Do the dark depths shelter the seagoing equivalent of living dinosaurs and mammoths—beasts long thought to be extinct but actually still dwelling in the obscurity of the deep?
In 1864, Norwegian biologists dredged up a brittle, plant-like sea lily from 1,800 feet, the likes of which had never before been seen alive. But the remains of similar forms had been chiseled and leached from rocks 150 million years old. Less than a half-dozen years later, a large scarlet sea urchin, of a kind known only from fossils in the 100-million- year-old white cliffs of Dover, was dredged up from the floor of the Atlantic.
Darwin had published his revolutionary theory only five years before the sea lily find, and the idea gained momentum that the depths of the sea might be “ . . . the safest of all retreats, the secret abysses where the survivors of former geologic periods would be sure to be found.”
But this expectation never materialized, although the science of marine biology was being born and more research nets dropped deeper and deeper than ever before. During the pioneering around-the-world voyage of HMS Challenger in 1872-1876, biologists were confident of finding examples of living dead. But, like those of most succeeding expeditions, Challenger scientists found no “missing links” in the depths.
They did, however, bring up a horde of bizarre and highly fascinating creatures, and dispelled once and for all an erroneous theory that had plagued marine biology for 20 years.
In 1841, Edward Forbes, on the basis of the deepest dredgings to date in the eastern Mediterranean, drew the conclusion that no life existed below 1,800 feet. This he did despite the fact that two rugged countrymen, Sir John Ross and his nephew James Clark Ross, had brought up worms, crustaceans, and starfish from polar depths of 6,300 and 2,400 feet, as many as 23 years before. In the same year that scientist Forbes worked in the Mediterranean, sailor James Ross wrote: “I have no doubt that from however great a depth we may be able to bring the mud and stones of the bed of the ocean, we shall find them teeming with animal life. ...”
Not being authorities, however, the findings of the Rosses and others were overlooked or discounted on the grounds that the animals had been caught by the dredge on its way up. The genial and lively Forbes, on the other hand, was a well-known scientist hailed as a “nineteenth century Aristotle,” and his ideas became widely accepted.
But, in 1860, an incident occurred that could be neither ignored nor discounted. Between Italy and Africa, some 40 miles of cable was brought up from depths of 7,200 feet and was found to have corals, squid eggs, oysters, snails, and scallops clinging to it. Since the bases of the corals were moulded exactly to the inequalities of the cable, they could not have been caught on the way to the surface. Forbes died at the age of 39, four years before this incident, so he never suffered the humiliation of seeing his theory shattered.
The brilliant Forbes, who was the first professional scientist to work exclusively with sea creatures, made many pioneering contributions to marine biology and inspired others to do the same. It is ironical that the “father of marine biology,” as some call him, should have committed one of the most notable boners in the history of science, but it proves that scientists are people, too.
The tremendous pressures in the deep sea made Forbes’ theory easy to believe. One noted contemporary wrote, “it is almost as difficult to believe that creatures comparable with those ... in the upper world could live at the bottom of the sea, as they could live in a vacuum or fire.” The more water over a creature the greater the weight pressing down on him. A one-foot cube of water weighs over 60 pounds, so man or beast does not have to go very deep to encounter crushing forces. For every 33 feet a fish or skin diver descends the pressure increases almost 15 pounds per square inch. Creatures living at 330 feet must withstand 150 pounds of pressure per square inch of body surface; at 3,300 feet this increases to 1,500 pounds, and anything living in the deepest parts of the ocean—33,GOO- 36, 000 feet—would have to survive 7½ tons pushing down on every square inch of its body.
Can animals live at such forbidding depths and, if so, how do they keep from being squeezed to jelly?
On 15 October 1950, a modern Challenger, the Galathea, left Copenhagen, Denmark, on a globe-girdling voyage to find out if life could exist in the basement of the world. By July of the following year, the research vessel had reached a deep gash in the ocean floor east of the Philippines and scientists swung a huge sled trawl over the ship’s sleek yachtlike sides. When it was brought back to the surface some 12 hours later, anxious fingers picked out 25 anemones, 75 sea cucumbers, five clams, and a bristle worm. Subsequent trawls revealed a whole community of animals,—polyps, worms, echinoderms, mollusks, and crustaceans—living at 33,431 feet.
