Comparative sequence analysis of Hsp70 gene from Mytilus edulis desolationis and Aulacomya ater of the Kerguelen Islands

Circumpolar studies have provided strong evidence of the vulnerability of marine ecosystems in response to anthropogenic activities. Such ecological disturbances are particularly impactful on biodiversity, which helps protect ecosystems from extreme conditions. It is thus imperative to develop biomarkers for long term monitoring of changes in marine biodiversity and to better assess comparative responses of different species. Because of their wide geographic distribution and their seeding and filter-feeding nature, mussels, such as Mytilus edulis and its closely related species, have been commonly used as sentinel species in ecotoxicological monitoring programs around the globe.1-3 Extensive research has been performed on their physiology and their genetic content in order to develop sensitive and specific biomarkers. This is especially true for M. edulis, which has been extensively characterized at the cellular and molecular levels, not only because of their ecological importance, but also because of their economical impact.4-6 However, because of their distinctive anatomy and physiology, it is logical to believe that other mussel species will respond differently to climate change and exposure to pollutants.7 Our recent comparative study between Mytilus desolationis (M. desolationis) and Aulacomya ater (A. ater) supports this hypothesis.8 A better knowledge of A. ater could thus provide a new and complementary tool for monitoring global climate changes in marine ecosystems, most notably in the Southern hemisphere, which is particularly sensitive to climate change. Because of its strategically geographical position, the Kerguelen archipelago is considered an important site to investigate the effects of global change on marine ecosystems.9 Although M. desolationis is normally the dominant species in most mussel beds in the Kerguelen archipelago, we found that some mussel beds, such as one found at tide depth at Port-aux-Français, is largely dominated by A. ater.8 Whether such diversity is permanently maintained or will change following environmental parturbation will depend on the ability of mussel species to respond to environmental stress. Because heat shock proteins (Hsps) play an important role of protection and maintenance of many vital cellular functions in response to thermal and toxic stress, they are commonly used as stress biomarkers.10,11 Their structural features are highly conserved among eukaryotes and prokaryotes, especially in the case of hsp70, a widely used biomarker to monitor the impact of environmental factors on various animal species, including mussels.12-16 Unfortunately, while a considerable amount of data exists on blue mussel stress response genes, our knowledge on A. ater remains fragmentary. In the present work, we report a detailed comparative analysis of hsp70 stress response gene from Mytilus desolationis (M. desolationis) and Aulacomya ater (A. ater).