Oxidative stress in gills of limpets from the Beagle Channel: comparison with limpets from the Antarctic

The aim of this work was to study the oxidative profile of gills of two limpet species (Nacella (Patinigera) magellanica and Nacella (Patinigera) deaurata) (Gmelin, 1971) exposed to different environmental conditions. Due to the tidal characteristics of the Beagle Channel, N. magellanica are exposed to air twice daily for 3 to 5 hours each time, whereas N. deaurata are exposed to air for 3 hours only during spring tides. The different regime of exposure includes extreme temperatures under 0 degrees C during winter and more than 20 degrees C in summer for N. magellanica, whereas N. deaurata are usually covered by more than 0.3 m of water at 4 degrees C in winter and 11 degrees C in summer. No significant differences were found between the two molluscs regarding the oxygen uptake, the content of alpha-tocopherol and beta-carotene and the activities of the antioxidant enzymes catalase and superoxide dismutase. Lipid peroxidation in gills was estimated as the content of lipid radicals, assessed by electron paramagnetic resonance (EPR). Lipid radical content and total iron content were respectively 80.6 and 62% lower in N. magellanica than in N. deaurata. A typical EPR spectrum of ascorbyl radical in gills from both limpets was observed. Both the ascorbyl radical content and the ascorbyl radical content/ascorbate content ratio were significantly lower in N. magellanica than in N. deaurata. In the Antarctic Nacella concinna inhabits all levels of the littoral zone. Limpets at the highest level in the intertidal showed significantly increased activities of both catalase and superoxide dismutase as compared to their intertidal and subtidal relatives. Thus, it seems that Antarctic high intertidal conditions, involving regular exposure to air and presumably also thermal stress on sunny days during the Antarctic summer, cause a necessity for N. concinna to ward off higher oxygen radical species production by increasing its antioxidant defence. Taken as a whole, the data presented here indicate that coping with environmentally demanding conditions requires a complex adjustment of the physiological metabolic pathways to ensure survival by minimising intracellular damage.