The organisms that live at the extreme depths of the ocean are highly specialized to survive in conditions of high pressure and total darkness. They have slow metabolisms and are able to live in water with very little dissolved oxygen. Many of the fish living in the abyssal zone are ambush predators such as anglerfish, black swallowers and gulper eels, who wait patiently for their prey to come to them, rather than expending energy by swimming. They have long, needle-sharp teeth, jaws that come unhinged and mouths and stomachs that can stretch like balloons in order to swallow prey that may be larger than the fish itself. It is common for deep sea predators such as flashlight fish to lure their prey by bioluminescence, light that is generated by a chemical reaction.
The greatest amount of biological diversity in the abyssal zone is found near hydrothermal vents. Since there is no sunlight, chemosynthetic (chemoautotrophic) bacteria convert compounds such as hydrogen sulfide into organic matter. These microorganisms are the primary producers and basis of the food chain. They are fed upon by small crustaceans, which in turn are eaten by a variety of predators including crabs, shrimp, snails and bivalves.
Tube worms are a species uniquely adapted to the abyssal zone. They have no mouth or digestive system, but absorb inorganic compounds through their skin and rely on the chemosynthetic bacteria within their bodies to provide them with food.
