Hard times in paradise? Oxidative status, physiology and fitness in the tropical Seychelles warbler

PhD ceremony: Ms. J. van de Crommenacker, 16.15 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Hard times in paradise? Oxidative status, physiology and fitness in the tropical Seychelles warbler

Promotor(s): prof. J. Komdeur

Faculty: Mathematics and Natural Sciences

In her study on the wild-living Seychelles warbler Janske van de Crommenacker found a number of interesting relationships between oxidative imbalance (oxidative stress) on one hand and poor environmental conditions or suffering from parasitic infection (malaria) on the other hand.

The use of oxygen for energy generation results in the continuous production of reactive oxygen species (oxidants) that can damage body molecules. Organisms attempt to reduce this harm by use of their antioxidant defence barrier. Yet, when more oxidants are produced than can be neutralized by this protective barrier, a state of oxidative stress may occur. Chronic oxidative stress and accumulation of oxidative damage to cells and tissues can stimulate the ageing process and the onset of degenerative diseases. As elevations in metabolism (e.g. through workload or immune activation) can stimulate oxidant generation, and as antioxidant defences require valuable resources, oxidative stress is proposed to be an important mediator of life-history trade-offs.

In her study on the wild-living Seychelles warbler Van de Crommenacker found a number of interesting relationships: oxidative imbalance (oxidative stress) was high when birds experienced poor environmental conditions or suffered from parasitic infection (malaria). The latter was particularly true for infected birds that were enduring the workload of provisioning their young. Sex, social status and reproductive stage appeared also to be linked with oxidative status: reproducing females had higher antioxidant capacity in the weeks before egg-laying, possibly to enhance the quality of their offspring. Although Van de Crommenacker found no clear evidence for relationships between oxidative status and fitness (reproductive success and survival), her study shows that various environmental-, behavioural- and individual-related variables were associated with oxidative status. The results emphasize the importance to first identify these ecological covariates before drawing general conclusions about oxidative stress as a life-history determinant.