engleski

The effects of selected herbicides on biomarkers and reproduction of earthworm Dendrobaena veneta (Rosa, 1886)

Object. Today's intensive agriculture has resulted in increasing usage of pesticides that carry a certain environmental risk. Inevitably, pesticides affect nontarget organisms as well. Due to their ecological significance, earthworms have been used as indicators for assessing the potential impacts of chemicals on soil organisms. The aim of this study was to determine the effects of commercial herbicidal preparations to the earthworm Dendrobaena veneta (Rosa 1886). Those effects were investigated by measuring biochemical biomarkers and reproduction of the earthworm D. veneta after exposure to selected herbicides. The applied concentrations were environmentally relevant, with the highest concentration resembling the maximum application rate of the commercial preparation. Method. Three herbicides were tested: tembotrione (TBT), glyphosate (GLF) and nicosulfuron (NCS), all of them widely and frequently used. The earthworms were exposed to environmentally relevant concentrations for 7 days (subchronic test) and 28 days (reproduction test). After each exposure molecular biomarkers were spectrophotometrically measured: acetylcholinesterase (AChE), glutathione Stransferase (GST), catalase (CAT) and lipid peroxidation level (TBARS). Additionally the earthworms were weighted prior and after the exposure. After 28 days, in reproduction test, the number of cocoons and after 56 days the number of juveniles and unhatched cocoons were recorded. Result. After both 7 and 28 days of exposure to selected herbicides a statistically significant changes (p < 0.05, p ≤ 0.01, p ≤ 0.001) were found between control and treated earthworms. No mortality was recorded in any of the treatments. Glyphosate significantly induced AChE after 7 days at the highest concentration, the CAT activities were higher (more at 7 days), GST was significantly induced after 18 days and TBARS produced at the highest concentration. Nicosulfuron induced AChE activity after 28 days, had no effect on CAT, depleted GST activity and induced TBARS production. Tembotrione inhibited AChE activities, inhibited CAT after 7 days, depleted GST activities after 7 and 28 days and induced TBARS production at the highest concentration after 28 days. After 28 days of exposure the number of cocoons per earthworm was significantly lower than control only in C2 treatments with GLF and TBT. Interestingly, the number of juveniles per earthworm was The 1st International Earthworm Congress (IEC 1) 24th-29th, June 2018, Shanghai, China 141 significantly higher than control after exposure to C2 and C3 treatments with NCS. There was no significant reduction of juveniles per earthworm under any treatment. Conclusion. The activities of measured biomarkers varied depending on the herbicide used and the exposure duration. Although the changes were unambiguous, they indicate that oxidative stress could be an important factor in the toxicity of the studied herbicides. In this research the strongest adverse effects to D. veneta were exerted by tembotrione which should be further investigated. The future research should focus on the consequences of oxidative stress in multigeneration experiments, as well as in the mixture experiments using environmentally relevant pesticide combinations. Additionally, this research points to the importance of testing commercial formulations as they often display different (stronger or weaker) effects than the pure active substance.

Herbicides, biomarkers, AChE, oxidative stress

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