Retinal characterization in the eyes of two bats endemic in the Egyptian fauna, the Egyptian fruit bat (Rousettus aegyptiacus) and insectivorous bat (Pipistrellus kuhlii), using the light microscope and transmission electron microscope

Abstract

Bats are the only mammals that can fly in the dark without eye usage. This study was conducted to describe the structural and functional adaptations of the retina of two bats very common in the Egyptian fauna having a different lifestyle: the Egyptian fruit bat (Rousettus aegyptiacus) and insectivorous bat (Pipistrellus kuhlii). Seven eyes were collected from adult individuals of each species. Examination of the retina using a light microscope and a transmission electron microscope was carried out. The retina of P. kuhlii was thicker than that of R. aegyptiacus, which had many projections extended from the choroid layer into retina forming papillae. Despite rods being dominant in retinae of both species, cone photoreceptors were encountered in both retinae. The outer plexiform layer of R. aegyptiacus was arranged into islets between the outer nuclear layer produced differences in its thickness. However, the retina of P. kuhlii showed a normal arrangement of retinal structure. The retinal pigment epithelium of both bat species consists of a single layer of the cuboidal cells with a round to oval vesicular nuclei, which showed a lack of pigmentation in R. aegyptiacus and poor pigmentation in the P. kuhlii. In conclusion, our investigation detected many structural and ultrastructural differences between the two bat species. The presence of many projections protruded from the choroid layer of R. aegyptiacus retina is considered the most characteristic difference between the retinae of R. aegyptiacus and

Ocular morphology of the fruit bat, Eidolon helvum, and the optical role of the choroidal papillae in the megachiropteran eye: a novel insight

“…The unusual choroidal and retinal morphology observed in this study for Eidolon helvum have since been reported for other megachiropteran, and in particular, pteropodid bats 10,29,30 . The role of the choroidal papillae in blood supply to retinal tissues has been well documented 31,32 but their role in vision has been a matter of controversy among scientists with some scientists asserting that the presence of the choroidal papillae led to improved visual sensitivity through an increase in the photosensitive area and number of photoreceptors 32,33 .…”

“…This perception is required for the survival of the organism especially during its periods of peak activity. The activity pattern of an animal is therefore related to its ocular morphological characteristics and has been reported by many ocular scientists [1][2][3][4][5][6][7][8][9][10] .…”

Snout cutis of the domestic pig (Sus scrofa domesticus, Linnaeus, 1758): Using light and transmission electron microscopy

“…Following the fixation, the samples were fixed at 1% osmium tetroxide (OsO 4 ), then dehydrated in a graded dilution of absolute ethanol (Aboelnour, Noreldin, Massoud, & Abumandour, 2020; Kandyel et al, 2021). After that, samples were embedded in epoxy resin.…”

Morphological adaptations on the eye of the golden gray mullet (Chelon aurata): Using light and scanning electron microscopical study

“…In addition, the inner side of the epithelial layer of the retina was appeared as a layer wrapped around itself (Figure 5b, c). The vertebrate visual system had a species-specific adaptation either in aquatic, semi-aquatic, or terrestrial conditions, in close relation to the morphological structure of the eye (Aboelnour et al, 2020;Jones et al, 2007;Katzir & Howland, 2003;Onuk et al, 2021). Several previously published articles were deeply discussed the mechanisms by which environmental factors can influence the adaptation of the aquatic eye and the visual quality such as temperature and subaquatic pressure, aquatic turbidity, and chromatic absorption of light, in addition to, other climatic changes.…”

“…The optical system of the teleost fish is considered of utmost importance, because it is involved in numerous pivotal activities of the fish lifestyle such as: migration, reproduction, food search, or swimming (De Busserolles et al, 2013; El‐Bakary & Abumandour, 2017a; Onuk et al, 2021; Schmitz & Wainwright, 2011b). Moreover, the visual adaptation provides good information on the ecological diversity of the Vertebrate World (Aboelnour et al, 2020; Akat & Arikan, 2013; Litherland et al, 2009).…”