Retinal movement (light and dark adaptation) and the effect of ultraviolet radiation in it and histological structure in two teleost species fishes

the rctinomotor movement (light & dark adaptation) of two teleosispecios : Chalccilburmisinossufansisand Noemctcheihi§ angora,<br /> have been studied. The adaptation carried out in a photoperiod of 12: 12 hrs dark : light. Under visible light intensity of 700 lux and 366 nm UV radiation. The UV radiation used in synchronized with dark & light. The histopathological effect of UV radiation, on the structure of retinal elements, also studied.<br /> The rctinomotor movement occurred in both species al visible light and d?rk condition of normal photoperiod. The lower tier of rods, cones and pigment epithelium undergo to the movements in opposite directions according to light and dark conditions. The short single cone in N. angora was exceptional, The complete light adaptation accomplished after 3hrs of light on in C.mossulenslstand after 4 hrs in A, angora. While dark adaptation accomplished after 4 and 3 hrs of light off subsequent.<br /> The UV radiations showed marked effects on the nature of retinomotor and cause injuries in some retinal elements. The retinornotor<br /> disturbed in the condition of visible light and UV svnehronization. Whilein the synchronization of dark and UV the pigment epithelium darkadapted bin rods and cones persist in their locations o flight adapted. The injureies UV appeared in the form ofpykfiosis, necrosis and degeneration of photoreceptors, especially outer segments, and swallowing of some cells. The injuries were more sever in the retina of A angora.