Effects of Light and Dark Environment on Weight Changes in Normal and Hypophysectomized Frogs

Abstract

It is a well established fact that the pituitary gland of the frog plays an important rôle in the dilatation and constriction of the melanophores in dark and light environments. It was shown by one of us 1 , 2 that injections of extracts of the posterior lobe of the pituitary gland produce a marked increase in water uptake in frogs as well as dilatation of the melanophores. Subsequently we became interested in the problem as to whether or not environmental background had any effect on the rate of weight changes in frogs kept constantly in water. The solution of this problem we feel, would help to determine whether the weight increase in frogs, resulting from the injection of pituitrin, is actually related to dilatation of the melanophores or to a more specific skin permeability.

Two sets of experiments were carried out. In the first, 3 different groups each containing 6 normal frogs, were removed from water, dried carefully with gauze, and then weighed accurately to 0.1 gm. They were then put back in water on a white background. Within 12 hours they had responded to this environmental change by becoming lighter in color, due to a contraction of melanophores. After 4 days in this environment they were again removed, dried, weighed, and then transferred to a black background to which they responded by a dilatation of melanophores, and where they remained for 4 more days. Following this they were transferred to a neutral background which consisted of a galvanized tank, for the same interval of time, and they were finally transferred back to the white background for the last 4 days of the experiment. Thus, each group of frogs was exposed to 4 different environmental backgrounds in 16 days with weights recorded between each change.