Ultrastructural studies of the pecten oculi of the Garganey (Anas querquedula, Linnaeus 1758) and the Eurasian common moorhen (Gallinula chloropus chloropus, Linnaeus 1758)

The present study represents the first attempts to give a full anatomical comparison of the vascular pigmented pectin oculi of the diurnal activity Anas querquedula and Gallinula chloropus chloropus. For achievement of this work, 10 mature birds from each species were examined under stereo- and electron microscope. The pecten oculi of A. querquedula is triangular fan-like, while in Gallinula c. thin like-fold. In both examined birds, the pecten oculi located postero-anteriorly intraocular just adjacent to optic nerve disc and attached to the retina by its base, while the free apex projected into vitreous body. A. querquedula had 14-15 pleats, while Gallinula c. chloropus had 22-24 pleats. In A. querquedula, all pecten pleats connected to each other apically by a connecting bridge. The pecten oculi was plicated type in A. querquedula, but folded type in Gallinula c. chloropus. In A. querquedula, the external surface of the pleats head carried 8-10 transverse ridges, in addition to the external and lateral surface of the pleat body carried numerous round prominences that indicated the presence of numerous afferent and efferent vessels. In both examined birds, there is a retinal elevated fold situated parallel to the slightly elevated basal fold which is clear and thicker in A. querquedula than in Gallinula c. chloropus. In Gallinula c. chloropus, the transverse section shows that the pleats had numerous afferent and efferent vessels capillaries. Statistical analysis comparing the relative measurements of the pecten oculi in the two examined birds showed that there was a significant difference.

Automated summary

This study provides a comprehensive anatomical comparison of the vascular pigmented pecten oculi of Anas querquedula and Gallinula chloropus chloropus. The differences in structure and organization of the pecten oculi, particularly in terms of the number and type of pleats, were significant between the two examined bird species.