Respiration, mineral excretion (nitrogen and phosphorus) and specific activity of amylase and trypsin were studied with several species of copepods from an oceanic tropical area of the Indian Ocean. O/N ratios were significantly different in some species or some groups of species. There was a direct relationship between these values and the ratio of specific activities of amylase and trypsin (A/T). Scolecithrix danae was maintained during 2 or 3 days under different food regime conditions (starvation, algae or mixed food). Its O/N ratio showed steady values but its O/P ratio increased with algal food or during starvation. The trypsin activity was activated only when animal material was present in the diet. These results are discussed according to the nutritional strategy of the species.