Comparative histological, histochemical, and histometric evaluation of the esophagus in two avian species with different feeding habits ( Ciconia ciconia and Buteo buteo

Abstract

The aim of this study was to conduct a comparative evaluation of the histological and histochemical organization of the esophagus in two avian species with different feeding ecologies. A total of 6 individuals were used for this purpose (3 storks, 3 common buzzards). The esophageal samples were examined using Crossmon's triple stain, PAS with Light green combination, Alcian blue/PAS (pH 1, pH 2.5) and Aldehyde fuchsin/Alcian blue (AF/AB) staining methods following routine histological processing. In the histological evaluation, it was observed that the esophagus in both species typically consists of the mucosa, submucosa, muscularis, and adventitia/serosa layers. Significant differences were identified between the species in terms of epithelial structure and gland distribution. In storks, the mucosal folds were more distinct, and the glands were more densely distributed. In common buzzards, the epithelial structure was relatively more compact, and the distribution of the glands was limited. Histochemical analyses revealed significant inter‐species variations in mucus content. PAS and AB/PAS staining showed that neutral, acidic, and mixed mucopolysaccharides coexist in the stork esophagus, whereas more limited and distinct distribution patterns were observed in common buzzards. AF/AB staining, on the other hand, revealed differences between species in the localization of sulfated and carboxylated mucopolysaccharides. The findings support the notion that the histological and histochemical characteristics of the avian esophagus are closely related to the species' feeding habits. In particular, differences in mucus composition and gland organization are thought to be important in terms of adaptive mechanisms for food transport and esophageal protection. This study contributes to the literature by providing comparative data on the structural differences of the esophagus in avian species with different trophic characteristics.