The invasive Chinese pond mussel Sinanodonta woodiana (Lea, 1834) as a host for native symbionts in European waters

Biological invasions are commonly observed in both the natural habitats and those which are altered by human activities. An understanding of the mechanisms involved in the successful introduction, establishment and invasion of exotic taxa is essential in predicting of changes in biodiversity and community structure. Symbiont-mediated interactions between exotic and native hosts are of special interest due to the indirect effects on population dynamics. The aim of this study was to estimate the presence of symbionts in Chinese pond mussel Sinanodonta woodiana (Lea, 1834), an exotic species of mussel in European fresh waters. The number of 340 individuals of S. woodiana was collected from Polish water bodies, including thermally heated lakes and fish ponds with natural thermal regime. The examination of mussels revealed the presence of Rhipidocotyle campanula sporocysts and cercariae (Digenea: Bucephalidae), water mites Unionicola ypsilophora (Acari: Hydracarina), oligochaetes Chaetogaster limnaei limnaei (Oligochaeta: Naididae) and chironomids Glyptotendipes sp. (Diptera: Chironomidae). The global prevalence of mussels inhabited by Ch. limnaei limnaei was 7.6%, by water mites and chironomids 3.5%, and by R. campanula cercariae 2.0%. The significant difference in the number of mussels with symbionts was identified between heated lakes and fish ponds (χ²=4.15; df=1, P=0.04), with a higher global prevalence of mussels in fish ponds (22.3%) compared to heated lakes (13.7%). R. campanula or U. ypsilophora were only found in mussels collected from thermally polluted lakes or fish ponds, respectively. Chironomid larvae and oligochaetes occurred in both types of water bodies. However, Glyptotendipes sp. inhabited mussels with a higher global prevalence in fish ponds than in thermally polluted lakes, while Ch. limnaei limnaei was observed mainly in hosts from heated lakes, and only from one fish pond that were not drained. Our findings indicate that the alien Chinese pond mussel S. woodiana can be inhabited by different groups of symbionts native to Europe, including digenetic trematodes. The results show that S. woodiana can affect directly and indirectly water habitats and the vulnerability of infection with symbionts depends on ecosystem conditions. It occurs that even considerable climate differences do not pose a barrier for exotic mussels to spread.