SPERMATOGENESIS IN LARVAL TESTES OF DROSOPHILA-HYDEI, CULTURED INVIVO

Testes of the early and middle 3rd larval instar of D. hydei were cultured for a period of 1-8 wk in adult hosts of both sexes. During the culture period spermatogonia and primary spermatocytes passed through meiotic divisions and differentiated into late elongated spermatids. The latter were seen with normal ultrastructure, and in different stages of degeneration. Autoradiographic studies revealed a normal time course of spermatogenesis during the 1st wk of culture in the adult host; further culture led to a retardation in development. Measurements of the testes'' length and autoradiographic labeling showed that the gonads grew only slightly while cultured in the adult host. Testes size and spermatogenic activity were correlated such that the number of postmeiotic germ cell cysts increased with gonad volume. Spermatogenesis was more intense in testes cultured in females than in those cultured in males, and was favored in metamorphozing hosts as compared to adult flies. Optimal nutritive conditions of host flies evoked an increase in testis length and number of postmeiotic cysts formed, compared to those reared on standard food. The addition of exogenous .beta.-ecdysone stimulated spermatogenesis and somatic growth, especially at suboptimal nutritive conditions. Nutritive conditions and ecdysone level probably play a role in gonad development.