Mise en évidence du contrôle endocrine des différentes étapes de la spermatogenèse chez l'ecrevisse Pontastacus leptodactylus leptodactylus (eschscholtz, 1823) crustacé, décapode, reptantia

Abstract

Study of the testes of mature Pontastacus leptodactylus leptodactylus over 1 year, and particularly during the “resting” season, makes possible the identification of the primary cytological changes occurring at the beginning of the annual spermatogenetic cycle. Moreover, observations, together with experimental data, reveal the mechanisms that control the course and maintenance of spermatogenetic activity. Thus, in a crayfish, and for the first time in a crustacean, the nature of the endocrine agencies controlling the different steps in spermatogenesis have been established. The mesodermal tissue surrounding the primary gonia inhibits the initiation of gametogenesis, as in Malacostracans with a germinative zone; its disappearance leads to the transformation of the primary gonia into secondary gonia and this can be experimentally induced by eyestalk ablation. Meiosis normally takes place in summer and its initiation appears to be controlled by a male factor originating in the brain; its complete achievement can take place only when there has been an increased synthesis of RNA in the secondary gonia; the androgenic hormone seems to be responsible for mediating this. The annual cycle of crayfish spermatogenesis is timed mainly by the existence of two “blocking” stages. The first of these occurs during winter and is mediated by the mesodermal cells; the second, which prevents the evolution of the secondary spermatogonia into primary spermatocytes, lasts until the end of the summer.