Abstract
BackgroundThe 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.ResultsLight 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.ConclusionsThe ocular globe of sand rat demonstrates a high degree of development and several specific features associated with adaptation to life style and arid environment.
Highlights
The visual system of desert rodents demonstrates a rather high degree of development and specific features associated with adaptation to arid environment
From the apex of ciliary processes, start the fibers, called zonule of Zinn (Fig. 3c). These fibers connect ciliary body to the Results The paired eyeballs or globes are situated in the bony sockets of the skull called orbits
The outermost fibrous tunic comprises the cornea in front and the sclera in other parts of the globe
Summary
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. Numerous studies of various species have demonstrated high variability in morphology, especially of the light-sensitive retina, reflecting adaptation to different ecological surroundings and life styles (McFarland, 1991). Desert rodents possess physiological and anatomical adaptations to endure the harsch conditions; these habitats have characteristic climatic factors (the heat and the lack of water) affecting probably the structure of the eyes. The only literature existing consists on the structure of the retina of Psammomys obesus (Saidi, Chaouacha-Chekir, & Hicks, 2011).The fat sand rat, Psammomys obesus lives in the arid zones of North Africa and Eastern Mediterranean region.
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