Student Activities 2012-2013

Jacob Burnett

The effects of inhibited reproduction by ovariectomy or vitellogenin-RNAi on the longevity of grasshoppers

Activity:
Society for Integrative and Comparative Biology Annual Meeting

Abstract:

 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.