Meeting Abstract

54.1  Tuesday, Jan. 6  Carbon turnover in tissues of a passerine bird: allometry, isotopic clocks, and phenotypic flexibility in organ size BAUCHINGER, U.*; MCWILLIAMS, S. R.; University of Rhode Island ; University of Rhode Island ulf.bauchinger@orn.mpg.de

Stable isotopes are an important tool for physiological and behavioral ecologists, their usefulness depending on a thorough understanding of the dynamics of isotope incorporation into tissue(s) over time. In contrast to hair, nails and feathers, most animal tissues continuously incorporate carbon (and other elements) and so carbon isotope values may change over time depending on resource use and tissue-specific metabolic rates. Here we report the carbon turnover rate for 12 tissues from a passerine bird, the zebra finch (Taeniopygia guttata). We measured carbon half-life (Ct1/2) of 2.6 d for small intestine, 4-7 days for liver, proventriculus, gizzard, pancreas, and kidney, 10-15 days for heart, brain, red blood cells, and flight muscle, and 18-20 days for leg muscle and skin. We used these data, along with the few other published estimates, to confirm that fractional rate of isotopic turnover for red blood cells, whole blood, liver, and leg muscle scales with body mass to the approximately -1/4 power. Our data also support several key assumptions of the isotopic clock model that uses differences in isotope value between tissues, along with estimates of turnover rate of these tissues, to predict time elapsed since a diet shift. Finally, we show that between-tissue differences in turnover rate largely, but not completely explained the extent of phenotypic flexibility in organs of garden warblers during their long-distance flight across the Sahara desert during spring. More studies are needed that measure tissue-specific protein synthesis, metabolic rate, and elemental turnover in many tissues from a variety of animals.