Development and Metabolism during Hypoxia in Embryos of High Altitude Anser indicus versus Sea Level Branta canadensis Geese

Abstract

The yolk-free body mass, the mass of selected organs, the rates of oxygen consumption, and the air cell gas tensions were measured throughout incubation in embryos of the bar-headed goose, Anser indicus, and the Canada goose, Branta canadensis. The embryo mass for both species increased exponentially with incubation time to a stage just prior to pipping when growth appeared to stop. The rates of oxygen consumption for the embryos paralleled the rate of growth for the first 40%-50% of the increase in embryo mass, followed by a period when the rate of oxygen consumption plateaued at a value of 43.9 ± 0.7 cm³ O₂/h for the embryos of the Canada goose and 39.1 ± 1.7 cm³ O₂/h for the embryos of the bar-headed goose. The oxygen tensions in the air cell decreased with time concomitant with the increase in oxygen consumption to a value of 96.3 ± 2.0 torr for the Canada goose and 88.0 ± 1.0 torr for the bar-headed goose. The lower air cell oxygen tensions in the bar-headed goose reflect a lower eggshell permeability and smaller egg size. When acutely exposed to hypoxic hypoxia, the normoxic embryos of the bar-headed goose were able to maintain rates of oxygen consumption at significantly lower oxygen tensions than were the embryos of the Canada goose. However, the embryos of the Canada goose were able to acclimate to incubation under conditions of hypoxic hypoxia as evidenced by a shift to the left in the oxygen tension necessary to reduce the rate of oxygen consumption.