Mathias Dezetter: Physiological responses to increasing temperature combine energy and water balance in a long-lived snake

Mathias Dezetter, PhD student at the Centre d’Etudes Biologiques de Chizé and the Institut d’Ecologie et des Sciences de l’Environnement de Paris, discusses with us his recently accepted paper, “Additive effects of developmental acclimation and physiological syndromes on lifetime metabolic and water loss rates of a dry-skinned ectotherm.”

About the paper

Mathias Dezetter
Mathias Dezetter

How organisms can adjust their physiology in response to climate warming is a crucial question. When facing warmer and drier conditions, some species can reduce their metabolic rate and water loss. However, various mechanisms may constrain the capacity of long-lived species to flexibly acclimate to changing climate conditions. For example, some key functional traits might be determined early in life, and these effects may be permanent. Yet, these patterns of physiological plasticity have been poorly investigated over the lifespan. This is because most experimental studies usually last over short time periods (i.e. weeks or months), which do not allow the detection of longer acclimation processes. 

We conducted an experimental study at the Centre d’Etudes Biologiques de Chizé (Ecophysiology team, UMR7372, France) on a long-lived ectotherm, the asp viper (Vipera aspis), during a 7-year period. We tested for the effects of thermal conditions during early life on developmental acclimation of standard metabolic rate and total evaporative water loss. We also investigated the patterns of co-variation between these two functional traits related to energy and water balance regulation over each individual’s entire lifespan.

We used climatic chambers to expose asp vipers to one of three contrasted daily thermal cycles (“warm”, ”medium” or “cold” cycle) over 4 years from birth to maturity, and then maintained all individuals in a common garden (“medium” cycle) for 3 years of adult life. We repeatedly measured metabolic rate and water loss of the same individuals over their life, using respirometry systems (Sable Systems).

We found that individuals reduced their metabolism in the warmer conditions, but flexibly adjusted their metabolism to common garden conditions at adulthood. Our calculations suggest that this acclimation capacity allows vipers to compensate for as much as 40% of the predicted increase in energy expenditure in warmer climates. In contrast, developmental changes in water loss persisted until adulthood. Remarkably, energy metabolism and water loss rates were positively related within individuals throughout their entire life. Altogether, this suggests that terrestrial ectotherms can exhibit individual physiological syndromes and different patterns of plastic responses in relation to energy and water balance. These findings emphasize the importance to consider physiological acclimation and individual variation when investigating organismal responses to climate change.

About the research

A female asp viper (Vipera aspis), basking to thermoregulate. Our experimental study unravels that this species may adjust its physiology to mitigate the impacts of warmer temperatures.
A female asp viper (Vipera aspis), basking to thermoregulate. Our experimental study unravels that this species may adjust its physiology to mitigate the impacts of warmer temperatures. Photo by Mathias Dezetter

The span of this study allows for a better understanding of long-term acclimation processes across an organism’s lifespan. Our paper raises new exciting research questions on the mechanisms underlying such acclimation responses and on how energy and water balance regulation interact as organisms respond to climate stressors. Our study provides great insights for the field of thermal physiology and evolutionary ecophysiology. Considering acclimation responses over longer time periods and testing for physiological syndromes in further experimental studies will help to better predict how long-lived species will respond to climate changes, and thus will better inform policy makers and conservationists.

Climatic chambers at the Centre d’Etudes Biologiques de Chizé (CNRS, France). We used this equipment to apply daily thermal cycles during 7 years.
Climatic chambers at the Centre d’Etudes Biologiques de Chizé (CNRS, France). We used this equipment to apply daily thermal cycles during 7 years.

This work was initiated by Olivier Lourdais (Ecophysiology team) who designed the study (ANR funded project ECTOCLIM and project AQUASTRESS funded by Région Nouvelle Aquitaine). Co-author Andréaz Dupoué collected the data with the climatic chambers and respirometry systems at the Centre d’Etudes Biologiques de Chizé and Jean-François Le Galliard (iEES Paris; ENS, CEREEP) contributed to the analysis of this long-term dataset.

About The Author

I have been fascinated with nature since my childhood, searching for insects and reptiles in the bush of Mali in West Africa, and later in the Mediterranean landscapes of Southern France. I got into science early and knew I wanted to work in biology. I first pursued a Master’s degree in agronomy, landscape management and conservation biology in France and Peru (VetAgro-Sup and UNALM) and then a Master’s in evolutionary biology at the University of Montpellier. It is at this time that I met Olivier Lourdais, one of my current PhD advisors, and started to get involved in this amazing project now published in Functional Ecology.  Starting my Master’s work at the Centre d’Etudes Biologiques de Chizé with Olivier is where I got passionate for ecophysiology. Understanding how organisms can adjust their physiology and behavior in response to environmental changes (i.e. climate conditions, habitats, landscape and agricultural changes) is fascinating in the frame of evolutionary ecology, and crucial for conservation biology.

I am currently a PhD student at the Institut d’Ecologie et des Sciences de l’Environnement de Paris (iEES, Sorbonne Université) and the Centre d’Etudes Biologiques de Chizé (CEBC CNRS) under the co-supervision of Olivier Lourdais and Jean-François Le Galliard. I am part of the ANR funded project AQUATHERM investigating the potential of hydroregulation and thermoregulation to influence ecological responses to climate change.

My research aims to provide a better understanding of the interactions between thermoregulation and hydroregulation in ectotherms, especially during the critical stages of reproduction and pregnancy. I use experimental approaches that jointly manipulate thermal conditions and water constraints to investigate physiological and behavioural responses in two ectotherm species: the European adder (Vipera berus), a boreal cold climate specialist, and the asp viper (Vipera aspis), a South-European species from warmer and drier climates. I recently demonstrated that a short-period of water deprivation during early-pregnancy can alter maternal physiology and reproductive success in the European adder, suggesting that more frequent and intense droughts could lead to population declines in boreal ectotherms (https://doi.org/10.1093/conphys/coab071).

In my spare time, I enjoy hiking, spending time in nature or with my animals, and working in my garden. I also set up an NGO with friends from my university to engage in science outreach, documentaries and conservation projects, named Nature Conserv’Action. Our main project at the moment is to conduct participatory biodiversity inventories with local and indigenous communities, who manage conservation concessions in the Peruvian Amazon, connecting them with local researchers and biology students. I believe collaborative and interdisciplinary projects are crucial for both research and conservation.

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