[Experimental studies on the sexual differentiation in some pectinid mollusc (Lamellibranchs) (author's transl)]

Histological studies on the gonadal morphogenesis of synchronic hermaphrodites (Pectenmaximus, Chlamys opercularis) has shown that it first appears an ovary from protogonia coming from the pericardial region and then moving into the distal part of the visceral mass. From this region, protogonia migrates into the middle and anterior part of the body and suddenly, when oogenesis has started into the ovary, give spermatogonia. In Chlamys opercularis and C. varia, an identical process of morphogenesis has been identified in adult animals during the stage of recovery which follows the period of sexual rest. Experimental studies carried out with organ culture (juvenile C. opercularis) suggest the existence of an ovarian autodifferentiation and the action of a masculinising factor coming from the cerebropleural ganglia. This acts over a short period allowing the differentiation of the spermatogonia. Very similar processes seen to be involved during the stage of recovery in the synchronic hermaphrodite C. opercularis or asynchronic C. varia.