Ontogeny of thermoregulation during the prenatal period in birds.
In contrast to the well-known thermoregulatory processes in the postnatal period the ontogeny of the thermoregulatory effector system as well as the central nervous control elements in the prenatal period is underinvestigated. Because of this, the aim of this paper is to characterize the development of thermoregulatory mechanisms in the embryonic period of one avian species, the Muscovy duck, Cairina moschata. The experiments were carried out in three series. In the first the influence of low ambient temperatures on call producing activity was investigated, in the second the oxygen consumption of single or pooled embryos was measured in the temperature range between 34.0 and 40.5 degrees C and in the last oxygen consumption, colonic temperature and preferred temperature were examined in birds incubated in reduced temperatures (34.5 degrees C) during the last 7 days before hatching. The results of experiments led to the conclusion, that (1) some days before hatching temperature perception is very well developed, (2) endothermic reactions occur in the last quarter of embryonic development, (3) the thermoregulatory setpoint is adjustable during the perinatal period. Altogether, embryos of the Muscovy duck show in the last days of incubation typical endothermic reactions. They activate the heat production as well as the heat loss mechanisms to control the body temperature. Besides this, when vocalization is used, behavioral thermoregulatory mechanisms support the autonomic reactions.
Nichelmann
M
M
Humboldt-Universität zu Berlin, Germany.
Tzschentke
B
B
D000367:Age Factors; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D001833:Body Temperature Regulation; D004372:Ducks / Q000502:physiology*