Impact of the Synthetic Pyrethroid Insecticide Fenvalerate on Tetrahymena thermophila

Fenvalerate is one of the most widely used synthetic pyrethroid insecticides and its influence with microbes has not been studied in detail. We have described the impact of this insecticide on cell growth and cell dimensions of fresh water ciliated protozoan Tetrahymena thermophila. Lower concentrations i.e., 1 μg/ml and 25 μg/ml are less toxic to the ciliates and reduced the cell number by 33% on the third day, and 45% on the second day of treatment respectively. Higher concentrations i.e., 50 μg/ml and 70 μg/ml are most toxic and reduced the cell number by 74 and 78% on the third day of treatment. Fenvalerate at concentration of 50 |ig/ml reduced the major axis by 24, and minor axis 18, surface area 33 and volume by 48% (maximum). The corresponding values for 70 ug/ml concentration were 27, 29, 49 and 61% (maximum) respectively. We found that at low concentration fenvalerate has no impact on morphology of the cell while the higher concentrations had impact on the ciliate protozoan Tetrahymena thermophila