This amazing find pushed the known limits of life 7,500 feet further into the abyss. Eight and a half years later, the limit of life was extended to the bottom of the world. Jacques Piccard and Lieutenant Don Walsh, U. S. Navy, spotted a sole-like fish and a bright red shrimp from the window of the bathyscaph Trieste 35,800 feet down in the Pacific’s Marianas Trench. In the same trench, the Soviet Union’s research ship Vitiaz later sounded the deepest part of the World Ocean —36,200 feet.
Because their tissues are permeated by fluids at the same pressure as the water surrounding them, creatures living at such depths take no more notice of the overlying water than we do of the ocean of air at the bottom of which we live. In both cases, pressure inside the body pushes outward with the same force as the air or water pushing inward.
Some creatures, like clams, snails, or sea cucumbers tolerate enormous differences in pressure, and range from the seashore to the abyss. One brittle star evidently feels equally at home at 15 or 15,000 feet. But these are a minority. Most shallow water creatures suffer irreparable damage when placed under high pressure. Therefore, we must assume pressure is a limiting factor and something which animals must adapt to before they can live in the depths. That shallow and deep species are fundamentally different has been demonstrated by some bacteria dredged from below 33,000 feet by Galathea scientists. Dr. Claude E. Zobell discovered that “germs,” so small that a period on this page would cover thousands of them, reproduce more rapidly at the high pressures and low temperatures of their habitat than they would at milder surface conditions.
A rich concentration of life exists around the thermocline where the warm, upper layers meet the cold, deeper waters. The late Dr. Anton F. Bruun, leader of the Galathea Expedition, believed this was because warmth- loving creatures are kept from going lower by the cold, and deep animals shrink from the higher temperature and perhaps also from the stronger light above this zone.
The upper layers are as deep as 1,600 feet in the tropics, about the depth where total darkness would begin for the human eye. Perhaps, then, so many animals congregate here because it is a good place to hide. Some deepdwelling fishes, however, have very sensitive eyes, so they must be able to see objects in what would be pitch blackness to human beings.
Photograph plates, much more sensitive than human eyes and perhaps fish eyes, have detected some glow as deep as 3,300 feet. The character of this light changes with depth. Sunshine (white light) is a combination of different colors (wave lengths) which have varying energies; therefore all colors do not penetrate to the same level. Red—least energetic—is absorbed first, followed by orange, yellow, green, and then blue.
This change of lighting with depth exerts a profound effect on the appearance of deep dwelling animals. In the well-lighted upper waters—down to about 500 feet—a transparent or blue-green livery is best to help a beast escape notice.
The upper twilight zone—between 500 and 1,600 feet—is the domain of the silvery fishes. Faint shadows are still cast in the dim, bluish light so counter-shading (dark backs and light bellies) has the same survival value as nearer the surface. Finger-long lantern and hatchet fishes have silvery, grayish or iridescent flanks and bellies combined with brownish backs.
Living in the dimmer light below and coming up to prey on these fishes are jet black, velvety brown, and unshaded silvery species. Some possess iridescent skins that gleam golden, copper, and green. Invertebrates cloaked in deep red, purple, and brown share the night zone below 1,600 feet. Scarlet shrimps snap up crimson worms and reddish corepods, bright red jelly fish float gracefully by in the blackness, while red, violet and black squid dart nervously to and fro in search of prey.
No one knows why the boneless beasts, especially crustaceans, wear such blushing livery while the fishes prefer somber blacks and browns. Such colorful attire seems a waste, since red rays do not penetrate this far, and the beasts appear gray or black to other animals. Thus, what would be a gaudy and conspicuous wardrobe in sunlit waters must have a concealing effect in the twilight. But why not just wear brown or black like the fishes?
Crustaceans are as numerous and important in the deep as in near-surface waters, scarlet or blood-red shrimps and prawns being the most characteristic members of the group. Some reach a foot in length and have strong swimming limbs. These are capable of pouncing on small black Cyclothone fish like a cat on a mouse. One jumbo shrimp was found with a two-inch fish filling its stomach. Larger fish anticipating a luscious shrimp cocktail are sometimes met with an explosion of liquid fire as an Acanthephyra shrimp discharges a blinding luminescent smoke screen into their faces.
One squid ejects a slimy secretion that turns into a luminous blue cloud on contact with water. In the darkness this sudden burst of brilliant light has the same effect as a cloud of dark ink does in sunlit waters.
