FISHES THAT LIVE OUT OF WATER.

Otago Daily Times, Issue 18446, 6 January 1922, Page 10

FISHES THAT LIVE OUT OF WATER.

, SOME MORE MISSING LINKS DT EVOLUTION, To call a man who is out of place “a fish out of water” ia insular arid unscientific, in fact mediaeval. Tho riiodern survey of Nature has discovered a score ot species of fishes which can live out of water. When it was first known' that all life was in the ocean, during at least half the story of life on the earth, many wondered how tho evolutionist was. going to start the story of land-life. Already, however, the naturalist was supplying the missing links, and to-day we nave no difficulty. There have ’ been Europeans in India and the islands of the Indian Ocean for a couple of centuries; but in the early days they were too busy making money to study the wonders of life in that region. There is, for instance, a wonderful fish called the Climbing Perch which prevents any Anglo-Indian from calling a man a fish out of water. Climbing Trees.— * , You may, on a hot summer’s day, meet a company of these fishes strolling—rather clumsily—across the fields. Their pool has dried up, and they seek a “better ’ole.” They can live for a day or two out ol water, because they ' hbve _ a special chamber in the head for assisting their breathing out of water. Early observers claim that they climb trees occasionally, and even their scientific name (Annabas scandens) sanctions this, but the' evidence is not. very good. . f There is, Jiowever, another fish in tropical Asia and Africa which undoubtedly does a little climbing. The bommi, as natives call it, remains on the shore when the tide goes out, hunting whatever the waters have left behind. Its breastfins are bent like elbow-joints, and are very strong, and by means of theese it. skips or "jumps about the shore. A close observer will, however, notice that it is very apt to retire speedily to a little pool and dip its tail JJjerein. It has a supplementary breathing aparatus in its toil, and it may remain a Iqng time resting on a stone with its tail 'in the water, its great goggle eyes staring round for some small victim. Living in Two Worlds. — These are what we may call crude experiments in the power of living in two worlds. There are, however, many kinds of fishes with lungs as well as gills, and these show us best how, ages ago, part of the poulation left the over-crowded ocean and began the story of life on land. Wo do not think to-dav that these are actual survivors of tho first fish eh to leave the land, but they are relics of a large population which at one time more or less developed the power of living on land. . Tho best known is tho "Burnett Salmon,” as it is popularly called, of Queensland, There is, of course, no salmon in Australia, but the “digger” has a facetious way of giving, aristocratic British names to native things, and more than one British politician has fallen into the trap and marvelled at the: cheapness of “salmon” in Australia. The Ceratodus is a coarser fish, but it is one of the marvels 6f Nature. It has a lung, as well as gills. , The Queensland ono-lunger is not pro-, perly called a "mud-fish.” It never lives in the dry mud when a stream ceases to' flow. In the Burnett and Mary Rivers it lingers in the pools at the bottom of the water, and the water never entirely disappears. It may, however, become so low and foul in the summer that _ every other typo of fish will be killed, while the Ceratodus suffers no more inconvenience than a sewage-man in a crowded Tube. It just rises to the surface now and again, qnd “spouts” like a miniature whale. Then" it fills its one lung with air, and sinks again Ito the bottom. ; V Two Lungs.-i-Bnt there is a cousip of Ceratodus, found over; the greater part of Africa, which lives entirely out of water during about six months of the year. It has two lungs in addition to gills. As a rule it is found in the marshes near tho rivers. For half the year it gorges on frogs and worms and other delicacies, for it must live on its fat during the long “summer sleep.” Its fins are really limbs. They are useless as paddles, and at the bottom of the watep 1 . Tho tail is the propeller. When the dry seaaoff Somes’ the fish bores down about 18 inches into the mud, coils' itself up, and wraps itself in a sort of cocoon made of mucus from its skin. Above its head it mhkes a sort of lid, to keep out the inquisitive, arsl it even has the remarkable instinct to make small holes in the lid to let the air through. So it remains sleeping for months, breathing entirely by its lungs. We riow know that these lung-fishes use, their lungs, even during' tho wet period, in addition 'to their gills. —Walking on Their Fins.— Still more advanced are certain fishes of Brazil. In 'an aquarium they will walk on their fins (which are really limbs) to take bread from the hand of the -keeper. Even in the water it does not swim, but wriggles like an eel, its limbs moving like those of X biped. Like its African cousin it spends the _ dry season asleep in a burrow which it hollows out in the mnd. It carefully closes the-tube with a plug of clay, through which it bores airpassages. At the return of the waters it pushes out the plug and gaily returns to its feeding. Both the African and American lung-fishes lay their eggs_ in nests; and they have the further distinction that it is the papa who guards the eggs and the babies .while mother disports herself. ■ ■ The development of these lungs is simpler than the inexpert would think. All the higher fishes have air-bladders in their bodies. They are submarines, and need to alter the weight of the body by com-' pressing or enlarging this air-bladder. Th 6 lungs are adaptations of the air-bladder, which is often double; and connected with tho gullet.—John o’ London Weekly.