Oxidative stress in natural developing tadpoles of Pelophylax esculentus complex frog

Anurans represent an interesting model organism for investigating changes in the oxidative stress during life time, as they have unique life cycle among tetrapods (consisted of eggs, tadpoles, juveniles, subadults and adults) related with terrestrial and aquatic environment. During the early phases of the life cycle, anuran individuals undergo drastic changes in the course of the transition from aquatic to terrestrial life style. Those changes are followed by metabolically demanding processes underlying rapid growth and responses to developmental pressures. All those processes could be responsible for the increased production of reactive oxygen species (ROS) and possible oxidative stress. The aim of this study was to investigate changes in antioxidative system response (SOD, CAT, GSH-Px, GR, GST, GSH and SH groups) and levels of oxidative damage (TBARS - lipid peroxidation) in natural developing Pelophylax esculentus complex frogs. Frogs were caught from May to July in 2017 at Special Nature Reserve Deliblatska Peščara. We divided development in four stages with clear differences: feeding and free-swimming tadpoles (covering 25-31 Gosner stage - GS), tadpoles with developed hindlimbs (35-41 GS), tadpoles with both limbs (42-46 GS) and juvenile individuals. Our results revealed that individuals at earlier stages (25-31 GS) faced with higher oxidative damage (higher TBARS and lower SH groups) that was followed by higher GR, GSH-Px and GST in comparison to other stadiums. Increased growth of individuals in this stadium and exposure to environmental factors directly for the first time may result in higher ROS production and as a consequence higher antioxidative system response and oxidative damage