THE LUNG FISH.

Auckland Star, Volume LXIX, Issue 282, 29 November 1938, Page 4

THE LUNG FISH.

SLEEPS FIVE YEARS. ITS EXTRAORDINARY ABILITIES A IJCVING FOSSIL. A fi-li thill ir- asphyxiated in water; th;tt liver- to l>o more than 100 years old; that buries itself in the mud, forme a cocoon and sleeps from one to five years; that ran exist without food by living on its own fat and liodv tissue*; that posse«-*e< lungs a* well a«s gills; that is literally "a living fossil," survivor of an incredibly ancient group that played an important part in evolution —these para, doxcri make the liinglish ( Protopterus) one of the iim-f remarkable, creatures in the wmld to-day. Once numerous in tho fre*h water* of the Palaeozoic continents 200,000.000 vears aim. now there are only three reprit-entatixet- left, one in Australia, one in Smith America and one ill Africa. The linii'fi.-h looks like an eel and lives much like any other lish except that it mint rise to the surface t-> breathe. But during tho annual dry iseason of \\\o tropics it demonstrates its extraordinary abilities. If it is trapped in a swamp l>y the recewioii of water, it burrows into the ground. As tho last wafer dries out. the fish rolls itself int>> a tight coil and to floe p. It cover* itself with a parchment-like cocoon of dried slime, secreted by its r-kin gluild«*. which completely eiivelojin tho body, ox. eept at the mouth. This prevent.* tho moisture, in the body from drying out.

In the hard dried mud it is as effectively imprisoned as though it were buried in cement. Asleep in Mud Nests. A number of encrusted luiislish have been dug out and shipped to various parts of the world in their blockts of mud. Some of these have been awakened by immersion in water and kept in aquariums for years. In New York a study was made by Dr. Homer Smith, who carefully cut away the mud nests of several specimens. The fish were in a state of profoundest sleep. They could I>e handled or kept for weeks without awakening: their sleep was like that of a very tired child, quite indifferent to the outside world. But they could be quickly awakened by putting them in water, as otherwise they would have suffocated through lack of air.

The thing about the. lunplish which makes it so important to the students of evolution is that it shows why limps became necessary and how they developed.

A couple of hundred million years apo. during the Ape. of Fishes, before vertebrate animals lived upon the earth, the climate was very dry. with only occasional rains. As a result the lakes and fresh-water ponds dried up or became, foul. Fishes trapped in these dirty pone's had to make greater and •jieater use of air unless they were to perish. Double Breathing Apparatus". Nature is quick to adapt itself to new conditions. Therefore, some of the Devonian* fishes developed a double breathing apparatus: lunps in addition to pills and a heart and cirolat '<■■■ ■■ adopted to breathing , both air and Wtitrr. During the ensuing miliums *>f \ — a> "Wind-living vertebrates evolved, Nature made use for them of the airbreathing apparatus which she already had invented for the Devonian fishes.

Although vestiges of lungs still exist in some of the higher fishes, for the most part they have let the air-breath-ing machinery* fall into disuse. But it has persisted in our friend the lungfish because the climatic conditions under which it lives to-day arc much like those of two hundred millions years ago. Thus, this "living fossil shows us how the vertebrates were enabled to live upon land with only auto breathe and how Nature set them free from an exclusively aquatic existence.