Biological features of the pecten oculi of the European wild quail (Coturnix coturnix): Adaptative habits to Northern Egyptian coast with novel vision to its SEM–EDX analysis

Abstract

The present investigation was prepared to give a complete ultrastructural characterization of the pecten oculi of the diurnal European wild Quail to describe their adaptation habits to the Northern Egyptian coast. Our work declares the first endeavor is the elemental analysis using scanning electron microscopy-energy dispersive X-ray (SEM-EDX) to show the migration effect on their eye. The intra-ocular quadrilateral trapezoid black pigmented plicated type pecten oculi were observed on the postero-inferior wall of the eyeball with craniocaudal and posterio-anterior directions along the fetal fissure. The pecten oculi consist of three parts: the basal, body, and apical. The basal part originated behind the optic nerve, forming the slightly elevated border, while the apical part was directed toward the ciliary body. There are 10-11 pleats with interpleat space. The coiled surface refers to numerous capillary vessels. The smooth head of each pleat was kidney-like, strongly attached to a bridge. The vitreopecteneal limiting membrane separated the pecten oculi from the vitreous body. There are numerous melanosomes and little hyalocytes on the pecteneal pleat's outer surfaces. The thick basal part of each pleat had numerous thick longitudinal microfolds that refer to the numerous blood capillaries attached to the retina as supporting roots. SEM/EDX elemental analysis revealed that carbon is the highest element (half), while oxygen represents about one-third. In the meantime, the lowest element is the phosphate at the apical part, while the lowest element in the rest is the sulfate. Finally, the pecten oculi are thought to be a reflection of the avian lifestyle and ecological adaptations. HIGHLIGHTS: Our work is the first description of the elemental analysis using SEM-EDX to show the migration effect on their eye. The quadrilateral trapezoid black pigmented plicated type pecten oculi were observed on the postero-inferior wall of the eyeball with cranio-caudal and posterio-anterior directions along the fetal fissure. The basal part of the pecten oculi originated behind the optic nerve, forming the slightly elevated border, while the apical part was directed toward the ciliary body. There are 10-11 pleats with interpleat space. The vitreopecteneal limiting membrane separated the pecten oculi from the vitreous body. There are numerous melanosomes and little hyalocytes on the pecteneal pleat's outer surfaces. SEM/EDX elemental analysis revealed that carbon is the highest element (half percent), while oxygen represents about one-third of the element's percent meanwhile, the lowest element is phosphate at the apical part, while the lowest element in the rest is the sulfate.