1985/09/01 by Warren W. Burggren, Warren Burggren · 1 citation
Environmental Science · #Amphibian and Reptile Biology #Physiological and biochemical adaptations #Turtle Biology and Conservation
paper · doi:10.1086/physzool.58.5.30158578
crossref issued 1985/09/01 · crossref published 1985/09/01 · crossref published-print 1985/09/01 · openalex publication_date 1985/09/01 · crossref created 2016/01/07 · crossref deposited 2018/04/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01 · crossref indexed 2026/08/01
Earlier studies of gelatinous egg masses laid by many amphibians suggested that the egg mass center was extremely hypoxic and that embryos located there suffered delayed growth and high mortality. The present study has reassessed conditions for respiration within the spherical egg masses of the pickerel frog, Rana palustris. Partial pressures of O₂ and CO₂, and the pH of egg jelly, as well as lactate concentration of embryonic tissue, were measured at 1-cm depth increments from surface to center of the egg mass. Oxygen uptake of intact egg masses and eggs separated from the mass was determined as a function of temperature and ambient O₂ levels. Although significant gradients for O₂, CO₂, and pH existed from surface to center, the magnitude of these gradients was too small to directly affect O₂ uptake of the egg mass or individual eggs under a variety of experimental conditions likely to occur in nature. Exchange of gases between the egg mass surface and center occurs primarily by diffusion through the egg jelly, which has a Krogh's O₂ diffusion constant 75% that of distilled water. However, intense convection of fluid within each egg, generated by the embryo's ciliated epithelium, functionally reduces by 17% the diffusion distance between egg mass surface and center by generating a convective "ventilation." These data collectively refute earlier findings by demonstrating that the center of ranid egg masses is not severely hypoxic and not limiting to aerobic metabolism.