The Karyotype of the Pacific Lion-Paw Scallop Nodipecten subnodosus (Sowerby, 1835)

The lion-paw scallop Nodipecten subnodosus is a commercially important Pectinidae species. Basic research is being carried for its genetic improvement and breeding. In this study, trochophore larvae of N. subnodosus scallop were used to obtain metaphase spreads and to describe the karyotype. The diploid chromosome number (2n) of this species is 38, as the only other species of the same genus Nodipecten nodosus, and in almost all the species studied so far in the Pectinidae group. The relative length of the largest chromosome is 6.92 and for the smallest is 4.22. Based on the constructed karyo-ideogram, three distinctive chromosomes with the longest size (1–3) are in the area of submetacentric (sm) and subtelocentric (st) chromosomes, whereas the others in the karyo-ideogram are difficult to be distinguished between metacentric (m), submetacentric (sm), or m-sm. Additional estimates of the centromeric index values indicated that the karyotype consists of 3 m, 8 m-sm, 6 sm, 1 sm-st, and 1 st chromosome pairs. The number of arms is 38. There are polymorphisms in the presence/absence of secondary constrictions. In one karyotype, the constrictions were in the two homologous chromosomes of one pair, whereas in other karyotypes, there were pairs with only one chromosome bearing the constriction, and other karyotypes had none. The chromosome morphology described here for the species N. subnodosus can serve as a basis for comparisons between scallops of the Nodipecten genus, which is composed of eight species.