We developed a method using PCR-RFLP to differentiate Perkinsus olseni and P. honshuensis, the latter of which was recently discovered as a new species in Mie, Japan, in the Manila clam Ruditapes philippinarum. In normal gill samples spiked with cultured trophozoites of the parasites, the minimum infection levels that could be detected by this method were 100 cells per 10 mg sample for P. olseni and one cell for P. honshuensis. Using this method, we found that clams from the western Seto Inland Sea were infected with both species of the parasites. This is the first report of P. honshuensis from areas outside the type locality of this species.
2009 The Japanese Society of Fish Pathology