Developmental toxicity of deltamethrin and 3-phenoxybenzoic acid embryo-larval stages of zebrafish (Danio rerio)

Synthetic pyrethroids are the major insecticides used widely in agriculture and household pest control. Deltamethrin (DM), a widely used type II pyrethroid insecticide, is a relatively potent neurotoxicant. 3-Phenoxybenzoic acid (PBA) is the major metabolite formed due to metabolism of DM. In order to illustrate the toxic response of zebrafish embryos/larvae to DM and PBA the present research was carried out. For this 4hpf embryos were treated with two concentrations of DM (100 and 200 mu g/L) for 48 h and PBA (1000 and 2000 mu g/L) for 96 h or 99.9% ethanol (solvent control). Early life stage parameters were observed at specified time points. DM-treated embryo/larvae exhibited increased mortality, delay in hatching time, decrease in percentage of hatched embryos, increase of heartbeat rate and decrease in blood flow; lightening of body and eye pigmentation in a dose dependent manner. Pericardial and yolk sac edema along with were also caused by DM. Along with these crooked notochord, tail deformation was noticed in hatched and unhatched embryos. In case of PBA treated embryos and larvae, increased embryos/larvae length and yolk sac size were observed. Other abnormalities like edema (yolk sac and pericardial), decreased eye and body pigmentation were also observed but in some embryos only. These were not as severe as observed in parental compound indicating that DM is more toxic than its metabolite PBA. The data contributes to a better understanding of the potential consequences of fish exposed to DM and PBA.