Clinical anatomy of the North American river otter (Lontra canadensis)

Published anatomic studies of North American river otters (Lontra canadensi s) include only comparative reviews of single anatomic systems, but this pa per includes multiple clinically relevant anatomic features. Both captive a nd free-ranging North American river otters were studied by gross dissectio n of nine specimens, radiography of 18 live otters, and physical examinatio n of 170 otters. Body fat in North American river otters is stored primaril y subcutaneously at the base of the tail and in the axillae, so lack of vis ceral detail on abdominal radiographs is due to a lack of coelomic fat. The heart and great vessels are oriented as in the dog. The cardiac radiograph ic silhouette measures three intercostal spaces laterally between the fourt h and sixth ribs and 4-4.5 intercostal spaces between the seventh through 1 1th ribs on the ventrodorsal projection. Subjective estimation of age by ev aluation of tooth wear is confirmed by histologic examination of cementum a nnuli. Structures of the feet were imaged by high-resolution mammographic t echnique. The adult thymus was prominent, but the gland was small in the on e juvenile animal studied. The spleen was unexpectedly large but consistent with findings in European otters (Lutra lutra). As in other otters and mam mals, kidneys are reniculated.