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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.

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