Biochemical basis of resistance to multiple contaminations in the native and invasive populations of Dreissena polymorpha

The zebra mussel Dreissena polymorpha (Pallas, 1771) is an invasive species and a valuable bioindicator in the inland waters. Nevertheless, the biochemical reasons for the unique competitiveness of zebra mussels are not clear. This study aimed to compare the native and invasive populations of D. polymorpha in their ability to withstand exposure to environmental pollutants of plastic (microplastics) and anthropic (caffein) pressures. The specimens from the invasive population in west Ukraine (Tn) and native population at lower streams of river Dnipro (south Ukraine, Kh) were sampled in the August of 2021 y. Molluscs from both sites were treated with microplastics (MP, 1 mg⋅L−1, pore size 2μm); caffeine (Caf, 20.0 μg⋅L−1) at 18 oC, elevated temperature (25 oC, T) and MP and Caf combinations at 18 oC (Mix) and 25 °C (MixT) for 14 days. Untreated molluscs exposed at 18 oC (C) represented control group. A set of the 20 markers of oxidative stress, biotransformation, detoxification and apoptosis were assayed in the total soft tissues. From the two controls, Kh-group indicated lower stresfull impact. However, both populations increased caspase-3 and glutathione-S transferase activities and lysosomal instability in most exposures, and cholinesterase and phenoloxidase activities under the heating and combine exposures, indicating the remarkable properties to respond to new challenges and synergistic effect of mixtures. Inter-population differences were related to the metallothionein, cathepsin D, cytochrome P540 and oxidative stress responses that reflect population-dependent adverse outcome pathways. The discriminant analysis separated two populations with a substantially lesser magnitude of responses in the invasive population as a sign of higher resistance.