Open Collections

Gill, Lauren

University of British Columbia

Molluscs live in diverse habitats, but the physiological mechanisms enabling their winter survival in temperate and polar environments remain poorly understood. Here I investigated the cold tolerance of two molluscan species: the terrestrial slug Ambigolimax valentianus and the intertidal bay mussel Mytilus trossulus. My first objective was to understand the cold tolerance of A. valentianus, an invasive slug that has established populations worldwide. To do this, I acclimated A. valentianus to different environmental conditions (differing day lengths and temperatures), then exposed them to sub-zero temperatures and measured survival. Then, I measured low molecular weight metabolites using ¹H NMR to see if they play a role in their cold tolerance as they do in other invertebrate species. I found that A. valentianus is not freeze tolerant but does become more cold-hardy after acclimation to shorter day lengths. I also found that low molecular weight metabolites were not upregulated in response to winter conditions, and instead I saw evidence of metabolic suppression leading up to winter. My second objective was to better understand the freeze tolerance of M. trossulus through investigating biological molecules and whole-body ice formation. I predicted that aquaporin water channels would play a role in freeze tolerance, that ubiquitin would exhibit seasonal differences in expression, and that ice formation would occur in a consistent way throughout the body. To test these predictions, I first used western blotting to measure aquaporin expression after a 3-hour freeze, and then used dot blotting to measure ubiquitin concentrations to estimate protein damage from mussels collected from different tidal heights across eight months. I then imaged whole-body ice formation using a thermal infrared camera. I found aquaporins were not up-regulated after freezing, and that protein damage increased in thermally stressful months in both summer and winter. I also found that mussels began ice formation at the anterior end of their body. Taken together, these findings contribute to a deeper understanding of how molluscs respond to cold stress at physiological and molecular levels, highlighting the role of environmental and species-specific factors in shaping the mechanisms underlying cold tolerance.

Text

2024-12-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89954

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/