Meeting Abstract

19.3  Friday, Jan. 4  Metabolic and behavioral variation with colony size and age: a manipulative test of the size-dependence theory of metabolic allometry WATERS, JS*; HARRISON, JF; Princeton University; Arizona State University jswaters@princeton.edu

The nonlinear relationship between animal metabolic rates and their body size is a “many-splendored thing” and the mechanistic basis for this relationship, if one exists, is highly controversial. One of the challenges in empirically testing the predictions of hypotheses regarding an organism’s size is that the necessary manipulations are likely destructive. Colonial organisms, including marine ascidians, encrusting bryozoans, and terrestrial social insects, are composed of functionally integrated modular subunits, making them ideal systems to study across a range of artificial sizes. We investigated the relationship between metabolic rate and colony size for a set of laboratory reared Pogonomyrmex californicus seed harvester ant colonies. Repeated measures of metabolic rates and patterns of behavior were conducted with minimal disruption to the social milieu of the nests by maintaining entire colonies within enclosures designed for flow-through respirometry and video analysis. Same-aged colonies ranging in mass from 0.32-1.7 grams were measured before and after a manipulation of their size to include only half of their workers, larvae, and pupae. Both sets of measurements, before and after manipulation, revealed metabolic hypometry and moreover, there was a significant increase in the mass specific metabolic rate of the manipulated colonies. Investigating the scaling of locomotory activity and interaction network structure among the workers within these colonies may help to identify the mechanistic basis for the size-dependence of their metabolic rates.