Uptake and biological effects of the insecticide Fipronil on seabass

Abstract

The phenylpyrazole Fipronil is one of the most widely used insecticides in crops worldwide. Its use was banned by the European Union in April/2013 (Directive ECC Nº 781/2013) due to its harmful effects to non-target species (Gripp et al., 2017; Schlenk et al., 2001; Stefani Margarido et al., 2013). Despite this, Spain, the largest Fipronil consumer in Europe in sunflower crops, is still reluctant to adhere to the European directive alluding to few on-site studies that proved their toxicity. The aim of the present study was to assess a suite of biomarker responses on seabass (Dicentrarchus labrax) exposed through diet to Fipronil under two environmentally-realistic temperature regimes. Juveniles of D. labrax were acclimated (14 days) to two temperature regimes of 13 and 16 ºC. Then, fish were fed spiked food with 10 mg/Kg of Regent®800WG (80% Fipronil) during two weeks, after which a depuration period of one week (feeding with unspiked food) was allowed. Eight fish were sampled at each temperature before Fipronil exposure (t0), after 7 and 14 days exposure (t7 and t14) and after a 7-day depuration period (t21), and dissected according to a standardized protocol. Feeding rate was calculated for each condition (temperature × time) and morphometric measurements were recorded for each fish. Concentration of Fipronil and its main metabolite Fipronil sulfone was determined in bile by LC-HRMS and in muscle (only Fipronil) by GC-MS. Metabolic and oxidative-stress related markers were assessed in different tissues: lactate dehydrogenase (LDH), six Cytochrome P450-related (CYP) enzymes, NAD(P)H cyt c and NADH ferricyanide reductases, uridine diphosphate glucuronyltransferase (UDPGT) and glutathione S-transferase (GST) and the antioxidant enzymatic responses catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GPX) activities, as well as the marker indicative of oxidative stress damage: lipid peroxidation (LPO) levels. Differences between temperatures and time-groups (t0, t7, t14 and t21) were tested by ANOVA contrasts