Animals of the deep sea are strange-looking creatures. They look very different from their relatives in shallower waters. It is not surprising that they do, since they live under very different conditions. Their bodies fit these conditions.Deep-sea creatures have thousands of pounds of water pressure on every square inch of their bodies. We do not feel the pressure of the air on our bodies because the pressure from the inside outward is as great as the pressure on the outside. Deep-sea animals are fitted to their environment in a similar way. The inside pressure is equal to the outside pressure.
When deep-sea animals are pulled up to the surface, they are likely to die at once. Not many of them can stand the sudden changes in temperature and pressure. A few kinds of fishes—those that have swim bladders—even turn inside out. They do so because at the surface the pressure inside their bodies is much greater than the pressure outside.
Most deep-sea animals are small. Any one that gets to be six feet long is a giant.
An animal as big as a man would have about six million pounds of pressure on its body at a depth of a mile. It is not surprising that most deep-sea creatures are small.
Many deep-sea fishes have enormous jaws, teeth, and eyes. The saber-toothed viperfish certainly has. The teeth of this fish are so long that it is difficult to see how it can ever close its mouth.
The viperfish often eats fish that are almost as large as itself. The black swallower can eat fish that are much bigger than it is. Its jaws and its stomach can stretch enormously.
Many animals of the deep sea eat other animals living there. Some live on the "rain" of dead plants and animals drifting down from surface waters.
Chemicals that glow in the dark are produced in the bodies of many deep-sea creatures. The angler has "lanterns" at the ends of stalks. The bathysphere fish has rows of pale-blue lights on its sides. And it has a red light and a blue one at the end of each of its two long tentacles. Both the teeth and the eyes of the viperfish glow in the deep-sea darkness with a weird light.
While many of the deep-sea fishes are ugly, others are beautiful. The five-lined constellation fish has a body which is flattened like that of a butterfly fish. Encircling the fish are glowing fringelike fins. On each side of its body there are five rows of gleaming lights.
The squids of the deep sea are beautiful creatures, too. Their long, graceful bodies are covered with organs that give off delicate red, blue, or green light. At the tip of each of a squid's two longest tentacles is a ball which glows with a reddish light.
Shrimp are very common in the deep sea. Organs inside their bodies make light-producing chemicals. These chemicals are dissolved in some of the water in their bodies. When the shrimp are in danger, this water pours out and forms glowing clouds. The light is believed to blind enemies and thus protect the shrimp by giving them a chance to escape.
Great numbers of very small animals swim or float about in the deep sea. Those that glow look to a deep-sea explorer like stars in a night sky. With its many-colored lights the "sky" of the deep sea must be as beautiful as the starry sky above us. But very few of us will ever see it.
