Background: The visual system of desert rodents demonstrates a rather high degree of development and specific features associated with adaptation to arid environment. The aim of this study is to carry out a descriptive investigation into the most relevant features of the sand rat eye. Results: Light microscopic observations revealed that the eye of Psammomys obesus diurnal species, appears similar to that of others rodent with characteristic mammalian organization. The eye was formed by the three distinct layers typical in vertebrates: fibrous tunic (sclera and cornea); vascular tunic (Iris, Ciliary body, Choroid); nervous tunic (retina). Three chambers of fluid fundamentals in maintaining the eyeball's normal size and shape: Anterior chamber (between cornea and iris), Posterior chamber (between iris, zonule fibers and lens) and the Vitreous chamber (between the lens and the retina) The first two chambers are filled with aqueous humor whereas the vitreous chamber is filled with a more viscous fluid, the vitreous humor. These fluids are made up of 99.9% water. However, the main features, related to life style and arid environment, are the egg-shaped lens, the heavy pigmentation of the middle layer and an extensive folding of ciliary processes, thus developing a large surface area, for ultrafiltration and active fluid transport, this being the actual site of aqueous production. The ciliary muscle is poorly developed and the dilator pupillae is not apparent. Conclusions: The ocular globe of sand rat demonstrates a high degree of development and several specific features associated with adaptation to life style and arid environment.

The purpose of this investigation was to study the morphological aspects of the Harderian gland in Gerbillus tarabuli. Tissues were obtained from both male and female adult Gerbillus tarabuli and processed for light and electron microscopy. The Harderian gland in gerbil is large and well developed, covered by a thin capsule, from which thin septae extend, subdividing the gland into lobes and lobules. The endpieces of the gland are tubuloalveolar, which produce a secretion of lipid character. The glandular epithelium is pseudostratified with two types of secretory cells, the type C cells are columnar in shape with large lipid vacuoles, and type P cells pyramidal and serous, they are basally located with no luminal aspect. The epithelium possesses well-developed myoepithelial cells. The wide lumina are filled with lipid vacuoles, cellular debris, and porphyrins. The Harderian gland of the gerbil has no morphologically distinct duct system; a single extraglandular excretory duct is detected. Electron microscopic examination revealed that type C cells contain large electron-light lipid vacuoles, a well and extensive reticulum endoplasmic and a large number of mitochondria. The pyramidal cells are characterized by a small number of PAS-positive granules at the basal region; these cells exhibit one or two round nuclei, many electron-dense granules, crystalloid bodies, abundant mitochondria and many ribosomes in their cytoplasm. The three mechanism of secretion are seen in the Harderian gland of Gerbillus tarabuli. In its overall characteristics, the Harderian gland of Gerbillus tarabuli conforms to the general pattern observed in rodents. However, further research will be needed to correlate the presence of cytoplasmic slashes, crystalloids bodies and glycoproteins in epithelial cells with the biology of these animals and to their functional significance.

No abstract

Background: Desert rodent, Gerbillus tarabuli, is a seed-eating animal and do not require drinking water. It depends upon metabolic water. Understanding the functional characteristics of ocular glands which produce a watery lacrimal fluid is of interest. In the present study, we described the macroscopic anatomy and microscopic structure of the paraorbital glands in tarabul's gerbil. Results: There are up to four distinct orbital glands: lacrimal (LG), Harderian (HG), Meibomian (MG), and conjunctival mucous glands. Each eye has three eyelids, the main upper and lower lids and a third lid hidden between them in the inner corner of the eye. The LG is bipartite, situated on the dorsolateral aspect of the eyeball. The HG is large and localized deep in the orbit. The MG is found in the dense connective tissue plate. Upon light microscopic examination, the LG is an acinar gland; its secretory cells have mucous and serous granular cytoplasm. The endpieces of HG consist of tubuloalveoli, with two cellular types: prismatic vacuolated cells and pyramidal basophilic cells. The MG acini are closely arranged one after another. Each acinus contains a basal layer of myoepithelial cells and a mass of rounded, vacuolated cells. The nictitating membrane is formed by a semilunar fold of conjunctiva, supported by a hyaline cartilage. Numerous goblet cell clusters are detected in the covering conjunctiva particularly in the bulbar conjunctiva. Mucin glycoproteins appear to be abundant in the precorneal tear film, probably acting against desiccation stress. Conclusions: Based on the data from this study, it could be concluded that the orbital glands of gerbil are welldeveloped, similar to other mammals.