Dispersed discrete length polymorphism of mitochondrial DNA in the scallop Placopecten magellanicus (Gmelin)

Three separate regions exhibiting incremental length polymorphism have been found in the mitochondrial genome of the scallop Placopecten magellanicus. Each locus has a discrete and different unit of variation, measuring 1450 bp at locus I, 250 bp at locus II, and less than 100 bp at locus III. At least six size classes were observed at each locus, and individual variation can account for the intraspecific mtDNA size range of 31-42 kb, but not for the unusually large base size of the genome. Intramolecular hybridization patterns with clones of two of the variable regions indicate that there is a dispersed sequence similarity with the 1,450-bp locus-I repeat and its flanks, and with some part of locus II.