Comparative study of tetraploid-based reciprocal triploid Portuguese oysters, Crassostrea angulata, from seed to marketsize

Abstract

The Portuguese oyster, Crassostrea angulata, is considered one of the most economically important aquaculture species because of its fast growth and good edibility. However, its small adult size and the flat meat quality poses problems for the aquaculture industry so a genetic improvement program needs to be conducted to solve these issues. Generally, triploid oysters compared to their diploid counterparts have reduced gonadal development, allowing for the larger adult size and better meat quality. To evaluate triploids performance characteristics, complete inter-ploidy hybridization between diploid and tetraploid Portuguese oysters were conducted at our experimental station in Zhanjiang, Guangdong Province. Experiments on two intra-ploidy groups (DD: Diploid♀ × Diploid♂, TT: Tetraploid♀ × Tetraploid♂) and two reciprocal triploid groups (DT: Diploid♀ × Tetraploid♂, TD: Tetraploid♀ × Diploid♂) were carried out successfully in duplicates. High fertilization rates and D larvae rates were observed in all groups, while the TT and TD groups have a lower hatching rate due to a dysfunction in tetraploid eggs. In grow-out stage, DT hybrids had a higher survival rate than intra-ploidy groups during the whole life history stage. Growth advantage of reciprocal triploid hybrids was evident in both, while DT progeny was always larger than TD in the whole process except in the D larvae stage. As for the two intra-ploidy groups, all tetraploid progeny was smaller than the progeny of diploids, and some tetraploid's progeny showed the ploidy loss phenomena as aneuploids and triploids at the grow out stage. Our results demonstrate that the diploid ♀ × tetraploid ♂ group has better commercial production of triploid C. angulata in the aquaculture industry.