Project Title

Escaping the Arrhenius Tyranny: Metabolic Compensation during exposure to high temperature in Daphnia

Authors' Affiliations

Bret L. Coggins and Dr. Lev Y. Yampolsky, Department of Biology, College of Arts and Sciences, East Tennessee State University, Johnson City, TN

Location

BAYS MTN. ROOM 125

Start Date

4-4-2018 2:40 PM

End Date

4-4-2018 2:55 PM

Name of Project's Faculty Sponsor

Lev Yampolsky

Faculty Sponsor's Department

Department of Biology

Type

Oral Presentation

Classification of First Author

Graduate Student-Master’s

Project's Category

Natural Sciences

Abstract Text

Poikilothermic organisms experience trade-offs associated with life at different temperatures caused by incompatible physiological and biochemical demands caused by temperature extremes. As the result many such organisms exhibit acclamatory effects, adjusting their metabolism and physiology to recently experiences temperatures. One such acclamatory effect is the metabolic compensation that allows an organism to withstand increases in temperature by decelerating biological rates below Arrhenius expectations, presumably reducing energetic demand and reducing stress. Daphnia magna is resilient across a wide temperature range, and if acclimated to mildly stressful temperatures first, exhibits longer survival in lethal temperatures. Certain genotypes of Daphnia also exhibit higher acute thermal tolerance than others, indicating the presence of genetic variation and local adaptation in heat tolerance. This study examined the effect of ambient temperature (5°C-37°C) and acclimation history (2 generations at 10°C or 25°C) on the oxygen consumption rates of 8 genotypes of Daphnia (4 with high acute temperature tolerance, and 4 low). There are nonlinear decelerations of Daphnia respiratory rates across a temperature gradient when acclimated to 25°C or following short 8-hour acclimation to measurement temperatures. Furthermore, Daphnia exposed to a near-lethal temperature (35°C) with a subsequent 24-hour recovery period at their native 25°C-acclimation temperature shows no indication of respiratory damage. Genotype showed no difference in metabolic compensation, indicating the process is genetically constrained. Regulation of mitochondrial and membrane function are promising areas to further characterize the mechanism of metabolic compensation found in this study.

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Apr 4th, 2:40 PM Apr 4th, 2:55 PM

Escaping the Arrhenius Tyranny: Metabolic Compensation during exposure to high temperature in Daphnia

BAYS MTN. ROOM 125

Poikilothermic organisms experience trade-offs associated with life at different temperatures caused by incompatible physiological and biochemical demands caused by temperature extremes. As the result many such organisms exhibit acclamatory effects, adjusting their metabolism and physiology to recently experiences temperatures. One such acclamatory effect is the metabolic compensation that allows an organism to withstand increases in temperature by decelerating biological rates below Arrhenius expectations, presumably reducing energetic demand and reducing stress. Daphnia magna is resilient across a wide temperature range, and if acclimated to mildly stressful temperatures first, exhibits longer survival in lethal temperatures. Certain genotypes of Daphnia also exhibit higher acute thermal tolerance than others, indicating the presence of genetic variation and local adaptation in heat tolerance. This study examined the effect of ambient temperature (5°C-37°C) and acclimation history (2 generations at 10°C or 25°C) on the oxygen consumption rates of 8 genotypes of Daphnia (4 with high acute temperature tolerance, and 4 low). There are nonlinear decelerations of Daphnia respiratory rates across a temperature gradient when acclimated to 25°C or following short 8-hour acclimation to measurement temperatures. Furthermore, Daphnia exposed to a near-lethal temperature (35°C) with a subsequent 24-hour recovery period at their native 25°C-acclimation temperature shows no indication of respiratory damage. Genotype showed no difference in metabolic compensation, indicating the process is genetically constrained. Regulation of mitochondrial and membrane function are promising areas to further characterize the mechanism of metabolic compensation found in this study.