Age-related Changes in the Response of Embryonic Motility to Acute Hypoxia during the Third Quarter of Chick Embryogenesis

Environmental factors may affect the growth, size, phenotype, behavior, and other characteristics of avian embryos at different developmental stages; however, the roles of individual embryonic physiological systems in these effects remain largely unclear. Embryonic motility is an important component of the prenatal development observed almost throughout embryogenesis and may be a precursor of post-hatching motor behavior. The influences of the environment on the development of motor behavior during embryogenesis (notably the embryonic motility affected by hypoxia) remain poorly studied. Consequently, using the chick embryo, we investigated the effect of acute hypoxia (10% or 5% О2 for 20 or 40 min) on embryonic cyclic motility at incubation days (D) 10, 12, 14, and 15 using in vivo video recording. Hypoxia inhibited motility; specifically, the average duration of activity and inactivity phases during hypoxic exposure were shortened and prolonged, respectively. Age-related changes in the responses to 10% and 5% O2 differed. The time course of the motility response to acute hypoxia varied during the D10-15 period and demonstrates that the embryo was capable of recovering motility under hypoxia. The recovery was likely enhanced with age due to maturation of regulatory capacity.