Surgical anatomy of the ear of the fat sand rat

Objective: This study was conducted to investigate and describe the anatomical details of the ear of the fat sand rat (Psammomys obesus). Methods: Thirty ears (15 in dry skull and 15 in live animals) were dissected with the aid of an operating microscope and microsurgical techniques. Photographs were taken through an operating microscope. Results: The temporal bone of the fat sand rat consists mainly of an unusually large bulla. Three distinct auditory ossicles were visualized and the manubrium of the malleus is relatively long in relation to the size of the ear. Most parts of the inner ear bulge into the bulla cavity and are easily accessible. The cochlea consists of 3.25 turns. The tympanic membrane, facial nerve, stapedial artery, and eustachian tube are described in detail. The large size of the bulla is probably related to the high sensitivity, particularly at low frequencies of the animals ear. Conclusion: The fat sand rat was found to be an excellent experimental animal for the investigation of middle and inner ear physiology.