Avian eggs—and the dinosaur eggs that preceded them—have a tough job. They have to be hard enough to protect a developing embryo during incubation, and later, weak enough to allow the hatchling to get out. Researchers reported last week (March 30) in Science Advances that they created a 3-D model of the chicken (Gallus gallus) eggshell’s nanostructure. The model shows that the molecular properties change from the shell’s outer to inner layers, affecting its hardness, elasticity, and dissolvability, and that the shell weakens later in incubation to allow the chick to hatch.
D. Athanasiadou et al., “Nanostructure, osteopontin, and mechanical properties of calcitic avian eggshell,” Science Advances, doi:10.1126/sciadv.aar3219, 2018.