Effects of temperature on complexes I and II mediated respiration,ROS generation and oxidative stress status in isolated gill mitochondria of the mud crab Scylla serrata

Effects of fluctuations in habitat temperature (18–30°) on mitochondrial respiratory behavior and oxidative metabolic responses in the euryhaline ectotherm Scylla serrata are not fully understood. In the present study, effects of different temperatures ranging from 12 to 40 °C on glutamate and succinate mediated mitochondrial respiration, respiratory control ratio (RCR), ATP generation rate, ratio for the utilization of phosphate molecules per atomic oxygen consumption (P/O), levels of lipid peroxidation and H₂O₂ in isolated gill mitochondria of S. serrata are reported. The pattern of variation in the studied parameters was similar for the two substrates at different temperatures. The values recorded for RCR (≥3) and P/O ratio (1.4–2.7) at the temperature range of 15–25 °C were within the normal range reported for other animals (3–10 for RCR and 1.5–3 for P/O). Values for P/O ratio, ATP generation rate and RCR were highest at 18 °C when compared to the other assay temperatures. However, at low and high extreme temperatures, i.e. at 12 and 40 °C, states III and IV respiration rates were not clearly distinguishable from each other indicating that mitochondria were completely uncoupled. Positive correlations were noticed between temperature and the levels of both lipid peroxidation and H₂O₂. It is inferred that fluctuations on either side of ambient habitat temperature may adversely influence mitochondrial respiration and oxidative metabolism in S. serrata. The results provide baseline data to understand the impacts of acute changes in temperature on ectotherms inhabiting estuarine or marine environments.