Trophic Sources and Pathways to the Developing Gametes of Pecten Maximus (Bivalvia: Pectinidae)

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Ultrastructural, histological and histochemical studies were performed on the gonad of adult Pecten maximus at various intervals during the reproductive cycle in St Brieuc Bay, France, in order to understand better the sources and transfers of energy to developing gametes in scallops. In addition to the well-known pathways of energy acquisition through feeding and transfer of somatic reserves, a number of novel pathways were demonstrated. These were grouped into two categories: atretic recycling and intestinal loop transfer. Evidence is presented for the recovery of lytic material (resulting from gamete atresia) in the gonad acini, gonoducts, and integument; and the direct transfer of metabolites from the gonad intestinal loop to the developing gametes via vesicular cell-haemocyte couples, which appear to follow fibrous pathways within the loose connective tissue extending from the base of the intestinal epithelium to the acini. A schematic diagram summarizes the sources and transfer mechanisms of the energy exchanges involving the developing gametes in Pecten maximus.