1911 Encyclopædia Britannica/Alytes
|←Alypius (geographer)||1911 Encyclopædia Britannica, Volume 1
|See also Midwife toad and Common Midwife Toad on Wikipedia; and our 1911 Encyclopædia Britannica disclaimer.|
ALYTES, the midwife toad, first discovered by P. Demours in 1741, on the border of a small pond in the Jardin des Plantes, in the very act of parturition which has rendered it famous, and described as Petit crapaud mâle accoucheur de sa femelle. Alytes obstetricans is of special interest as the first known example of paternal solicitude in Batrachians, and although many no less wonderful cases of nursing instinct have since been revealed to us, it remains the only one among European forms.
Alytes obstetricans is a small toad-like Batrachian, two inches in length, of dull greyish coloration, plump form with warty skin and large eyes with vertical pupils. Although toad—like it is not really related to the toads proper, but belongs to the family Discoglossidae, characterized by a circular, adherent tongue, teeth in the upper jaw and on the palate, short but distinct ribs on the anterior vertebrae, and convex-concave vertebrae. It inhabits France, Belgium, Switzerland, Western Germany (eastwards to the Weser), Spain and Portugal. A second species, A. cisternasii, occurs in Spain and Portugal.
Alytes is nocturnal and slow in its movements. It is thoroughly terrestrial, selecting for its retreat in the daytime holes made by small mammals, or interstices between stones. Towards evening it reveals its presence by a clear whistling note, which has often been compared to the sound of a little bell, or to a chime when produced by numerous individuals. The breeding season lasts throughout spring and summer, and the female is able to spawn two, three or even four times in the year. Pairing and oviposition take place on land; the male seizes the female round the waist. The eggs are large and yellow, and produced in two rosary-like strings, as if strung together by elastic filaments continuous with the gelatinous capsules. After impregnation, the male twists them round his legs and returns to his usual retreat, going about at night in order to feed himself and to keep up the moisture of the eggs, even resorting to a short immersion in the water during exceptionally dry nights. The development of the embryo within the egg takes about three weeks. When the time for eclosion has come, the male enters the water with his burden; the larvae, in the full tadpole condition, measuring 14 to 17 millimetres, bite their way through their tough envelope, which is not abandoned by the father until all the young are liberated, and complete in the ordinary way their metamorphosis. The tadpoles grow to a large size considering that of the adult, the body equalling in size a sparrow's or even a small pigeon's egg, and they often remain more than a year in that condition.
See A. de l'Isle, “Mémoire sur les mœurs et l'accouchement de l'Alytes obstetricans,” Ann. Sci. Nat. (6) iii. 1876; G. A. Boulenger. Tailless Batrachians of Europe (Ray Society, 1897). (G. A. B.)