A note on the duodenum of the West Indian manatee (Trichechus manatus), with emphasis on the duodenal glands.

The anatomy of the duodenum of the West Indian manatee has both macroscopic and microscopic features that are unusual when compared to other mammalian forms. Macroscopically, the voluminous duodenal ampulla and the paired duodenal diverticula are distinctive. The general microscopic structure of the manatee duodenum is not unusual, but the duodenal glands secrete an acid mucin (sialomucin). The cells of these glands appear to be intermediate between classical serous and mucous cell types. These cells also contain granules with regions of high peripheral electron density. The overall structure of the manatee duodenum most strongly resembles that of the dugong, another member of the order Sirenia.