Adaption and stress defence in intertidal and subtidal Antarctic limpets (Nacella concinna): A Study of the plasticity of molecular and biochemical stress response in Antarctic invertebrates

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Antarctic marine ectotherms look back on several million years of adaptation to constant extreme cold temperatures and high oxygen concentrations (Clarke 1998, 2003). Most endemic species are cold stenothermal and stenoxic with narrow tolerance windows and have a low scope for activity. Long lasting evolutionary adaptation to very constant environmental lconditions in typically Antarctic subtidal areas could potentially have caused loss of regulatory plasticity and of molecular and biochemical stress tolerance. Intertidal Antarctic areas are comparably "high stress environments". Interestingly, out of the multitude of subtidal macrofauna from the coastal waters surrounding the Antarctic Peninsula, only one species has successfully colonized most accessible intertidal areas: the limpet Nacella concinna. This species splits up into two distinct morphotypes, often described as "intertidal and subtidal subpopulations". In addition to the morphological difference, the intertidal subpopulation needs behavioural and physiological stress tolerance, superior to their subtidal congeners. In this project we aim to study the capacity for the induction of a metabolic stress response, distinguishing between subtidal and intertidal N. concinna specimens. HIF-1 is a master regulator of hypoxic survival, as it regulates a number of hypoxia stress response genes, and can be used as a molecular tool to study animal stress response capacity. As ROS are being discussed to modulate the HIF-1 induced stress response in several different ways, we will also investigate physiological and biochemical oxidative stress markers and antioxidant defence. Our aim is to clarify, whether the morphological differentiation between the intertidal and the permanently subtidal subpopulation is going along with adaptive changes in molecular and physiological differences of metabolic regulation under hypoxic stress. The South Shetland Islands are volcanic islands and characterized by extraordinarily high concentrations of particulate iron in coastal waters. Extremely high concentrations of iron and other transition metals have been found in tissues of macrobenthic filter feeders, but also of grazers like N. concinna. Iron is a Fenton catalyst and a major cause of reactive oxygen species (ROS) formation and can be toxic to animals, if not closely controlled by iron binding proteins and chelators. On top of that, iron induced ROS formation has been shown to interfere with cellular stress signalling in mammals. The second objective of this study is to assess the impact of iron on stress response signalling in N. concinna.