Abstract
Limnoperna fortunei fortunei (Dunker, 1856) and L. fortunei kikuchii Habe, 1981 were introduced in Japan in the 1990's and 1970's, respectively. The latter has been recognized as a subspecies on the basis of features of shell morphology. However, validity of its subspecific status has been questioned, because these two mytilids are clearly distinguished also by several other characteristics. In the present study, genetic differences were examined between these two mytilids, which were collected from two sites in the Nagara River flowing into Ise Bay along the Pacific coast of central Japan. The sample of L. fortunei fortunei was from an upstream site while that of L. fortunei kikuchii was from a downstream site. Examination of these samples for 10 enzymes using gel electrophoresis showed genetic variation to be found at 14 loci, 13 of which indicated complete allelic substitution between the two samples. No hybrid was observed in samples containing the two mytilids. Nei's genetic distance (D) was very high (2.78) between the two. The observed average heterozygosity (Ho) was 0.0048 in L. fortunei fortunei and 0.0783 in L. fortunei kikuchii, the values being significantly different between the samples. These support that their genetic difference would be in the specific level.
