Meeting Abstract
P3.221 Sunday, Jan. 6 Flexible adjustments of internal organs in cold acclimated shorebirds VEZINA, F.*; GUGLIELMO, C.G.; DEKINGA, A.; PIERSMA, T.; Universite du Quebec a Rimouski; University of Western Ontario; Netherlands Institute for Sea Research; University of Groningen francois_vezina@uqar.ca
Seasonal cold acclimatization in the red knot (Calidris canutus islandica), a long distance migratory shorebird, has been shown to result mainly from adjustments in body mass. Since pectoral muscles are the largest shivering muscles in birds and because their size tracks variations in body mass, adjusting body mass to cold temperatures results in higher shivering heat production capacity (summit metabolic rate: Msum) and cold endurance. However, little is known on possible adjustments of other body components that may play an essential role in cold acclimatization. In this study we investigated the effects of thermal treatments on body composition, metabolic performance and tissue metabolic intensity of captive individuals maintained under constant cold (5°C) and constant thermoneutrality (25°C). As expected, preliminary results show that when controlling for body size cold acclimation is associated with a higher body mass and metabolic performance (basal metabolic rate: BMR and Msum). Dissection data also revealed significant increases (8-30%) in the mass of the intestines, stomach, liver, kidney, heart, flight muscles (pectoralis and supracoracoid), leg muscles and carcass (skeleton and other muscles). Enzyme analyses in muscles (pectoralis, leg, heart), kidney and liver highlighted no changes in lactate dehydrogenase (LDH), 3-hydroxyacyl-CoA dehydrogenase (HOAD) and citrate syntase (CS) but a significant increase in the activity of carnitine palmitoyl transferase (CPT) in pectoralis and leg muscles of cold acclimated individuals. These findings suggests that, in addition to flight muscles, most internal organs increase in size during cold acclimation and that an upregulation of fatty acid transport in mitochondria may be required to improve fuel delivery to support shivering in skeletal muscles.
