Electrolyte and Water Balance of the Early Avian Embryo: Effects of Egg Turning

Abstract

Formation of sub-embryonic fluid (SEF) is a key aspect of the physiology of the early avian embryo. Here we review the process of SEF formation and the factors which influence its composition and the rate of SEF production and depletion in the Japanese quail and domestic fowl. There is particular emphasis on the role of turning of the egg during incubation and we briefly consider the broader role of egg turning during avian incubation. The bulk of the review deals with the growth of the area vasculosa of the yolk sac membrane, the cellular processes of SEF formation, and the water and electrolyte physiology of the avian embryo during the first half of incubation.We conclude with a brief discussion of the areas for future investigation.

Effect of egg turning and incubation time on carbonic anhydrase gene expression in the blastoderm of the Japanese quail (Coturnix c. japonica)

“…SEF mass is also reduced if eggs are unturned during this critical period (Deeming et al, 1987;Deeming, 1989c;Baggott et al, 2002). In the blastoderm samples only gene expression for CA IV was affected by egg turning, with maxima at 84 and 96 h of incubation (0Á20 and 0Á24 of the incubation period), times located approximately in the middle of the critical period.…”

“…In the Japanese quail the bulk production of SEF started at 48 h of incubation, with a peak in mass from 84 h (Babiker and Baggott, 1992). In both the domestic fowl and Japanese quail, static incubation reduced the mass of SEF during the period of its formation (Deeming, 1989c;Babiker and Baggott, 1992;Baggott et al, 2002).…”

“…Egg turning increased the sodium concentration at this location by the same magnitude throughout the period of SEF production, whereas unturned eggs retained this 'depleted layer'. Baggott et al (2002) suggested that in unturned eggs this 'depleted layer' would reduce the sodium available for ion transport by endodermal cells and thus decrease SEF formation. Alternatively, or in addition, it was suggested that the lower rate of expansion of the area vasculosa present in unturned eggs (Deeming, 1989a) might also reduce SEF mass.…”

Dynamics of Structural Barriers and Innate Immune Components during Incubation of the Avian Egg: Critical Interplay between Autonomous Embryonic Development and Maternal Anticipation

“…During incubation, water from the EW is transferred to egg yolk (76% by ED10) [72, 73]. On ED12, EW is transferred to the amniotic sac.…”

“…During the second half of incubation, these fluids will be reabsorbed directly or indirectly by the embryo, to support the acceleration of its metabolism during the growth phase (Fig. 2) [72, 122]. …”