Endocrinological and other factors influencing testis development in Rhodnius prolixus

Abstract

In Rhodnius, as in many insects, the testis undergoes a tremendous increase in size during late larval development. An histological study of this growth shows three clearly separable phenomena: production of spermatogonial cysts through synchronous division to a size of 27 cells per cyst; massive accumulation of spermatocytes (28 cells per cyst) during the late fourth and early fifth instar; production of spermatids and maturation of spermatozoa in the period from the fifth-larval blood meal to the adult. All of these processes continue in the adult.Germ-cell differentiation appears to be a sequential process, the spermatocyte stage being reached at 28 cells per cyst. Accumulation occurs as a result of the lengthy period of meiotic prophase maturation, but no specific inhibition of meiosis is evident. Spermiation during the diapause before the fifth-instar blood meal is prevented by specific autolysis of spermatid cysts. The application of a juvenile hormone analogue (FME) produces a dose-linked depression of spermatocyte meiosis, evidenced by a decline in the number of spermatid cysts. The spermatocyte-compartment level remains constant, indicating an equivalent depression of spermatogonial mitosis. Acceleration of division activity can be correlated with times of known ecdysone presence.