Organisms that live in the perpetual darkness and extreme pressures of the deep sea have a variety of bizarre and ingenious adaptations to enable them to survive. In the twilight zone between 200 and 1,000 metres, animals are often equipped with huge eyes to find food and mates, and to evade predators. The giant squid Architeuthis dux was eyes the size of dinner plates. In the total darkness found past 1,000 metres, many deep-sea animals have evolved light-producing organs that are used either for recognition or as lures to catch prey.
With no phytoplankton (microscopic plants) available as a primary food source, the inhabitants of the deep must rely on a slow, steady rain of waste food particles from above, or hunt and scavenge in the darkness. Sometimes, a shipwreck or the carcass of a large organism such as a whale or the trunk of a tree will arrive on the seabed and the slow pace of life is transformed as a range of animals take advantage of the nutritional bonanza, which can last a number of years.
Guy J Baker, Marine Biological Association of the UK