Sophie Beltran-Bech

Invertebrate Iridescent Virus 31 (IIV-31, or Iridovirus armadillidium1) is a large double-stranded DNA virus that induces iridescence and high mortality in terrestrial isopods. Despite its broad distribution, its pathogenic mechanisms and interactions with host immunity and endosymbionts are poorly understood. We examined the effects of IIV-31 infection on survival, hemocyte concentration and viability, septicemia, and viral load in Armadillidium vulgare, while testing for protective effects of the feminizing endosymbiont Wolbachia (wVulC strain). Virgin adults from asymbiotic (W-; males and females) and Wolbachia-infected (W+; females only) lineages were experimentally infected via needle pricking. Infected individuals exhibited typical iridescence from ~6 days post-infection (dpi), culminating in 100% mortality after 80 days. Wolbachia conferred no significant survival benefit (log-rank test, p = 0.42). However, despite attaining 100% mortality in both sexes by 80 dpi, females exhibited delayed mortality kinetics compared to males (Cox proportional hazards model, p = 0.04). Infected isopods displayed marked hemocyte depletion (negative binomial GLMM, p < 0.0001) and elevated septicemia (p = 0.008), with stronger septicemia in infected females relative to their controls, but no sex difference in viral load at 30 dpi (p = 0.81). Transmission electron microscopy revealed paracrystalline virion arrays in hemocytes and fat body cells. These findings demonstrate that IIV-31 causes immunosuppression and opportunistic septicemia, with female-specific tolerance but no Wolbachia-mediated protection, underscoring sexual dimorphism in immune responses as a pivotal factor in isopod–iridovirus dynamics.

We tested independently the influences of increasing temperature and decreasing moisture on life history and physiological traits in the arthropod Armadillidium vulgare. Both increasing temperature and decreasing moisture led reproductive success to decrease. While the density of immune cells decreased and the β-galactosidase activity increased with increasing temperature and decreasing moisture, which suggests a negative impact of these stressors on individual performance, increased temperature and decreased moisture affected differently the other biomarkers conjuring different underlying mechanisms depending on the stress applied. Our findings demonstrate overall a negative impact of high temperature and low moisture on woodlouse welfare. Changing temperature or moisture had slightly different effects, illustrating the need to test further the respective role of each of these key components of climate change on organisms to predict more reliably the future of our ecosystems.

We tested independently the influences of increasing temperature and decreasing moisture on life history and physiological traits in the arthropod Armadillidium vulgare . Both increasing temperature and decreasing moisture led reproductive success to decrease. While the density of immune cells decreased and the β-galactosidase activity increased with increasing temperature and decreasing moisture, which suggests a negative impact of these stressors on individual performance, increased temperature and decreased moisture affected differently the other biomarkers conjuring different underlying mechanisms depending on the stress applied. Our findings demonstrate overall a negative impact of high temperature and low moisture on woodlouse welfare. Changing temperature or moisture had slightly different effects, illustrating the need to test further the respective role of each of these key components of climate change on organisms to predict more reliably the future of our ecosystems.

The protection conferred by a first infection upon a second pathogenic exposure (i.e. immune priming) is an emergent research topic in the field of invertebrate immunity. Immune priming has been demonstrated in various species, but little is known about the intrinsic factors that may influence this immune process. In this study, we tested whether age, gender and the symbiotic bacterium Wolbachia affect the protection resulting from immune priming in A. vulgare against S. enterica. We firstly primed young and old, symbiotic and asymbiotic males and females, either with a non‐lethal low dose of S. enterica, LB broth or without injection (control). Seven days post‐injection, we performed a LD₅₀ injection of S. enterica in all individuals and we monitored their survival rates. We demonstrated that survival capacities depend on these three factors: young and old asymbiotic individuals (males and females) expressed immune priming (S. enterica‐primed individuals survived better than LB‐primed and non‐primed), with a general decline in the strength of protection in old females, but not in old males, compared to young. When Wolbachia is present, the immune priming protection was observed in old, but not in young symbiotic individuals, even if the Wolbachia load on entire individuals is equivalent regardless to age. Our overall results showed that the immune priming protection in A. vulgare depends on individuals’ states, highlighting the need to consider these factors both in mechanistical and evolutionary studies focusing on invertebrate's immunity.

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. Cellular senescence biomarkers are available in woodlouse and are age-related. These biomarkers provide relevant biomarkers to test the impact of environmental conditions, through changes in temperature and photoperiod, on individuals of the same age maintained in different environmental conditions. 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 β-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 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.