When males outlive females: Sex‐specific effects of temperature on lifespan in a cyclic parthenogen

Abstract

Lifespans of males and females frequently differ as a consequence of different life history strategies adopted to maximize fitness. It is well visible in cyclic parthenogens, such as water fleas of the genus Daphnia, where males appear in the population usually only for periods when receptive females are available. Moreover, even within one sex, different life history strategies and mechanisms regulating lifespan may exist. Previous studies suggested that Daphnia males may regulate their lifespan by staying in colder waters than females. We hypothesize that such behavioral mechanism should be associated with stronger reaction to low temperature–that is greater lifespan extension in males than in females. In this study, we monitored survivorship of Daphnia magna females and males of three clonal lines cultured at 16 or 20°C. The results did not provide a species‐level corroboration of our hypothesis; instead, they revealed very strong intraspecific differences in the responses of male and female lifespan to temperature change. They further suggest the existence of parallel life history strategies, hypothesis whose tests would bring new insights into the ecology of males in cyclic parthenogens.

A comprehensive epigenomic analysis of phenotypically distinguishable, genetically identical female and male Daphnia pulex

“…In contrast, genes containing higher CpG methylation levels in female Daphnia were enriched for partially linked pathways related to immune response (Toll like receptor cascades, Interleukin-17 signalling, Class I MHC mediated antigen processing & presentation, and TRAF6 mediated induction of NFkB and MAP kinases upon TLR7/8 or 9 activation) and ageing (Cellular senescence, Senescence-Associated Secretory Phenotype, MAP kinase activation, and Negative regulation of FGFR signalling). Enrichment of these particular pathways in female Daphnia may be related to the fact that female Daphnia typically have a longer lifespan compared to male Daphnia [21][22][23], although few male strains maintained under specific conditions have shown to outlive females [51]. The enriched pathways could explain some of the phenotypic differences observed between female and male Daphnia.…”