In today's world, microplastics are pervasive across all ecosystems and are small enough to be ingested by some invertebrate species. Tire wear is a significant source of microplastics. Our study investigated the survival and immune response of the terrestrial isopod Porcellio scaber to bacterial infection after pre-exposure to tire particles. We also examined the effect of the pre-exposure to insecticide chlorpyrifos, which served as a positive control due to its known negative effects on invertebrates. Isopods were exposed to tire particles (1.5 % w/w dry weight) or chlorpyrifos (2 mg/kg dry weight), which we referred to as primary exposure. After one or two weeks of exposure, we injected them with lipopolysaccharides (LPS) to simulate a bacterial infection (secondary exposure). Results indicated that exposure to tire particles did not affect isopod survival or immune response. In contrast, chlorpyrifos exposure led to changes in immune parameters, although survival rates remained unaffected. After a secondary LPS challenge, the immune response was enhanced in isopods previously exposed to chlorpyrifos, whereas those pre-exposed to tire particles showed no significant changes. In no case did pre-exposure affect woodlice survival. Further research is necessary to evaluate the long-term and sublethal effects of these pollutants on the immune response of isopods.
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