Occurrence and structure of epipharyngeal pouches in bears (Ursidae)

Abstract

The infrequent mention of epipharyngeal pouches occurring in some species of bears indicates the scarcity of morphological and functional knowledge about these structures. In order to provide precise morphological data on the structure of these remarkable formations and to verify their taxonomic utility, the pharyngeal regions of 1 spectacled bear and 3 brown bears were examined. All these individuals possessed epipharyngeal pouches, which are tubular, blind-ending outpouchings of the caudodorsal pharyngeal wall equipped with respiratory epithelium and a thick layer of elastic fibres. While the spectacled bear and Ursus arctos syriacus possessed a single pouch on the caudodorsal wall of the nasopharynx, in Ursus arctos and Ursus arctos beringianus 2 unequally sized pouches were present. Two additional sacs of smaller size, representing outpouchings of the lateral pharyngeal wall, occurred in the spectacled bear. These findings prove epipharyngeal pouches to be constant and unique morphological features of the family Ursidae, the anatomical features suggesting involvement in the respiratory system most probably in important aspects of ursid phonation. This is the first description of epipharyngeal pouches in the spectacled bear.