Abstract
A marked change in coloration occurs at the time of metamorphosis in most salamanders. We have obtained evidence that this change is not produced by the thyroid hormone in the case of red pigment formation. Thyroidectomized larvae of Hemidactylium scutatum will assume the red coloration of the adult although they do not metamorphose. 1 Larvae of the red salamander Pseudotriton ruber when precociously metamorphosed with thyroid extracts are yellow and not red. Since the anterior pituitary is known to play a part in normal metamorphosis we have tested the effect of anterior pituitary implants upon red salamanders which have been precociously metamorphosed with thyroid solutions.
Fifty larvae of Pseudotriton ruber, 30 to SO mm. in length, were metamorphosed in a solution of 1:15,000 desiccated thyroid. Before transformation was completed 7 of the largest specimens of the same size (Group A) were selected and each of 4 given subcutaneous implants of 2 pars anterior of toad pituitary. Three specimens received muscle, to serve as controls. The gland material was taken from freshly killed adult Bufo fowlerii, and given at regular intervals, 3 times a week. The salamanders, throughout the experiment, were kept without food, in separate dishes, at room temperature, with just enough spring water in the dish to keep the surfaces moist.
A few days later 5 fully metamorphosed salamanders of the series (Group B) were implanted in the same manner, 3 serving as experimental, 2 as control animals. At the same time 9 more specimens (Group C), also completely transformed, were implanted, but on a different schedule. The 5 experimentals were implanted twice a week, with 3 pars anterior each, the 4 controls with muscle. A fourth group (D), of 4 specimens, completely transformed, received implants of pars intermedia plus pars posterior.
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