Polydorid species (Polychaeta: Spionidae) associated with commercially important mollusk shells in Korean waters

Polydorid species (Polychaeta: Spionidae) are widely known for their boring activities in mollusk shells and they often become harmful invaders. A total of seven species of the genera . Polydora, Dipolydora, and . Boccardiella were collected and described from wild and cultured mollusk shells from the intertidal to subtidal for the first time in Korean waters. The most common species observed to bore shells were . Polydora haswelli and . Polydora aura. . Polydora haswelli is recorded for the first time in Asian waters. Wild and cultured abalone . Haliotis discus discus, wild . Atrina pectinata, and cultured oyster . Crassostrea gigas were heavily infested by . P. haswelli and . P. aura. . Polydora uncinata was very abundant only from the cultured oyster . C. gigas from southeastern Korea, indicating that this species may have been transported with a different oyster population introduced to the area. . Polydora limicola inhabited mud deposits in crevices of wild . Chlamys farreri shells and caused severe damage to them. Small sized . Dipolydora giardi and . Dipolydora alborectalis were extracted only from wild shells. . Boccardiella hamata was common associated with wild . C. gigas in mud flats. We discuss the polydorid species from the viewpoint of aquaculture and unintentional transportation of alien species which have been introduced with commercially important host shells.