Comprehensive characterization of the pecten oculi of the laughing dove (Spilopelia senegalensis) using light microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and immunofluorescence.

The pecten oculi is a highly specialized vascular structure unique to avian eyes, crucial for visual performance. In the laughing dove (Spilopelia senegalensis), its detailed microstructural and molecular organization remains poorly defined. This study provides a comprehensive morphological, elemental, and immunofluorescence characterization of the pecten oculi using light microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (SEM-EDX), and ten specific antibodies. SEM showed a pleated-type pecten composed of a basal part, 12-13 folded pleats and connecting bridges at the apex. The pleats had convoluted surfaces lined by capillaries and the vitreopectineal limiting membrane, with inter-pleat spaces containing pigment cells and amoeboid hyalocytes. SEM-EDX revealed carbon, oxygen, and nitrogen as major elements, with sodium at the apex, fluorine in middle pleats, and magnesium at the base. Light microscopy confirmed vascular channels surrounded by melanocytes and hyalocytes. Immunofluorescence demonstrated CD34 immunoreactivity in the vitreopectineal limiting membrane and endothelial cells, while PDGFRα immunoreactivity was detected in the vitreopectineal limiting membrane and cells associated with the blood capillaries. Vimentin immunoreactivity was observed in endothelial cells and along the vitreopectineal limiting membrane. Melan-A immunoreactivity identified melanocytes within the pectineal pleats, whereas SOX10 immunoreactivity was detected in melanocytes and additional cells located within or adjacent to the blood capillaries. CD45 immunoreactivity identified macrophage-like cells within the interstitial tissue. Collagen I/III immunoreactivity was distributed in the vitreopectineal limiting membrane, basement membrane, extracellular matrix surrounding endothelial cells, and interstitial tissue, whereas laminin immunoreactivity was detected in the basement membrane and endothelial cells. Tom20 immunoreactivity was detected in mitochondria within the blood capillaries, while α-SMA immunoreactivity was localized to the pectineal pleats, the base of the pecten, blood capillaries, and interstitial tissue. Collectively, these findings provide a comprehensive morphological and immunophenotypic characterization of the pecten oculi in the laughing dove and establish a valuable reference for future comparative and functional studies of the avian eye.