Parasites and pathogens of the endosymbiotic pea crab (Pinnotheres pisum) from blue mussels (Mytilus edulis) in England

A histopathological survey of the commensal pea crab (Pinnotheres pisum) from the mantle cavities of blue mussels (Mytilus edulis) has been conducted. A total of 266 pea crabs from eight sites around the English coastline were examined. Of these, 82 were negative for any visible infections by histology. The remaining pea crabs were infected with an intranuclear bacilliform virus designated as P. pisum bacilliform virus (PpBV) in the hepatopancreatic epithelial cells, peritrichous ciliates on the gills, an intracytoplasmic microsporidian infection of the hepatopancreatocytes, a myophilic microsporidian infection, the gregarine Cephaloidophora fossor in the hepatopancreas, the entoniscid isopod Pinnotherion vermiforme, a low level nematode infection and an acanthocephalan cystacanth. Host reactions to infections were generally subdued. Results are discussed in relation to the endocommensal habitat of the pea crabs.

Parasites and pathogens of pea crabs – histological sections through pea crabs showing an infection with the isopod Pinnotherion vermiforme (top), an unidentified nematode (bottom left) and an unidentified acanthocephalan (bottom right).Figure optionsDownload as PowerPoint slideHighlights
► Eight infections were recorded during a survey of pea crabs.
► A new virus of pea crabs is described.
► Limited host responses were noted to any infections.
► All pea crab populations examined contained at least one infection.