AMOUNTS OF POLYMORPHISM AT MICROSATELLITE LOCI IN THE SEA SCALLOP PLACOPECTEN-MAGELLANICUS

Seven microsatellite DNA markers have been developed for the commercia lly important scallop Placopecten magelianicus. For four of these loci , the core sequence consists of tandemly repeated dinucleotides (GA). For the other three loci, the core consists of trinucleotide or tetran ucleotide repeats with or without intervening sequences. An analysis o f a full-sib family produced results compatible with Mendelian transmi ssion and also produced evidence for linkage between two of the loci. A sample from a commercially harvested population produced results tha t varied markedly among loci. Most of these interlocus differences can be explained in terms of the repeat unit. The four loci with dinucleo tide repeats produced comparable results with regard to the observed n umber of alleles, observed heterozygosities, and range and distributio n of allele length. The three loci whose variation has a more complex basis differed from each other and from the other four loci in one or more of these aspects. Excess of homozygosity, however, appears to var y irrespective of core sequence. The large number of alleles and the a bility to score larvae and juveniles make this set of markers a powerf ul instrument for the study of both natural and cultured populations o f this species.