Sex-dependent variations in the immune status of the terrestrial isopod Porcellio laevis (Crustacea, Isopoda) as a response to environmental perturbation: a case of microplastic exposure in soil.

Sex-dependent variation in immune responses in arthropods is well established in cases of microbial infection or parasitism but remains less explored under environmental stress. In this study we examined whether the sex of terrestrial isopods Porcellio laevis affects their immune response to soil microplastic (MP) exposure. Animals were exposed for 14 days to polypropylene MPs at 0.05%, 0.5%, and 5% (w/w soil), and immune parameters, including total haemocyte count, haemocyte viability, phenoloxidase (PO)-like activity, and haemolymph protein content, were assessed alongside survival and growth. Overall, MP exposure induced sex-dependent alterations in immune status, with males and females exhibiting distinct response patterns: females exhibited reduced haemocyte-related parameters at specific MP concentrations, whereas males showed higher haemolymph protein levels and increased growth at the highest concentration. PO-like activity was consistently higher in females. Although not all responses were statistically significant, effect size analysis indicated medium to large sex-related differences across multiple endpoints. Most of the effects were related to the dose of MP, with changes detectable already at lower concentrations. These findings highlight the importance of incorporating sex as a biological factor in ecotoxicological studies and support the use of immune markers as sensitive indicators of sublethal environmental stress.