Histological Characterization of the Oviducal Structures in Guinea Fowl (Numida meleagris).

Abstract

The goal of this study was to determine the mechanism by which thicker eggshell is formed in the guinea fowl as compared with chickens. The structures of the magnum, isthmus, and shell gland as well as the localization of immunoreactive calcium binding protein-D28K (CaBP-D28K) in the shell gland were compared between the guinea fowl and chickens. The mucosal folds in each oviducal segment consisted of the mucosal epithelium and lamina propria containing tubular glands in both the guinea fowl and chickens. In the magnum the secondary mucosal folds were well developed with forming many large duct-like structures in the lamina propria in the guinea fowl, whereas such structures were not observed in chickens. There was no significant difference in the structures of mucosal tissues in the isthmus between the guinea fowl and chickens. In the shell gland, the distribution of tubular glands in the lamina propria at the bottom region of mucosal folds was denser than that at the apical region of the fold in both the guinea fowl and chickens. In both species, the tubular gland cells of the shell gland contained dense immunoreactive CaBP-D28K. The height of the mucosal folds was significantly greater in the shell gland than in the magnum and isthmus in the guinea fowl, whereas it was greatest in the magnum in chickens. The height of the mucosal fold in the shell gland was greater in the guinea fowl than in chickens. These results suggest that structural differences in the oviducal mucosal tissues may be responsible for the formation of thick eggshell in the guinea fowl.