Assessment the toxic effects of dimethoate to rotifer using swimming behavior.

The toxic effects of the common organophosphorus pesticide dimethoate on freshwater zooplankton Brachionus calyciflorus (rotifer) were tested. Because of the advantages of behavioral response in environmental monitoring, swimming behavior was used as the endpoint in this research. After exposure 6 h at five dimethoate concentrations (0.18, 0.53, 0.88, 1.23 and 1.59 mg·L(-1)), the pesticide disrupted the balance in rotifer swimming direction and caused an obvious direction preference. It also inhibited significantly the swimming angular and linear speed. Our results showed that dimethoate has a sublethal toxic effect on this aquatic invertebrate.