Heat shock proteins, thermotolerance, and biogeography in intertidal Tegula snails

Lars Tomanek
Hopkins Marine Station

Wednesday, July 21, 1999
3:00 p.m.—Pacific Forum

tomanek2.tif (320406 bytes)Heat shock proteins (hsp’s) confer thermotolerance in organisms by preventing the denaturation of proteins during the heat stress and by facilitating the refolding of already damaged proteins. Their effect on interspecific differences in thermotolerance and thereby the thermal niche that a species can occupy is still largely unknown. To examine this effect, we compared the phenotypic variation of the heat shock response in several marine snail species of the genus Tegula that occupy widely differing thermal niches along the sub- to intertidal transition. Temperature at which the synthesis of hsp’s was first induced, temperature of maximal hsp synthesis and temperature at which hsp synthesis was heat-inactivated were lowest in the most cold-adapted (predominantly subtidal) and highest in the most warm-adapted (intertidal) Tegula species. Acclimation shifted induction temperature and temperature of maximal hsp synthesis for certain hsp’s, but did not affect the temperature at which hsp synthesis ceased. Hsp synthesis and protein synthesis in general were heat-inactivated in cold-adapted species at 33C, a temperature that is commonly experienced by the warm-adapted species in the intertidal. Protein synthesis in intertidal Tegula species was heat-inactivated at temperatures only slightly above the highest body temperatures recorded, and because they induce the energetically costly heat shock response frequently, intertidal species may live close to the upper end of their thermal-tolerance range. This may make intertidal species more susceptible to the effects of climate change.

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