Acclimatization of Anemonia viridis (Forskäl 1775) by thermal preconditioning: potential role of catalase

Abstract

The phenomenon of cnidarian bleaching has attracted much attention in the literature, as the frequency of coral bleaching events and mass mortality have increased over the last few decades, driving the degradation of coral reefs and loss of coral cover worldwide. This has also led to increased interest in exploring the underlying physiological and biochemical mechanisms of acclimatization of reef building corals and other symbiotic cnidarians to thermal stress. Thermal history and/or previous exposure to thermal stress have been linked with the thermal acclimatization of scleractinian corals in many studies. In this study, it was demonstrated that short term thermal preconditioning by stepwise increase in temperature for a period of 16 days (19 ± 1°C for 7 days and 21 ± 1°C for 9 days) provides thermal tolerance to a temperate symbiotic anemone Anemonia viridis. Preconditioned A. viridis exposed to the experimentally determined bleaching threshold temperatures for a period of 9 days (23 ± 1°C for 7 days and 25 ± 1°C for 2 days) did not show bleaching whereas non-preconditioned A. viridis, exposed to the same bleaching threshold temperatures, for the same duration, showed significant bleaching. Biochemical measurements of samples revealed significant increase in the activity of antioxidant enzyme catalase in preconditioned A. viridis, suggesting the potential role of catalase in acclimatization of A. viridis to thermal stress and thermal stress-induced increased production of reactive oxygen species.