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First published online March 16, 2007
Journal of Experimental Biology 210, 1161-1169 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003012

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Lipid mobilization of long-distance migrant birds in vivo: the high lipolytic rate of ruff sandpipers is not stimulated during shivering

Eric Vaillancourt and Jean-Michel Weber^*

Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada

View larger version (11K): [in this window] [in a new window]   Fig. 1. Rates of (A) oxygen consumption (O2), (B) carbon dioxide production (CO2) and (C) respiratory exchange ratio (RER) of adult ruff sandpipers before (22°C) and during cold exposure (5°C). Values are means ± s.e.m. (N=5). *Means different from thermoneutral values (P<0.05).

View larger version (6K): [in this window] [in a new window]   Fig. 2. Rates of lipid (filled triangles) and carbohydrate oxidation (CHO; open triangles) in adult ruff sandpipers exposed to cold (5°C). Values are means ± s.e.m. (N=5). *Different from thermoneutral values (P<0.05).

View larger version (10K): [in this window] [in a new window]   Fig. 3. Relationships between the rates of lipid oxidation (filled circles) or carbohydrate oxidation (CHO; open circles) and metabolic rate (O2) in adult ruff sandpipers exposed to cold (5°C). Lines were fitted by linear regression. Slope (m), intercept (b), coefficient of determination (r2), probability that the slope is equal to 0 (P), and power of the analysis of variance are also indicated.

View larger version (11K): [in this window] [in a new window]   Fig. 4. (A) Plasma glycerol concentration, (B) glycerol specific activity, and (C) rate of appearance of glycerol (Ra glycerol) in adult ruff sandpipers before (22°C) and during cold exposure (5°C). Units for specific activity are disintegrations per min (d.p.m.) per micromole (d.p.m. µmol–1). Sample sizes for all panels are indicated in parentheses in A. *Differences from thermoneutral values (P<0.05).

View larger version (6K): [in this window] [in a new window]   Fig. 5. Relationship between the rate of appearance of glycerol (Ra glycerol=lipolytic rate) and body mass for resting mammals (open squares), exercising mammals (filled squares), resting penguins (triangles) and ruff sandpipers (filled circle). The mean value plotted here for ruff sandpipers is for shivering birds (note that the mean value for non-shivering birds was even higher, although not significantly so; see Table 1). Each point is the mean value from a different study [rat (Kalderon et al., 2000; McClelland et al., 2001), rabbit (Himms-Hagen, 1968; Reidy and Weber, 2002), dog (Issekutz et al., 1975; Shaw et al., 1975), pigmy goat (Weber et al., 1993), sheep (Bergman, 1968), human (Bahr et al., 1990; Mora-Rodriguez et al., 2001; Wolfe et al., 1990) and king penguin (Bernard et al., 2002a; Bernard et al., 2002b; Bernard et al., 2003)]. Lines were fitted by linear regression for resting mammals (broken line; y=–0.31x+21.8; r2=0.333) and exercising mammals (solid line; y=–0.34x+28.8; r2=0.390). Curved dotted lines indicate 95% confidence limits around the values for exercising mammals.