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.