The motility of the chicken embryo: Energetic cost and effects of hypoxia

•The cost of embryonic motility was computed in chicken embryos (day 10–18) from the pressure produced and the corresponding changes in oxygen consumption.•At all ages, it was an almost negligible fraction of the embryo's energy budget.•At day 18, hypercapnia and cold respectively increased and decreased motility, while hypoxia had variable effects.•Because of its low cost, motility can be maintained in hypoxia; conversely, reduction of motility in hypoxia does not provide an important energy saving.

We estimated the energetic cost of embryonic motility by relating the changes in embryo's motion to the changes in oxygen consumption (V˙O2). Measurements were conducted on chicken embryos between day 10 and 18 of incubation. Embryonic gross body movement was quantified over ten continuous 3-min periods from the pressure oscillations inside the egg, measured through an implanted catheter, and was correlated to the synchronous changes in V˙O2, measured by an open-flow methodology. Over the 30 min recording, movements could vary around the mean by up to four folds. The corresponding changes in V˙O2 were minuscule (0.116 μl O2/mmHg) or, for all age groups combined, only 2.3% of the mean V˙O2, ranging from ∼8% (day 10) to ∼0.5% (day 16). At E18, hypercapnia and cold respectively increased and decreased motility. Differently, the effects of hypoxia on motility were variable among embryos. It is concluded that, in chicken embryos over the age period investigated, the cost of motility represents an almost negligible fraction of the total energy budget. Because of its low cost, motility can be maintained in hypoxia; conversely, reduction of motility in hypoxia does not provide an important energy saving.