Effects of temperature on modulation of oxidative stress and antioxidant defenses in testes of tropical tasar silkworm Antheraea mylitta

Abstract

High temperatures are known to cause physiological stress in organisms. This is often associated with enhanced generation of reactive oxygen species (ROS) leading to oxidative damage. The commercially important tropical tasar silkworm Antheraea mylitta has to endure high summer temperature before egg production on the onset of monsoon. In this study the status of pro-oxidants and antioxidants was studied in the testes of male pupae of tasar silkworm A. mylitta under thermal stress condition. Further, to find out the impact of temperature on physiological activity, oxygen consumption rate was measured. The result indicated higher level of thiobarbituric acid reactive substances (TBARS, as an index of lipid peroxidation) and total hydroperoxides in the male pupae exposed to high temperature (40±1°C). Similarly, it was found that increased levels of antioxidants such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), ascorbic acid (ASA) and low molecular thiols (L-SH) in testes are more prominent in high temperature rather than in moderate temperature (35±1oC) suggesting the activation of physiological mechanism to scavenge the ROS produced during stress. Further more, the order of higher level of oxygen consumption rate was observed as high temperature (40±1°C) > moderate temperature (35±1°C) > control groups (28±1°C). Oxygen consumption rate was positively correlated with oxidative stress and antioxidant defence indices. We infer from these findings that the testes of A. mylitta pupae modulate testicular antioxidant responses to thermal stress.