On 20 November at 10:15 Janek Urvik will defend his doctoral thesis „Multidimensionality of aging in a long-lived seabird“.
Research Fellow Tuul Sepp, PhD (TÜ ÖMI)
Professor Peeter Hõrak (TÜ ÖMI)
Senior Research Fellow Sveinn Are Hanssen, PhD (Norwegian Institute of Nature Research, Norra)
Natural selection favours the fittest. The best measure of fitness is the amount of offspring produced during lifetime. Hence every species should evolve towards a longer life and greater fecundity. Nevertheless, there are species with drastically different life-spans and fecundities. The reason behind it is the fact, that in nature, there is a limited amount of resources that each individual must optimally utilize. That creates trade-offs between using those resources for self-maintenance or reproduction. Senescence has traditionally been studied on short-lived organisms, whose senescence has been modified by different trade-offs than long-lived species. The aim of the current thesis is to determine the trade-offs shaping senescence of a long-lived bird species. The thesis suggests that common gulls as long-lived species invest more into somatic maintenance as they age. From the studies incorporated in the thesis, it is evident, that older birds do not differ from younger ones by their ability to combat oxidative stress (the potential harmful side-effect of oxygen metabolism). Older birds can also take care of their plumage with the same efficiency as their younger counterparts, for their preen glands (a gland, that produces waxes that defend feathers) are even larger, than those of their younger counterparts. On the other hand, common gulls invest less into reproduction with advancing age. It begins with mate attraction, for older gulls have smaller wing patches. The size of those patches is related to health and therefore good indicators of quality. By investigating egg composition of gulls of different ages, I found out, that older birds deposited less carotenoids into their eggs. Carotenoids can potentially defend against oxygen's toxicity and have also been shown to positively correlate with offspring size. It is evident from the thesis that long-lived species prioritize long life and somatic integrity over maximal reproduction.