Effect of salinity on antioxidant defence system of the mud crab, Scylla serrata, a commercially important species from Chilika lagoon

Abstract

Reactive oxygen species (ROS; superoxide radicals, hydroxyl radicals and H2O2) are unenviable products of metabolism of aerobes. A steady state is maintained in aerobic cells newlinebetween generation and neutralization of ROS. ROS are highly reactive and if not neutralized they can damage all most all cellular macromolecules such as proteins and lipids as protein carbonylation (PC) and lipid peroxidation (LPx). Disturbance of this dynamic equilibrium in favor of generation of ROS is referred as quotoxidative stressquot (OS). PC and LPx are considered as indices of OS. Aerobes are equipped with both enzymes (superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase) as well as non-enzymatic molecules (ascorbic acid and free non-protein sulphydrils) to neutralize ROS and, thereby, protect organisms from OS. Therefore, the above molecules are considered as biomarkers of OS physiology (OSP). The mud crab (Scylla serrata) is an important commercial estuarine crustacean with high potentiality for aquaculture. The mud crabs are cosmopolitan in distribution and have exploited every aquatic niche thereby considerably contributing to the food web in its habitat. Despite its high commercial value, information on its biochemistry and physiology especially in relation to free radical mediated metabolism is scanty. The present thesis describes the status of antioxidant defenses in tissues (muscle, gills and hepatopancreas) of mud crabs and newlinecritically analyses biomarkers of OS in different experimental conditions.