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One step down from the bathypelagic is the abyssopelagic zone (also called the abyss), extending from 4,000 to 6,000 meters (13,000+ to nearly 20,000 feet) below the surface. Imagine totally dark, near-freezing temperatures (though stable), and super high pressure. For animals adapted to these harsh conditions, the pressure is no problem. Unlike animals with gas-filled organs (such as lungs and swim bladders) that would be crushed at these depths, deep-sea creatures are pretty much made up of tissue and fluid. While the high pressure may limit species diversification, it isn’t the hardest part about living here. The more challenging factor is the scarcity of food.

Source: Woods Hole Oceanographic Institution, P. Caiger – www.whoi.edu

FIGURE 4-8: The gulper eel; say ahh!

Source: Schmidt Ocean Institute – www.schmidtocean.org

FIGURE 4-9: Dumbo Octopus; isn’t she (or he) cute?

Generally, the farther down you go, the fewer species you encounter, because these are tough environmental conditions to adapt to. Life here is thought to have changed little over millions of years. Some abyssal species include the common fangtooth, the tripod fish shown in Figure 4-10 (they’re hermaphroditic, meaning they have both male and female reproductive organs, which means they can produce young either with another fish or on their own!), hagfish, cusk eels, grenadiers, and viperfish (Figure 4-11). In some places, you can find deep-sea corals, which don’t need sunlight to survive.

Source: Schmidt Ocean Institute – www.schmidtocean.org

FIGURE 4-10: The tripod fish.

Deep-sea creatures must be able to tolerate intense pressure (from the weight of the water above), total darkness, and near freezing temperatures. (See Chapter 5 for more about these ecosystems that thrive under extreme conditions.) That’s not to say that animals living closer to the surface have an easy life; they face a greater risk from predators and from changes in environmental conditions.