The depressed river mussel

This study explores the utilisation of European freshwater mussels as hosts by the European bitterling (Rhodeus amarus) at their current sympatric occurrence range. Our study confirms Pseudanodonta complanata as a suitable, occasional host for bitterling. The spawning relationship of R. amarus with freshwater mussels has physiological costs for the hosts, leading to resource competition and potential negative effects on host fertility. Further research is needed to assess the dynamics of host-parasite interactions, mussel adaptations to prevent parasitism, and the consequences of the bitterling recent and possible future expansion in Europe for mussel populations.