Dressed in sinister cloaks of dark red, black, and deep purple, squids have been brought up from 11,500 feet and one octopus, Grimpoteuthis, lives on the icy 9,000-foot bottom of Antarctica’s Weddell Sea—the coldest part of the World Ocean. Here in grave-like cold and darkness, Grimpoteuthis slithers over the siliceous “headstones” of billions of diatoms.
In warmer water from about 3,000 to 10,000 feet lives a true little demon of the deep, and a living fossil to boot—a beast once described by William Beebe as “a very small but very terrible octopus, black as night, with ivory white jaws and blood-red eyes . . . its cupped arms all joined together by an ebony web.” Scientists have given it a name as terrible as its appearance—Vampiroteuthis injernalis. Actually infernalis is neither octopus nor squid, but a ten-armed survivor of a once- large band of cephalopods that disappeared millions of years ago. Two of its arms are long, worm-like feelers which coil up in special pockets. Although the “vampire squid” spends all of its life in darkness or in the faintest of green light, this rare, velvety black beast has large, keen eyes. Perhaps it uses them to spot the living lights of other night creatures, such as those scattered over the body and fins of its brothers and sisters.
Roaming the same levels as infernalis is another antique cephalopod called Spirula spirula. To go with its tamer name, this little squid has a much less ferocious appearance. It swims upside down along the steep sides of the warm ocean basins, its fringe of short, thick arms dangling downward and its small, jar-like white and rust-spotted body buoyed up by a curious gas-filled skeleton. A limey spiral in its posterior end contains 25 to 37 gas-filled chambers, and Spirula probably regulates its depth by varing the amount of gas in the last open chamber. This marine balloonist is the only living member of a tribe that flourished 125 million years ago. One individual was the prize catch of the Challenger, whose scientists anxiously searched every net for a ghost of the past. But, alas, even the best naturalists of that day did not recognize Spirula’s ancient ancestry.
Although “the stuff of which legends are made,” infernalis, Spirula, and others, do not measure up to such gigantic monsters of magazines and movies as the two-ton rubber squid that required 24 men to manipulate in Walt Disney’s 20,000 Leagues Under the Sea. No Vampyroteuthis found was longer than 8| inches. Spirula is usually three inches long including its tentacles, and a deep cephalopod longer than one or two feet becomes a rarity. Although some crustaceans reach gargantuan size, no deep-dwelling fish or squid grows very big. One zoologist, in fact christened them the “Lilliputian fauna.” Professor C. P. Idyll comments in his book Abyss: “If a group of surrealist artists had engaged in a contest to see which could create the most grotesque and improbable monstrosities, surely they could not have approached the astonishing shapes exhibited by the fishes of the deep ocean. . . . And then having had the audacity to invent such creatures, which of our competing surrealists would have had the imaginativeness to reduce the monsters to diminutive size, making them objects not of awe but of absurdity?”
But small size does not mean small appetite. Equipped with huge mouths and expandable stomachs, somber gulpers and swallowers living in the gloom below 5,000 feet can engulf meals as big as or even bigger than themselves. Their jawbones form a system of hinged levers which permit the mouth to gape open like a living cave. The stalactites and stalagmites of these caves are dagger-like teeth, some of which bend inward to permit the easy entrance of prey. The rubbery stomachs at the end of the caverns expand to several times their normal size. One captured big mouth had a nine-inch cod-like fish in its stomach, although its own body was only six inches long.
Gulpers sometimes attain the comparatively enormous size of six feet but most of this length may be a long rope-like tail. One species has a red light on the end of its tail which attracts victims. When the prey gets close enough, the tail whips around it and the surprised beast is passed, struggling, into an enormous mouth. Another odd member of this improbable group, Eurypharynx Pelecanoides or “pelican mouth,” is a two-foot long, flabby bag of mouth and tail found in all warm oceans. Lacking strong bones and muscles, it sinks long, curved teeth into a victim then draws itself over the body like a snake.
The swallowers take even greedier mouthfuls. Toothy, black Chiasmodus niger never grows longer than six inches but it swallows fish eight or ten inches in length. One finger- length individual was found with an eye staring through its grotesquely distended stomach; the eye belonged to an unfortunate member of its own species that was twice as long as the swallower.
Such eating equipment comes in handy in the deep where meals are few and far between. The diner must accommodate itself to whatever food comes along and the bigger the mouthful the longer the hunger pains stay away. But unlike snakes and humans, gulpers do not become lazy and sluggish after a big meal. “Quiescence is impossible in the depths,” so the search for food must begin again at once.
