Meeting Abstract

P3.44  Monday, Jan. 6 15:30  Allocation of ingested nitrogen upon life-extending dietary restriction in grasshoppers PEHLIVANOVIC, M; HECK, M*; PURCELL, JU; HAHN, DA; HATLE, JD; Univ. of North Florida; Univ. of North Florida; Univ. of North Florida; Univ. of Florida; Univ. of North Florida jhatle@unf.edu

Dietary restriction reduces reproduction and extends lifespan in most animals. The disposable soma hypothesis predicts that upon dietary restriction, allocation of ingested nutrients will be shifted toward somatic tissues (i.e., away from reproduction), enhancing tissue maintenance and increasing lifespan. This has been tested rigorously only in fruit flies. Here, we test this prediction of increased allocation to somatic tissues and maintenance upon dietary restriction using grasshoppers. These large insects allow estimating allocation to multiple tissues (e.g., muscle, storage proteins, and fat body) and simultaneous analysis of protein damage (i.e., carbonyls), none of which was possible in fruit flies. Artificial diets for grasshoppers do not allow normal development. Hence, to produce diets with distinct signatures of nitrogen-14 and nitrogen-15 that also allow normal development, we grew Romaine lettuce hydroponically and spiked the nutrient solution with KNO₃ high in nitrogen-15. Within each feeding level (i.e., ad libitum or dietary restriction), four diet regimes were used: 1) high nitrogen-15 throughout (the ceiling of nitrogen-15 levels), 2) low nitrogen-15 throughout (the floor of nitrogen-15 levels), 3) initially high, switched to low nitrogen-15 during a 28-day test period, or 4) initially low, switched to high nitrogen-15 during the 28-day period. This allows determination of the percentage of nitrogen in tissues that originated from the diet during the 28-day test period. Results will be discussed in terms of the hypothesis, which predicts dietary restricted grasshoppers will show greater allocation of ingested nitrogen to somatic tissues and fewer damaged proteins.