The current observation was designed to give a complete ultrastructural description of the pecten oculi of the common ostrich (Struthio camelus). Moreover, this study represents the first attempt to measurements the elements composition of the pecten oculi using scanning electron microscope–energy dispersive X‐ray (SEM–EDX) at three regions (apical, body, and basal). To accomplish this study, eight ostrich were examined grossly and under the electron microscope. The vaned‐shaped pecten oculi consisted of three regions (apex, body, and base) with 24–25 plates. The pecten oculi was located postero‐anteriorly near to the optic nerve disc that was attached by their bases to the retina forming a slightly elevated basal border joining the bases of all pleats, while the apex was linked in a circular bridge. The pleats are separated from each other by the inter‐pleat spaces that are very clear at the base and nearly not observed at the apical part. The outer pleat's surface carried numerous prominences that pointed to the existence of numerous afferent and efferent pecteneal blood capillaries vessels. The vitreopecteneal limiting membrane separated the pecten oculi from the vitreous body. Our findings concluded that, the high number of thick pecteneal pleats was related to the diurnal activity of the common ostrich. SEM–EDX shows that the carbon percentage in the three regions is the highest that representing about half of all elements, while the oxygen percent is about one‐third; meanwhile, the lowest percentage is the sulfate at the apical region, and the calcium at the body and basal regions.

The current study aims to illustrate the gross and scanning electron microscopic characterizations and ultrastructural adaptation of the lingual papillary system of Egyptian Ossimi sheep to Egyptian ecological conditions. The tongue had three regions: the apex (with a slightly bifurcated tip), the body (subdivided into rostral and caudal parts) and the root (subdivided into rostral papillary and caudal non‐papillary parts). Torus linguae had two parts: the triangular rostral part (the caudal part of the body) and the quadrilateral wide part (the rostral part of the root). The lingual papillary system had mechanical (filiform, conical and lentiform) and gustatory (fungiform and circumvallate) types. Filiform papillae were heavily scattered on the dorsal surface of the apex, the rostral part of the body and the ventral surface of the papillary region of the tip. Filiform papillae had five subtypes (ventral and dorsal processed, triangular, leaf‐like and triangular‐processed papillae), while the conical papillae had three subtypes: two lingual (small, large) and one paralingual (elongated pointed), and the fungiform had two subtypes: the high‐density ovoid (on the ventral surface of the tip) and round papillae (on the dorsal surface) that possessed a high number of taste pores, not previously described. They ranged from 5 to 10 for ovoid and 25 to 25 for round papillae. Each circumvallate papilla had an ovoid bulb (with 2–5 taste pores) encircled by an annular groove and two pads (i.e. not described previously). The papillary system's regional divergence was specialized for their harsh and semi‐harsh diet.

The current study aimed to investigate the ultrastructure of the retinal photoreceptors of the African catfish and to demonstrate their adaptation to nocturnal or diurnal visions or by the two ways. The eyes of eight adult catfish were collected during the daytime, and the retinae were separated and examined by light and transmission electron microscopy. The photoreceptors' layer appeared in contact with the retina's pigmented epithelium. Two photoreceptors were detected in cones and hidden rods.Cones predominate in light-adapted retinae. The outer segments of cones appeared between the retinal pigmented epithelium protrusions, which indicates the movement of melanosomes away from the photoreceptors as a retinomotor response of the catfish. The two types of retinal tapetum were in between cones. The first type, the cored granules, were large, spherical, and had black peripheral parts and central lucent parts, and contained some granules. The second type was Guanine crystallites of tapetum lucidum, which were small electron-lucent, and their shape varied from spherical to rectangular. Melanosomes vary in shape from spherical to elliptical. The Müller cells were darkly stained elongated cells that measured about 5.5-8.5 μm in length and 2.2-2.5 μm in width, and their microvilli appeared between the inner segments of the rods and cones. Müller cell processes were extended from the photoreceptor layer to the inner limiting membrane. Zonula occludentes appeared between the Müller cell processes and the internal segment of the rods and cones. African catfish have eyes which are adapted not only for nocturnal but also for daytime light.

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This investigation was led to depict the structural and functional adaptations of the oral cavity of herbivorous Egyptian tortoises using scanning electron and light microscopes. The SEM showed that the triangular papillary tongue possessed three conical papillary subtypes: the rectangular conical on the tip, the round conical on the rest of the dorsal lingual surface and the elongated conical on the caudal portion of the lingual wing. The presence of the serrated lips with their valves compensated for the absence of the teeth. The rostral part had a vomeronasal opening while the middle part had the choana, but the caudal part had numerous openings of the salivary glands. There are three palatine folds: a single median palatine fold, two peripheral palatine folds and the choanal fold. The current histological results show the keratinized dorsal lingual surface, in which the keratinized layer extended to cover the papillae. Two types of lingual glands, according to their position, are papillary superficial and deep lingual glands. Papillary or superficial glands open in the interpapillary spaces via narrow openings, while the deep glands are surrounded by well‐developed muscles and open via wide openings on the dorsal lingual surface. An entoglossal cartilaginous structure of hyaline cartilage was found in the mid‐ and hindtongue, with numerous chondrocytes lodged within the lacunae. Our results conclude that the oral cavity of the herbivorous Egyptian tortoise was adapted to the dietary and vigorous demands of the Egyptian fauna.