Morphological and functional relationship between the orbital gland and olfaction in Upupa epops (hoopoe) and Bubulcus ibis (cattle egret)

Abstract

This study used both anatomical and histological techniques to investigate the orbital gland's topographic relationship with the surrounding system, using the hoopoe and cattle egret as biological models. Hoopoe has a spindle‐shaped lacrimal gland that is suspended on the lateral edge of the frontal bone, whereas cattle egret has a tiny lacrimal gland that is embedded posteriorly within the periorbital fascia. The hoopoe's lacrimal gland has a single duct that runs parallel to the nasolacrimal duct and opens into the posterior nostril hole. In the cattle egret, the tubule‐alveolar secretory components comprise neutral and acid glycosaminoglycan. In addition, the Harderian gland is found in both these species, but their draining ducts differ; the Harderian gland of the hoopoe opens into the anterodorsal to the conjunctival fornix, whereas the Harderian gland of the egret opens anteriorly. In both hoopoe and egret, the secretions of Harderian gland include neutral and acid glycosaminoglycan. The Harderian gland is categorized as type II in hoopoe and type I in cattle egrets. The present results concluded that both orbital glands of two bird species studied play an essential role in eye health, where cleaning and lubrication of the cornea surface. Furthermore, the lacrimal gland's location and secretory features may strengthen the olfactory sensitivity of hoopoe, which relies heavily on scent to locate their food, whereas egret relies heavily on visual cues.

Macro- And Microanatomical Study of the Orbital Glands of the Common Moorhen "Gallinula Chloropus"

“…Based on this finding, the Harderian gland in the common moorhen can be classified as type I in accordance with Burns' classification [12] of the avian Harderian gland, who classified it into three distinct types based on the acinar type and lobular epithelium structure. Similar results were described in the little owl [2] , ostrich [5] , quail [14] , capercailis [7] , and in cattle egret and hoopoe [4] .…”

“…The common moorhen possesses dorsal and lateral lacrimal glands that differ in size, location, and shape. Several studies of avian ophthalmology concluded that only one lacrimal gland has appeared in the avian eye dorsal or lateral but not two, for example, in the cattle egret [4] , only a small lacrimal gland with a drop-like shape appeared at the posterior pole of the eye; while in other avian species such as the little owl and hoopoe [2,4] , only the dorsal lacrimal gland has been observed.…”

“…Shawki et al [2] mentioned that the structure of eyelids, the position of orbital glands, and the nature of their secretion play a significant role in determining the optical quality of the cornea, thereby directly affecting the quality of the retinal image. According to Al-Nefeiy et al [4] , there is a correlation between the anatomical features of the lacrimal gland in hoopoe and cattle egret the requirements of their environments, and suggested that the mucins of the lacrimal gland play a significant role as anti-inflammatory and antibacterial agents, avoiding microbial growth in the nasal cavity and on the cornea surface.…”

“…The orbital glands, eyelids, and ocular muscles are among the ocular adnexa of the eye, which are crucial components of the ocular system [1][2][3] . The major orbital glands in vertebrates are the lacrimal and Harderian glands [4][5][6][7] . The anatomical structure of the orbital glands exhibits great variability among bird species [8,9] .…”

“…Therefore, numerous studies have recently investigated the extra-orbital functions of the orbital glands. For instance, Al-Nefeiy et al [4] have clarified how the orbital glands influence vision and olfaction. Rehorek et al [9] have revealed the correlation between these glands and the vomeronasal organ, which is involved in reptilian olfaction.…”