Invasive oysters as new hosts for native shell-boring polychaetes: Using historical shell collections and recent field data to investigate parasite spillback in native mussels in the Dutch Wadden Sea

Biological invasions can have manifold effects on native biota, including impacts species interactions in invaded ecosystems. Among those are parasite-host interactions, for example cases where invaders serve as a new host parasites, leading to an amplification of the parasite population which may ultimately result increased infection levels original hosts (parasite spillback). In this study, we investigated potential spillback shell-boring polychaete Polydora ciliata from invasive Pacific oysters ( Crassostrea (Magallana) gigas ) mussels Mytilus edulis Dutch Wadden Sea. A field survey intertidal revealed that majority P. nowadays be found shells live but also dead and much less other species: periwinkles Littorina littorea ). Using unique historical shell collection based long-term sampling programmes subtidal western Sea, compared infections before after invasion oyster by means x-ray scans. Both subtidal, did not detect differences prevalence between pre- post-invasion periods. This suggests caused strong regarding thus probably had little indirect infection-mediated condition fitness mussels. Instead, acquisition they themselves affected warrant further research. • affect via spillback. Invasive polychaetes. We whether lead No periods were detected.