The influence of temperature on the thyroid gland of Chthonerpeton indistinctum (Gymnophiona, Amphibia).

The thyroid gland of the tropical amphibian Chthonerpeton is markedly stimulated when the animal is exposed for two days to relatively high temperatures (36 degrees C). Control animals were kept at 20 degrees C. The stimulated gland exhibits collapsed follicles and a very tall follicular epithelium. At the ultrastructural level the activated epithelial cells were characterized by an increased number of apical microvilli, increased amounts of rough endoplasmic reticulum, an extended Golgi apparatus and a high number of various granular and vesicular inclusions. These differences in histology and fine structure were not paralleled by quantitative results, which were approximately the same in both groups of animals. The values of these determinations were relatively high.