Infestation of the Japanese Scallop Patinopecten yessoensis by the Boring Polychaetes Polydora on the Coast of Hokkaido and Tohoku District

Abstract

The condition of infestation by the spionid polychaetes which bore into the shells of the scallop Patinopecten yessoensis on the coast of Hokkaido and Tohoku district was studied. The boring polychaetes were identified as Polydora convexa, P. concharum, P. variegata and P. websteri. Large numbers of P. convexa and P. concharum bore into the shells of the cultured and natural scallops in Shibetsu and Notsuke. Polydora variegata were extracted from almost all the sampling stations. Many borings of P. websteri were seen in Hiranai. Heavy infesta-tions by Polydora were observed in the scallops collected in 3 stations, Shibetsu, Notsuke and Kukurizaka. Each Polydora species had morphological characters in its burrow formed by itself. The soft-Xray photographs are very useful in identifying the boring species and also the condition of inner infestation.