Ecophysiological responses of the desert isopod Hemilepistus reaumurii to the combined effects of thermoperiod and photoperiod

Abstract

Life in desert ecosystems forces animals to adopt adaptive strategies to cope with severe environmental conditions. Their ability to colonize these bioclimatic stages makes Hemilepistus reaumurii, a xeric terrestrial isopod, a very interesting model where the different strategies of its life history can be studied. In the present work, we aim to emphasize the inflexibility and the dependence of the reproductive features of this xeric species to day length and temperature type (periodic or constant). Their ability to change the timing of the breeding onset and adjust their life-history traits according to the stimulating experimental conditions to better succeed during the breeding period and therefore their survival, and to succeed in the colonization of severe bioclimatic stages are also highlighted. To do so, six photoperiodic regimes were combined with two different thermophase and cryophase (durations of 25:15 °C. Two additional conditions were tested where females were maintained under both aperiodic regimes and a constant temperature of 20 °C. Our results suggest that under constant temperature, the lag time is significantly shorter in females maintained under continuous light compared to those kept in the dark. In addition, we noted that between delaying the breeding and breeding earlier, the response shown by the animals varied significantly between the shorter and longer photophases when combined with the thermoperiodic regime. However, only the females that had been reared under breeding conditions with longer photophases, from 12 to 24 h, were observed to successfully release their manca.