Embryonic oxygen consumption and organ growth in the wedge-tailed shearwater

Embryonic oxygen consumption and organ growth were measured in the Wedge-tailed Shearwater (Puffinus pacificus), a tropical seabird characterized by slow embryonic growth and a prolonged pipping process prior to hatching. In most organs, growth in unpipped eggs could be represented by a linear regression of organ mass on whole-embryo mass. However, the slopes of the regression lines varied considerably between organs. The slope was steepest for the stomach and lowest in the heart and lungs. Oxygen consumption also increased linearly with embryo mass up to 25g in unpipped eggs, until just prior to pipping. In pipped eggs, however, there was a considerable increase in oxygen consumption, and acceleration of growth in some organs (eg. liver, intestine) while in others (eg. stomach, pectoral muscles, eyeballs) growth rates diminished. Comparison with the reported growth of other species revealed a number of similarities between the embryos of the semi-precocial shearwater and the precocial domestic fowl, together with several differences between the shearwater and the altricial pigeon embryo.