Ultramorphological and histological studies on the tongue of the common kingfisher in relation to its feeding habit

Abstract

The tongue of common kingfisher (Alcedo atthis, Alcedinidae, Aves) was investigated by means of light and scanning electron microscopy to elucidate its ultramorphological and histological features.The tongue of the studied bird is an elongated, tubby and consistent organ of triangular shape of about 8.9mm in length. It drops in the posterior quarter of the lower part of the very long bill. It is composed of three successive regions; blunt apex, stocky body and root. In addition to the giant conical papillae demarcating the tongue’s body from root, numerous caudally directed spiny conical papillae are differently distributed on the dorsal and lateral surfaces of the lingual body and root. Both papillae appears to help catching and directly swallowing preys, however the apex is covered with superposed foliate papillae. By light microscope, the dorsal lingual epithelium is composed of a keratinized stratified squamous epithelium. The stratum basale is followed by a thick stratum spinosum of polyhedral cells containing some deeply embedded taste buds and gives rise to the stratum corneum cell layer. The loose connective tissue core (lamina propria) which embraces some blood vessels and melanocytes forms finger-like dermal papillae of different heights under the epithelium. It also contains branched tubulo-alveolar salivary glands mainly of massive gelatinous mucus secreted on the epithelial surface to facilitate food-intake indicating a close relationship of the lingual structure with the common kingfisher feeding habit which feeds mainly on fishes and aquatic arthropods.