Disaggregation behavior in the terrestrial isopod Porcellionides pruinosus as a new ecotoxicological endpoint for assessing infochemical disrupting activity

• Aggregation and avoidance characterize isopods behaviour. • A new effect endpoint is proposed to assess gregarious alterations. • A multiple indicator approach is used to determine disaggregation EC50. • Avoidance and disaggregation behaviors occurred separately. • Disaggregation leads to infochemical disruption. Among rapid ecotoxicological bioassays for screening soil quality, avoidance behavior tests on gregarious edaphic species such as Porcellionides pruinosus are widely used. However, the effect of soil contamination on adaptive aggregation ability has not been investigated. The aim of this study was to develop a new ecotoxicological endpoint related to the disaggregation effect under infochemical disruption at the population level during an avoidance behavior test. This new endpoint was evaluated using tire particles (TPs) and benzothiazole (BT) as preliminary physical and chemical substances. The disaggregation index (DI) and disaggregation groups (DG) are presented as measures of fragmentation of the population to quantify the effect of contaminants on aggregation behavior. Aggregation disruption in a group of ten individuals was assessed alongside the sub-lethal avoidance test after a 48 h exposure. The degree of disaggregation is measured by the number of subgroups formed. The DI and DG indices range from 0 to 1, representing the highest degree of aggregation and disaggregation, respectively, achieved at the end of the test. Our results show that all woodlice exposed to TPs ⩾ 1,250 mg/kg d.w. and BT ⩾ 500 mg/kg d.w. successfully avoided contaminated soil, but failed to show gregarious behavior, indicating fragmentation within the population, even if in uncontaminated soil. The disaggregation effects in woodlice occurred at higher concentrations (TPs ⩾ 7,500 mg/kg d.w.; BT = 1,000 mg/kg d.w.) than the avoidance ones, suggesting a possible effect on the adaptive capabilities of the population even if they move to the control soil. These results suggest a combination of avoidance behavior and disaggregation in individuals of P. pruinosus . Consideration of both aspects may provide more accurate and robust results for environmental risk assessment.