11.15.2016 // Heath MacMillan, York University, Department of Biology

Chill susceptible insects: a slow battle against entropy

​The timing and severity of the winter season are key predictors of insect distribution and abundance, but we lack an integrative understanding of why chilling causes tissue damage and death in insects. Most insect species are chill susceptible, meaning they enter a cold-induced coma (chill coma) and suffer irreversible chilling injury well before any freezing of their body fluids occurs. I will give a overview of our recent efforts to connect natural variation in chilling tolerance to the capacity of insects to maintain osmotic homeostasis in the cold. Cold-adapted or cold-acclimated flies and crickets can maintain ion balance at low temperatures and survive prolonged cold exposure. By contrast, warm-adapted species or warm-acclimated individuals lose Na+ and water balance when chilled, which causes a progressive rise in extracellular [K+] that depolarizes cell membranes and causes cell death. The gut and Malpighian tubule epithelia of insects are central to the maintenance of whole animal ion and water balance, and appear to play a critical role in the ability to survive chilling. As an example, I will discuss how cold acclimation reduces the tendency for solute leak through the paracellular septate junctions of the Drosophila gut before and during chronic cold stress. This tightening of paracellular pathways appears to primarily be driven by plastic changes in the abundance of several major structural components of the junctions, and is likely to have cascading impacts on metabolism, growth, and development.

11:30-12:30 BioSci Rm. 3110
*** And Free Pizza Meet & Greet after 12:30-1:30 in BioSci 3rd floor lunch room (Rm 3406)