The digestive gland and gills of the mussel Crenomytilus grayanus extracted from three locations -(i) sampled from a clean and (ii) polluted site and (iii) transplanted from the nonpolluted to polluted site -were analysed for antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase), total oxyradical scavenging capacity and levels of lipid peroxidation products (malondialdehyde, conjugated dienes and lipofuscin). Perturbation of redox status was found in both digestive gland and gill tissues of mussels living in the polluted area. As the activities of superoxide dismutase and catalase were 1.2-3 times higher, the total oxyradical scavenging capacity was lower by 20-35% and the levels of lipid peroxidation products were 2-7 times higher compared to mussels from the reference site. In transplanted mussels, the lipid peroxidation process in both tissues was significantly stimulated (the level of conjugated dienes was increased 1.7-2.5-fold; malondialdehyde and lipofuscin contents were increased 3.5-5-fold) and the total oxyradical scavenging capacity fell by 50-70%. In addition, the transplantation generally resulted in transient and variable responses of antioxidant enzymes for both tissues. Complex response-behaviour of the antioxidant enzymes strongly points to the necessity of employing a combined approach that takes into account activities of antioxidant enzymes and the total oxyradical scavenging capacity, as well as measurement of oxidative damage (e.g., lipid peroxidation) to evaluate the physiological health of molluscs.
The marine and ocean water pollution with different-sized plastic waste poses a real threat to the lives of the next generations. Plastic, including microplastics, is found in all types of water bodies and in the organisms that live in them. However, given the chemical diversity of plastic particles, data on their toxicity are currently incomplete. Moreover, it is clear that different organisms, depending on their habitat and feeding habits, are at different risks from plastic particles. Therefore, we performed a series of experiments on feeding the gastropod scraping mollusk Littorina brevicula with two types of polymeric particles—polymethylmethacrylate (PMMA) and polytetrafluoroethylene (PTFE)—using a special feeding design. In the PMMA-exposed group, changes in gastrointestinal biochemical parameters such as increases in malondialdehyde (MDA) and protein carbonyls (PC) were detected, indicating the initiation of oxidative stress. Similarly, a comet assay showed an almost twofold increase in DNA damage in digestive gland cells compared to the control group. In mollusks fed with PTFE-containing food, no similar changes were recorded.
The ingress of nanoparticles of metal oxides and microfragments of synthetic polymers (microplastics) into a marine environment causes unpredictable consequences. The effects of such particles cannot be predicted due to a lack of ecotoxicological information. In this research, a series of laboratory experiments were conducted on the combined effects of CuO-nanoparticles (CuO-NPs) and polystyrene microspheres (µPSs) on the development of oxidative stress processes in the marine filter-feeder mollusk Mytilus trossulus. Biomarkers of oxidative stress, including the lysosome membrane stability of hematocytes (LMS), the index of antioxidant activity (IAA), the levels of malonaldehyde (MDA) and protein carbonyls (PCs), and DNA damage in digestive gland cells, were measured after 5 days of exposure. Based on a battery of biochemical markers, it was shown that oxidative stress was induced at varying degrees in the experimental mollusks when exposed to CuO-NPs and µPSs both separately and in combination. In contrast, the single-treatment effect on the lysosomal membrane was enhanced by the combined CuO-NPs and µPSs (from 77.14 ± 8.56 to 42 ± 4.26 min). In addition, exposure to both the compounds alone and in combination decreased the IAA (from 22.87 ± 1.25, to 19.55 ± 0.21, 10.73 ± 0.53, and 12.06 ± 1.62 nM/mg protein, respectively). The PC level significantly increased only after CuO-NP exposure (from 0.496 ± 0.02 to 0.838 ± 0.03 μM/mg protein). Furthermore, the results showed that the investigated particles, both alone and in combination, promoted DNA damage in digestive gland cells (from 2.02 ± 0.52 to 5.15 ± 0.37, 18.29 ± 2.14, and 10.72 ± 2.53%, respectively), indicating that these compounds are genotoxic. Overall, the results obtained suggest that oxidative stress is the leading factor in the negative effects of CuO-NPs and µPSs. Considering the exceptional role of genome integrity in the functioning of biological systems, the revealed damages in the DNA molecule structure should be attributed to the most important manifestations of the toxicity of these two forms of marine pollution.
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