Relation of Body Size to Food Intake, Oxygen Consumption, and Trace Element Metabolism in Forest Floor Arthropods

Abstract

Food intake and respiratory heat loss are the major pathways of energy flow through animal communities. In certain cases flow rates can be estimated for the total population from selected measurements of individual species. Metabolic parameters (Y) of arthropods from the floor of a Libriodendron tulipifera forest were correlated with size (X) of species: Y = aX b. This power function relationship is similar to the "active surface area" hypthesis of animal metabolism. The species examined ranged in size from 2.1 mg to 1.6 g live weight, and spanned a diversity of food habits and taxonomic categories. Food consumption was proportional to the 0.68 power of body weight. Metabolism (μl O 2 hr—1) varied with the 0.84 power of body weight, while metabolic rate (μl O 2 g—1 hr—1) was inversely proportional (b = —0.16) to body size. Within closely related species, 137 Cs turnover rates were closely correlated with metabolic rates. These rates varied with temperature and followed a Q 1 0 of approximately two. By applying appropriate temperature corrections, body size relations can be used to estimate food intake and metabolism of species in their natural habitats. Radiotracers also may permit measurement of temporal fluctuations in metabolism resulting from activity in the field.