ABYSSAL ANIMALS, are organisms that live at depths of 6,500 feet to 19,500 feet in the world’s oceans, below the limit of light penetration. The environment in this region is extreme: pressure is about 1,000 atmospheres, temperature is as low as 41° to 30° F (5° to — 1° C), and there is total darkness. As a result, abyssal animals are almost ali blind and colorless. Bioluminescence is also a common characteristic of these animals.
Examples of abyssal animals are squids, sea anemones, bristle worms, bivalve mollusks, and sea cucumbers.
Since the absence of light precludes the manufacture of organic material by plants in the region inhabited by abyssal animals, they depend for food on organic matter that falls from the higher levels of the oeean. The ecological balance of the abyssal regions is relatively stable because of the high degree of specialization that animals living at these depths must acquire. Thus there is little competition from new forms, as only animals adapted to the extreme pressure can survive in the abyss.