Disrupting Spermatogenesis to Determine the Effects of Sperm Age on fertility in Drosophila Males.
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Schwartz, Yonatan U.
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Senior thesis ; YU access only
Abstract In Drosophila males, germline stem cell number and proliferative capacity decrease with age. Consistent with this, our lab has observed that germline cyst production declines steadily throughout the life of the fly. Surprisingly, our initial measurements of male fertility did not show a coincident drop with age, even in 30-day-old males. This was determined to be due to sperm storage throughout the lifetime of the males. When males were mated throughout the course of their life to deplete sperm storage, fertility was seen to decline at 30 days, but not at 15 days of age. Seminal vesicles of unmated males were significantly larger than those of mated males, confirming that sperm were stored. In males aged for 15 days, average germline cyst number per testis was significantly reduced compared to younger flies but was similar between mated and unmated males, despite large differences in seminal vesicle size, indicating that seminal vesicle size and sperm storage do not feed back on cyst production. We conclude that sperm production in Drosophila males declines steadily with age under the influence of an intrinsic gonadal clock. Our experiments focus on blocking sperm production at distinct age points using temperature sensitive spermatogenesis mutations. The goal of these experiments is to reveal whether sperm made by younger males (and stored) are equally viable to sperm made by older males.
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