Polydorid species (Annelida: Spionidae) associated with commercially important oyster shells and their shell infestation along the coast of Normandy, in the English Channel, France

Abstract

Abstract Polydorid species (Annelida, Spionidae), which inhabit the shells of the commercially important oyster Crassostrea gigas, were investigated along the coast of Normandy, France. Eight species, including five new records for Normandy (Polydora onagawaensis, Polydora websteri, Boccardia pseudonatrix, Boccardia proboscidea, and Boccardiella hamata) and two first records in European waters (P. onagawaensis and B. pseudonatrix), were identified based on morphological, molecular biological, and ecological characteristics. Polydora onagawaensis, which belongs to the Polydora ciliata/websteri complex, was discovered in the shells of wild and suspended cultured oysters, as well as in limestone substrates. In the phylogenetic analysis of mitochondrial COI gene sequences, specimens of P. onagawaensis collected from Normandy were grouped together with specimens from the USA into a single clade and were distinguished from the other three lineages that comprised Japanese and USA specimens. Polydora websteri inhabited shells of suspended cultured oysters. Polydora hoplura, Dipolydora giardi, and Dipolydora sp. were observed in shells from the sandy oyster culture grounds. Boccardiella hamata has been found in wild oyster shells from muddy oyster culture grounds. Boccardia pseudonatrix was observed in the shells of both the wild and cultured oysters. Adult and juvenile Boccardia proboscidea were observed in coralline algae, as well as in suspended cultured oysters. Mud tubes were observed to protrude from the outer surface of the shells, and abnormal black and calcareous deposits were secreted on the inner surface of the shells against polydorid penetration.