Water Relations of Desert Iguana (Dipsosaurus dorsalis) Eggs

Publisher Website
Google Scholar
Abstract
Egg mass increased for about the first 65% of the incubation period, and then declined. The mean maximum gain in mass was 47.6%, and on the last day of incubation the mean mass of an egg was 32.7% greater than the mass at oviposition. The water potential of eggs varied throughout incubation. Frequent measurements are required to define the complex changes in egg mass and water potential that occur during incubation. Changes in the water potential of an egg may be related to ontogenetic patterns of nitrogen excretion. Calculated net hydraulic conductance varied throughout incubation. It may be inappropriate to define a unique hydraulic conductance value to reptile eggs with membranous shells. Measurements of mass change and water potential of eggs indicate that eggs may simultaneously transpire and absorb water while maintaining a net water potential below ambient water potential. Metabolic heat generation and active regulation of solute concentrations in extraembryonic water compartments may explain these observations. Eggs should not be considered as passive systems responding solely to changes in their physical environment. Ontogenetic changes in the water potential of eggs indicate that physiological processes of developing embryos may influence their rates of water exchange with the environment.