1999 Volume 58 Issue 3 Pages 101-117
One species and its subspecies of the genus Limnoperna are known from Japan : L. fortunei fortunei (Dunker, 1856) and L. fortunei kikuchii Habe, 1981. The former was reported first in the 1990's in Japanese freshwaters, while the latter was described by Habe (1981) as an endemic subspecies of the species found in brackish waters. According to morphological and isozymatic studies done by Kimura (1994a) and Kimura and Tabe (1997), specimens which have been identified so far in Japan as L. fortunei kikuchii are clearly distinguishable from L. fortunei fortunei. Deducing from that L. fortunei kikuchii shares characteristics in its anatomy and shell morphology with the Xenostrobus species, and is probably identical to X. securis (Lamarck, 1819), a species that is endemic to the brackish waters of Australia and New Zealand. In order to confirm L. fortunei kikuchii is a synonym of X. securis, we examined characteristics of shell morphology, anatomy and isozymes of specimens collected from Japan and Western Australia. Specimens from the above two localities shared characteristics relating to shell morphology and anatomy, while they showed genetic variations for 10 loci (in 8 enzymes examined) without allelic substitution between the samples from the two localities. The present study indicates that L. fortunei kikuchii should be a junior synonym of X. securis and must have been introduced from Australia and/or New Zealand.