INVIABLE HYBRIDS OF CRASSOSTREA-VIRGINICA (GMELIN) WITH C-RIVULARIS (GOULD) AND C-GIGAS (THUNBERG)

Interspecific hybridization may provide important tools for selective breeding programs in oyster culture, especially for enhancement of disease resistance, and may have a bearing on debates concerning the introduction of non-native species. Factorial crosses of C. virginica with C. rivularis (C. arakiensis) and C. gigas were made, producing control and hybrid larvae. Larval survival and growth were documented. After several replicated experiments it became apparent that diploid hybrids were inviable, and so triploid hybrids were also tested and found to be equally inviable. Feeding studies with hybrids were initiated to determine if lack of growth and viability were related to capture of food. Overall, hybrids of C. virginica with C. rivularis and C. gigas can be readily produced, but are inviable after 8-10 days and grow little. With regard to the species examined here, previous reports of successful hybridization should be questioned. Introduction of C. gigas to the native range of C. virginica will not have direct genetic effects on C. virginica.