Influence du complexe céphalique (tentacules oculairescerveau) sur l'évolution, en culture in vitro, de gonades infantiles et juvéniles d' Arion subfuscus Drap. (Gastéropode Pulmoné)

Abstract

Infantile gonads (obtained from animals 8 to 10 days old, i.e., at the earliest postembryonic stage, the genital gland then containing no oocyte) and juvenile ovotestes (taken at stage 2, characterized by the appearance of oocytes) were kept in culture for 3 weeks on G 2 medium, alone or in association with either autologous or heterologous brain-tentacles complexes (taken from slugs in the female phase) or in presence of homologous or heterologous extracts (from organs extirpated from adults in the late male or in the female phase of their gonadal cycle) of one of the three following types: tentacular, cerebral, or mixed. Our results indicate that: (1) when cultured in isolation, in a medium devoid of hormone, there is a tendency for an infantile or juvenile gonad to progress toward the female line; (2) the cephalic complex promotes maintenance of the male line; (3) the optic tentacles exert an inhibiting influence on the female differentiation during the infantile and the juvenile stages but are ineffective during the female phase; (4) the brain favors oocyte growth, more specially in adults of late male and female phase. Thus, this series of cultures provides new evidence for the role of the cephalic complex in sex expression of Arion subfuscus. The results agree with those from earlier in vivo experiments with respect to the role of the optic tentacles in sexual differentiation in slugs.