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UBC Theses and Dissertations

Inducible stress tolerance in fish : the role of heat shock proteins Todgham, Anne Elizabeth


Although there are a large number of studies on the role of heat shock proteins (Hsps) in stress tolerance, this literature consists mainly of studies conducted in the laboratory, making a comprehensive understanding of the ecological significance of Hsps in an animal's natural stress tolerance difficult to obtain. The rocky intertidal is an ideal environment in which to examine the physiological and biochemical responses of organisms to changing abiotic factors and to investigate mechanisms underlying an organism's ability to thrive in such a variable environment. My PhD thesis explores the role of environmental variation in modulating both the stress tolerance and the Hsp response of tidepool sculpins (Oligocottus maculosus). Stress tolerance in tidepool sculpins displayed a significant amount of plasticity that was sensitive to both short and longer-term changes in the thermal environment. A mild heat shock conferred a transient increase in tolerance to both subsequent osmotic and hypoxic stressors. Similarly, exposure to the daily fluctuations in environmental conditions inherent in living in the intertidal zone also imparted a certain degree of enhanced stress tolerance to sculpins. There was no endogenous diurnal rhythm in the Hsp response entrained to the tidal cycle in the tidepool sculpin; rather hsp gene expression was rapidly induced in response to routine fluctuations in environmental conditions. The Hsp response of sculpins was sensitive to slight differences in environmental temperature that occurred over differing temporal (different times during a month) and spatial (tidepool vs. subtidal) scales. Tidepool sculpins maintained a large and relatively constant standing pool of Hsc70 to cope with the daily variability of their natural environment, but had the capacity to rapidly regulate hsp expression when environmental conditions approach their tolerance thresholds. These results highlight the importance of an animal's thermal history in structuring it's Hsp response to natural environmental fluctuations and demonstrate that the variable intertidal environment is able to module Hsp levels at both the transcriptional and posttranscriptional levels. Taken together, the research presented in this thesis provides novel ecological insights into the significance of Hsps in allowing organisms to cope with large and frequent fluctuations in their natural environment.

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