Development of senescence biomarkers in the common woodlouse

Abstract During their lives, organisms accumulate, damages in their cells leading to a process called cellular senescence. Senescent cells display many cellular modifications that can be assessed through different biomarkers. Senescence biomarkers are highly studied in humans and are particularly useful to understand the processes involved in age-related diseases. However, while studies on invertebrate ageing are increasing, senescence biomarkers remain poorly developed in these taxa. In order to develop useful senescence biomarkers in invertebrates and more particularly in the common woodlouse Armadillidium vulgare, we looked at the effect of age on three known biomarkers in vertebrates: immune cells (cell size, density and viability), β-galactosidase activity and Telomerase Reverse Transcriptase (TERT) (essential subunit of the telomerase protein) gene expression on this species. As expected, we observed that the size of immune cells was higher in older individuals while their density and viability decreased, the β-galactosidase activity increased with age while the Telomerase Reverse Transcriptase (TERT) gene expression decreased. These biomarkers classically used in vertebrates are thus correlated with age in our invertebrate model and make reliable biomarkers to highlight cell senescence in A. vulgare. A strong gender effect was also observed on senescence biomarkers that could indicate different resource allocation strategies. These biomarkers, allowing us to highlight differential cellular senescence between males and females, could be a new tool to test the impact of different factors influencing life history traits and related resources allocation and consequently help us to understand the diversity of senescence patterns observed between individuals, sexes, populations and species.