The deepest regions of the ocean are known as the hadal zone, which extends between 6,000 meters and 11,000 meters beneath the ocean surface itself. These trenches, formed where tectonic plates collide, simulate tears in the ocean floor. Because of the depth of these zones, there is no light; therefore, plants cannot develop and thrive there. However, amphipods, decapods, rat-tail fish and liparid fish have adapted to these dark trenches.
Amphipods, found up to 9,100 meters below the ocean surface, are a soft-shelled arthropod called crustaceans. They are scavengers of the deep. They eat decomposing non-living organic material found at the very bottom of the hadal zones. This material consists of such things as dead organisms, decomposing fish and fecal material that settle in the trenches. Amphipods clean the trench bottoms and are a food source for other creatures such as the decapods.
The Kermadec and Japan hadal zones are currently the most studied zones. Scientist observing these zones spotted decapods preying on amphipods and found that the Benthescymus crenatus decapods exist in large numbers here. Decapods (meaning ten-foot) are a form of crustaceans within the Malacostraca class, which contains over 15,000 species. This class of crustaceans includes crayfish, crabs, lobsters, prawns and shrimp. Though they feast on amphipods in the hadal zones, decapods also scavenge for food.
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The macroufid known as the rat-tail also populates the hadal zones. This deep-sea fish has developed a good sense of smell to locate food in these dark depths. They are tadpole shaped with large mouths and a tapering tail. Their diet consists of other fish as well as crustaceans found along the trenches. Scientists spotted the rat-tail fish as deep as 7,000 meters below the ocean surface. To conserve energy, they are slow moving even when they hunt, tending to sneak up on their dinner.
The liparid fish, also known as the snailfish, is part of the Liparidae marine fish family. Normally found in shallower water, scientists found them in depths up to 7,500 meters. The liparid has an elongated body similar to the rat-fish, with a large head and very small eyes. These fish have well-developed, prominent sensory pores on their heads to assist in locating food. They feast on amphipods and small invertebrates.