COMPARATIVE METABOLIC RESPONSES TO PROLONGED COOLING IN PRECOCIAL DUCK (ANAS-DOMESTICA) AND ALTRICIAL PIGEON (COLUMBA-DOMESTICA) EMBRYOS

1. 1. Embryos and hatchlings of the duck and pigeon were exposed to a lowered temperature for 6 hr. The oxygen consumption ( dot MO2) was measured before and after cooling and the ratio of the two was compared with that predicted for a temperature coefficient of 2 (Arrhenius value). 2. 2. Late prenatal ducks kept the dot MO2 above the Arrehenius value at 28°C, while the dot MO2 of pigeon hatchlings became the same as the Arrhenius value even at 32°C. 3. 3. Thus, incipient homeothermic ability appears in the duck during prenatal development, but it is not evident in the pigeon even after emergence from the shell. The precocial chicken and semi-precocial noddy previously studied are intermediate in their metabolic response between the duck and the pigeon. © 1990.