Evaluation of advantages in the growth, survival and reproductive aspects of triploid hybrids derived from Crassostrea gigas tetraploids and C. ariakensis diploids in northern China

Abstract

Crossbreeding and polyploid breeding are two important tools for the genetic improvement of oysters, and their cross-application is expected to provide new benefits to oyster breeding. To evaluate the aquaculture traits of allotriploids between Crassostrea gigas and Crassostrea ariakensis, two triploid hybrids (TAG (diploid C. ariakensis ♀ × tetraploid C. gigas ♂) and TGA (tetraploid C. gigas ♀ × diploid C. ariakensis ♂)) were established. Phenotypic traits including growth, survival and reproduction were analyzed in two diploid hybrids (AG (diploid C. ariakensis ♀ × diploid C. gigas ♂) and GA (diploid C. gigas ♂ × diploid C. ariakensis ♀)) as controls. The results showed that TAG presented triploid advantage in fertilization rates and hatching rates, up to 11.34% and 26.50% respectively, while TGA did not. The survival rate of TAG and the shell height of TGA exhibited triploid advantage throughout the larval stage and were significantly higher (P < 0.05) than those of AG and GA at day 25. During the grow-out stage, triploid advantages appeared in the shell height of TAG and TGA, but only TAG showed triploid advantages in the survival rate. The triploid rates of TAG and TGA began to decrease during the grow-out stage, and reached 96.11% ± 4.41% and 90.56% ± 3.47%, respectively, at day 350. It was also found that the reproduction of TAG and TGA on day 350 was poor, manifesting as a high proportion of individuals with no gametes or a low number of gametes. Overall, TAG always presents triploid advantages in terms of growth and survival throughout the grow-out stage and shows potential value as a new resource of oyster farming or genetic improvement.