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