Insect Low Temperature Biology
The Sinclair Lab at UWO

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We are interested in all manner of things associated with arthropods at low temperatures (and sometimes at high temperatures, too!).  Below you can read about some of the things happening in the lab. Watch this space and the publications page to see how things develop.

Cold tolerance in Ontario
Overwintering energetics
Evolution and mechanisms of cold tolerance
The mechanisms underlying cold tolerance in insects
Chill Coma

Cold tolerance of insects in southwestern Ontario... and the world

We are interested in how the insects that surround us in southwestern Ontario survive the winter.  This is of interest not just because we like freezing bugs (who wouldn't!?), but because climate change in southwestern Ontario is predicted to result in an increase in mean annual temperature and a decrease in precipitation.  Although this scenario predicts an increase in the length of the growing season, it also implies reduced snow cover (which reduces insulation) and therefore an increase in freeze-thaw cycles.  In addition, a decrease in winter length or intensity may result in a drastic increase in overwinter survival of pest species, leading to larger spring populations of pest insect species.  Finally, the predicted milder climate may increase the impact of invasive insect species in southwestern Ontario.  So understanding how overwintering conditions affect survival and population processes in the field is an important priority for predicting and managing insect populations during a period of rapid climate change. Our local 'guinea pigs' include the goldenrod gall fly, the banded woolly bear caterpillar, and the acorn weevil Curculio glandium.  In addition, we are exploring the potential impacts of Ontario's changing winter conditions on the spread and performance of invasive insect species like spotted wing Drosophila and the brown marmorated stink bug, as well as the irruptive native Eastern spruce budworm.  I know they aren't insects, but a few people in the lab also like freezing slugs and snails.

We also have collaborations looking at overwintering biology of insects in the sub-Antarctic, the Sierra Nevada of California and lots of other exciting places, too.

Overwintering energetics of insects

Many insects overwinter in a state of quiescence or diapause and are thus unable to feed while overwintering.  This means that their energy stores are fixed, and changes in winter conditions (e.g. because of anthropogenic climate change) can result in changes to the amount of energy left to an insect at the end of winter.  Using a number of different model systems (e.g. swallowtail butterflies and heather beetles), we are exploring the relationships between temperature, climate, energy use and the performance of overwintered insects in subsequent years.  You can read some of the results of this work here.

Evolution of insect cold tolerance

Evolutionary themes pervade many of the questions we ask in the lab, and I have a long-standing interest in how insect cold tolerance strategies may have evolved and how different climatic conditions and variability influence the success of the different strategies. Insects in variable, cold environments in the Southern Hemisphere have evolved freeze tolerance under different selective pressures to insects that have done the same in the Northern Hemisphere.  The influence of the Great Lakes means that SW Ontario is located in an 'island' of unusually warm and unpredictable climatic conditions, and we are curious as to whether this will have a long term influence on responses to climate change and northward migration of both invasive and native species.  We are particularly interested in analysis of microclimate.  The latest version of a set of Excel macros I wrote to facilitate this is available here.

Allied to this, we are utilising several different Drosophila model systems to investigate the evolution of cold tolerance.  We have been using lines of flies selected for cold tolerance to explore cross-tolerance between tolerance to cold and other stresses, and we are also using multiple species of Drosophila to examine the biochemical correlates and performance tradeoffs of cold tolerance.  There is opportunity for enthusiastic students to work on this project.


The mechanisms underlying cold tolerance in insects

A major theme in our lab is trying to understand the physiology, biochemistry and molecular biology behind the ability of some insects to tolerate low temperatures... and why others are killed by cold.  As well as the Drosophila system described above (did I mention that this would be ideal for enthusiastic students?), we are exploring the physiology of thawing and ice-redistribution processes in insects, and also starting to use high-throughput '-omics' techniques to identify candidate genes underlying susceptibility to cold. 

Brent Sinclair is also part of an exciting collaboration with Thomas Buckley at Landcare Research in New Zealand, where we are using high-throughput RNA sequencing to understand how some stick insects have evolved the ability to survive internal ice formation (yes, you read that right: you can freeze these guys so they snap like twigs, but if you thaw them out, they'll wander off quite happily).  This will give us exciting insights into the mechanisms underlying freeze tolerance in other species. 

Finally, and at the moment I'll include this in this section, lots of recent evidence suggests that the immune system is upregulated by insects when they are exposed to cold.  We are just beginning a series of projects to figure out whether this is the case, and then to examine the what, why and how of low temperature eco-immunology in insects.

The biology of chill coma in insects

When insects are cooled down, they enter a reversible state of paralysis called chill coma.  Chill coma temepratures are very plastic, and respond quickly to acclimation in the lab and evolution in the field.  Surprisingly, the mechanisms of chill coma in insects are relatively poorly understood.  It seems that chill coma is caused by a slowing down of transmembrane ion pumps, particularly Na+,K+-ATPase with decreasing tremperature, leading to equilibration of ions across nerve cell membranes.  We have made some pretty good progress on this - we have confirmed that loss and restoration of ion balance underlie onset and recovery from chill coma, and we are figuring out the mechanisms that underlie this.  Some of this work involves getting into epithelial transport in the gut and Malpighian tubules - an exciting and terrifying prospect all at once, and another awesome direction for a top-quality PhD student.