Seromucous anal gland in a New World hystricognath rodent Thrichomys apereoides (Lund, 1839)

New World species of the Hystricognathi comprise a group of rodents that exhibit poorly understood social behaviour. One such species, the echimyid Thrichomys apereoides, has a behavioural and social repertoire which suggests the use of its eversible anal gland in communication between individuals; however, no information on the morphology of this gland is available. In this study, the anal gland of nineteen adult individuals (11 males and 8 females) was analysed through histological and histochemical techniques. The gland was located in the submucosal of the anal region, cranial to the anus, and had an opening located dorsally in the rectum mucosa at approximately 1 mm from the anus. The gland was characterized as seromucous, secreting neutral glycoprotein. Not all individuals studied presented secretion in the glandular ducts, indicating a possible functional variation in the gland. This was the first record of an anal gland of the seromucous type in rodents.