Effect of High Temperature on the Gonads of Frog Larvae.

Abstract

Frog larvae (R. sylvatica) which had been raised under nearly optimal conditions up to the 7th week were subjected after the 34th day to the maximal temperature they can endure permanently, i. e., 32° C. The gonads of both males and females grow much slower than those of normal controls. However, the spermatogonia of the testis are of about normal size and the seminiferous tubules differentiate in a typical way. The reactions of the ovaries are more complex and more important. At the time when the temperature was raised the ovaries contained large numbers of young ovocytes in the synapsis stage. Two weeks later this type of germ cells has completely disappeared. The ovogonia are still present and the deeper layers of the cortex contain now large auxocytes. The latter, however, are in way of degeneration. Their nucleoli are extremely large and basophilic and the ovoplasm contains coarse granules. During 2 more weeks the eggs disappear completely, the ovogonia being the only germ cells spared from degeneration.

Immediately after the differentiation of further ovocytes has come to an end, the medullary part of the ovaries starts to grow rapidly. Within a few weeks the ovarial sac (rete ovarii) transform into a typical rete testis, vasa efferentia and seminiferous tubules. At first the latter lack completely any germ cells. However, sooner or later the ovogonia migrate from the cortex to the medulla, and after having entered the seminiferous tubules transform into spermatogonia.

Thus the experiment leads to the total reversal of sex of the females. The normal controls consisted of 100 females and 96 males. The experimental group contained no typical females after the 2nd week of rise in temperature; but between the 15th and the 33rd day 53 females in different stages of sex transformation and 62 typical males were preserved.