How do bird eggs breathe? Gas exchange and formation of avian eggshells

Abstract

This thesis explores the biophysical mechanisms underlying gas exchange and pore formation in avian eggs. Drawing from biological data and applying principles from diffusion theory, chemical physics, and applied mathematics, we develop a comprehensive model of gas transport through complex pore geometries. With a diffusive resistance framework, we show that gas conductance is related to both internal pore geometry and density of pore openings on the egg surface. Using this, we derive a novel criterion for the number of pores at which gas flux saturates. Pore branching is shown to reduce access resistance without high cost to internal resistance, and is thus proposed as an explanation for steep scaling of functional pore area with egg size. Finally, we review previous frameworks of eggshell and pore formation, and build on this work by advancing a novel theory of pore formation. We propose that the organic matrix in the palisade layer plays a central role in shaping pores during shell calcification. Together, these analyses deepen our understanding of avian developmental physiology.