Susceptibility to oxidative stress in different species of Antarctic birds: preliminary results

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. If the antioxidant capacity is exceeded (i.e. as a consequence of enhanced intracellular formation of ROS) a pathological condition, generally termed as oxidative stress, may arise.
In this preliminary work, susceptibility to oxidative stress has been compared in Adélie penguin (Pygoscelis adeliae) and South polar skua (Catharacta maccormicki), breeding at Edmonson Point (Wood Bay, Ross Sea). At the time of sampling, Adélie penguins were rearing chicks and also for skuas, the redation of eggs and chicks make this period of their biological cycle very stressful.
In the framework of the Italian Research Program in Antarctica (PNRA) , blood samples were collected during the Austral summer 1998-99 and the Total Oxyradical Scavenging Capacity (TOSC) analyzed. The TOSC assay, measuring the capability of biological samples to neutralise different oxyradicals, has been recently standardized to provide a quantifiable value of biological resistance to toxicity of ROS.
Penguins exhibited higher scavenging capacity towards peroxyl radicals than South polar skua. The greater resistance to toxicity of oxyradicals might suggest that penguins are naturally exposed to an higher basal prooxidant pressure in comparison to skuas.