Trematode infections reduce clearance rates and condition in blue mussels Mytilus edulis

Abstract

Suspension feeders are important players in coastal food webs: by filtering particles suspended in the water column and depositing faeces and pseudofaeces in sediments, they mediate the coupling of pelagic primary and benthic secondary production. However, the potential interference of parasite infections on suspension feeding is not well investigated. We experimentally determined the effect of infections with metacercariae of the common trematode Renicola roscovita on clearance rates and condition of blue mussels Mytilus edulis. We also investigated whether there were differences in the effects of infections between different size classes of mussels. Using controlled infections under lab conditions, our experiment showed that infections significantly reduced the clearance rates of mussels. This effect was less pronounced in small (42% reduction) than in large mussels (71%). In addition, infections significantly reduced mussel body mass index in large (23% reduction) and small (17%) mussels compared to uninfected mussels. These reductions most likely resulted from a combined effect of an interference of the parasites with the mussel’s feeding apparatus (with the palps being the preferred infection site of the parasite) and of the energetic demands of the parasites (with metacercariae growing in size after initial infection). These negative effects on mussel filter feeding capacity indicate that parasites can alter a crucially important functional trait of marine suspension feeders.