Radiosensitivity of developing reproductive cells in female Cochliomyia hominivorax.

HE stage of cell development at the time of irradiation is one of the most Timportant natural conditions that influence radiosensitivity. This relationship has been demonstrated in detail for the various stages of gametogenesis in male Drosophila, but corresponding studies of females have been far less extensive. For establishing a relationship between the maturation of the female reproductive cells and their radiosensitivity, an ideal organism is one in which the germ cells develop synchronously; this type of cell development occurs with the screwworm fly, Cochliomyia hominiuorax (Coquerel) (Diptera, Calliphoridae). The results reported here are an extension of the original radiation experiments with this species (then known as Callitroga hominiuorax) reported by BUSHLAND and HOPBINS (1951, 1953). In studies on radiosensitivity of the various meiotic stages, the criterion of damage has been the induction of chromosome aberrations in plants (SPARROW 195 1 ) , hatchability of parthenogenetically produced haploid Habrobracon eggs (WHITING 1940, 1945a,b), or the analysis of aberrations in the salivary gland chromosomes in F, Sciara larvae (BOZEMAN and METZ 1949; REYNOLDS 1941). The criterion of damage in the present study was the induction of dominant lethal changes in the oogonia and oocytes, as measured by the hatchability of eggs fertilized by unirradiated males.