Animals World

Deep-sea animals

Early in the nineteenth century, an English naturalist, Edward Forbes, theorized that there was an azoic or lifeless environment in the ocean deeper than about two thousand feet. However, as technology advanced, broken submarine cables recovered from depths greater than five thousand feet were found to be teeming with living organisms, many of which were new to science. In the 1950's and later, collections from deep-water zones, made both with collecting devices and through explorations by scientists aboard submersibles, revealed fishes, snails, and other animals in the deepest part of the world ocean, the Mariana Trench in the southwest Pacific Ocean. This trench, at 6.8 miles deep, with crushing pressure, near-freezing temperature, and complete absence of light, supports life.

Deep-Sea Exploration
Scientists exploring in submersibles such as Trieste and Alvin watched in wonder as bizarre-looking fishes swam past the viewing ports. Many of the fishes were brightly colored-red and orange- and most of them featured light organs on their skin, glowing or flashing a bioluminescent light in the otherwise total darkness. Some of the fishes were equipped with body parts which resembled fishing rods and lures. The advent of submersibles offered the promise that someday soon, scientists might actually see one of the mythical sea monsters. This was not to be. Most of the strange-looking fishes were in many cases only a few inches long.

Gulpers and Anglers
In the lightless depths of the sea there is no primary production of food from plants as there is in the surface waters. Thus, the deep-sea fishes depend for food on whatevermaydescend fromsurface waters. A dead whale drifting down is a bonanza of nutrition to the organisms below. However, many of the deep-water fishes are unable to handle such large matter and are reduced to eating each other: their own kind or even a larger neighbor. The gulpers are remarkably adapted to the necessity of seizing and swallowing whatever comes along. The gulper, or pelican eel, has a huge mouth, jaws that open fantastically wide, and a belly that can contain a fish larger than itself. Some gulpers are about two feet long but one remarkable species reaches a length of six feet. Most of its length consists of a long, whiplike tail, with the mouth making up the rest of the body. The feeding action of the gulpers has been described as not swallowing their prey, but instead drawing themselves over it like a snake consuming a mouse. Many deep-sea fishes are anglers; that is, they are fishes that fish. Most of them bear a long, flexible appendage dangling from the top of the head. A light organ at the tip of the rod is dangled provocatively. Any fish that comes closer to investigate the glowing, wormlike bait is rapidly taken in to the angler's mouth and swallowed. Most anglers are jet black with enormous heads and mouths. The mouth is fitted with long, sharp, curved teeth that effectively trap the prey. Abizarre variation of the angler is the bottomdwelling, deep-sea fish that has a lighted appendage hanging from the roof of its mouth. It rests on the bottom, mouth agape, with the glowing "worm" wiggling in the dark. Any fish that is attracted into the angler'smawby an apparent bit of live food is quickly swallowed with little effort on the angler's part.

Sea Monsters Most scientists discount stories of sea monsters in the sense of serpentine animals that resemble the mythical dragon. None has ever been seen or examined by a reputable biologist. There are, however, denizens of the sea that are monstrous. Except for the whales (which are mammals, not fish), the three largest fishes are sharks. The megamouth shark (only discovered in 1976) is up to seventeen feet long. The basking shark reaches a length of forty feet. The giant of all fishes is the whale shark, reaching lengths of more than fifty feet. All three species are docile and feed on tiny plankton near the surface at night, but each day descend into the dark depths. Probably the source of most sea-monster stories is the giant squid. Related to the six- to eight-inch squid eaten as calimari or used as fishing bait, the giant squid truly lives up to its name. It grows to a length of sixty feet, has eyes the size of automobile hubcaps, and bears eight arms. It feeds on fishes and any other marine creature it can capture in its natural domain, three thousand feet down. It frequently is attacked and eaten by sperm whales. The squid is not a fish, but is a member of the same group of sea organisms that includes oysters and clams.

Look also:

Most Popular Animals

Principal Terms

bioluminescence: production of visible light by living organisms
deep sea: water depths below six hundred feet, also below penetration of light
gulper: a fish that captures and ingests its prey in one swallow
plankton: marine organisms, usually small, that are free-floating
submersible: a vessel, like a submarine, that can operate with or without occupants

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