Growth, Chitin and Respiratory Metabolism of Tetrahymena pyriformis Exposed to the Insecticide Novaluron

The struggle against the agricultural ravagers was increased in few last years; many products were appeared and destined to kill the harmful insects, of which we did not know their effects on ecosystem and non-target animals. In present work, we try to investigate the ecotoxicological effects of Novaluron; an Insect growth Regulator (IGR) pesticide, on ecosystem and biomasses by the estimation of the growth, chitin and respiratory metabolism of Tetrahymena pyriformis as a non-target aquatic organism exposed to this pesticide. The pesticide was tested in vitro by the addition of three concentrations (1, 10 and 20 μg/ml) in strictly controlled conditions, to the culture medium before/after apparition of the protozoan. Tetrahymena population growth was evaluated by optic density at 600nm method, for the cells number we used the account under an optical microscope, the generation time and number were evaluated, also we evaluated the respiration of Tetrahymena population by oxygen electrode. Treatment with 1, 10 and 20 μg/ml of the pesticide affects the growth (proliferation) of T. pyriformis in concentration-dependent manner, also it increases the generation time and response percentage in concentration-dependent manner. The respiratory metabolism of protozoan is perturbed with the treatment by Novaluron at three concentrations, noting that the oxygen consumption was increased at 10 μg/ml, contrarily to the other two concentrations, which they had an inhibition effect especially for 20 μg/ml of pesticide. The effect on chitin synthesis was followed by neutral red coloration method; the effect on chitin is translated by the quantity and speed of the neutral red penetration. The results showed an alteration of the chitin integrity in concentration-dependent manner. All data showed an ecotoxicological effects on this protozoa, this perturbation might be transferred to the higher organisms by bioaccumulation in trophic chain.