Comparison of performance and traits of interspecific hybridization between C.nippona and C.hongkongensis

Hybridization between distinct oyster species is a remarkably efficient method that offers the opportunity to combine parental traits and pass these traits to the next generation. Crassostrea nippona is widely acknowledged as a high-quality oyster on account of its unique flavor, suitability for aquaculture in summer, and suitable for growing a euhaline environment. C. hongkongensis is a most important oyster species cultured in low-salinity estuaries, valued for its excellent meat texture and high market prices. This study first conducts bidirectional hybridization between these two species, resulting in the establishment of four combinations: C.nippona ♀ × C.nippona ♂(NN), C.nippona ♀ × C.hongkongensis ♂(NH), C.hongkongensis ♀ × C.nippona ♂(HN), C.hongkongensis ♀ × C.hongkongensis ♂(HH). The ideal salinity for C.nippona , C.hongkongensis and hybrid offspring were 26ppt,18ppt and 20ppt. At the optimal salinity, the fertilization rates, hatching rates, and D -type rates of NH and HN was lower than those of the self-crossing group, moreover, all the indicators of the HN group were significantly lower than NH. However, the advantages of NH group in terms of hatching indicators did not persist into the larval stage. Multiple experiments have confirmed that the NH group could only survive until the umbo-larvae stage, while the HN group could survive normally and progress to the grow-out stage. HN exhibited significant heterosis in shell height both in Chaozhou (18.21%) and Zhoushan (8.4%), respectively. Meanwhile, in terms of cumulative survival rate, the HN group exhibited a single-parent heterosis over the NN group in Chaozhou (24.24%), and a single-parent heterosis over the HH group in Zhoushan (176.44%). Notably, although the gonads of the HN group show a phenomenon of delayed development, HN is still capable of producing viable gametes. These results indicate that the HN group has a higher tolerance to salt concentration and a wider range of application in aquaculture, having promising prospects for practical use in aquaculture.