THE MORPHOLOGICAL DEVELOPMENT OF THE LOCOMOTOR AND CARDIAC MUSCLES OFTHE MIGRATORY BARNACLE GOOSE (BRANTA-LEUCOPSIS)

The masses of the locomotor and cardiac muscles of wild barnacle goose goslings, from a migratory population, were examined systematically d uring development and their values compared to those of pre-migratory geese. Pre-flight development was typified by approximately linear inc reases of body, leg, and heart ventricular mass with respect to age. F light muscle showed an exponential increase in mass. Pectoralis muscle mass was 14.2 +/- 0.3% of body mass (1297 +/- 738, n=7) in early flyi ng goslings compared to 16.6 +/- 0.3% of body mass (2318 +/- 109 g, n = 8) in pre-migratory geese. Post-flight development was typified by s tasis of leg muscle mass but hypertrophy of ventricular and pectoralis muscle mass in proportion to body mass. Ventricular mass relative to body mass showed the lowest values at 5 weeks of age (0.62 +/- 0.01%) with peak values at 1 week of age (1.04 +/- 0.04%). The latter may be associated with both the requirements of thermoregulation in these pre cocial, arctic breeding geese and the need to forage approximately 24 hours post-hatch. Peak Values for leg muscle mass, relative to body ma ss, were found at 3 weeks of age (12.7 +/- 0.36%), with lowest values in the pre-migratory geese (6.7 +/- 0.21%), while peak values for pect oralis muscle mass were expressed in the premigratory geese with lowes t values at 1 week of age (0.94 +/- 0.07%). Ventricular mass was propo rtional to leg muscle mass up to 5 weeks of age (M(v) = 0.38 M(t)(0.68 ), r(2) = 0.95), but subsequent increase in ventricular mass was propo rtional to pectoralis muscle mass (M(v) = 0.25M(p)(0.73), r(2) = 0.81) .