PHOTOREACTIVATION OF ULTRAVIOLET LIGHT INJURY IN GAMETES OF THE SEA URCHIN STRONGYLOCENTROTUS PURPURATUS

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Abstract
1. Ultraviolet radiation induced cleavage delay in eggs of the sea urchin Strongylocentrotus purpuratus can be reduced by exposure to visible light before fertilization. 2. Photoreactivation by visible light occurs in injury by any of the wavelengths of ultraviolet light which we tested: λ2450Å, λ2537Å, λ2654Å, λ2804Å, λ3025Å, λ3130Å. The phenomenon is less pronounced at λ2450Å than at the other wavelenths tried. 3. Wavelengths shorter than λ4300Å are most effective in photoreactivation. The minimum visible light exposure giving an effect near maximal is determined. 4. Zygotes formed from ultraviolet injured eggs are more readily photoreactivated than the unfertilized eggs. 5. Ultraviolet irradiated eggs show no increase or decrease in injury when kept in the dark for several hours before fertilization. 6. Visible light is injurious to sperm. 7. Sperm injured by ultraviolet radiations can be photoreactivated, even though the visible light is itself harmful. 8. The results are compared with photoreactivation data in the literature and discussed with reference to possible mechanisms of action for the phenomena observed.