Thesis (Ph. D.)--Illinois State University, 1999. / Title from title page screen, viewed July 24, 2006. Dissertation Committee: David W. Borst (chair), Angelo P. Capparella, Sabine S. Loew, Edward L. Mockford, Carleton J. Phillips, Douglas W. Whitman. Includes bibliographical references (leaves 77-89) and abstract. Also available in print.

Reduced reproduction has been shown to increase lifespan in many animals, yet the mechanisms behind this trade-off are mostly unknown. A previous study has shown that in the lubber grasshopper, Romalea microptera, ovariectomized (OVX) individuals have a 30% increase in lifespan relative to controls (Sham). In a separate study, an increase in fat body mass and a halting of ovarian growth were seen upon reduction of vitellogenin transcript via RNAi (VgRNAi). These data suggest that VgRNAi increases lifespan through the trade-off between reproduction and longevity and animals with combined ovariectomy and VgRNAi, might show additive physiological responses. In this study, we used two injection control groups for the VgRNAi treatment, namely buffer injection or injection with RNAi against a 90kDa hexamerin storage protein (Hex90RNAi). We have combined these manipulations to test lifespans upon: OVX & VgRNAi, OVX & Hex90RNAi, OVX & Buffer, Sham & VgRNAi, Sham & Hex90RNAi, and Sham & Buffer. Ovariectomy and VgRNAi exhibited similar reductions in feeding (~40%) and extensions in lifespan (13-21%) but showed differences in vitellogenin protein levels. This study also observed the effects of reduced reproduction on hexamerin storage proteins. We observed that upon ovariectomy and VgRNAi, hexamerins were increased, emphasizing the importance of protein in insect life extension. When methods to reduce reproduction were combined (OVX VgRNAi), no additive physiological responses were observed, suggesting ovariectomy and VgRNAi each extend lifespan by overlapping or convergent pathways.