LIGHT AND SCANNING ELECTRON MICROSCOPIC STUDY OF THE TONGUE IN THE ZEBRA FINCH CARDUELIS CARDUELIS (AVES: PASSERIFORMES: FRINGILLIDAE)

The tongue of adult zebra finch (Carduelis carduelis) was examined by light and electron microscopy. The tongue resembles a thick rod with a pointed tip. The length of the tongue is about 8 mm. Three parts are distinguished in the dorsal surface of the tongue: the apex, the body and the root of the tongue in each bird. A unique feature of the organ is the presence of many fine densely populated needle-like processes in both lateral sides of the anterior lingual apex. The caudal processes are of equal lengths and are tangent to the tongue. Afterwards, the length of the processes increases progressively towards the free point of the organ. The median sulcus is absent on the tongue. Large conical papillae with a W-shaped arrangement are present between the body and the root of the tongue, the apices of which are pointed toward the posterior part of the organ. According to their positions, the PAS-positive compound tubuloalveolar salivary glands can be classified as lingual and laryngeal salivary glands. The lingual salivary glands extend from the lingual apex to the lingual root, whereas the laryngeal salivary glands are situated in both sides of the laryngeal cleft. The ventral side of the tongue is devoid of any glandular structure.