HALPIN, P. M.; HOFMANN, G. E.; Univ. of California, Santa Barbara; Univ. of California, Santa Barbara: Relationship between heat shock response and body temperature in natural population of intertidal mussels during spring

Organisms must quickly respond to environmental changes at the physiological level. In the heat shock response (HSR), heat shock proteins (Hsps) are rapidly upregulated to repair proteins damaged by stress. While the dynamics of the response have been examined intensively in the laboratory, for many organisms the dynamics of the response in their natural environment remains unknown. A better understanding of natural fluctuations in response to the environment is key to the use of Hsps as bioindicators. We sampled California mussels, Mytilus californianus, from a site on the central Oregon Coast from April to June 2002 to examine changes in levels of Hsp70, as measured through western blotting, during a period when warming was expected. Additionally, we deployed temperature loggers designed to thermally match living mussels in the areas sampled. These temperature data reflect the body temperatures of living mussels and allow us to examine the relationship of body temperature in the natural environment to physiological responses at the population level. Results indicate that levels of an inducible form of Hsp70 do not correlate with temperatures experience shortly before collection, but rather with temperatures several days previously. Levels of the constitutive isoform have a negative correlation with temperatures immediately preceding collection, and little correlation subsequently. Data also indicate that Hsp70 levels can fluctuate rapidly and differ between high and low intertidal areas of the mussel bed.