RESEARCH: Evolutionary physiology of insects, especially aging and reproduction

I am interested in the physiology of life histories. That is, how do animals adjust their rate of maturation, reproduction, and aging? I use lubber grasshoppers (Romalea microptera) and flesh flies (Sarcophaga crassipalpus) to address these basic questions in biology.

Lifespan can be extended in many experimental animals by calorie restriction and reduced reproduction. We have shown that calorie restriction, eating only 70% of that consumed when offered free access to food, extends lifespan in female grasshoppers. More important, this life extension was not due associated with a reduction in storage of proteins, the limiting nutrient for grasshoppers. This result is inconsistent with the dominant model on aging, the disposable soma theory (=the nutrient allocation theory).

We are now studying the effects of reduced reproduction on aging by using ovariectomy. Our early results suggest that ovariectomized females lived longer than sham operated females, independent of calorie restriction. We are now pursuing the role of protein allocation to reproduction underlying this life extension.

In addition, we are studying the role of storage thresholds in life history tactics, in collaboration with Dan Hahn at the University of Florida. Flesh flies must ingest protein as adults to produce a full clutch of eggs, and these protein meals are associated with an increase in protein storage in the hemolymph. We are studying whether a threshold level of these proteins is needed to start egg production.

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