Temperature and photoperiod influence survival and biomarkers of senescence in common woodlouse
Most living organisms display a decline in physiological performances when ageing, a process called senescence that is most often associated with increased mortality risk. Previous researches have shown that both the timing and the intensity of senescence vary a lot within and among species, but the role of environmental factors in this variation is still poorly understood. To fill this knowledge gap, we investigated the impact of environmental conditions on the strength of senescence using an experimental design applied to a population of common woodlouse Armadillidium vulgare intensively monitored in the lab. As no cellular senescence biomarker was available in woodlouse, our first step was to identify two biomarkers of senescence in this species: the {beta}-galactosidase activity and the profile of immune cells. These biomarkers provided evidence of sex-specific senescence patterns, with a higher {beta}-galactosidase activity and lower immune cell viability in females than in males at old age. We then tested the impact of environmental conditions, through changes in temperature and photoperiod, on these biomarkers. We found different effects of the environmental changing: The increasing of day light modification leaded the same effect as age on our senescence biomarkers while temperature modifications leaded the opposite effect as age on the {beta}-galactosidase activity and cell size. We also demonstrated the existence of sex-specific responses to changes in environmental conditions. By using an experimental approach and new biomarkers of senescence in woodlouse, we show that environmental conditions and sex both shape the diversity observed in senescence patterns of woodlouse and underline the importance of identifying senescence biomarkers to understand how environmental conditions influence the evolution of senescence.