Mass-Scaled Rates of Respiration and Intrinsic Growth in Very Small Invertebrates

Abstract

This review compares rates of oxygen uptake and intrinsic growth of very small invertebrate species near 20 degree C with those of larger invertebrate and unicellular animals by means of the allometric relation (rate alpha M super(b) where M = mass). Respiration rates of small species of major invertebrate taxa are lower than those extrapolated for larger invertebrates but generally higher than those for protozoans of the same mass. Mass-specific rates of samll metazoans and protozoans are lowered accordingly; therefore, their total food and oxygen consumption is likely to be small relative to that of large metazoans in average pelagic and benthic communities where most of the biomass is in large animals. Thus, the respiration of these taxa is about as mass dependent as that of large animals. Metabolic reduction is set in relation to small adult size as such, and previous inferences about the phylogeny of metazoan metabolism do not seem warranted any more. Intrinsic growth rates of benthic rotifers and marine free-living nematodes are not only lower than those extrapolated for larger invertebrates but fall below those for protozoans of the same mass.