Toxicity of the herbicide chlorpropham towards the freshwater ciliated protozoan Tetrahymena pyriformis GL

Chlorpropham (CIPC), widely used in agriculture as a herbicide, displays genotoxic and antimitotic properties. Its toxic action was studied on the ubiquitous freshwater ciliate Tetrahymena pyriformis, in short term (six hours) and longer term (24 hours) experiments. The results show that CIPC induces an inhibition of cell division during the first hours of treatment. A slow recovery of cell multiplication was then observed. CIPC treatment in both short and long-term experiments affected the somatic ciliature pattern equally, with irregular arrangement of kineties, giving daughter cells exhibiting an aberrant distribution of nuclear apparatus. Specific toxic action of CIPC was detected on the macronuclear structure, inducing a segregation and concentration of nucleoli. DNA and RNA synthesis was clearly disturbed in the presence of CIPC, DNA synthesis decreasing by about 20% during the four first hours of treatment, and RNA synthesis by about 50% after 24 hours. Hence CIPC toxicity is lasting, still disturbing cells even after several generations.