Fish that live in the deep ocean have adapted to survive under extreme pressures that can reach over 1,000 times atmospheric pressure at sea level. The deepest parts of the ocean are known as the hadal zone, named after the Greek god of the underworld, Hades.
The hadal zone, which extends from 6 to 11km (20,000 to 36,000ft), is a forbidding place, characterized by complete darkness, crushing pressure, and near-freezing temperatures. For a long time, scientists believed that life in the ocean depths was impossible due to these hostile conditions.
Still, that perception changed dramatically in 1977, when a US research team dropped a remotely operated vehicle 8,000ft (2,440m) into the Pacific Ocean to take images from hydrothermal vents, where seawater meets magma. They were astonished to find these deep-sea vents teeming with life.
Since 1977, marine scientists have discovered up to 600 never-before-seen species around these vents, including a scaly-foot gastropod, (Chrysomallon squamiferum), a type of snail with iron armour, and a new crab named ‘The Hoff’ (Kiwa tyleri) after US actor David Hasselhoff due to its hairy chest.
Here are a few ways how fish survive the extreme pressures of deep ocean:
- Specialized bodies: Many deep-sea fish have bodies adapted to withstand the pressure of the deep ocean. For example, some fish have gelatinous bodies that can compress without damage, while others have thick scales or cartilage instead of bones.
- Swim bladder adjustment: Deep-sea fish also have special adaptations to their swim bladder, an organ that helps control their buoyancy. The swim bladder of deep-sea fish is typically filled with fluid instead of air, which allows it to withstand the pressure.
- Slow metabolism: The cold temperatures and low food availability of the deep ocean mean that many deep-sea fish have slow metabolisms. This helps them conserve energy and survive in environments where food is scarce.
- Specialized enzymes: Some deep-sea fish have specialized enzymes that can function under the extreme pressure of the deep ocean. These enzymes help the fish to digest food and carry out other biological processes.
- Bio-luminescence: Some deep-sea fish also use bioluminescence to communicate, attract prey, or defend themselves. This adaptation allows them to survive in the dark depths of the ocean where there is little to no light.