Another diverse piscian group characterized by trap-door mouths, runt size, and “rubber” stomachs, are the soft-finned stomiatoids. One stomiatoid is probably the most common fish in the sea, possibly exceeding even the multitudinous herrings, sardines, and menhaden in numbers. Called Cyclothone elongata or “bristlemouth,” the minnowsized fish lives at mid-depths and is seldom seen by anyone except scientists. This rapacious creature and its cousins look like “normal” fish except for big heads and a mouth, full of bristle-like teeth, that drops open like a trap door. If economical deep-water fishing gear could be developed, bristlemouths might be caught and canned like anchovies or serve as the base of fish protein concentrate (fish flour) to help alleviate the cruel grip hunger holds on half the world.
On bathyscaph dives off San Diego, Dr. Eric G. Barham spotted concentrations of siphonophores lying motionless between 850 and 1,450 feet, their long tentacles stretched out in all direction like “a living net.” He has repeatedly seen concentrations of two-inch fish between 1,650 and 11,000 feet, and on one dive spotted so many shrimp between 1,200 and 1,500 feet he could not count them. In the next 200 feet were a large number of lantern fish; then, between 2,150 and 2,300 feet, Barham encountered the greatest concentration of fish on any dive.
The famous aquanaut and aqua-lung pioneer Jacques-Yves Cousteau never had such good luck sighting creatures. He always keeps a sharp lookout when descending but never has viewed any exceptional increase in life. He did, however, fall through a submarine snowfall that became thicker as he dove deeper. Five other bathynauts, including Beebe and R. S. Dietz observed the same thing. Cousteau concluded: “So far as we can see, there is, biologically speaking, no DSL, but rather a great bowl of living soup . . . growing thicker and deeper into the ‘tureen’ we go.” The French undersea explorer thought the “snowflakes” were living animals, but Professor A. C. Hardy suggested they were mostly dead material such as the slowly sinking shells of moulting crustaceans and armored plankters. But they both, along with others, agreed that the long-accepted notion of the ocean population thinning out with increasing depth and pressure had received “something of a shock.” Cousteau guessed “there must be somewhere an unsuspected link in the cycle of marine life yet to be discovered,” and Hardy commented, “We must keep our minds open for some startling new discovery.”
This discovery was made by three Americans in 1964. Drs. Gordon Riley, E. R. Baylor, and W. H. Sutcliffe proved that organic material dissolved in the oceans could come out of solution by sticking to air bubbles and build up to bite-sized blobs that would be used as food by the smallest deep dwellers. Riley believes the mysterious undersea snowfalls consist of just such blobs. According to him they form a “population of edible matter more stable than living plants and animals.”
It was always known that the oceans contain dissolved and particulate organic matter in amounts exceeding that which is built into living animals. But this was thought to be unavailable as food until bacteria broke it down into minerals which plants could take in. Now the laboratory experiments of Riley and his colleagues have revealed that this organic material can be reconstituted and will collect as a film on air bubbles, building up to larger clumps as they sink deeper. To perpetually hungry animals living in the cold night zone these shapeless clumps must look like manna from heaven. Riley says this bubble food decreases with depth for the first 1,500 feet, then a steady level is maintained by new organic matter created at all depths.
This remarkable discovery of a vast, unsuspected food supply after a century of ocean research, solves the vexing problem of how deep zoo-plankters survive. Scientists long doubted that the slow rain of dead and dying organisms escaping through the many waiting mouths above was enough to sustain deeper creatures. About nine-tenths of the slowly sinking plants are devoured in the upper 600 feet or so. And as Anton Bruun pointed out, “dead organisms are as rare a sight in the sea as they are on land. Sick or weak animals fall prey to stronger enemies and are devoured; at most, a large whale or giant shark might sink to the bottom without being completely eaten.”
Ghosts of the Past. The Russian research ship Vitiaz, which, since 1953, has taken up where Galathea left off, dredged almost 2,000 specimens of an interesting creature recently “discovered” by science from 29,500 feet in the Kurile Trench of the northwest Pacific. In the 1920s, these “gubbins” were shoveled overboard by the ton, some of the best biologists of the day failing to recognize their status. But it is now known that these fibrous, insignificant-looking creatures represent an entirely new and major division of the animal kingdom on a par with vertebrates, mollusks, and arthropods. This left zoologists who were certain they knew all the major groups of animals on earth somewhat aghast. As Dr. Libbie Hyman, the distinguished American zoologist, remarked: “The finding of an entirely new phylum of animals in the 20th century is certainly astounding.”
