Aquaculture performance comparison of reciprocal triploid C. gigas produced by mating tetraploids and diploids in China

Crassostrea gigas is an important species of oyster culture in northern China, which has important economic value. In recent years, triploid cultivation of C. gigas has gradually emerged because of the advantages of poor fertility and fast growth, but the comparative studies on tetraploid, triploid and diploid C. gigas are not comprehensive and systematic. In addition, forward or reverse mating tetraploids and diploids all can produce triploids, it is necessary to compare the performance of the two triploid groups. This study was conducted to understand the growth, survival, ploidy level and fertility of tetraploids in China, and to figure out how to mass-produce triploids. Aritificial hybridization was made between diploid (D) and tetraploid (T) to produce DD, TD, DT and TT groups (males are listed first). The results showed that the fertilization rate, cleavage rate, D larval rate and larvae survival rate of TD group were significantly higher than those of DT and TT groups, and the larval growth of TD group was significantly faster than that of the other three groups. In cultivation period, the growth and survival rate of TD in the 2 sites were significantly higher, and the 100% triploid rate was stable. In addition, some triploids in TD and DT groups were fertile and could produce functional gametes. But the proportion of female and hermaphrodite in fertile triploids was higher than that in diploids and tetraploids, and the fertility of triploids was still poor overall. However, some tetraploids in TT group would lose chromosomes during growth and become triploids, diploids or aneuploids. Tetraploid had the slowest growth and the lowest survival rate at the both sites, but its fertility was normal and could produce a large number of functional gametes, which could provide sufficient sperm for large-scale production of triploids. All these data support tetraploid male x diploid female is a good strain for commercial promotion in China. In conclusion, this study provides comprehensive data for understanding the performance of tetraploid and the aquaculture potential of triploid C. gigas, and also supports the commercial promotion of triploid C. gigas (tetraploid male x diploid female) in China.

Automated summary

Crassostrea gigas is an economically valuable oyster species cultured in northern China. Triploid cultivation of C. gigas has become popular due to its advantages in poor fertility and fast growth. However, there is a lack of comprehensive and systematic comparative studies on tetraploid, triploid, and diploid C. gigas. This study aimed to understand the growth, survival, ploidy level, and fertility of tetraploids in China, as well as to explore the mass production of triploids. The results showed that tetraploid male x diploid female produced triploids with better performance, indicating its potential for commercial promotion in China.