Does group living protect offspring from the toxic effects of cadmium ingestion in juvenile earwigs?

In general, group living can protect offspring against a wide range of environmental risks, such as predation, extreme temperature and pathogen infections. However, its role in mitigating the effect of toxic stressors, such as anthropogenic chemical pollution, remains unclear. At present, chemical pollution is steadily increasing and is considered as a great environmental threat to biodiversity. Here, we investigated whether family group living contributes to the remarkable robustness of European earwig juveniles to cadmium, which is a toxic pollutant for many animal species, by mitigating individual stress response. Earwig nymphs were reared alone, with siblings or in a full family group (siblings plus mother) while feeding them with a cadmium concentration (0–100 mg/L) for 3 months. During this time, a series of parameters was measured at juvenile and adult stages. Results indicated that family group living does not mitigate the toxic effects of cadmium, as exposure to cadmium did not affect any of the measured parameters, regardless of whether juveniles had access to siblings, mother or none. However, the social environment influenced the juvenile activity, survival and development, although it had no detectable impact on adult morphometry, sperm viability and DNA damage. Therefore, although the absence of social interactions can alter juvenile development and survival, it does not modulate the toxic effect of chemical pollutants such as cadmium in facultative family living species. This study highlights that exploring the physiological, genetic and microbial mechanisms underlying the apparent robustness to cadmium in the European earwig is necessary. • Social living mitigates some environmental risks for group members. • We investigated whether social buffering can be applied to pollutants like cadmium. • Earwig juveniles were reared alone, with siblings or in a full family. • Cadmium ingestion effects on behaviour, development and physiology were determined. • Social environment was not attributed to strong robustness of earwigs to cadmium.