Toxic Effect of a Pesticide, Diflubenzuron on Freshwater Microinvertebrate （ Tetrahymena pyriformis ）

The impact of diflubenzuron （DFB） on Tetrahymena pyriformis, a ciliated protiste was studied. The treatment with DFB at concentrations of 10 and 20 μg/mL could appreciably reduce the growth of the protiste. The surveillance of protozoa＇s respiratory metabolism with polarography technique showed a sensitive inhibition of its oxygen consumption, and at 20μg/mL concentration the oxygen consumption was increased. For any malformation of morphology and perturbation in swimming trajectory, the neutral red coloration was done. This technique （ neutral red） showed that there was a toxic effect of DFB on T. pyriforrnis, especially at the highest concentration; this toxicity was translated by rotatory swimming in same place and the increas- ing of coloration quantity in digestive vacuoles.