New people in the lab!

We'd like to welcome Camilla, Christian, Christina, Jeppe, Lisa, Mathias, and Nikolaj to the lab! 

Their research will cover a wide range of topics, ranging from the effect of cold on ion and water balance regulation to behvaioural thermoregulation - all in a variety of different insect species.

We're looking forward to working with you!

We're back after the summer holiday!

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Since the last update, many papers have been published by our group. Topics include cold tolerance in insects and upper thermal tolerance in ectotherms


Overgaard, J. and MacMillan, H.A. (2017) The integrative physiology of insect chill tolerance. Annual Reviews in Physiology 79:187-208

Can be found HERE

Jensen, D.L., Overgaard, J., Wang, T., Gesser, H. and Malte, H. (2017). Temperature effects on aerobic scope and cardiac performance of European perch (Perca fluviatilis). Journal of Thermal Biology 68, 162-169.

Can be found HERE

Jørgensen, L.B. MacMillan, H.A. and Overgaard, J. (2017). Cold mortality is not caused by oxygen limitation or loss of ion homeostasis in the tropical freshwater shrimp Macrobrachium rosenbergii. Cryobiology 76, 146-149

Can he found HERE

Andersen, M.K., Jensen, S.O. and Overgaard, J. (2017) Physiological correlates of chill susceptibility in Lepidoptera. Journal of Insect Physiology 98, 317-326

Can be found HERE

Messamah, B., Malte, H., Loeschcke, V., Kellermann, V. and Overgaard, J. (2017) Metabolic cold adaptation contributes little to the interspecific variation in metabolic rates of 65 species of Drosophilidae. Journal of Insect Physiology 98, 309-316

Can be found HERE

Andersen, M.K., Folkersen, R., MacMillan, H.A., Overgaard, J. (2017) Cold acclimation improves chill tolerance in the migratory locust through preservation of ion balance and membrane potential. Journal of Experimental Biology 220, 487-496

Can be found HERE

Sørensen, J.G., Kristensen, T.N. and Overgaard, J. (2016) Evolutionary and ecological patterns of thermal plasticity in Drosophila: Is it important for keeping up with climate change? Current Opinions in Insect Science 17, 98-104

Can be found HERE

Olsson, T., MacMillan, H.A., Nyberg, N., Stærk, D., Malmendal, A. and Overgaard, J. (2016) Hemolymph metabolites and osmolality are tightly linked to cold tolerance of Drosophila species: a comparative study. Journal of Experimental Biology 219, 2504-2513

Can be found HERE

Dohn, N.B., Fago, A., Overgaard, J., Madsen, P.T. and Malte, H. (2016). Students’ motivation toward laboratory work in physiology teaching. Advances in Physiological Education 40: 313-318.

Can be found HERE

Rohde, P.D., Krag, K., Loeschcke, V., Overgaard, J., Sørensen, P. and Kristensen, T.N. (2016). A quantitative genomic approach for analysis of fitness and stress related traits in a Drosophila model population. International Journal of Genomics. 2016, Article ID 2157494

Can be found HERE

Findsen, A., Overgaard, J., and Pedersen. (2016) T.H. Reduced L-type Ca2+ current and compromised excitability induce loss of skeletal muscle function during acute cooling in locust. Journal of Experimental Biology. 219:2340-2348

Can be found HERE

Vanthournout, B., Greve, M., Madsen, A., Bechsgaard, J., Overgaard, J., Bilde, T. (2016). Benefits of group living include increased feeding efficiency and lower mass loss during desiccation in the social and inbreeding spider Stegodyphus dumicola. Frontiers in Physiology

Can be found HERE

Verberk, W.C.E.P., Overgaard, J., Ern, R., Bayley, M., Wang, T., Boardman, L., and Terblanche, J.S. (2016) Does oxygen limit thermal tolerance in arthropods? A critical review of current evidence. Comparative Biochemistry and Physiology A. 192: 64–78

Can be found HERE

New paper published in Journal of Thermal Biology

Lisa’s paper on ion balance and cardiac performance in crabs exposed to heat stress titled “Paralysis and heart failure precede ion balance disruption in heat-stressed European green crabs” is now published in the Journal of Thermal Biology!

"Acute exposure of ectotherms to critically high temperatures causes injury and death, and to find out which physiological mechanisms set the thermal limits, we need to comprehend in what order the physiological perturbations occur. In this paper we found that extracellular ion balance is lost when crabs are exposed to heat stress, but that this loss only follows AFTER the crab is paralyzed, and cardiac performance is compromised. Accordingly, loss of ion balance does not cause paralysis, and this loss might instead be a consequence of tissue damage caused by failure of other physiological systems."

