BROADENING OF THE GENETIC BASIS OF THE ATLANTIC BAY SCALLOP ARGOPECTEN IRRADIANS AFTER INTERSPECIFIC HYBRIDIZATION AND BACKCROSSING

The growth characteristics and morphological features of the Atlantic bay scallop (Argopecten irradians irradians Lamarck), Chilean scallop (Argopecten purpuratus Lamarck), F1 hybrids of these species, and the offspring produced via 2 cycles of backcrossing between hybrid populations and the Atlantic bay scallop were examined to determine the feasibility of broadening the genetic basis of the bay scallop. Bidirectional fertilization and successful hatching were observed in F1 hybrids. Notable heterosis (i.e., >1% of the midparent values) was detected in growth and survival throughout the whole life span of the scallops. The F1 hybrids showed universal feminization, but with low fertilization and hatching rates observed in backcrosses with bay scallops (partial sterility). Hematoxylin-eosin staining of paraffin sections of the feminine gonads of the hybrids was performed in this study. The male gonad was found to be vestigial, without any active sperm, whereas the female gonad was well developed and presented abundant eggs with a normal appearance. Increasing fertilization and hatching rates were observed in the second generation of backcrosses between hybrid populations and bay scallops compared with the first backcrosses. At the same time, a growth advantage and low temperature resistance were regained in the offspring produced from backcrossed breeding. This study describes a promising way to broaden the genetic basis of bay scallops with the aim of improving the growth characteristics of cultured scallop stocks.