Age-related differential catabolism in the snail, Viviparus georgianus, and its significance in the bioenergetics of sexual dimorphism

Catabolic partitioning of carbon and nitrogen was investigated to clarify the sexual dimorphism of bioenergetics in Viviparus georgianus. Experiments involved summer stocks of 3-, 15-, 27-, and 39-month-old male and female snails grazing on an artificial high protein diet and, for 15-month snails only, comparison tests using a lower protein diet. Per snail ingestion and partitioning rates and growth are generally maximal for 15-month snails and decline with age in both sexes. In each age group, females have lower rates for weight-specific ingestion of protein carbon and nonprotein carbon than males. For protein carbon, females also show lower rates of catabolism. Compensation for the lower protein diet is more marked in females, which increase total carbon intake by 58% and reduce catabolic use of protein carbon by 40% (against a male reduction of 25%). When discussing evolutionary problems in terms of actuarial bioenergetics, quantification of both physiological rates and ecological efficiencies can be o...