Role des neurohormones dans la différenciation sexuelle de Lampyris noctiluca

Abstract

Parabiosis and grafts have been attempted with Lampyris noctiluca to discover if there is endocrine control of the formation of apical tissue of the testes by neurosecretory cells. Parabiosis between young males and females of the fourth larval stage (stage of sexual differentiation) induces maleness in the female larva. This inversion is essentially due to the androgenic hormone produced by the testes of the male larva. Parabiosis between castrated fourth larval stage males and fourth larval stage females, decerebrated and allatocardiacotectomized, shows that the larval males are able to induce maleness in female ovaries. When parabiosis is performed, the apical tissue of the testes is not yet formed. Thus the androgenic secretion is not yet elaborated, and the two grafted animals are only under the influence of the male neuroendocrine complex. Consequently the masculinization of the ovaries can only be due to the action of the male brain hormones. In grafting experiments we have substituted the brain and the corpora cardiaca-corpora allata system of a male of the fourth larval stage for the neuroendocrine complex of a fifth larval stage female. In this case we have observed the masculinization of the ovary and specially the formation of the apical tissue which is peculiar to the testicular follicles. Indeed, as we have shown in previous work, these brain cells are characterized by a very intense activity during the formation of the apical tissue. In the grafting experiments too we observe this same high activity. In summary, these results seem to provide some further arguments in favour of an endocrine rôle of the neurosecretory brain cells in the formation of apical tissue in the tests.