Stress response in terrestrial isopods: A comparative study on glycaemia

Abstract

Stressors are omnipresent in the environment and trigger specific physiological and/or behavioural responses that remain relatively less known in invertebrates. Among the parameters used to quantify the impact of stress on physiology, the circulating level of glucose is commonly used in aquatic crustacean species. Terrestrial isopods are small crustaceans commonly used as bioindicators of soil quality; however, their response to environmental stressors remains poorly documented. In laboratory conditions, we investigated how different stressors influence the physiological response of two terrestrial isopod species. Thus, we exposed Armadillidium vulgare and Porcellio dilatatus to a series of both acute (physical) and chronic (temperature, social isolation, and exposure to herbicide) stressors that mimic potentially stressful situations encountered in their environment. Our results revealed that, for both species, glycaemia is not impacted by thermic shock (1 h at 4 °C), mechanical disturbances (1 min of shaking or upside-down motion) or social isolation (4 weeks) at the population level. Nevertheless, we observed a significantly higher sensitivity in male P. dilatatus exposed to upside-down movements and in males of both species exposed to social isolation. Acute (96 h) and chronic (21 days) exposure to glyphosate (1.8–2.5 kg.ha⁻¹) did not impact glycaemia levels in A. vulgare. However, at both tested doses, individuals exposed to glyphosate for 25 days and subjected to an additional stressor (haemolymph sampling at 96 h) had significantly higher glycaemia in comparison to their control. Survival was also impacted by the joint application of chronic glyphosate exposure and intermediate haemolymph sampling. We conclude that glucose is a potentially good indicator to study the stress response of terrestrial isopods. Additional studies for this parameter, combined with other physiological indicators, are needed to better characterize this response.