Abstract
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 0oC during winter and more than 20°C in summer for N. magellanica , whereas N. deaurata are usually covered by more than 0.3 m of water at 4°C in winter and 11°C in summer. No significant differences were found between the two molluscs regarding the oxygen uptake, the content of ?-tocopherol and ?-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.
Highlights
Since the discovery of the importance of radical reactions in normal biological processes, there has been an explosion of research into pro-oxidant and antioxidant processes, principally in mammalian systems (Halliwell and Gutteridge, 1984)
The normal fate of most of the molecular oxygen consumed by animals is tetravalent reduction to water coupled with the oxidation of food and the production of energy
N. magellanica are exposed to air twice daily for 3 to 5 hours each time, and N. deaurata are exposed to air daily for 3 hours only during spring tides (Morriconi and Calvo, 1993; Morriconi, 1999)
Summary
Since the discovery of the importance of radical reactions in normal biological processes, there has been an explosion of research into pro-oxidant and antioxidant processes, principally in mammalian systems (Halliwell and Gutteridge, 1984).
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