Thermal stress in the Antarctic clam Laternula and the temperate mussel Mytilus.

There is ample evidence that a period of global warming is already affecting ecosystems worldwide. In order to predict the effects of a warming climate on organism physiology and biogeography, a description of the mechanisms involved in species responses to elevated temperatures is needed. Comparative studies examining species inhabiting different environments provide important information on the relative susceptibility of ecosystems to climate change. Antarctic marine ectotherms have evolved in a stable cold environment. They live within a narrow thermal window and experience stress with small elevations in temperature. In contrast, temperate intertidal species experience considerable temperature changes on a daily basis. The Antarctic clam Lateniula elliptica and temperate mussel Mytilus edulis were selected as representative species for their respective environments. This thesis presents i) a description of the construction of a cDNA microarray for L. elliptica, ii) analysis of gene expression in L. elliptica upon acute exposure to 3°C, iii) a comparative study between the two species at the protein level via two dimensional electrophoresis, and iv) analysis of corticosteroid synthesis in Mytiliis. Significant changes in the expression of 294 clones, representing 160 transcripts were observed. Of these, 33 were identified by sequence similarity searches and classified to a variety of cellular functions including protein turnover, folding and chaperoning, intracellular signalling and trafficking and cytoskeletal activity. In addition, the expression of 264 and 375 proteins in L. elliptica and M. edulis respectively was studied, 14 and 26 of which presented changes in expression between treatments. Only changes in proteins involved in energy metabolism were detected in both species. A higher level of biological variation in response to stress was observed in M. echilis at the protein level. The relevance of the observed results in determining the relative susceptibility of these species to climate change is discussed