Laboratory evaluation of dimilin on growth and glutathione activity in mosquitofish, a non-target species

Recently, dimilin was found to be effective on Culex pipiens (Diptera: Culicidae). Although considerable research has evaluated the efficacy of diflubenzuron, a benzoylphenylurea derivative, against target pest populations, impacts of this compound on nontarget organisms are comparatively unknown. Therefore, this study evaluate toxicity of dimilin (25% W.P), a trade formulation of diflubenzuron, on a larvivorous non-target species, Gambusia affinis (Pisces, Poeciliidae). The compound, applied for 24h at a concentration of 78 ng/l corresponding to the LD90 obtained against the fourth instar larvae of C. pipiens, was first tested on growth and development of G. Affinis by measuring some morphometric indexes. Results showed that dimilin caused a significant (p<0.01) reduction in both the length and the weight of juveniles. It had no significant effect on the gonadosomatic index and the condition index (K) measured in adult females. A significant reduction in hepatosomatic index was only observed at day 30 during the exposure. In addition, the body level of glutathione was also determined in order to provide information on their toxicity. Treatment resulted in a significant reduction in both the amount of ovarian proteins and the level of body glutathione starting day 15 compared to controls of the same age.