Isopod physiological and behavioral responses to drier conditions: An experiment with four species in the context of global warming

In the context of global warming, an increase in soil drought is suspected by the IPCC predictions and litter breakdown activity could be affected. An experiment was conducted using microcosms (controlled conditions) and woodlice which are recognized as shredders of litter and bioindicators of global warming. The impact of relative air humidity (90 and 50% RH) on litter breakdown by woodlice was studied through the monitoring of one behavioral (distribution of individuals on microcosms), one morphological (Absolute Growth Rate) and four physiological traits (Survival rate, Relative Consumption Rate, Relative Growth Rate, Feeding rate). Four species of isopods known to have different microclimatic sensitivities (Armadillidium vulgare, Porcellio scaber, Oniscus asellus, Philoscia muscorum) were used simultaneously. Sensitivities of males and females have also been tested. Main results showed that the seven studied parameters under the two relative humidity conditions were not affected in the same way according to the species nor genders. A. vulgare is the most affected species followed by O. asellus. The least affected species are P. scaber and P. muscorum. Their morphological and physiological differences allow to the most evolved species to be more resistant to drier conditions but in return they are no longer active, which can affect soil functionality. With global warming, it could be envisaged that woodlice spend less time foraging and more time seeking refuge to reduce the risk of mortality from desiccation stress. Modifying the feeding behavior of terrestrial isopods could slow down litter degradation with consequences on the process of organic matter recycling. -Litter breakdown by woodlice decreased in the driest tested condition-Absolute Growth Rate, survival rate, Relative Consumption Rate, Relative Growth Rate and feeding rate decreased in the driest tested condition-Genders were not affected equally by the driest tested condition-The four studied species of woodlice were not affected equally by the driest tested condition