Radiosensitive Stages in the Spermatogenesis of Drosophila melanogaster

Abstract

THE existence of differential radiosensitivity during certain stages of spermatogenesis in Drosophila melanogaster was first proposed by Lüning¹. Further evidence provided by Auerbach's² three-day brood technique suggested that the highest mutation frequency observed in the 3–6-day period following treatment indicated peak sensitivity in immediately post-meiotic stages. Additional support for this view that spermatids were particularly susceptible to the mutagenic action of X-rays was derived principally from the results of irradiating immature sperm in the pupal testis^3,4. More definitive daily brood analysis⁵, however, established a marked dominant lethal frequency ranging over the sixth, seventh and eighth days following the irradiation of newly emerged males, but from these results Bateman was able to draw no firm conclusion other than that this probably represented sensitive meiotic and post-meiotic stages. Using the same technique, Ives⁶ ascribed the first appearance of induced cross-overs on the seventh day after irradiation to the utilization in this brood of sperm treated in early meiotic and pre-meiotic stages. In a similar experiment, he obtained a maximum frequency of both autosomal recessive and sex-linked recessive lethal mutations on this same day. Sävhagen⁷ considered sex chromosome loss and non-disjunction also in parallel investigations. Here again, the highest frequencies of X0 males were observed on those days which, by comparison with the non-disjunction experiment, probably corresponded to stages treated before anaphase I of meiosis.