Sinanodonta woodiana Lea, 1834

All three mussel species are host fish generalists and compete for hosts. The invasive S. woodiana and the two native Anodonta species Anodonta anatina and Anodonta cygnea have the same habitat preferences and often co-occur in the same water bodies (Beran 2008; V. Huber, J. Geist Bo¨ssneck and Klingelho¨fer 2011; Wojton et al. 2012). Because S. woodiana is a broad generalist in host use (Douda et al. 2012), has a high competitive potential and produces a higher number of glochidia than native anodontines (Wa¨chtler et al. 2001), S. woodiana shows a higher initial infestation of the tested fish species and a higher juvenile mussel excystment compared to A. anatina and A. cygnea. (Huber, V., & Geist, J. 2019)

We report for the first time that parasitic larvae (glochidia) of the invasive freshwater mussel Sinanodonta (Anodonta) woodiana (Unionidae, Bivalvia) cause an unexpected reduction in the condition factor of parasitized native fish species. The reduction in the body mass and condition factor of experimentally infested European chub (Squalius cephalus) was associated with changes in several physiological parameters measured in host fish plasma. Ion concentrations (potassium, chloride) and enzymes activities (aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase) were significantly affected; hence, the results reveal the complex effects of non-native glochidia on the homeostasis of the individually tested fish. (Douda et al. 2017)

Nevertheless, adverse effects are likely, and S. woodiana has already been identified as the major cause of decline of native A. anatina in Lake Balaton in Central Hungary, where its relative abundance has already dropped from 17.8 to 8.6% (Benkő‐Kiss et al., 2013). In Italy, it has completely replaced some native mussel species (especially A. anatina) in ecosystems throughout the country (Cappelletti et al., 2009), and the same situation has been observed recently in southern France (Vincent Prié, personal communication). (Benko-Kiss et al. 2013) S. woodiana may affect native mussel populations, including the negative impact via cross-resistance of host fishes (Donrovich et al., 2017; Sousa, Novais, Costa, & Strayer, 2014).