| A Scanning Electron Microscope Study of Pigment Distribution in Pectin Oculi of the Domestic Fowl and Eagle Owl (2007) | |||||||||||||
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| The pectin oculi is a highly vascular and pigmented organ that projects from the optic disc into the vitreous body in the avian eye. The pigmented tissue and blood vessels are contained in a capsule of laminated vitreo-pectineal membrane. Whereas the role of the pectineal blood vessels in nutrient delivery to the retina is well understood, the function of the pectineal pigmented tissue remains an enigma. In a previous study, we putatively assigned the pigmented tissue in the pectin a protective role against damage of the blood vessels by ultraviolet (UV) light. In order to ascertain whether pectineal exposure to light has any influence on the extent of pigmentation in the pectin, we have compared the distribution of pigmentation in the pectin of a diurnal bird, the domestic fowl and a nocturnal bird, the eagle owl. Our results show that the pectineal vasculature of the eagle owl is effectively covered by a thick layer of pigmented tissue and the blood vessels are visible on the entire surface of the pectin. In contrast, a modestly pigmented tissue covers the apical aspect of the pectin in the domestic fowl and most of the capillaries lay bear. The thickly pigmented tissue of the pectin in the eagle owl may effectively protect the pectineal blood vessels against UV light, whereas the modest pigmentation in the pectin of the domestic fowl is a compromise to the nutritive demand placed on the pectin by the diurnal lifestyle exhibited by this bird. A lower density of pigmented tissue in the pectin of the domestic fowl would facilitate unhindered diffusion of metabolites between the vitreous and pectin to cater for higher metabolic demands of the retina. Kenya Veterinarian Vol. 26 (1) 2004: pp. 43-50 | |||||||||||||
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