This paper investigates the localization within the Xenopus egg of the factors responsible for the periodic activities such as the cyclic rounding-up and flattening, related to the cleavage cycle. Denuded eggs were bisected along the boundary line between the animal and the vegetal hemispheres immediately after being rotated through 90 degrees off the vertical axis (Early Bisection). The result...

Do reproducing female reptiles adaptively manipulate phenotypic traits of their offspring by selecting appropriate nest sites? Evidence to support this hypothesis is indirect, mostly involving the distinctive characteristics of used (vs. available) nest sites, and the fact that physical conditions during egg incubation can modify hatchling phenotypic traits that plausibly might influence fitnes...

A study with a 2 × 3 × 2 factorial arrangement was conducted to determine the effects of 2 dietary protein levels (high = CPh and low = CPl) during rearing, 3 dietary energy levels (3,000, MEh1; 2,800, MEs1; and 2,600, MEl1, kcal/kg AMEn, respectively) during the first phase of lay, and 2 dietary energy levels (2,800, MEs2; and 3,000, MEh2, kcal/kg AMEn, respectively) during the second phase of...

Carbonic anhydrase is an enzyme that plays important roles in the conversion of carbon dioxide to bicarbonate, acid-base balance, and in subembryonic fluid formation in the early Japanese quail embryo. While turkey egg storage longer than 10 d is known to increase the rate of embryo mortality, little is known of the biological mechanisms that contribute to this phenomenon. In this study, we exa...