Deep Ocean Adaptations
Despite the seemingly inhospitable conditions, Drazen said a diversity of life exists there—small crustaceans, worms, brittle stars, and fishes. They all have adaptations to cope with the near-freezing temperatures, crushing pressures, lack of light, and sparse food.
"There are many amazing adaptations to living in the deep sea," he said. "Examples include incredibly sensitive eyes—designed to pick up even the faintest blue glow of another animal's bioluminescence."
Creatures such as anglerfishes, of which there are some 150 different species, have bioluminescent lures—many look like small, glowing crustaceans—on their dorsal fins to attract their prey.
The prey, often of almost equal size to the anglerfish, fit neatly into the anglerfish's expandable stomachs, Drazen said.
Other fish have developed huge mouths and fangs so that they can eat practically whatever food they come across.
Some adaptations are less readily observable, such as cell membranes adapted to remain fluid even under the extreme pressure of the deep sea. "[Human] cell membranes faced with such pressure would lock up, lose their fluidity, and thus their function," Drazen said.
Lethargic Life
Preliminary analysis of this deep-sea life suggests a lethargic pace—the creatures are slow-moving with low metabolisms and low rates of reproduction.
Although scientists are far from understanding the full story of the lethargy, Drazen said the primary reason is related to the darkness of the deep sea, which affects the way animals react to predators and prey.
"In a dark environment you only need to burst a short distance to lose a predator and disappear in the blackness, and it is very difficult to sustain a chase after a prey item you cannot follow visually," he said.
Since deep-sea animals do not have to be constantly on the move to eat or avoid being eaten, they have smaller muscles and lower metabolisms. It is also becoming apparent that deep-sea fishes grow slowly, reproduce little, and live a long, long time.
For example, Drazen said, orange roughy can live for up to 125 years, rockfish up to 100 years, and rattail fish about 70 years. Many species do not reach sexual maturity until they are at least 15 years old.
"It has been hypothesized that some deep-sea fish may only spawn once before dying, and others may spawn only every several years," Drazen said. "The reasons for this slow growth and reproduction are unclear, but may be linked to food availability and other factors."
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