ULTRAVIOLET RADIATION AND THE FERTILIZATION REACTION INARBACIA PUNCTULATA

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Abstract
Radiation is particularly suited to injure the sperm and impair its fertilizing power because exposures may be very short and may be discontinued before staling sets in, and because on fertilizing eggs the possibility of carrying over small amounts of reagent is absent. Measured dilutions of Arbacia sperm were exposed to radiation from a Cooper Hewitt mercury-vapor arc at 30 cm. for 1 min. Samples of radiated and non-radiated sperm were then transferred to measured amounts of a known concentration of eggs in sea-water. At intervals thereafter, up to 3 hrs., similar samples were used to fertilize normal eggs. At the end of 4-5 hrs. the percentages of eggs which had formed membranes and those which had cleaved were determined and compared with results obtained with normal sperm. In normal cultures, it was found (as stated by F. R. Lillie) that both dilution and time are factors in determining the fertilizing power of sperm. Ultraviolet radiation augments the influence of both factors. Weaker dilutions of sperm are more susceptible than more concentrated suspensions. Although loss of motility occurs, it is probably rather the loss by diffusion of a substance necessary for fertilization which is responsible for the falling off in fertilizing power.