A Cytological Study of Radiation Effects in Testes of the Screw-Worm Fly, Cochliomyia hominivorax (Diptera: Calliphoridae)

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Abstract
When pupae were irradiated with gamma rays from Co60, wide differences were found in the radiosensitivity of different cell types in screw-worm testes. Almost all very young primary spermatocytes were apparently killed after having received only 100 R. Most secondary spermatogonia were killed with 500 R, and total destruction of the primary spermatogonia in different testes occurred over a range of dose levels from 1500 to 3000 R. In testes irradiated with 6000 R, necrosis of most young spermatocytes and of all but a few early secondary spermatogonia was evident at 6–7 hours. Until the eighth hour most primary spermatogonia did not show evidence of necrosis and some nondegenerate cells of this class were still seen at 12 hours but not at 25 hours. Death of all cells apparently occurred during interphase or perhaps very early prophase. Even at the highest dose level (6200 R), secondary spermatocytes and those primary spermatocytes that had reached a certain stage of development were not killed. However, they did suffer gross chromosomal damage, and most of spermatids formed from them failed to develop into normal-appearing sperm. No morphological changes could be seen in those cells irradiated as spermatids or as immature sperm, and they developed into normal-appearing mature sperm. The stages in the recovery of spermiogenic activity were traced out in flies that had received 1500 R as 2-day-old pupae.