Physiological variability in neonatal armadillo quadruplets: within- and between-litter differences.
The role of genetics on neonatal physiological variability was examined in the nine-banded armadillo (Dasypus novemcinctus). Since armadillos give birth to only monozygous quadruplets, the genetic variation within litters is essentially zero. Quadruplets born in captivity were isolated and weighed within 8 h of birth. Oxygen consumption (V.(O2)) was measured in resting neonates by flow-through respirometry, heart rate obtained from an electrocardiogram and ventilation was measured by impedance techniques. Following the measurements, neonates were returned to the mother. Measurements were repeated at 4 and 8 days after birth. Mean heart rate significantly increased from 132 beats min(-1) on the day of birth to 169 beats min(-1) on day 8. Mean ventilation rate significantly decreased from 81 breaths min(-1) on the day of birth to 54 breaths min(-1) on day 8. During this same developmental period, mean mass significantly increased from 100 g to 129 g, and mean mass-specific oxygen consumption significantly decreased from 32.2 ml O(2)kg(-1)min(-1) to 28.6 ml O(2)kg(-1) min(-1). For all variables measured, within-litter variability was always significantly less than between-litter variability, confirming a 'sibling effect' that we attribute to the genetic components determining physiological characters.
Bagatto
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Department of Biological Sciences, University of North Texas, Denton, Texas 76203-5220, USA. bagatto@unt.edu
Crossley
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DA
Burggren
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WW
D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001135:Armadillos / Q000235:genetics* / Q000502:physiology*; D001835:Body Weight; D014644:Genetic Variation; D006339:Heart Rate; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation