In this study, we aimed to perform structural and proteomic analysis of the vitelline membrane (VM) of two species birds belonging to the family Turdidae: blackbird (Turdus merula) and song
thrush (Turdus philomelos). We performed structural analyses using scanning electron microscopy. The VM
proteins were identified and compared to the best-known chicken VM
proteins. According to our results, VM of both species has a typical three-layered structure: the outer layer, inner layer, and the continuous membrane between them. An unusual observation was the finding of "convexity" formed by the inner layer in blackbird. The role of these convex structures is not known, but they can be typical for the species and can be used in their identification. In addition, we identified two
proteins in the VM of both species of birds, of which U3KEZ1 FICAL was not previously identified in any other bird species, and the U3JXV8 FICAL
protein was confirmed only once in cockatiel parrot VM. The function of these
proteins is not exactly known, but their structure shows similarities to the
SERPIN proteins that are involved in microbiological defense, i.e., they are immune
proteins. This study contributes to the current knowledge about the structure and composition of
proteins of VM, especially because similar analyses have never been performed for Turdidae family. Knowledge of the structure and specific
proteins of blackbird and song
thrush VM can be beneficial in research on ecology and bird biology and also helpful in developing noninvasive and nongenetic identification methods.