Intraspecific variation in gametogenesis in two populations of the Chilean molluscan bivalve, Argopecten purpuratus (Lamarck)

An increased understanding of the general biology of Argopecten purpuratus (Lamarck) is necessary to produce successfully high quality larvae in hatcheries and to collect enough spat in situ for growth on long lines. In the present study, the reproductive cycles of two populations of A. purpuratus were examined, the Mejillones and Rinconada scallop banks, from 1989 to 1993. Calculation of the gonosomatic index and a complementary histological study of the gonad revealed differences between the two populations in their reproductive cycle as well as in the quantity of gamete emissions. The Rinconada population has a major spawning period occuring at the end of the year and lasting about three months. Minor spawnings also occur in early July to late September. In Mejillones individuals, only one major period of gametogenesis and spawning occurs. Gametogenesis begins in January and spawning occurs between February and March. This is followed by a period of quiescence lasting four to five weeks. These results suggest that the Mejillones individuals are a more appropriate source of genitors to be used for conditioning in hatcheries. Existing data on biometrics, particularly the dimensions of the adductor muscle, as well as enzyme polymorphism, suggest that the Rinconada population would be a more appropriate source of genitors to be used in future aquaculture attempts.