SEM studies of cross sectional cuts of biomineralized tissues from Gallus and Coturnix eggshells using an Argon ion millin CP-system

Argon ion milled prepared cross sections (CP) of eggshells from chicken (Gallus) and quail (Coturnix) investigated by SEM reveal details of the native ultrastructure that previously required prefixation, embedding and ultramicrotomy for study by TEM. CP cross sections match high resolution data from published TEM but also reveal new aspects because the mineral phase is intact and the architecture is not distorted by mechanical forces. Open spaces in the architecture nor fibrous structures hinder the CP preparation. Details visible in the ion milled surface demonstrate subnanolevel equally sharp cuts through organic and inorganic structural elements. High resolution SEM pictures on CP prepared surfaces in the mammillary region, the palisade crystal layer and the cuticle show ordered arrays of nanocrystals inside the shell membrane polymer mass attached to the mammilla of the hen, ordered rows of about 350 nm vesicles inside in the palisades under angles relevant to the calcite crystal mass and composite Ca-P containing spherulitic particles in the cuticle. The packing of the spherulites suggests a role in the mechanical protection of the subsurface structure.