Meeting Abstract

S2.8  Monday, Jan. 4  Functional linkages for the pace of life, life-history, and environment in birds WILLIAMS, J.B; Ohio State University; University of Michigan; University of Michigan williams.1020@osu.edu

Although physiological systems have likely altered as a result of evolutionary diversification of life histories, our understanding of the functional linkages between life-history and physiological mechanisms remains poor. We studied metabolic rate, basal and peak, of tropical and temperate birds. Our data show that tropical birds have a 10-18% lower basal metabolic rate (BMR) than temperate birds, whereas their peak metabolic rates (PMR), elicited by low temperature or forced exercise, were 34% and 28% lower, respectively. This reduction in overall metabolic performance is related to long life span and low rates of reproduction, in contrast with temperate birds, which have higher BMR and PMR, and higher rates of reproduction and mortality. As a beginning to search for underlying mechanisms for differences in metabolic rate between these two groups, we measured their organ masses. Data showed that the mass of heart, liver, kidney, and pectoral muscle were smaller for a given body mass for birds in tropical envi-ronments, which may contribute to their reduced metabolic performance. In addition, we are now culturing fibroblast cells from birds. Thus far, we have compared fibroblasts from temperate birds with similar sized mammals. Fibroblast cells from temperate birds, which have a higher rate of metabolism per unit body mass than do mammals, are more resistant to various stress agents than similar sized mammals. Studies are underway to compare resistance of fibroblasts from tropical and temperate birds. Progress in understanding associations between metabolic rate, reproductive rate and longevity will require an understanding of the functional linkage between whole-organism metabolism and underlying physiological mechanisms that influence its magnitude.