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PLASTICITY OF ONTOGENY OF ENERGY SAVING MECHANISMS IN HETEROTHERMIC MAMMALS

Abstract
In the context of global change and increasing frequency of unpredictable climate events, there is growing interest in how well physiological flexibility can buffer organisms from environmental hazards. One key metabolic constraint imposed by environmental fluctuations is food shortage. Heterothermy (daily torpor and hibernation) allows energy savings in response to reduced food availability. But flexibility of heterothermy has almost exclusively been investigated in adult animals. How do conditions of heterothermy expression in juveniles during their development shape the efficiency of torpor? Are individuals born under harsh conditions better prepared to use torpor later in life? Is there a multigenerational epigenetic transmission of heterothermy regulation? Heterothermic juveniles are under strong selective pressure to grow and fatten fast before their first winter, which is critical for their survival. We have chosen to study the developmental sequences of torpor in a hibernator, the garden dormouse (Eliomys quercinus, Rodents) that uses both winter hibernation and daily or prolonged torpor before winter. We propose to investigate how exposure to food shortage during growth shapes the use of torpor during adulthood (calorie restriction vs. reference diet; Objective 1).Social thermoregulation is a widespread energy-saving strategy that is complementary to torpor. Only few species use both strategies but we expect their combination to permit individuals to maximise energy savings in relation to their environmental constraints. A major advantage of social thermoregulation resides in the simultaneous possibility to minimize energy expenditure but maintaining a relatively high body temperature (Tb), which is necessary for sufficient growth. Huddling is also believed to allow a reduction in energy costs for the rewarming phase from a torpid state. Periodic phases of arousals from torpor are particularly demanding in terms of energy and are associated with greater levels of oxidative stress, impacting on the animal’s somatic maintenance. Minimising these costs could be advantageous for young individuals raised in groups, on both a short-term and a long-term basis (Objective 2).In the final part of the project, we will test whether between-individual differences in torpor use could have an epigenetic basis that can potentially be transmitted to the next generation (Objective 3). This is a fundamental mystery in the regulation of phenotypic flexibility: can the phenotype of descendants be optimized by parents to improve offspring performance in response to future food shortage?
Lemma
Ontogeny of Heterothermy
Project leader
Giroud Sylvain
Duration
01.08.2018-31.05.2022
Programme
FWF Einzelprojekte
Type of Research
Basic research
Staff
Stalder G., Project team member
Painer J., Project team member
Vetmed Research Units
Konrad Lorenz Institute of Ethology
Institute of Pathology, Pathology of Laboratory Animals
Research Institute of Wildlife Ecology
Funded by
FWF - Fonds zur Förderung der wissenschaftlichen Forschung, Sensengasse 1, 1090 Wien, Austria

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