Multibiomarker approach to fipronil exposure in the fish Dicentrarchus labrax under two temperature regimes

Abstract

Fipronil is a phenylpyrazole insecticide widely used to control pests in agriculture even 29 though evidence of harmful side effects in non-target species has been reported. A 30 comprehensive study on the effects of dietary administration of Regent®800WG (80% 31 fipronil) in European sea bass juveniles was carried out under two temperature regimes: 32 a) natural conditions, and b) 3 ºC above the natural temperature (an increase predicted 33 for the NW Mediterranean by the end of this century). Fipronil was added to the fish 34 food (10 mg fipronil /Kg feed) and the effects were studied at several time points 35 including right before administration, 7 and 14 days after daily fipronil feed and one-36 week after the insecticide withdrawal from the diet (depuration period). A wide array of 37 physiological and metabolic biomarkers including feeding rate, general condition 38 indices, plasma and epidermal mucus metabolites, immune response, osmoregulation, 39 detoxification and oxidative-stress markers and digestive enzymes were assessed. 40 General linear models and principal component analyses indicated that regardless of 41 water temperature, fipronil resulted in a significant alteration of several of the above 42 listed biomarkers. Among them, glucose and lactate levels increased in plasma and 43 decreased in epidermal mucus as indicators of a stress response. Similarly, a depletion 44 in catalase activity and higher lipid peroxidation in liver of fipronil-exposed fish were 45 also indicative of an oxidative-stress condition. Fipronil induced a time dependent 46 inhibition of Cytochrome P450-related activities and an inhibition of phase II 47 glutathione-S-transferase. Moreover, fipronil administration was able to reduce the 48 hypo-osmoregulatory capability as shown by the increase of plasmatic osmolality and 49 altered several digestive enzymes including trypsin, lipase, alpha amylase and maltase. 50 Finally, analyses in bile and muscle confirmed the rapid clearance of fipronil but the 51 persistence of the metabolite fipronil-sulfone in bile even after the 7-day depuration 3 52 period. Altogether, the results reveal a notable impact of this compound on the 53 physiological condition of the European sea bass. The results should be considered in 54 future environmental risk assessment studies since fipronil could be hazardous to fish 55 species, particularly those inhabiting estuarine ecosystems exposed to the discharge of 56 agriculture runoffs where this pesticide is mainly used.

Multi-organ characterisation of B-esterases in the European sea bass (Dicentrarchus labrax): Effects of the insecticide fipronil at two temperatures

“…The generally weak effect of a modest temperature increase on B-esterase responses in the present study was supported by other biomarkers in the complementary study of Dallarés et al (2020). However, similar temperature increases (+4 ºC) modified the bioaccumulation of Hg and some biochemical responses, including brain AChE in D. labrax, according to Maulvault et al (2017).…”

“…Behavioural, physiological and biochemical changes were also observed in the same fish species at warmer conditions by other authors, although temperature gradients were from 7 to 10 ºC larger (Vinagre et al, 2012;Almeida et al, 2015). Nevertheless, and as noted Dallarés et al (2020) a more realistic simulation of future climate change-induced environmental conditions (i.e. including alterations of salinity or pH) should be considered to truly estimate potential metabolic/physiological alterations due to this phenomenon.…”

“…This study is part of a larger experiment, whose water conditions, maintenance and fish characteristics are detailed in Dallarés et al (2020). Briefly, juvenile specimens of European sea bass (D. labrax) of an average weight of 131.6 ± 46.1 g and reared at the IRTA (Sant Carles de la Ràpita, Spain) aquaculture facilities, were further acclimated in the experimental aquaria facilities (ZAE) of ICM-CSIC (Barcelona, Spain) for 2 weeks.…”

“…Fish were fasted for 48 h before each sampling. Fish were anesthetised with 0.2 % 2-J o u r n a l P r e -p r o o f phenoxyethanol (Sigma-Aldrich, St. Louis, MO, USA), and sacrificed by severing their spinal cord, eviscerated, weighed and the weight of liver, gonads and visceral fat were also recorded (data shown in Dallarés et al, 2020). Skin mucus was collected as described in (Fernández-Alacid et al, 2018) using sterile glass slides from the overlateral line in the caudal direction.…”

“…Its use was banned by the European Union in April 2013 (Commission implementing regulation (EU) Nº 781/2013) but some countries like Spain did not adhere to the directive blaming the lack of sufficient scientific evidence of its toxicity on non-target species. Up to now, fipronil toxicity evidence in fish has been provided by studies with the freshwater species D. rerio (Wu et al, 2014), carp, Cyprinus carpio (Qureshi et al, 2016) and the marine fish D. labrax (Dallarés et al, 2020). The latter study is complementary to the present one and demonstrated that spiked food at a concentration of 10 mg/kg fipronil (under the same commercial Regent800WG brand) was bioaccumulated and further metabolised by European sea bass causing metabolic disturbances and gonadal histological alterations over time (Dallarés et al, 2020;Blázquez et al, 2018).…”