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Student Activities 2012-2013

Jacob Burnett

The effects of inhibited reproduction by ovariectomy or vitellogenin-RNAi on the longevity of grasshoppers
Society for Integrative and Comparative Biology Annual Meeting

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). The protein vitellogenin is a precursor to vitellin, which constitutes 90% of egg protein. These data suggest that VgRNAi may increase lifespan through the trade-off between reproduction and longevity. We used two injection control groups for the VgRNAi treatment, namely buffer injection or injection with RNAi against a 90kDa hexamerin storage protein (Hex90RNAi). In this study we have combined these manipulations to test lifespans upon: OVX & VgRNAi, OVX & Hex90RNAi, OVX & Buffer, Sham & VgRNAi, Sham & Hex90RNAi, and Sham & Buffer. By combining these treatments we wish to determine if they use separate mechanisms in lifespan extension. To date, 40 of the 151 individuals have died; OVX & Buffer, and OVX & VgRNAi individuals are currently showing the highest survival rates at 77% and 84% respectively, while OVX & Hex90RNAi and Sham & Hex90RNAi individuals exhibit the lowest survival rates at 68% and 56%. Consistent with previous data, OVX groups are showing a reduction in feeding rates (all P < 0.03). However, all other treatment groups show no differences among feeding rates. Survivorship and feeding rates will be discussed in terms of whether or not reduced feeding is consistently associated with life-extension via reduced reproduction. Funding provided by NIH 2R15AG028512-02A1 to JDH.