Comparative analysis of cadmium-induced toxicity and survival responses in the wolf spider Pirata subpiraticus under low-temperature treatment

Cadmium (Cd) pollution is a serious heavy metal pollution in paddy fields, but its effect and underlying mechanism on soil arthropod overwintering and cold resistance are still unclear. In the present study, adult females of the wolf spider Pirata subpiraticus exposed to Cd stress underwent a simulated temperature process (25 degrees C -> 16 degrees C -> 8 degrees C -> 4 degrees C). The mortality rate and content of nutrients in the Cd-treated spiders were dramatically elevated after low-temperature treatment compared to those in the Cd-free control spiders under the same temperature condition. To uncover the putative modulatory mechanism of Cd on cold tolerance in P. subpiraticus, we employed an in-depth RNA sequencing analysis and yielded a total of 888 differentially expressed genes (DEGs). Besides, we characterized genes that participate in multiple cryoprotectant syntheses, including arginine, cysteine, glucose, glycerol, heat shock protein, and mannose. The enrichment analyses found that most of the DEGs involved in biological processes and pathways were related to carbohydrate, lipid, and protein metabolism. Notably, ten Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, such as starch and sucrose metabolism, arachidonic acid metabolism, amino acid metabolism, mineral absorption, and vitamin digestion and absorption, were distinctively enriched with downregulated genes. Meanwhile, we also identified that seven DEGs might inhibit the KEGG pathway of ovarian steroidogenesis and potentially cripple ovarian function and fecundity in the spider. The decreased egg sac weight, number of hatched spiderlings, and vitellin concentration further supported the view that Cd exposure vitiates the overwintering spider's fecundity. Collectively, the comparative analysis provides a novel perspective regarding the survival response and fecundity on the cold tolerance of spiders under Cd stress and offers a profound insight for evaluating Cd-induced toxicity on overwintering arthropods.