Ultrastructural characterizations of the pecten oculi of the common ostrich (Struthio camelus): New insight to scanning electron microscope–energy dispersive X‐ray analysis

Abstract

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.

Gross, ultrastructural, and histological characterizations of pecten oculi of the glossy ibis (Plegadis falcinellus): New insights into its scanning electron microscope–energy dispersive X‐ray analysis

“…Our SEM and histological observations revealed that the strongly vascularized pecten oculi of the predatory diurnal visual active behavior glossy ibis ( Plegadis falcinellus ) was originated from the retinal layer neighboring the optic nerve and was in contact with the vitreous body and orientated to the ciliary body and the lens. These results were identical to those reported in the pecten oculi of all avian species for the various nutritional mechanisms and behavior of different visual activity hours (Abumandour et al, 2021; Braekevelt, 1993; Braekevelt, 1994, 1998; Braekevelt & Richardson, 1996; Elghoul et al, 2021; Kiama et al, 1994; Kiama et al, 2001; Orhan et al, 2011; Yilmaz et al, 2021).…”

“…Moreover, some different shapes of the pecten oculi have been described in avian species, such as; the trapezoid shape in quail and jungle crow (Pourlis, 2013; Rahman et al, 2010), the shell shape in quail (Orhan et al, 2011), the fan‐shape in the black kite (Kiama et al, 1994), the accordion‐shape in the stork (Onuk, Tutuncu, et al, 2013), and the snail‐shape in the seagull (Onuk, Tutuncue, et al, 2013). The folded appearance of the pecten oculi was also described in the ostrich (Elghoul et al, 2021). Physiologically, the different shapes and appearances of the pecten oculi may have a strong correlation with the different avian species' lifestyles (Micali et al, 2012; Segovia et al, 2020).…”

“…Functionally, the pecten oculi was acclimatized to play a specific role in the most vital functions through visually acclimatized active hours with various feeding strategies and visual active patterns. Avian diurnal visual activity includes a variety of feeding behaviors, including predatory species like the crow and black kite (Braekevelt, 1994; Kiama et al, 1994; Rahman et al, 2010), as well as omnivorous species like the Garganey, Eurasian moorhen, stork, seagull, and duck (Abumandour et al, 2021; Ince et al, 2017; Onuk, Tutuncu, et al, 2013; Scala et al, 2002), and the herbivorous species as in the budgerigar, quail, emu, ostrich, and sparrow (Braekevelt, 1998; Elghoul et al, 2021; Micali et al, 2012; Orhan et al, 2011; Rajab, 2012). However, the nocturnal visual active avian species include mainly predatory birds such as the great horned owl (Braekevelt, 1993), the great blue heron (Braekevelt, 1991a), spotted eagle owl (Kiama et al, 2001).…”

“…Seven pecten oculi of the glossy ibis were prepared for examination under the SEM (Elghoul et al, 2021; Kandyel et al, 2021). The prepared samples were fixed in 2% formaldehyde and 1.25% glutaraldehyde in 0.1 M sodium cacodylate buffer, pH 7.2, at 4°C.…”

“…The foremost microscopic explanation of the pecten oculi is defined by Sillman (1973). Nevertheless, there is little attraction to explaining the pecten oculi due to its small size and its presence exclusively in bird species (Elghoul et al, 2021). The pecten oculi originate from the non‐vascular retinal layer and are closely related to the origin of the optic nerve.…”