent in most species (present in Myrophinae)
3) branchiostegal rays numerous (15–49), overlapping at ventral midline to form a basket
4) scales absent
5) trunk lateral-line canal complete, left and right sides connected by a canal across nape
ILLUSTRATED SPECIMENS:
A) Callechelys eristigma, SIO 65–263, 503 mm TL, holotype
B) Scolecenchelys chilensis, SIO 65–645, 284 mm TL, holotype
ANGUILLIFORMES : CONGRIDAE—Conger Eels
DIVERSITY: 32 genera, 196 species
REPRESENTATIVE GENERA: Conger, Heteroconger, Paraconger
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; continental shelf to abyssal plain, benthic on soft bottoms, often burrowing into substrates
REMARKS: Like the Ophichthidae, the Congridae is a speciose family exhibiting significant morphological and ecological variation, and is difficult to characterize. Conger eels generally have well-developed pectoral fins and large eyes for use in visual predation, but there are exceptions to both traits. They live in association with the benthos and range from depths of less than 5 m to more than 2,000 m. Most species actively feed on small fishes and invertebrates at night, but the Heterocongrinae form vast “gardens” in sands adjacent to reefs and are visual plankton pickers. Conger eels are important in the fish leather industry (Grey et al., 2006).
REFERENCES: Castle and Randall, 1999; Grey et al., 2006; Smith, 1989b; Smith, in Fischer et al., 1995.
CONGRID CHARACTERISTICS:
1) dorsal-fin origin over or just posterior to pectoral-fin insertion
2) posterior nostril just anterior to eye
3) pectoral fins usually present and well-developed (except in the Heterocongrinae)
4) scales absent
5) eight to twenty-two branchiostegal rays
6) trunk lateral-line canal complete
ILLUSTRATED SPECIMENS:
A) Ariosoma gilberti, SIO 69–235, 165 mm TL (Congrinae)
B) Heteroconger canabus, SIO 61–261, 760 mm TL, holotype (Heterocongrinae—garden eels)
ANGUILLIFORM DIVERSITY:
A) NEMICHTHYIDAE—snipe eels: Nemichthys scolopaceus, SIO 88–55, 706 mm TL
B) COLOCONGRIDAE—shorttail eels: Thalassenchelys foliaceus, SIO 70–333, 228 mm TL, leptocephalus larva
SACCOPHARYNGIFORMES—Swallowers and Gulper Eels
DIVERSITY: 4 families, 5 genera, 28 species
REPRESENTATIVE GENERA: Cyema, Eurypharynx, Monognathus, Neocyema, Saccopharynx
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; midwater, lower mesopelagic to bathypelagic
REMARKS: The deep-sea swallowers and gulper eels are among the most distinctive and bizarre fishes, considered by some (e.g., Nelson, 2006) to be among the most morphologically modified vertebrates. With their huge mouths and highly distensible pharynx, they are clearly adapted for capturing and ingesting large prey items in the food-poor environment of the deep sea. In addition to the features listed below, they lack opercular bones and ribs, and have long, posterior extensions of both jaws. Swallowers and gulpers feed primarily on other fishes, and can swallow items at least as large as their body size. The tail of the swallowers ends in a luminous organ that might be used to attract prey.
REFERENCES: Nelson, 2006; Nielsen et al., 1989; Tighe and Nielsen, 2000.
SACCOPHARYNGIFORM CHARACTERISTICS:
1) mouth greatly enlarged
2) tail extremely elongate, caudal fin absent
3) abdominal portion of body much deeper than tail
4) body quite flaccid
5) scales absent
6) branchiostegal rays absent
ILLUSTRATED SPECIMENS:
A) Saccopharynx lavenbergi, SIO 75–272, 602 mm TL (Saccopharyngidae—swallowers)
B) Eurypharynx pelecanoides, SIO 72–180, 430 mm TL (Eurypharyngidae—pelican eels)
OTOCEPHALA
This group, called the Otomorpha by Wiley and Johnson (2010), includes the herrings and anchovies (Clupeiformes) and their sister group, the Ostariophysi (Arriata, 1999). Its members share several osteological features of the skull, vertebral column, and caudal fin, as well as a unique silvery area associated with the gas bladder (Lecointre and Nelson, 1996; Wiley and Johnson, 2010).
CLUPEIFORMES—Herrings, Anchovies, and Relatives
