WAYS OF THE WILD.

Auckland Star, Volume LXVI, Issue 260, 2 November 1935, Page 1 (Supplement)

WAYS OF THE WILD.

SALAMANDERS. NOT REPTILES, RELATED TO FROG AND TOAD. (By A. T. PYCROFT.) The salamanders have, like lizacds, an elongated body, four feet, and a long tail, but are destitute of scales, and are not reptiles but amphibians. They ar« related to the frog and toad, and Tike them pass through two distinct life stages after hatching out of the egg, the larval or tadpole and adult. Lizards are reptiles and show their relationship to -the snake, the turtle and the alligator in numerous characteristics, particularly in the absence of a larval stage in their development. Lizards are hatched as miniature adults. Salamanders represent a crucial stage in the evolutionary development of the higher back-boned animals. The amphibians became the masters of the earth, the dominant form of life in the coal forests of the carboniferous period. And only after millions of years did they give ground to the larger and apparently better adapted reptiles. The salamanders living to-day represent merely a remnant of their fossil ancestors. All salamanders have a moist, glandular and scalelcsa skin, whereas all lizards are scaled, their skin being hard and dry.

Salamanders require moisture to live, frequent springs, wet moss and bark or the damp earth under boards and stones. Lizards, on the contrary, avoid water, and are found most often in dry, sandy places, or clambering up the trunk or branches of trees, seeking a spot where they can bask undisturbed in the sun. A knowledge of the habits of salamanders explains the first paradox that their name suggests. That is the relation between the superstitious belief in the salamander as an animal born of fire, and its known aversion to anything hot and dry. For centuries past peasants and nobles alike have been startled by seeing this creature come crawling out of the fire as they threw logs onto the blazing hearth. That they actually saw salamanders is not doubted, but their assumption that the salamander made its home in the fire, and that it could withstand heat was erroneous. Obviously, the salamanders had hidden themselves under the bark of the log or in the dark dampness of its crannies whilst it lay in the forest, and thus were brought indoors as wood was gathered. When placed in the fireplace, they were driven out by the heat, which was no more pleasant for the salamander than, it would be for a human being.

The World's Largest Amphibian. The living giant, salamander was first discovered in the rivers of Japan in 1820. , The ordinary length of this salamander is about 3ft, but some have attained a length of at least 4ft. _ It is also found in western central China. Except in search of food, which consists of worms,, crustaceans, fishes and frogs, these, amphibians do not leave their hiding places, which are round masses of rock in the bed of streams and then only at night, and they never venture on land. Another group includes the gilled mud-puppy, which may be thought of as a permanent larva, although it becomes sexually mature and reproduces. This peculiar condition is called neotony, and is explained by the conjecture that the adult stage has been lost during geological history, the larval stage assuming the reproductive function. Scarcely less remarkable than these permanent larvae are those salamanders which develop on land and so require the passage of the whole larval life within the egg. Another amphibian, the New Zealand frog, liopelma, also develops on land and passes its larval life within the egg; in other words the tadpole stage is passed within the egg. Some salamanders shun the light to such an extent that they have lost the use of their eyes. One American blind cave-dwelling salamander is characterised by translucent skin, which is practically without pigmentation. Strangely enough the larvae of this species densely pigmented and have well-developed eyes. A number of destructive changes accompany the change from the tadpole to the adult; the eyeballs withdraw somewhat into the head, the retina' degenerates and the eyelids fuse together, although the dark eyeballs still show through them. Laboratory experiments have demonstrated the amazing fact that individuals undergoing the change from the tadpole to the adult stage retained serviceable eyes. The lids never fused, nor did the retina degenerate. On the contrary the eyes developed more fully. "Further, these individuals were distinctly darker than those which transformed in darkness. These investigations show that the apparently unfavourable cave environment has produced no permanent effect on the eyes or colouration of this salamander, for, while this loss of sight has occurred in every generation, perhaps for centuries, there is no .evidence of this environmental effect becoming inherited.

I Courtship and Breeding Habits.* i The breeding habits of salamanders I are often extraordinary in character. There is usually a well-defined courtship of the female by the male, after which the male deposits a spermatophore, a gelatinous-stalked sac of sperm cells which is later taken into the cloaca of the female, fertilisation of the eggs ensuing. Unfortunately the details of breeding are rarely witnessed. The habits of the terrestrial species are very incompletely known. The pondbreeding salamanders offer the greatest opportunity for observation. The courtship commences by the males,* which are about as numerous as the females, prodding and rubbing them with their heads. Egg-layin? usually occurs durinsr the second night following. A visit to a pond on such a night would reveal dozens of female salamanders clasping overhanging branches in the water or clinging to the stems of dead water plants. Many individuals may he laying eggs at one time on the branches of a single water plant. One female may produce three hundred eggs, although* half that number is more nearly the averase. The eggs normally are deposited in masses of 10 to 40, with an average of about 20. They are within a gelatinous mass which is quite small at the moment of deposition, but within a few hours jfc absorbs a large quantity of wafer and fuses with other masses adhering to the same branch. The larvae, which need no guardian, develop rapidly, hatchins: from the ego' capsule at the end of four weeks. Thev are equipped with external trills, broad bodies and tail fins, in addition they have a curious pair of rod-like balancing organs. wh>h are formed even before the legs. The Icts soon anpear. however, the front limbs developing first.