Equatorial sandhoppers do not have a good clock


time measurement was made, the effect of aging is to reduce the size of the diurnal modulation as measured. When the difference is found, instead, by subtracting the nighttime value from the daytime value that would be expected for an embryo of the same age, the amplitude of the diurnal modulation very nearly coincides with that found for adult birds [2]. That is, these data provide strong evidence that even under constant external conditions a diurnal rhythm of energy metabolism is already present in the early days of embryonic development. Similar results were obtained by Barnwell [3], who found that the metabolic rate of chicken embryos was lower at night than during day. The opposing view, that circadian rhythms are not (yet) present in vertebrate embryos, has been supported by Rensing [4]. A diurnal rhythm has also been demonstrated in the herring gull (Larus argentatus) by Drent [5], though his experiments were indirect: he measured the egg temperature, keeping the incubation temperature constant, and found lower values at night, which could be explained only by reduced metabolism in this phase. Although no other relevant studies on birds have been published [6], the available data show quite clearly that phenomena with a circadian rhythm, perhaps already under endogenous control, cannot be ruled out in the embryo. Received January 7 and February 3, 1992

DOI: 10.1007/BF01175398

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Cite this paper

@article{Ugoliui2005EquatorialSD, title={Equatorial sandhoppers do not have a good clock}, author={A. Ugoliui and L . A . Pardi}, journal={Naturwissenschaften}, year={2005}, volume={79}, pages={279-281} }