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

Objective Overview

• This study investigated the anatomical and histological characteristics of the nasal diverticulum (ND) in Grant’s zebras, a unique nasal structure in equids, and compared these features with those known from horses and donkeys.

Introduction and Background

• The nasal diverticulum (ND) is a distinctive blind pouch extending from the nasal vestibule found only in members of the Equidae family, which includes horses, donkeys, and zebras.
• Prior detailed anatomical and histological descriptions have primarily focused on horses and donkeys—zebras have been less studied in this regard.
• The ND’s functional and morphological aspects are important for understanding species-specific adaptations within the equid family.

Research Objective

• The main goal was to conduct an in-depth morphological (anatomical and histological) study of the ND in Grant’s zebra, scientifically known as Equus quagga boehmi.
• The study also aimed to compare the zebra’s ND features with those of other equids to reveal species-specific characteristics.

Methods

• Specimens: Three female Grant’s zebra carcasses were used; silicone casts of the nasal diverticula were made from two of them for detailed anatomical analysis.
• Anatomical Measurement:
  • Measurements were taken from the silicone molds of the NDs.
  • CT scans of the casts were performed to create three-dimensional reconstructions, enabling precise morphological measurements.
• Gross Morphological Examination:
  • Direct dissection of the nasal diverticula was performed to observe physical structure and relations.
• Histological Analysis:
  • Tissue samples were embedded in paraffin, sectioned, and stained with hematoxylin and eosin for microscopic evaluation.
  • Morphometric analyses were conducted to quantify features such as epidermal thickness and gland distribution.

Results

• Shape & Size:
  • The ND in Grant’s zebra was identified as a curved and slightly mediolaterally compressed blind pouch.
  • It extended over the nasal process of the incisive bone and was divided into cranial and caudoventral regions based on bone impressions.
• Anatomical Features:
  • The nasolacrimal orifice — where the tear duct opens — was found on the lateral side of the nostril.
  • An undulating fold was present on the medial wall of the ND’s cranial region, which may have implications for airflow or mucosal surface area.
  • The total volume of the ND was measured at about 36 mL.
  • The internal surface of the ND was covered with fine hairs emanating from secondary hair follicles, indicating a specialized mucocutaneous lining.
• Histological Characteristics:
  • The epidermis lining the ND was significantly thinner than that of the nasal vestibule.
  • The ND contained fewer sebaceous (oil) glands, sweat glands, and fewer secondary hair follicles compared to the nasal vestibule, highlighting differences in secretion and sensory structures.

Conclusions and Significance

• The study provided new and detailed anatomical and histological data on the nasal diverticulum specifically in Grant’s zebra, an under-researched species.
• Observed differences from horses and donkeys indicate species-specific adaptations in the morphology and tissue composition of the ND in zebras.
• Understanding of these species-specific traits can enhance knowledge of equid nasal anatomy and may elucidate functional roles of the ND related to environmental adaptation, olfaction, or respiratory biology.
• This baseline knowledge can support further comparative anatomical studies and possibly influence veterinary approaches to diseases affecting the nasal structures of zebras and related species.