Herbicides exposed to low concentrations of toxicants (Lee

Herbicides are important chemicals used in agriculture that can be introduced
into the aquatic environment due to runoff and leaching, cussing adverse
effects on non-target organisms, particularly fish fauna
(Wany et al., 1992).

Oxadiazon (Ronstar) is a widely used
herbicide commonly used in rice fields against both mono and dicotyledonous
weeds, as well as in fruit trees, vines, grasses, cotton, soybeans, onions, and
sunflowers (Ahmed et al., 2008).

Different oxadiazon residue concentrations ranged 0.4 to 7.24 ?g/ L
in different water bodies such as river/stream waters (Mamun et al., 2009; Kim
et al., 2014), as well as up to 0.442 ppm in different tissues of fish and
shellfish have also been reported (Imanaka et al., 1981).

Exposure to oxadiazon have been revealed
a retarding
growth in African Catfish (Clarias
gariepinus; Ajani et al., 2015), and adverse effects on serum biochemical profile in common carp (C. carpio; Saravanan et al., 2017) and Platy
Fish (Xiphophorus maculatus; Sadeghi and Imanpoor, 2015), as well
as induced peroxisome proliferation in the rodents (Richert et al., 1996).

The exposure of
aquatic organisms such as different fish species even to low
environmentally-relevant concentrations of pesticides can result in severe
effects on genetic and physiological parameters that can be considered as biomarkers for evaluation of fish
health as well as monitoring of environment pollutants (Wendelaar-Bonga, 1997; Blahova et al., 2014; Ahmadivand et al.,
2016; Mitkovska et al., 2017).

Comet assay is a sensitive technique for the detection of DNA
damage, practically applied in all nuclear eukaryotic cells and biological species, especially
for biomonitoring and confirming DNA damage in aquatic organisms (Jin et al.,
2004; Kim and Hyum, 2006; Klobucar et al., 2010; Mitkovska et al., 2017).

The method allowing to detect a wide variety of DNA damage,
including DNA single-strand breaks, double-strand breaks, alkali-labile sites and reparation, as well as oxidatively induced base damages, even when exposed to low concentrations of toxicants (Lee
and Steinert, 2003; Frenzilli et al., 2009).

The common carp (C. carpio) is one of the most important and
valuable commercial fish species in Iran that mainly farmed in the Caspian
littoral provinces (Gilan, Mazandran and Golestan), the area of high
agricultural use and depends largely on surface water supplies (Salehi, 1999).
Moreover, this species is widely used in the evaluation of the physiological and
genotoxic effects of pesticides in both laboratory and field conditions (Poleksic
and Karan, 1999; Jin et al., 2004; Kim and Hyum, 2006; Klobucar et al., 2010; Blahova et al., 2014; Mitkovska
et al., 2017). In this study, we examined the DNA damage in erythrocyte cells
using the comet assay, as well as the hematological and serum biochemical
changes in common carp (C. carpio) fingerling after 30 days exposure to different concentrations
(1, 1.5 and 2 ppm) of the herbicide, oxadiazon.