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Targeting Insect Reproduction as a Control Mechanism: Sperm Movement From the Seminal Vessicles to the Egg

  • Author(s): Stephens, Kimberly Denise
  • Advisor(s): Cardullo, Richard
  • et al.
Abstract

Mosquito sperm are produced in the testis, transferred to the seminal vesicles and subsequently transferred along with accessory gland fluid to the female. Sperm from the water strider, Aquarius remigis, are unusually long, possessing a complex acrosome and flagellum. In order to be fertilization competent, sperm in both species must undergo several developmental steps in both the male and female reproductive tract before the sperm is competent to fertilize an egg. Once the sperm reaches the egg, it must have a mechanism for interacting with the egg. In this dissertation, I follow the sperm from the testis, the site of spermiogenesis, to the egg where it interacts with the sperm. In the second chapter, I explore the role of muscle contractions of the seminal vesicles and accessory glands that likely move sperm and accessory gland fluid from the male to the female. Nicotine and acetylcholine both activate muscle contractions but not pilocarpine, octopamine, serotonin indicating that muscle contractions are activated by a nicotinic acetylcholine receptor. In the third chapter, I identify and characterize trypsins from accessory glands of Culex pipiens that are necessary for sperm motility initiation. I show activity levels and pH optima of accessory gland trypsins and identify several potential trypsin-like proteins that could be involved in activating sperm motility. In the fourth chapter, I characterize glycosidases on Aquarius remigis sperm. These glycosidases are potentially involved in recognizing glycosylation that is present on the egg surface near the micropyle. In the fifth chapter, I explore the possibility of circadian rhythms being involved in timing the movement of sperm from the testes to the seminal vesicles. Three genes: ssr, npy and 5ht, are expressed in the testes and are commonly involved in regulating circadian rhythms in other organisms. In this dissertation, I discuss movement of sperm from the testes to the seminal vesicles via circadian rhythms, movement of sperm from seminal vesicles to the female via muscle contractions, activation of the sperm motility, allowing it to reach the egg, and recognition of the egg via glycosylation. Taken together, the chapters in this dissertation provide insight into movement of sperm from the testes to the female reproductive tract.

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