THE DEEP SEA FAUNA

Taranaki Daily News, 5 January 1935, Page 11 (Supplement)

THE DEEP SEA FAUNA

LIVING UNDER PRESSURE

(By 0.M.A.) Each year as it passes destroys a few illusions, breaks down the structure of a few theories and’.reveals a basis upon which a few new conceptions may arise. To the scientist who makes a study of the evolution of life in its infinite manifestations 1934 was interesting in that it saw the solution beyond doubt of the identity of the Loch Ness monster. From being a creature that was to furnish a clue to tangled questions of prehistoric anatomy the Scottish monster became a submerged German aeroplane. Finally it was definitely proved to be a not unusual grey seal, and another hope went to ground. Popularly, the Loch Ness mystery attracted such attention as is usually accorded to searches for the Missing Links between man and the apes. In that way it recalls an incident about 60 years ago which first opened the eyes of civilisation to the possibility of discovering life in the ocean depths. A submarine cable of the Mediterranean Telegraph Company broke in deep water and a ship was sent out to examine and repair" the damage. When the broken line was brought on deck it bore several forms of animal life attached to it that must have lived at the bottom of the sea in water extending to a depth of 1200 fathoms. This indication of the existence of a deep-sea fauna aroused an immediate response. High hopes were entertained and wild surmises made of discovering in the abysses the keys to the ultimate secrets of evolution. Of various expeditions commissioned to explore, the most famous was that of H.M.S. Challenger, fitted out by the British Government in 1873. The results of this voyage have formed the. nucleus of our knowledge, the centre round which all new facts cluster and the guide for further investigations.

Contrary to expectations life on the sea floor was proved to be closely allied to that above it. There were no extinct forms to light the way of evolution, no masses of pure protoplasm in the shape of the famous but unfortunately nonexistent Bathybius. The weirdness of some types pointed not to the origin of life in the depths as had been suspected, but merely to the effect of a strange environment on known species.

In considering the conditions of the abysmal zone there is one aspect in the conception of which our imagination falters. That is the enormous pressure. At a depth of 2500 fathoms the pressure is, roughly speaking, two and a-half tons per square inch, several times greater than the pressure exerted by steam upon the pistons of our most powerful engines. Or, put in other- words, the pressure per square inch upon the body of every animal that lives at the bottom of the Pacific Ocean is about 25 times greater than the pressure that will drive a railway train. It can only reasonably be supposed that the ability to sustain such pressure is acquired by animals after generations of gradual migrations from shallow water. Thos_ forms that are brought up by dredges from the depths of the ocean are usually killed and distorted by the rapid 'diminution of pressure in their journey to. the sqr r face, and it is extremely probable- that shallow-water forms would be similarly crushed out of shape were they plunged into very deep water. The fish that live in the abyss are on account of the pressure subject to a. curious accident. If, in chasing their prey or for any other reason, they rise to a considerable distance above the floor of the ocean, the gases of their swimming bladder become expanded and their specific gravity greatly reduced. Up to a certain limit the muscles of their bodies can counteract the tendency to float upwards and enable the fish to regain its proper sphere of life at the bottom; but beyond that limit the muscles are not strong enough to drive the body downwards, and the animal with bulging eyes and body increasingly distended, is gradually killed on its long and involuntary journey to the surface of the sea. The deep sea fish are therefore exposed to a danger that no other animal is liable to, that of tumbling upwards. That such accidents do occasionally occur is shown by the fact that some fish, which are known to be true deep sea forms, were discovered dead and floating on the surface of the ocean long before dredging was undertaken. Apart from the element of pressure, to which the fauna has become adapted, the abysmal zone is a gloomy realm. It is shrouded in blank darkness for no sunlight penetrates deeper than about 500 fathoms. The only glimmer of brightness is caused by the uncanny glow' of the bodies of the animals themselves, which are frequently phosphorescent. In the everlasting murkiness they shine like torches so that some regions of the abysmal world may be as brightly illuminated as a city street at night. There is an element of repose in the life of deep sea animals. In their dark domain they are far below the vicissitudes of wind and rain. The raging of storms do not disturb their tranquillity or sound break in upon the utter stillness, and the only current that is conjectured is a slow, almost imperceptible sweep from the poles. The temperature is icy, varying at most only a few degrees and never above 12 degrees centigrade. The scarcity of food gives the struggle for existence a desperate intensity. No plants grow in the lower reaches of water, for plant life cannot survive in the absence of sunshine. The fauna is cannibalistic in habit, though the bulk of the food consists of the bodies of dead animals that drift down from above. There is very little fighting, or pursuit and capture to vary the monotony of existence. The sea bed is covered with a vast undulating carpet of fine mud, obscuring every rock or stone, which is composed of the shells of infinite numbers of unicellular organisms which have died.

Of the general characters presented by animals living in deep water the most important are those that are directly or indirectly related to the fact that the animals live either in total darkness or in the faint and probably intermittent light emitted by phosphorescence. Mainly it is the colour of the skin and the eyes—either abnormally large or small to the point of complete absence—that are affected by-these phenomena. - In the quiet world beyond the sunfight there are apparently no gigantic monsters —a belief perhaps due to our limited methods of collection. There are unicellular organisms, sea-anemones, members of the star-fish tribe, creatures that closely resemble attenuated crayfish and contorted species of worms and molluscans. Most uncanny of all are the true fish. Many of them move like ghosts, the perpetual glimmer of their phosphorescent bodies throwing into relief their appalling scragginess. Pale and cruel, with enormous saucer eyes and their great jaws, sometimes one third as large as the whole animal, fined with rows of razor-sharp teeth they glide slowly through their black world like the horrible figments of some wild 'ightmare.