Hammond K, Chappell MA, Cardullo RA, Lin RS, Johnsen TS (2000) The mechanistic basis of aerobic performance variation in red junglefowl. Journal of Experimental Biology 203: 2053-2064
SUMMARY -- We examined aerobic performance, organ and muscle mass, and enzymatic activity in red junglefowl (Gallus gallus). We tested three models of performance limitation (central limits, peripheral limits, symmorphosis) and explored relationships between basal metabolic rate (BMR), aerobic capacity (VO2max), and social rank. Males had lower BMR, higher VO2max, and greater aerobic scope than females. Females possessed larger peritoneal and reproductive organs, while males had larger hearts, lungs and leg muscles. In females BMR was correlated with spleen mass and VO2max was correlated with hematocrit and large intestine mass. Male BMR was correlated with intestinal tract and lung mass, and VO2max was correlated with heart and pectoralis mass. Male citrate synthase activity averaged 57% higher than that of females and was correlated with VO2max (this correlation was not significant in females). Female social status was not correlated with any variable, but male dominance was associated with higher scope, larger hearts and lungs, smaller peritoneal organs, and higher leg citrate synthase activity. We conclude that aerobic capacity is controlled by system-wide limitations (symmorphosis) in males, while in females it is controlled by central organs. In both sexes, elevated aerobic capacity is not associated with increased maintenance costs.