Morphological study of nasal diverticulum in Grant's zebra (Equus quagga boehmi Matschie, 1892).

IMPORTANCE: The nasal diverticulum (ND), a blind cutaneous pouch extending from the nasal vestibule (NV), is unique to Equidae. Although anatomical and histological descriptions of the ND are available for horses and donkeys, detailed studies in zebras remain limited. OBJECTIVE: To investigate and characterize the anatomical and histological features of the ND in zebras and compare these findings with those observed in other species. METHODS: Silicone casts of the NDs were prepared from two of three female Grant's zebra carcasses for anatomical measurements, followed by dissection for gross morphological examination. Three-dimensional reconstructions generated from computed tomography images of the casts were used to obtain morphological measurements. In addition, paraffin-embedded sections stained with hematoxylin and eosin were prepared for histological evaluation and morphometric analysis. RESULTS: The NDs of zebras were curved blind pouches, slightly compressed mediolaterally, and extended over the nasal process of the incisive bone. Based on the impression of the nasal process, the ND was divided into cranial and caudoventral regions. The nasolacrimal orifice was located on the lateral aspect of the nostril. An undulating fold was observed on the medial wall of the cranial region of the ND. The total volume of the ND was approximately 36 mL. The surface was covered with fine hairs associated with secondary hair follicles. Compared with the NV, the ND exhibited significantly reduced epidermal thickness and fewer sebaceous glands, sweat glands, and secondary hair follicles. CONCLUSIONS AND RELEVANCE: This study provides novel anatomical and histological data on the ND in zebras, highlighting species-specific differences compared with other animals.