The sublethal effects of widely used two insecticides in Malatya region on Danio rerio (zebrafish) and time dependent recovery of their toxic effects

This study was aimed to determination of toxicity and also recovery of toxic effects using various biochemical markers on zebrafish (Danio rerio, (Hamilton 1822)) adults who were exposed to phosalone and cypermethrin pesticides or their mixtures as an organophosphate or pyrethroid groups, respectively. Due to this, LC50 values of 96h exposure to the selected pesticides were calculated as 2.254 mg AI/L for phosalone and 0.0144 mg AI/L for cypermethrin and the application concentrations of selected pesticides were determined according to the calculated LC50 values. Fish were exposed to the pesticides separately or their mixtures using LC50/2, LC50/4 and LC50/10 concentration with the binary mixtures (1:1) were used for 96 hour static renewal test system. After the 96 h exposure periods, some fish samples were stored for further assays in ultra-freezer, but remaining were transferred into clean tanks and they were continued to feed daily during the study for recovery studies. The media in the tanks were changed every other day and remaining fish were collected on day 10 or 20 for biochemical assays to compare 96 h exposed samples with together. For this aim, glutathione S-transferase (GST), carboxylesterase (CaE), acetylcholinesterase (AChE), glutathione reductase (GR), catalase (CAT), glutathione peroxidase (GPx), lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST) were assayed as biochemical markers. It was determined for exposed fish in both pesticide or mixture groups that the selected enzyme markers were significantly activated or inhibited by the pesticide exposures. Also, the results show that D. rerio samples were affected by even in very low concentrations of sublethal exposures of the pesticides. The GST, CaE, AChE and GR were represented the toxicity of pesticide exposures which are the most suitable biomarkers for evaluating the toxicity. On the other hand, results show that 20 days of recovery period after the termination of pesticide exposure was not enough to recovery of enzyme activities in normal levels such as in control groups and it was also showed that the recovery period may need more time than 20 days in their natural habitat if the fish was exposed to such pesticides. This study also represented that D. rerio is suitable test organisms to determine pesticide pollution and recovery of the toxic effects of used pesticides in aquatic systems and the selected biochemical markers are the suitable to determine pesticide toxicity on these organisms.