Morphological study of the northern pike (Esox lucius) tongue.

The northern pike (Esox lucius) is a fresh water species belonging to the Esocidae family. It is a carnivorous fish feeding mostly on invertebrates and fishes. Due to the scantiness of relevant literature regarding the morphology of the tongue in fish we carried out this study with the aim of providing information on the dorsal surface morphology and histological structures of the tongue in E. lucius. The tongues of five E. lucius were examined using light- and scanning electron- microscopy (SEM) techniques. The SEM studies revealed the presence of numerous teeth, longitudinal mucosal strands and scattered taste buds spread on the tongue surface. Histological studies using hematoxylin and eosin and Masson's trichrome staining showed that the musculature was not visible in the tongue of E. lucius. The tongue is composed of mucosa, and submucosa supported by osteocartilagionous skeleton. The mucosa consists of several layers of unicellular mucous cells interrupted by numerous teeth. The derivation of teeth from the underlying bronchial skeleton was visible in longitudinal section. The scattered taste buds with a typical onion shape were also present. Overall, the morphological features of the E. lucius tongue together suggested its mechanical and sensory roles. The findings of this study together with morphological and physiological data from other fishes contribute to the knowledge of the nutrition and feeding behavior in aquaculture species.