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!
The paper "How to assess Drosophila cold tolerance: chill coma temperature and lower lethal temperature are the best predictors of cold distribution limits" is now avaliable online.
Five metrics of cold tolerance were measured for 14 Drosophila species to determine which metrics most strongly correlate with geographic distribution. Measures of chill coma onset temperature, lethal temperature and lethal time at low temperature proved to be the best predictors to describe the variation in realized latitudinal distributions and estimated environmental cold exposure. Measures of chill coma recovery time also correlated significantly with estimated minimum temperature, while the supercooling point did not.
Considering the findings of the present study, data from previous studies and the logistical constraints of each measure of cold tolerance, we conclude that chill coma onset temperature and lethal temperature are superior measures when estimating the ecologically relevant cold tolerance of drosophilids. Of these two traits, chill coma onset temperature requires less equipment, time and animals and thereby presents a relatively fast, simple and dynamic measure of cold tolerance.
Sensitivity to thermal extremes in Australian Drosophila implies similar impacts of climate change on the distribution of widespread and tropical species
Global Change Biology
we demonstrate that it is especially the extreme temperature events that define the distribution ofAs climate change is progressing, the temperature of our planet increases. This is particularly important for the large group of animals that are cold-blooded (ectothermic), including insects. Their body temperature is ultimately determined by the ambient temperature, and the same therefore applies to the speed and efficiency of their vital biological processes. But is it changes in average temperature or frequency of extreme temperature conditions that have the greatest impact on species distribution? In a recent recent publication in the journal both tropical and temperate drosophila species. Thus climate change affects ectotermic animals primarily because more periods of extreme weather are expected in the future.
Linkt to paper:
See also the news links below:
In this study we describe a method for obtaining reliable estimates of standard metabolic rate for small ectothermic animals. Using repeated stop-flow respirometry we were able to investigate the effects of inbreeding on standard metabolic rate in Drosophila melanogaster. We hypothesized that inbreeding results in increased metabolic rate, and further that this effect would be more pronounced at stressful low and high temperatures. However, contrary to our hypothesis we did not find any interaction between temperature and the effect of inbreeding or any general difference in metabolic rate between inbred and outbred individuals. However, inbreeding did affect the variance. Nonetheless variance in metabolic rate was higher between the inbred lines compared to the outbred lines with some inbred lines having very high or low metabolic rate, indicating that genetic drift, and not inbreeding, seem to explain the variation in metabolic rate in populations of different size.
In this study we found that cold tolerance in Enchytraeus albidus was varied in a reliable manner with location from where the populations originated such that cold adapted arctic populations were more cold resistant than populations from temperate environments. Glucose accumulation, glycogen reserves and metabolic rate also varied significantly between populations but this variation was not related directly to cold tolerance suggesting that the metrics important for cold tolerance are complicated. When measuring metabolic rate of frozen and unfrozen animals at the same temperature (-2°C) we found a metabolic depression of approximately 50%. Interestingly this depression was larger in the arctic than temperate population suggesting that frozen artic animals may have lower energetic turnover than temperate conspecifics. http://link.springer.com/article/10.1007%2Fs00360-013-0788-6
We are happy to announce that the paper “Why do insects enter and recover from chill coma? Low temperature and high extracellular potassium compromises muscle function in Locusta migratoria” has been accepted for publication in the Journal of Experimental Biology.
This year we are organizing a session entitled
“What sets the limit? How thermal limits, performance and preference in ectotherms are influenced by water or energy balance”
that will include a number of interesting talks by Martin Holmstrup, Art Woods, Brent Sinclair, Vladimir Kostal, Wilco Verberk, Fiona Clissold, Kate Michell and others
We are happy to announce that Jonas Andersen (along with 2 other students) was awarded a certificate of excellence, for his oral presentation on “Drosophila cold tolerance measurements”, at the ISEPEP5 meeting in Canada.
Validity of thermal ramping assays used to assess thermal tolerance in arthropods” is scheduled to be published in PLoS ONE on 3/9/2012 with the press embargo ending at 2 p.m. Pacific Time (5 p.m. Eastern) on 3/9/2012. On publication, your paper will be available online at http://dx.plos.org/10.1371/journal.pone.0032758.
The homepage is under constuction, coming along nicely! -Jonas