Interesting larval development and ecology of spionid polychaete Polydora websteri inhabiting mollusc shells

Abstract

Spionid polychaete Polydora websteri is known to inhabit commercially important mollusc shells and is reported globally. This review introduces the ecology and larval development of Polydora websteri inhabiting wild oyster shells (Crassostrea gigas) in Gamo Lagoon, Miyagi, Japan. Notably, over 100 worms were found in a single oyster valve and many mud blisters were observed on the inner surface of oyster shells. Females were observed to deposit a string of egg capsules from May to October. Culturing of these egg capsules revealed unique larval development of P. websteri, with adelphophagic and planktotrophic larvae coexisting within a capsule at the time of hatching. Those different larval developmental modes, also observed in other Polydora species, may be a key factor contributing to their widespread global distribution.