Light and scanning electron microscopic study of the lingual structure in the budgerigar (Melopsittacus undulatus)

Abstract

BACKGROUND: The tongue, which plays a very important role in food intake by vertebrates, exhibits significant morphological variations that appear to represent adaptation to the current environmental conditions of each respective habitat. OBJECTIVES: The aim of the present investigation was to investigate lingual structure in adult budgerigar. METHODS: Tongues of 12 adult budgerigars were used in the investigations. Samples of the apex, body and root of the tongue were studied using light and electron microscopy. RESULTS: The tongue in budgerigar is about 5 mm in length. The deep concave rostral portion of the lingual apex is devoid of any glandular structure and is continuous with a semicircular caudal portion. The caudal portion of the lingual apex is divided into two symmetrical halves by a median longitudinal fissure. The rostral part of the lingual corpus is distinctly divided by fissures of varying depth into many irregular raised areas with different sizes. Several large caudally directed conical papillae are situated on the posterior end of the lingual corpus and along the thick border region between the lingual body and root. There are also some giant conical papillae on the laryngeal mound. According to their positions, the PAS-positive compound tubuloalveolar salivary glands can be classified as dorsal and dorsolateral salivary glands. The dorsal lingual salivary glands are situated beneath the dorsal lingual epithelium. They extended from the caudal end of the fissure on the caudal lingual apex to the front of the laryngeal cleft. The dorsolateral salivary glands on each side extend from the beginning of the body of the tongue to the level of the laryngeal cleft. The ventral side of the tongue is devoid of any glandular structure. Neither the morphology nor the dimensions of the tongue show sex-specific differences. CONCLUSIONS: lingual structure shows considerable differences in budgerigars in comparision to other birds studied so far.