NEWT (a corrupted form from "an evet" or "an effet," a term of Anglo-Saxon origin, still used in many parts of England),. the name usually applied to the aquatic members of the family Salamandridae which constitute the genus Molge, formerly known as Triton. But the name Triton, applied to these Batrachians by N. Laurenti (1768), has already been used by Linnaeus (Systema Naturae) for parts of the barnacle (Lepas anatifera). B. Merem (1820) proposed to substitute for it the name Molge, said to be derived from the Gr. MOXyns or MOXyos, "slow," in allusion to the movements of these animals on land. The similar name Molch designates these Batrachians in German.
The newts are very closely related to the true Salamanders, Salamandra, from which they differ principally in the shape of the tail, which is compressed, in relation to their aquatic habits during a considerable part of the active period. Their aquatic progression is effected principally by means of the tail, and during the act of swimming the legs are turned backwards and folded against the body and tail, so as to admit of the smallest possible degree of resistance.
A very marked sexual dimorphism prevails in most species of this genus, the males being more brilliantly coloured than the females and provided with a dorsal crest which attains its greatest development during the breeding season; lasting through the spring and the early summer. Later in the season the males more or less completely lose their crests and other nuptial ornaments, and the two sexes are more alike; they then retire on land, concealing themselves under stones, logs of wood, or in holes in damp earth, but leaving their retreat at night or in wet weather to search for earth-worms and slugs which constitute their principal food. In the water they are very destructive of tadpoles, insect larvae and crustaceans.
A remarkable feature of the newts, which they share with the other tailed Batrachians and the larvae of the frogs and toads, is the great facility with which they regenerate lost parts, such as the tail, limbs, and even the eye, a faculty which has given rise to a great variety of experiments, from the days of Charles Bonnet and Spallanzani to those of the present school of Entwickelungsmechanik. Extraordinary as it may appear, considering the abundance of these creatures and the attention they have received from naturalists, it was only in 1880 that their mode of fecundation was correctly ascertained, from observation of the common newt by the Italian zoologist F. Gasco. The amorous games of the newts, so graphically represented by M. Rusconi, had been repeatedly described, and Abbe Spallanzani, as early as 1766, had ascertained the impregnation to be internal. The then current belief that the water served as a vehicle to convey the spermatozoa to the female organs had received a blow on Karl Theodor von Siebold's discovery of a receptaculum seminis in the female, but no satisfactory explanation had been given of the manner in which the spermatozoa reach these pouches. This mystery Gasco succeeded in elucidating in his masterly paper published in 1880, which has since been supplemented by his own investigations on the axolotl, and those of E. Zeller, E. O. Jordan and others on the European and American newts.
All who have kept newts in an aquarium have witnessed the curious antics of the male placing himself before the female and rapidly vibrating his folded tail, or bending his body in a semicircle, as if to prevent her from passing ahead of him. The male then emits, at short intervals, in front of the female, several conical or bell-shaped spermatophores (a gelatinous secretion from the cloaca), adhering to the ground and crowned by a spherical mass of spermatozoa, which the female afterwards gathers in the lips of her cloaca either by mere application or by holding the spermatophore between her hind legs and pressing the mass of spermatozoa into the cloaca, whence they ultimately find their way into the lower part of the oviducts, where the eggs are fecundated as they descend.
The larvae are provided with three pairs of long, fringed, plumelike external gills, which are not lost until the very last stages of the metamorphosis, and, in exceptional. cases are even retained throughout life, the newt breeding in the branchiate condition, as often happens in the axolotl. The fore limbs are developed before the hind limbs.
The genus Molge has a wide distribution, extending over Europe, north-west Africa, south-western Asia, eastern temperate Asia (China and Japan) and North America as far south as southern California and the Rio Grande del Norte. Twenty species are distinguished. The British species are the crested newt (M. cristata), the common newt (M. vulgaris) and the palmated newt (M. palmata). The first is the largest, and measures 4 to 6 in. The skin is more or less rugose, with granular warts, a strong fold extends across the throat, and the male is provided with a very high dentate dorsal crest which is interrupted over the sacral region; the upper parts are dark, with more or less distinct black spots; the sides are speckled with white, and the lower parts are yellow or orange, spotted or marbled with black; a silvery stripe adorns the side of the tail in the male. The common and the palmated newts are smaller, 2 to 4 in. in length, and have a smooth skin. The dorsal crest of the male is high and festooned in the former, low and straight-edged in the latter; during the breeding season the feet of the common newt are lobate like a grebe's, whilst they are webbed like a duck's in the palmated newt, which is further distinguished in having the tail truncate and terminating in a filament.
It is a remarkable fact that, although related so closely and occurring so frequently together in pools of small extent, the common and palmated newts are not known ever to produce hybrids, whilst the crested newt, when coexisting (in some parts of France) with a south-western ally, the beautiful Molge marmorata, to which it is by no means more nearly akin than are the two above-named species to each oth r, regularly gives rise to the form known as M. blasii, which has been proved to be a cross between M. cristata and M. marmorata. Principal references: G. A. Boulenger, Catalogue of Batrachia Gradientia s. Caudata (1882); J. de Bedriaga, Lurchfauna Europas, II. Urodela (1897); F. Gasco, "Sviluppo del Tritone alpestre," Ann. Mus. Geneva, xvi. (1880); E. Zeller, "Befruchtung bei den Urodelen," Z. Wiss. Zool. xlix. (1890) and li. (1891); M. Rusconi, Amours des Salamandres aquatiques (1821); W. Wolterstorff, "Ober Triton blasii," Zool. Jahrb., Syst., xix. p. 647 (1904).
- Please bookmark this page (add it to your favorites)
- If you wish to link to this page, you can do so by referring to the URL address below.
This page was last modified 29-SEP-18
Copyright © 2021 ITA all rights reserved.