Production traits and fertility of reciprocal hybrids between Argopecten irradians irradians and A. i. concentricus

The two bay scallop subspecies, Argopecten irradians irradians (NN) and A. i. concentricus (SS), are fast growing and major cultured bivalves in China. However, their relatively small sizes and decreasing production traits caused by long-term inbreeding have been major concerns to the industry in the last two decades. Hybridization between the two bay scallop subspecies may provide a new approach to breed a new variety with superior production traits for the industry. For this end, in this study, we hybridized the two bay scallop subspecies in order to obtain a new strain that incorporates the genes of both subspecies. No significant difference was found in fertilization rate, hatching rate and metamorphosis rate between the purebred and crossbred cohorts (NN♀×SS♂, denoted as NS; SS♀×NN♂, denoted as SN). Both mating strategy (intra- vs. inter-population crosses) and egg origin had significant effects on growth and survival at the larval stage. Heterosis was observed in the crossbred and was more pronounced in older stages. Genetic diversity of the reciprocal hybrids, especially that of SN, was increased compared with the purebred cohorts. Almost all hybrids were completely fertile and able to reproduce by self-fertilization or by backcrossing with either parent. Apparently, male sterile individuals whose gonads were fully occupied by the ovary part at mature stage were found in the hybrids for the first time. The hybrids, especially SN, may provide precious germplasm resources for the production of ternary hybrids with the Peruvian scallop, A. purpuratus .