Scanning electron microscopic study on the tongues of seven avian species.

The dorsal lingual surface of the grey crowned crane (Balearica regulorum), American flamingo (Phoenicopterus rubber), great egret (Ardea alba), mallard (Anas platyrhynchos), Himalayan monal (Lophophorus impejanus), black-necked stilt (himantopus mexicanus) and green macaw (Ara militaris) were examined by scanning electron microscopy. In the grey crowned crane, the surface of the lingual apex was relatively rough. Many openings of the lingual glands in both lateral regions of the lingual body were observed. The surfaces of many conical papillae were smooth. Many openings of the lingual glands were observed in the region of the lingual root. In the American flamingo, the surface of the lingual apex was relatively smooth. The surfaces of many fang-like and mustache-like structures were smooth. In the great egret, the surfaces of the lingual apex, central part of the posterior lingual body and giant conical papilla were relatively smooth. Many openings of the lingual glands were observed on the lingual root. In the mallard, the surface of the lingual apex was relatively smooth. The thread-shaped and scale-shaped structures were observed on the anterolateral region of the lingual body. The saw-shaped papillae on the posterolateral region of the lingual body consisted of the thread-shaped structure and big processes. In the Himalayan monal, the dorsal surfaces of the lingual apex and body were relatively smooth. The posterior part of the lingual body consisted of several conical papillae. Many openings of the lingual glands were observed on the lingual root. In the black-necked stilt, the surface of the lingual apex was relatively smooth. The dorsal surface of the lingual body was rough to comparison with that of the lingual apex. The posterior part of the lingual body consisted of several conical papillae. In the green macaw, the surface of the lingual apex had many grooves. The posterior part of the lingual body consisted of several conical papillae. These findings indicate a close correlation between the shape of the tongue and the method of food intake, the type of food, and bird's habitat.