The phylum has been named Pogonophora or “beard-bearers.” Once scientists started looking for these beasts instead of throwing them overboard, they found over 80 species inhabiting all seas from shallows to 33,000 feet, but mostly from below 6,500. Anchored to the bottom in an enclosed vertical tube of their own making, these remarkable animals are as thin as a piece of string and as long as five feet. The “beard” is a plume of hairy tentacles which the bearer retracts into its chitinous tube when in danger or pushes out the top when feeding. What puts them in a group by themselves is the fact that they have no viscera. A simple brain, nervous system, sex, a heart and red blood—yes; but stomach, intestines, anus or mouth—no. Vibration of tiny hairs drives water into the hollow tentacles and both oxygen and nourishment are extracted from it.
In a primitive way, the organ arrangement of beard-bearers bears a similarity to that of vertebrates, and they are related to echinoderms, sea squirts, acorn worms and Amphioxus—the fishlike lancelet. Because these wormy ones fit into the unknown area between invertebrates and vertebrates, zoologists believe that an intense study of them will solve some of the most perplexing mysteries of evolution.
The deep sea continues to yield additional clues to these mysteries—pieces of the evolutionary jig-saw puzzle. Near the end of their cruise, Galathea fishermen found ten live specimens of a remarkable limpet-like mollusk. They were imbedded in dark, muddy clay dredged up from 11,878 feet off the Pacific coast of Costa Rica. Each creature lives in a fragile, spoon-shaped shell ½ inches long and f-inch high. Pale yellowish in color, the oval shell resembles a flat night cap with a low peak at the front end that tilts forward. The animal probably eats mud and slides along on the large bluish-pink foot which fills the bottom of the shell. The foot is surrounded by five pairs of primitive gills.
Despite careful examination scientists could not place Neopilina galathea, as it came to be called, into any classification pigeonhole. The beast resembles none of the modern mollusks, neither limpet, clam nor snail. Its closest look-alike is a make-believe beast put together by paleontologists—their idea of the molluscan ancestor from which evolved chitons, clams, snails and squid. Scientists thought such a creature had become extinct 350 million years ago, but so close was the similarity, Neopilina could have been used as a model for constructing the ancient ancestor. The discovery so startled the two biologists entrusted with publishing its description that they hesitated from 1952 to 1957 before announcing that an important living fossil had been found.
Neopilina turned out to be an evolutionary link, tying together worms and mollusks. Its gill region has segments similar to those of annelid worms, dispelling any doubt that clams and kin evolved from ancients much like the familiar earthworm. Neopilina’s lopsided shell and horny rasping “teeth” are proof of its relationship to snails and cephalo- pods.
As with the coelacanth, one catch was soon followed by others. Dr. Robert J. Menzies, reporting on a second find at a depth of 19,150 feet in a trench off northern Peru, wrote, “The discovery suggests that more relic types may exist alive in the deep sea off Central and South America.” He fulfilled his own prediction in December 1960 by recovering 14 small Neopilinas from the 9,000-foot deep slope of the Cedros Trench off Lower California.
Together with the coelacanth Latimeria, upside-down Spirula, the fearsome vampire squid and others, Neopilina seems to argue pretty strongly for the idea that the deep sea is full of fossils. But these spectacular catches are an exception rather than the rule, and no serious scientist believes they justify the conclusion that the night zone is full of missing creatures that will link together all living animals and those ancients that we know only from their stony remains.
Probably during every geologic age, some creatures withdrew from the populous shallows into the dark depths to escape powerful enemies and those with whom they could not compete for the same food. After gradually adapting to increased pressures, such individuals would change very little because of stable or very slowly changing conditions in the deep. With little opportunity or necessity to change, the slow hand of evolution would be all but stilled.
Such living fossils undoubtedly exist at all depths (Latimeria was found at 230 feet, Neopilina at 19,000). Whether there are more in the shallows or in the abyss is something scientists still argue about, sometimes heatedly. The debate will be settled only as the watery Hades, dark abyss, and twilight zone yield their secrets to net, camera, and hydrospace ships. Ocean biologists are ever on the alert for more beard-bearers and Neopilinas. Always there is great excitement and quickened pulses when the nets come up from the hidden corners of the world’s basement. For who knows what new creatures the sea will give up for the first time to delight the eye and stimulate the intellect of man?