The eggshell in the species Serinus canaria: structure, biomineralization and associated pathologies

Bird eggshells represent one of the most sophisticated biomineralized structures found in nature. In the species Serinus canaria, commonly bred both in domestic settings and in selective programs, the eggshell performs essential functions for mechanical protection of the embryo, antimicrobial defense, and regulation of gas exchange. The eggshell of Serinus canaria is a complex biomineralized microstructure designed to ensure mechanical protection, microbiological defense, and regulation of gas exchange during embryonic development. Despite the absence of studies dedicated exclusively to canaries, the literature on avian biomineralization allows the outline of a plausible structural and functional model. The canary eggshell presents a fibrillar organic matrix that guides the deposition of calcium carbonate in the form of calcite, organized into hierarchical layers (mammillae, palisade and vertical crystal layer). The outer cuticle, although thin, plays a decisive role in antimicrobial protection and in modulating permeability to gases and moisture. The cuticle is particularly sensitive to water: contact with liquids can dissolve or damage it. The aim of this study is to reorganize and deepen the available knowledge on shell structure, biomineralization mechanisms and the main pathologies observable in the eggs of Serinus canaria, with particular attention to implications for breeding.