Perkinsus protozoan infection in short-necked clam Tapes (=Ruditapes) philippinarum in Japan.
An infection of Perkinsus was found in Tapes philippinarum in Japan. This is a new geographic record. Histology revealed clusters of trophozoites forming cyst-like structures in connective tissues of the gill, heart, mantle, digestive gland and adductor muscle of infected clams. The nucleotide sequences of 2 internal transcribed spacers within the 5.8 small subunit ribosomal RNA region were PCR-amplified from DNA of prezoosporangia obtained by a culture of the infected clam tissue. These sequences were almost identical to those of P. atlanticus and P. olseni, suggesting that the Perkinsus infecting T. philippinarum in Japan is P. atlanticus or a closely-related species. A PCR method was designed for the diagnosis of this species and indicated high infection rates (64-94%) of Perkinsus in T. philippinarum in Japan.