Polydorid species (Polychaeta, Spionidae) associated with commercially important mollusk shells from eastern China

The genus Polydora (Polychaeta, Spionidae) includes many species well known for their activity as borers. They often become harmful invaders by reducing the growth rate and meat yield of, or inducing the mortality of commercially important mollusk species. Three species of the genus Polydora (P. onagawaensis, P. brevipalpa, and P. websteri) and one species of the genus Boccardiella (B. hamata) are here described for the first time from mollusk shells from Chinese waters. Sown cultured scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai) were heavily infested by large P. brevipalpa, which is considered to cause them severe damage. The most abundant and common species observed to bore shells is P. onagawaensis. Polydora onagawaensis was recently described originally from Pacific waters of northeastern Japan so it is speculated that the species is distributed widely along the coast of northeastern Asia. This is the first record of P. brevipalpa extracted from shells other than P. yessoensis.