abyssal fauna

One of the three divisions of marine fauna, the others being littoral or shallow-water, and pelagic or surface fauna. Abyssal fauna exist in the greatest depths of the ocean, from about 2,000–6,000 m/6,500–19,500 ft.

The cold temperature, absence of light, and pressure of water cause various modifications in the abyssal fauna. Many are blind, while others see by means of the phosphorescent glow emitted from their own bodies and those of other fish. Their organs of touch are often highly developed. In colour they are very vivid; scarlet, violet, orange and purple being the predominant colours.

As no plants can grow in the abyssal depths because of lack of light, the fauna are carnivorous, catching in their wide jaws the falling debris of the organisms which exist above them.