Histological changes in Xenopus laevis Daudin specimens kept under dry conditions, then moved back to their natural aquatic environment. I. Pituitary, thyroid and testis.

The histofunctional picture of the hypophysis, thyroid and testis was studied in Xenopus laevis specimens 1) kept in their natural aquatic environment; 2) gradually exposed to dehydration conditions under which they were kept one week; and 3) returned from the dry environment to water for 24 hr or 7 days. Of particular interest are the changes displayed in the hypophysis by type II acidophils, i.e. presumably prolactin producing cells. In the pituitary of "dry" animals and of those 24 hr after their replacement in water these cells appear numerous, large-sized and heavily stained whereas they are small and slightly stainable in the pituitary of control animals or of "dry" ones 7 days after their replacement in water. On the basis of these results it is surmised that prolactin is continuously synthesized and released into the circulation in Xenopus specimens kept or replaced in water, thereby contributing to the animals adaptation to the aquatic environment, whereas in those kept under waterless condition prolactin synthesis is not discontinued, but its release into the bloodstream declines or is abolished. In the testis of the animals kept in dry conditions or 24 hr after replacement in water, the germ cells do not seem to have undergone substantial changes, while the sudanophilic material, which can be detected in interstitial tissues in the animals kept in water, is lacking. In all groups the thyroid histofunctional pattern suggests an intense activity, particularly in control animals or in "dry" specimens 7 days after replacement into water.