Competition between the Rotifer Brachionus calyciflorus and the Cladoceran Moina macrocopa in Relation to Algal Food Concentration and Initial Rotifer Population Density

Abstract

ABSTRACT The rotifer Brachionus calyciflorus occurs simultaneously with the cladoceran Moina macrocopa in tropical water bodies, and mass cultures of M. macrocopa are sometimes contaminated with B. calyciflorus. The effects of algal food concentration (Chlorella vulgaris) and initial rotifer population density on the competition between B. calyciflorus and M. macrocopa were tested using population growth experiments, and the influence of adult M. macrocopa on the instantaneous reproductive rates, egg ratios, and survivorship of B. calyciflorus females was investigated in short-term experiments. M. macrocopa rapidly excluded B. calyciflorus from mixed-species cultures but was itself unaffected by the presence of the rotifers, regardless of the algal food concentration or initial rotifer population density. Adult M. macrocopa imposed significant negative effects on the instantaneous reproductive rates, egg ratios, and survivorship of newborn individuals of B. calyciflorus. The magnitude of effects imposed by M. macrocopa increased with decreased food level and increasing density of adult M. macrocopa.