Diazinon is an OP which is extensively used in trade and agriculture. Because of its wide-spread applying, its toxicity is common. Several studies have shown that OPs are able to induce oxidative stress by generating free radicals and depletion of endogenous antioxidants (Moshiri et al., 2013). It is activated internally to become diaxoxon (Figure 2), which is a more potent choli-nesterase inhibitor than diazinon is (El-Shenawy et al., 2010). Most of the data relating to this transformation are from terrestrial species. However, Tsuda et al (1997) actually tested both the parent diazinon and the diazoxon metabolic in killifish. They reported 48-hour LC50 values to be 4400 ppb for the diazinon and 220 ppb for the diazoxon; the diazoxon
