Spiders are among the most abundant predators of insects and other invertebrates in agroecosystems and forest ecosystems, and they can play an important ecological role by regulating invertebrate population abundance. Biological control using spiders may represent a sustainable method of controlling the abundance of agricultural pest species and reducing the amount of damage inflicted to crops. However, application of pesticides to agricultural crops may directly or indirectly impact on the foraging spiders in the crop. In particular, pesticides may have mutagenic effects on spiders, which negatively affect the spider population abundance and importantly these effects can be transferred to the next generation of spiders. The study of the genetic toxicity of pesticides to spiders should be therefore as one element of the safety evaluation of pesticides.
In this study, we used both the micronucleus test and the single cell gel electrophoresis assay (the comet assay) to assess the effects of two pesticides (acetamiprid and chlorpyrifos) on the DNA of the wolf spider, Pardosa astrigera Koch. The objective of the study was to achieve a more comprehensive understanding of the effects and potential risks of using these pesticides on spider populations. The results of the micronucleus test showed that there were significant differences in the frequencies of micronuclei in spiders exposed to different concentrations of acetamiprid and chlorpyrifos (P<0.01) compared with the control spiders that were not exposed to pesticides. There was an effect of increasing the concentration of the pesticides. The linear regression equations between the frequencies of micronuclei in cephalothorax hemocytes and abdomen hemocytes and the concentration of acetamiprid were y=3.192x+8.129 (r=0.954) and y=3.206x+12.829 (r=0.932) and those with the concentration of chlorpyrifos were y=0.443x+6.833 (r=0.993) and y=0.524x+12.214 (r=0.986). The results of the comet assay showed that there were significant differences in the proportion of cells with DNA tails and tail length of nuclear DNA between different concentrations of acetamiprid and chlorpyrifos. The linear regression equations between the frequencies of damage (degree Ⅱ and Ⅲ) in the cephalothorax and abdomen hemocytes and the concentration of acetamiprid were y=6.856x+99.377 (r=0.984), and y=9.039x+100.795 (r=0.983) and those with the concentration of chlorpyrifos were y=0.308x+98.315 (r=0.981), and y=0.241x+100.762 (r=0.966). The frequencies of micronuclei and DNA damage in the abdomen hemocytes of P. astrigera were higher than the damage in the cephalothorax hemocytes.
The findings of this study provide valuable information on the potential risks of pesticide-use to spiders, which are natural enemies of agricultural pests. The sensitivity of the single cell gel electrophoresis assay is higher than the micronucleus test as it can detect chemicals on the damaged DNA single-strand and the DNA damage repair capacity. The single cell gel electrophoresis assay therefore provides a sensitive and reliable detection method to reveal the potential hazards of pesticides. Evaluation of the mutagenicity of pesticides and other chemicals to non-target organisms is important to ensure their safe use in agricultural ecosystems.