Toxicological comparisons of Tetrahymena species, end points and growth media: Supplementary investigations to the pilot ring test

Parallel to an international Pilot Ring Test to standardize a multigeneration test protocol with the protozoon Tetrahymena pyriformis supplementary investigations were made. Effects on growth rate and 46 h population density were measured using an extended set of 12 chemicals, a further Tetrahymena-species (T. thermophila) and 4 different media (axenic and bacteria based). Results are compared for sensitivity with effects on additional end points (chemosensory response, respiration and vitality). Both species exhibit similar sensitivity towards the chemicals. In some cases the media composition influenced the toxic potential of chemicals. Both growth parameters proved to be a sensitive integral end point for toxicological studies, confirming the one point, photometric measurement of population density after 46 hours in axenic (preferably proteose peptone-) medium an obvious choice for a standard test procedure.