Browsing by Subject "Torpor"

Now showing 1 - 3 of 3
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    Body Mass and Tail Girth Predict Hibernation Expression in Captive Dwarf Lemurs.
    (Physiological and biochemical zoology : PBZ, 2022-03) Blanco, Marina B; Greene, Lydia K; Klopfer, Peter H; Lynch, Danielle; Browning, Jenna; Ehmke, Erin E; Yoder, Anne D
    AbstractHibernation, a metabolic strategy, allows individuals to reduce energetic demands in times of energetic deficits. Hibernation is pervasive in nature, occurring in all major mammalian lineages and geographical regions; however, its expression is variable across species, populations, and individuals, suggesting that trade-offs are at play. Whereas hibernation reduces energy expenditure, energetically expensive arousals may impose physiological burdens. The torpor optimization hypothesis posits that hibernation should be expressed according to energy availability. The greater the energy surplus, the lower the hibernation output. The thrifty female hypothesis, a variation of the torpor optimization hypothesis, states that females should conserve more energy because of their more substantial reproductive costs. Contrarily, if hibernation's benefits offset its costs, hibernation may be maximized rather than optimized (e.g., hibernators with greater fat reserves could afford to hibernate longer). We assessed torpor expression in captive dwarf lemurs, primates that are obligate, seasonal, and tropical hibernators. Across 4.5 mo in winter, we subjected eight individuals at the Duke Lemur Center to conditions conducive to hibernation, recorded estimates of skin temperature hourly (a proxy for torpor), and determined body mass and tail fat reserves bimonthly. Across and between consecutive weigh-ins, heavier dwarf lemurs spent less time in torpor and lost more body mass. At equivalent body mass, females spent more time torpid and better conserved energy than did males. Although preliminary, our results support the torpor optimization and thrifty female hypotheses, suggesting that individuals optimize rather than maximize torpor according to body mass. These patterns are consistent with hibernation phenology in Madagascar, where dwarf lemurs hibernate longer in more seasonal habitats.
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    Investigating the Intrinsic and Extrinsic Drivers of Primate Heterothermy
    (2016) Faherty, Sheena Lee

    Seasonal heterothermy—an orchestrated set of extreme physiological responses—is directly responsible for the over-winter survival of many mammalian groups living in seasonal environments. Historically, it was thought that the use of seasonal heterothermy (i.e. daily torpor and hibernation) was restricted to cold-adapted species; it is now known that such thermoregulatory strategies are used by more species than previously appreciated, including many tropical species. The dwarf and mouse lemurs (family Cheirogaleidae) are among the few primates known to use seasonal heterothermy to avoid Madagascar’s harsh and unpredictable environments. These primates provide an ideal study system for investigating a common mechanism of mammalian seasonal heterothermy. The overarching theme of this dissertation is to understand both the intrinsic and extrinsic drivers of heterothermy in three species of the family Cheirogaleidae. By using transcriptome sequencing to characterize gene expression in both captive and natural settings, we identify unique patterns of differential gene expression that are correlated with extreme changes in physiology in two species of dwarf lemurs: C. medius under captive conditions at the Duke Lemur Center and C. crossleyi studied under field conditions in Madagascar. Genes that are differentially expressed appear to be critical for maintaining the health of these animals when they undergo prolonged periods of metabolic depression concurrent with the hibernation phenotype. Further, a comparative analysis of previously studied mammalian heterotherms identifies shared genetic mechanisms underlying the hibernation phenotype across the phylogeny of mammals. Lastly, conducting a diet manipulation study with a captive colony of mouse lemurs (Microcebus murinus) at the Duke Lemur Center, we investigated the degree to which dietary effects influence torpor patterns. We find that tropical primate heterotherms may be exempt from the traditional paradigms governing cold-adapted heterothermy, having evolved different dietary strategies to tolerate circadian changes in body temperature.

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    Variation in gut microbiome structure across the annual hibernation cycle in a wild primate.
    (FEMS microbiology ecology, 2022-07) Greene, Lydia K; Andriambeloson, Jean-Basile; Rasoanaivo, Hoby A; Yoder, Anne D; Blanco, Marina B
    The gut microbiome can mediate host metabolism, including facilitating energy-saving strategies like hibernation. The dwarf lemurs of Madagascar (Cheirogaleus spp.) are the only obligate hibernators among primates. They also hibernate in the subtropics, and unlike temperate hibernators, fatten by converting fruit sugars to lipid deposits, torpor at relatively warm temperatures, and forage for a generalized diet after emergence. Despite these ecological differences, we might expect hibernation to shape the gut microbiome in similar ways across mammals. We, therefore, compare gut microbiome profiles, determined by amplicon sequencing of rectal swabs, in wild furry-eared dwarf lemurs (C. crossleyi) during fattening, hibernation, and after emergence. The dwarf lemurs exhibited reduced gut microbial diversity during fattening, intermediate diversity and increased community homogenization during hibernation, and greatest diversity after emergence. The Mycoplasma genus was enriched during fattening, whereas the Aerococcaceae and Actinomycetaceae families, and not Akkermansia, bloomed during hibernation. As expected, the dwarf lemurs showed seasonal reconfigurations of the gut microbiome; however, the patterns of microbial diversity diverged from temperate hibernators, and better resembled the shifts associated with dietary fruits and sugars in primates and model organisms. Our results thus highlight the potential for dwarf lemurs to probe microbiome-mediated metabolism in primates under contrasting conditions.