EXPOSURE TO ELEVATED-TEMPERATURES AND HYDROGEN-PEROXIDE ELICITS OXIDATIVE STRESS AND ANTIOXIDANT RESPONSE IN THE ANTARCTIC INTERTIDAL LIMPET NACELLA-CONCINNA

This study deals with the occurrence of oxidative stress and antioxida nt response in the Antarctic intertidal limpet Nucella concinna, as an effect of temperature increments and H2O2 exposure under controlled l aboratory conditions. Experiments were designed to simulate transient conditions of increased T and/or H2O2 accumulation met by the limpets in intertidal rockpool habitats [5]. Specimens were collected at Juban y Station, South Shetland Islands, transferred to the Alfred-Wegener I nstitute, Bremerhaven and maintained in seawater aquaria at 0 degrees C. Different groups of animals were acclimated at 4 and 9 degrees C fo r 24-48 h (controls at 0 degrees C). The effect of starvation was stud ied at 0 degrees C and of H2O2 exposure at 4 degrees C. Temperature ac climation above 0 degrees C resulted in a progressive alteration of th e lysosomal compartment in digestive gland cells, as shown by cytochem ical analyses (lipofuscin and neutral lipid accumulation and lysosomal membrane destabilization). Concurrently, real activities of the antio xidant enzymes superoxide dismutase (SOD) and catalase (i.e. measured at the respective experimental temperature or calculated by means of p reviously determined Q(10) values) increased in gills and digestive gl and tissues. Measurements of intracellular pH at the different tempera tures showed a rise from pH 7.21 at 0 degrees C to 7.36 at 9 degrees C . These changes in pH are indicated to increase SOD activity by approx imately 10% in both kinds of tissue at 9 degrees as compared to 0 degr ees C. H2O2 exposure at 4 degrees C produced physiological alterations at the systemic (lowered O-2 consumption) and at the cellular levels (enhanced lysosome damage). Starvation induced lysosomal alterations i n animals kept at 0 degrees C and inhibited CAT activation under H2O2 exposure at 4 degrees C. The complex of data suggests that when Nacell a migrates to intertidal levels during the Austral Spring it experienc es oxidative stress which induces an antioxidant response, which is fa cilitated by higher temperatures and increasing intracellular pH and t he exploitation of intertidal food resources. Yet, the occurrence of c ellular damage and systemic alterations shows that the limpets approac h their boundaries of physiological tolerance during prolonged exposur e to higher temperatures and H2O2 in intertidal habitats. (C) 1998 Els evier Science Inc. All rights reserved.