Embryonic motility is an important component of development and may be a precursor of posthatching motor behavior. In chickens, it accompanies almost the entire embryogenesis and depends on environmental conditions, whose effects on embryonic motility have been poorly studied. The effect of acute hypoxia (10% O 2 for 10 min) on the temporal parameters of chick embryo motility on incubation days 10 (D10) and 14 (D14) was estimated; the results were compared with data on the heart rate (HR). A force transducer connected with an embryo limb was used to record embryonic movements simultaneously with HR video recording. In the control, the duration of the activity phase (APh) and HR increased, while the inactivity phase (IPh) decreased in the period from D10 to D14. In response to hypoxia, the APh did not change significantly on either day, but the IPh significantly increased on D14 and tended to increase on D10. A distinct pattern of the motor activity response to hypoxia was observed on D14: the IPh increased after 0.5-2.5 min of hypoxia, peaked at a value 6 times as large as the control one, and then partly recovered. Under hypoxia, the mean HR significantly decreased to 87% of the control value and then partly recovered, increasing to 93% on both days studied. The similarity of the hypoxic patterns of IPh and HR on D14 suggests that the hypoxic recovery of HR contributes to the recovery of the embryo motility under hypoxia in late embryos.
Oxygen consumption by eggs of European pond turtle was determined at two constant incubation temperatures of 25 and 28 ° C during the second half of embryogenesis. During development at both temperatures, the rate of oxygen consumption initially increased to remain constant during the last quarter of embryogenesis. The difference between the rates of oxygen consumption at these temperatures decreased during the studied period. The coefficient Q 10 for the rate of oxygen consumption decreased from 9 to 1.7. At an incubation temperature of 28 ° C, the changes in the rate of oxygen consumption in response to a short-term temperature decrease to 25 ° C or increase to 30 ° C depended on the developmental stage and were most pronounced at the beginning of the studied period. During late embryonic and first 2.5 months of postembryonic development, the rate of oxygen consumption did not significantly differ after such temperature changes. The regulatory mechanisms formed during embryonic development are proposed to maintain the level of oxygen consumption during temperature changes.
Experiments on developing eggs of European pond turtle ( Emys orbicularis ) demonstrated S-shaped changes in the rate of oxygen consumption and body weight during embryonic development. The rate of oxygen consumption and weight progressively increased within 70 days after hatching. During embryogenesis, the mass-specific rate of oxygen consumption decreased. After hatching, it increased but then decreased to a certain level, which remained constant to the end of the studied period. We observed unidirectional changes in the mass-specific rate of oxygen consumption and specific weight gain during embryonic development and this pattern was maintained after hatching. The coefficients of the allometric relationship between oxygen consumption and body weight were a = 0.33 and k = 0.52 during embryonic development and a = 0.17 and k = 0.89 during postembryonic development.
ANIMAL PHYSIOLOGY
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