The paper can be found HERE

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New Paper Published in Scientific Reports

"The capacity to maintain ion and water homeostasis underlies interspecific variation in Drosophila cold tolerance" has been published in Scientific Reports.

In a recent paper we have used a comparative approach to investigate the role of the Malpighian Tubule in regulating hemolymph ion balance during cold exposure. This work confirms earlier observations that insect chill tolerance is very closely related to preservation of ion balance and highlights a potential important role of the insect renal system.

The paper is available HERE

More news can be found on these links: Danish & English

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Paper published in Functional Ecology

The paper: "Tropical to subpolar gradient in phospholipid composition suggests adaptive tuning of biological membrane function in drosophilids" is now published.

This paper concerns the structural modifications in cell membranes that modify its physical properties to secure suitable fluidity at different temperatures. Such adaptive mechanisms in phospholipid fatty acid (PLFA) composition have never been examined via a multispecies approach including appropriate phylogenetic analysis.

We found that the tropical- to subpolar-species gradient in PLFA composition suggests adaptive regulation of biological membrane function and suggest that modification of membrane composition is likely an important adaptive trait in insects and perhaps invertebrates in general.

Find the paper HERE

Find a summary of the paper HERE (Danish)

Paper published in Proceedings B

"Concurrent effects of cold and hyperkalaemia cause insect chilling injury" has been published in Proceeding of the Royal Society B.

The paper concerns whether whether chill injury occurs during cold exposure or following return to benign temperature, specifically if elevated extracellular [K+], low temperature, or a combination thereof causes cell death in muscle tissue of the migratory locust (Locusta migratoria)

 

Download the paper HERE

Paper in JIP

The paper "Temperate Drosophila preserve cardiac function at low temperature" by Jonas, Heath and Johannes has been accepted for publication in the Journal of Insect Physiology.

By examining the continually active heart of five Drosophila species with markedly different cold tolerance, we investigated whether cardiac performance is related to the whole animal critical thermal minimum. 

 

Adult and developmental acclimation alter ion balance in similar ways

A new article is now available in early view at the American Journal of Physiology, Regulatory, Integrative and Comparative Physiology. Here, we show that improvements in cold tolerance acquired through adult acclimation and acclimation during development are both associated with similar changes in ion and water balance. This integrative study was a collaboration among Heath MacMillan, Jonas Andersen, Volker Loeschcke and Johannes Overgaard. Read the abstract or download the paper here (sorry about the paywall!).

Prize bonanza at APS meeting in San Diego

At this years APS intersociety meeting in San Diego the lab participants claimed a considerable portion of the prices. Jonas, Anders and Heath received travel awards on the merits of their abstract, Anders also won the third prize in the poster competition and finally, but not least Heath won the runner up price for the very prestigious Scholander award.

 

As is also clear from the picture – Johannes did not win any awards in his attempt to take a focused photo!

Thermal plasticity is similar in temperate and tropical Drosophila simulans

It is often assumed that populations living in more variable environments are endowed with higher degree of thermal plasticity, but this question is rarely examined eventhough phenotypic plasticity may be an important initial mechanism to counter environmental change. Using populations of Drosophila simulans collected from a latitudinal cline spanning the entire east coast of Australia, Belinda Van Heerwaarden and others assessed thermal plasticity, measured as hardening capacity (the difference between basal and hardened thermal tolerance) for multiple
measures of heat and cold tolerance across both adult and larval stages of development. This allowed us to explicitly ask whether the evolution of thermal plasticity is favoured in more variable, temperate environments. We found no relationship between thermal plasticity and latitude, providing little support for the hypothesis that temperate populations have evolved higher levels of thermal plasticity than their tropical counterparts.
 
 
B. van Heerwaarden, B., Lee, R. F. H., Overgaard, J. and Sgrò, C.M. (2014)

No patterns in thermal plasticity along a latitudinal gradient in Drosophila simulans from eastern Australia.

In press in Journal of Evolutionary Biology 27:2541-53.

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Paper in JEB

The paper: "Cold-induced depolarization of insect muscle: Differing roles of extracellular K+during acute and chronic chilling” has now been published in The Journal of Experimental Biology (link). In this manuscript, we collaborated with Thomas Pedersen and used the migratory locust as a model to examine whether depolarization of resting membrane potential (which is thought to cause insect chill coma) can be attributed to a loss of K+ balance, and how recovery of K+ balance following cold exposure might permit recovery from chill coma. Our findings suggest that chill coma onset and chill coma recovery are mechanistically independent, which explains why these traits often do not correlate within and among insect species. A good example of this lack of correlation (among species of the genus Drosophila) can be found in our recent Functional Ecology paper described below. This is an important finding, because it implies that focusing on one of these two traits might lead to molecular targets of cold tolerance selection that are only half of the story!