Triploid and diploid interspecific and conspecific crosses between the Pacific oyster, Crassostrea gigas (Thunberg), and either Crassostrea virginica (Gmelin) or Crassostrea rivularis (Gould)

Previous studies demonstrated that some fish and amphibian hybrid crosses that were inviable as diploids proved viable as triploids. It appeared that the extra set of chromosomes allowed the hybrid offspring to overcome genetic incompatibility. This study examined the potential for using this technique on oyster crosses between C. gigas and either C. rivularis or C. virginica.; G/R interspecific crosses demonstrated a consistent gametic incompatibility, while some interspecific G/V crosses survived at diploid conspecific levels. Interspecific G/R larvae then survived and developed normally. In contrast, it appeared that all of the interspecific G/V larvae stopped developing at the veliger stage. Triploidy was successfully induced in the interspecific G/R and G/V crosses, but it reduced initial survival in all of the crosses.; Bay temperature and productivity affected growth, glycogen utilization, and gametogenesis. GG oysters develop smaller gonads in colder bays and therefore continue to grow during gametogenesis, which in this case eliminated the growth advantage of GGG oysters. The retarded sexual development of GGG still led to significantly higher levels of glycogen than GG oysters.; C. rivularis and C. gigas showed similar timing in their glycogen utilization, but there were differences in their glycogen storage. RR and RRR (30%) utilized less of their reserves than GG (45%), but more than GGG (20%). Glycogen profiles for RRR and RR were not different: this result is the first time that triploids of a molluscan species did not maintain significantly higher nutritive reserves than their diploid cohorts. Glycogen profiles for GGG and RR were similar, but there were two differences: RR maintained a consistently higher glycogen reserve and utilized more of its reserve than GGG did.; Although the hybrids were to some extent intermediate between the two parents for most of the characteristics monitored, they consistently performed closer to GG or GGG than to RR or RRR. For example, GR had a glycogen profile intermediate between the parental species, but closer to GG than to RR because its follicle development was more similar to GG.; The interspecific triploid crosses did not show aquaculture potential. (Abstract shortened by UMI.)...