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.…”

Short lifespan is one’s fate, long lifespan is one’s achievement: lessons fromDaphnia

“…Thus it remains to be tested if males react to experimental treatments and longevity interventions differently from females. There is evidence that such differences may be clone- (Pietrzak et al 2018) and temperature-dependent (Pietrzak et al 2018;this study).…”

“…Using male-only cohorts eliminates the need of neonate removal (and of course any possibility of Jeanne Calment effect), but also takes any possible trade-offs with the large energy expenditure of producing eggs out of the consideration and reduces generality of finding if the two sexes age differently, and respond to interventions differently, i.e., there are sex-by-age or sex-by-treatment interactions. Males in Daphnia consistently show a shorter lifespan than females (Constantinou et al 2019; but see Pietrzak et al 2018), an observation made nearly a hundred years ago (Macarthur and Baillie 1926) that served as one of the first evidence supporting the rate of living hypothesis (Rubner 1908; Pearl 1928; Speakman 2005). Considering the more recent interpretation of the rate of living hypothesis in terms of the amount of oxidative damage accumulated over the lifetime as the limiting factor for lifespan extension (Austad 2018), one would expect the shorter lifespan in Daphnia males to be associated with faster, in astronomical time, but similar, over relative age, accumulation of reactive oxygen species-mediated damages.…”

“…Using male-only cohorts eliminates the need of neonate removal (and of course any possibility of Jeanne Calment effect), but also takes any possible trade-offs with the large energy expenditure of producing eggs out of the consideration and reduces generality of finding if the two sexes age differently, and respond to interventions differently, i.e., there are sex-by-age or sex-by-treatment interactions. Males in Daphnia consistently show a shorter lifespan than females (Constantinou et al 2019; but see Pietrzak et al 2018), an observation made nearly a hundred years ago (Macarthur and Baillie 1926) that served as one of the first evidence supporting the rate of living hypothesis (Rubner 1908;Pearl 1928;Speakman 2005).…”

“…An effect similar in magnitude and presence of strong interactions was demonstrated by the two species of food algae – a green alga Scenedesmus and a stramenopile alga Nannochloropsis, which is, in contrast to green algae, known to be rich in PUFAs. It remains unknown if the use of other, less commonly used algal species, such as Chlamydomonas reinhardtii (Pietrzak et al 2018) or Chlorella vulgaris (Constantinou et al 2019) would produce a lifespan altering effect in a common-garden experiment. An attempt to replace freshly grown algal food by commercially available dry cyanobacterial diel, which could have been advantageous in term of diet standardization, demonstrated that this is probably going to be difficult to achieve without a significant decrease of longevity, i.e., without possible masking of beneficial longevity-extending intervention effects.…”