Abstract
Morphological and genetic differences between Japanese and Chinese red ark shell Scapharca broughtonii were examined. Differences were recognized between the two forms in all of the morphological characters examined. In particular the number of radial costae and shell weight index differed sufficiently for unequivocal differentiation of the forms, when used in combination. Isozyme analyses of genetic characters indicated differences in allelic frequencies at the MEP-1*, PGM* and PROT* loci. The genetic distance (D value) between the Japanese and the Chinese forms, calculated from isozymic allele frequencies was 0.108, suggesting significant genetic independency of the two forms. The considerable morphological and genetic differences suggested that the Chinese red ark shell is a distinct subspecies or species from Scapharca broughtonii.
