Comparative Studies on the Tongue of White-throated Kingfisher (Halcyon smyrnensis) and Common buzzard (Buteo buteo)

The aim of the current study was to investigate and evaluate the ultrastructural and histological aspects of the tongue as well as the histochemical features of the lingual salivary glands of thewhite-throated kingfisher (Halcyon. smyrnensis); a piscivorous bird and common buzzard (B.buteo); an omnivorous bird. The tongues of the two selected species were investigated in an attempt to elucidate whether variations in the nature of diet may associate with special adaptive lingual structures. Six animals of each studied species were used for the present work. The observed results elucidated that, the tongue of white-throated kingfisherwas triangular and occupied 1/2 length of the beak while, the tongue of common buzzard was elongated and biforked at its apex and occupied 2/3 length of the beak. The tongue of common buzzard was longer than that of H. smyrnensis. Morphologically, three parts were distinguished in the dorsal surface of the tongue for the two studied species: the apex, the body and the root. The results showed numerous fine hard processes on dorsal surface of H.smyrnensis tongue. On the other side, such processes were apparently absent in the tongue of common buzzard. The dorsal surface of common buzzard tongue was keratinized. In contrast, such keratinization was absent in the tongue of white-throated kingfisher. The recorded results manifested that the salivary glands of both species were mostly simply branched tubular that open on the surface of epithelium by glandular orifices.  The glands were well developed and widely distributed in the lingual mucosa of the common buzzard in compared with those of white-throated kingfisher. However, the latter species showed a unique feature that represented by existence of numerous simple tubular mucus glands arranged as one raw on the dorsal lingual epithelium. In addition, the present findings indicated that, the lamina propria of H.smyrnensis tongue had connective tissue and filiform papillae. In particular, the dorsal surface at junction between the lingual body and root of H.smyrnensis was covered by pseudostratified ciliated columnar epithelium.
The histochemical investigations revealed that, the salivary glands were made of mucoserous cells that elaborate neutral mucosubstances, acid mucosubstances and   proteins, in which the glands of H. smyrnensis showed stronger reaction for neutral and acid mucosubstaces and weaker reaction for protein comparing to those of common buzzard.