Susceptibility to oxidative stress in Adélie and Emperor penguin

The antioxidant defences in aerobic organisms represent the detoxification pathway against toxicity of reactive oxygen species (ROS). These highly reactive molecules are normally produced during the 4-electrons reduction of molecular oxygen to water coupled with oxidative phosphorylation, and during the activity of several enzymatic systems which produce ROS as intermediates. However, the endogenous generation of oxyradicals may be influenced by different environmental and biological factors, and the basal efficiency of antioxidant systems generally reflects the normal prooxidant pressure to which organisms are exposed. If the antioxidant capacity is exceeded (i.e. as a consequence of enhanced intracellular formation of ROS), a pathological condition, generally termed oxidative stress, may arise. In this preliminary work, susceptibility to oxidative stress has been compared in plasma of Adélie penguin (Pygoscelis adeliae), emperor penguin (Aptenodytes forsteri), south polar skua (Catharacta maccormicki) and snow petrel (Pagodroma nivea). Within the framework of the Italian Research Program in Antarctica, blood samples were collected during the austral summer 1998-1999 and the Total Oxyradical Scavenging Capacity (TOSC) analysed. The TOSC assay, measuring the capability of biological samples to neutralise different oxyradicals, has been recently standardised to provide a quantifiable value of biological resistance to toxicity of ROS. Penguins exhibited higher scavenging capacity towards peroxyl radicals than south polar skua and snow petrel. The greater resistance to toxicity of oxyradicals might suggest that penguins are naturally exposed to a higher basal prooxidant pressure in comparison to other analysed Antarctic birds.