DISSERTATION RESEARCH: Study of sickness behavior and its costs in relation to immunosenescence

Iowa State University, Ames IA

Investigators

Abstract

Carol M Vleck & Maria G. Palacios IOS-0808555, Study of sickness behavior and its costs in relation to immunosenescence. The decline of immune function with age, or immunosenescence, is a pervasive phenomenon in animals. This project is designed to investigate what aspects of immune function are most affected by age in a free-living bird population and what are the consequences for individuals. Tree swallows are the model system because an adequate number of known-aged individuals can be repeatedly sampled and their reproductive success can be easily monitored. The researchers have already shown that the pattern of immunosenescence in tree swallows resembles that of humans. A field experiment will be carried out while swallows are caring for their young to assess the consequences of this aging pattern. Researchers will simulate a pathogenic insult by challenging birds of disparate ages with a non-infectious bacterial component, which elicits sickness responses without causing actual disease. Parental behavior, in the form of chick feeding, will be monitored using video recording and blood samples taken before and after the challenge will allow assessment of hormonal and immunological responses. Chick growth rates and fledging success will be measured. Researchers will test the hypothesis that older, immunosenescent individuals pay higher costs of defense against pathogens than younger ones with the prediction that older individuals will show more extreme sickness responses, both behavioral and physiological, that will result in reduced reproductive success and/or survival compared to young individuals. The project will include training of undergraduate students in the field and in the lab. This research on sickness responses and their effects on reproductive behavior and survival has implications for disease ecology and conservation of threatened/endangered species. In addition, this research will be of general interest to physiologists, gerontologists, and evolutionary ecologists, and of increasing importance to the general public as our population ages.