A study of rotifer feeding and digestive processes using erythrocytes as microparticulate markers

Feeding and passage of nutrient particles through the digestive tract of th e rotifer Brachionus plicatilis was examined using the following types of p articles: yeast cells, mammalian (human, bovine, ovine) erythrocytes and er ythrocyte-ghosts. The decrease of erythrocytes within the medium was found to follow first order kinetics. The rate constant was influenced by the den sity of rotifers, as well as by the initial density of particles in suspens ion at the beginning of the experiment. Passage of particles through the di gestive tract depended on the supply of fresh particles taken up by the whe el organ. Passage time approximately doubled when the rotifers had no acces s to fresh particles. On provision of fresh particles, the contents of the digestive tract were expelled even if they included absorbable substances. The contents of the digestive tract of B. plicatilis can be quickly and eas ily exchanged by introducing a new type of particle to the medium. By repla cing fluorescence-labelled erythrocyte ghosts with unlabelled ghosts, resid ual fluorescence indicating absorptive processes could be demonstrated.