Morphology of the complex laryngeal gland in the Atlantic bottlenose dolphin, Tursiops truncatus

A complex lymphoepithelial gland is a constant feature in the larynx of Atl antic bottlenose dolphins, Tursiops truncatus, based on study of 56 animals . Larynges were removed from fresh, non-decomposed beach-stranded animals for gross examination and histological sampling. A large lymphoepithelial gland occurs in the rostro-ventral mucosa of the l arynx, overlying the cricoid cartilage. It presents as a well-defined, elev ated, and heavily trabeculated area. Histological examination reveals a pse udostratified columnar epithelium which branches into the underlying submuc osa. The epithelial-lined folds and crypts thus formed are surrounded by ag gregations of lymphocytes, which infiltrate this epithelium. Mucous glands are often associated with these lymphoid aggregations. The histological appearance of the laryngeal gland is remarkably similar to the palatine, or dorsal oropharyngeal tonsils, of T. truncatus. It may be analogous to the nasopharyngeal adenoid of terrestrial animals. Age-related involution of the laryngeal gland is not as obvious with increasing animal age (or length) as it is in other mucosa-associated lymphoid tissue. The d istribution of this gland among cetaceans is not yet known. We have observe d it in individuals of every species we have studied, including Lagenodelph is hosei, Stenella coeruleoalba, Stenella attenuata, Globicephala macrorhyn chus, Steno bredanensis, Physeter catodon, Pseudorca crassidens, Mesoplodon europaeus, and Kogia breviceps. Anat Rec 254:98-106, 1999. (C) 1999 Wiley- Liss, Inc.