GENETIC CONFIRMATION OF HYBRIDIZATION BETWEEN CRASSOSTREA-GIGAS (THUNBERG) AND CRASSOSTREA-RIVULARIS (GOULD)

Of the numerous reports of hybridization attempts in the genus Crassostrea, none has been confirmed genetically. Three replicates of a 2 x 2 factorial mating of Crassostrea gigas x C. rivularis (C. arakiensis) were produced to examine the viability of this cross. Fertilization rate, yield of 48-h-old larvae, and survival of fertilized eggs was lower in the hybrids than pure crosses. All crosses showed similar larval growth rates, except C. rivularis x C. gigas, which grew more slowly. Genetic control of eyed larval size was indicated by the intermediate size of hybrids compared to pure crosses. Spat were obtained from most cultures and were shown by protein electrophoresis to be hybrids. Contaminants were also present, underscoring the need for genetic confirmation in studies on bivalve hybridization.