Meeting Abstract
Dietary restriction extends lifespan and reduces reproduction in most animals. The disposable soma hypothesis attributes these effects to a shift in the allocation of ingested nutrients. It suggests longevity is the result of reduced investment in reproduction and increased investment to the soma, permitting an increase in cellular maintenance and in turn extending lifespan. To further investigate the role of nutrient allocation upon life-extending dietary restriction, tissue-specific allocation of ingested nitrogen was tracked in grasshoppers ( Romalea microptera) upon a full or restricted diet. Carbonyl assays were performed in the same individuals to examine protein oxidation and tissue maintenance. To develop a labeled diet on which grasshoppers could thrive, hydroponically grown Romaine lettuce was enriched with 15N. Each day, individual grasshoppers were fed ‘appetizers’ (either high 15N or low 15N lettuce) followed by a low 15N full or restricted quantity ‘meal’. This allowed quantification of the relative proportions of nitrogen distribution upon a normal or restricted diet (60%). There was a 50% decrease in reproductive investment upon dietary restriction. Correspondingly, while ovary sizes differed, relative allocation of 15N to the ovary did not change. For somatic tissues (e.g., mandibular muscle, femur muscle, and hemolymph proteins), allocation was similar between restricted and full diet grasshoppers. Carbonyl assays of some somatic tissues revealed reduced protein oxidation in diet-restricted individuals. At present, the data suggests dietary restriction does not alter nutrient allocation but does reduce protein oxidation, a finding that is inconsistent with the disposable soma hypothesis.
