Toxicity Of Fipronil Research Articles

Ingestion Toxicity of Fipronil on Reticulitermes speratus kyushuensis (Isoptera: Rhinotermitidae) and Its Applicability as A Termite Bait

Historical wooden buildings in Korea are being damaged by Reticulitermes speratus kyushuensis Morimoto, a type of subterranean termite, and the scale of this damage is increasing gradually because of global warming. This study evaluated the ingestion toxicity of the phenylpyrazole insecticide fipronil to R. s. kyushuensis and its applicability as termite bait with the aim of controlling termite colonies more efficiently. An ingestion toxicity assessment was conducted and the LT50 was determined to be 4.43 day at concentrations of 10 ppm, indicating a slow-acting effect; therefore, 10 ppm was selected as an appropriate dose. A field applicability assessment was conducted in which the number of foraging workers and the rate at which the termites fed decreased 2 weeks after baiting, and termite colony activity was no longer apparent after 4 weeks demonstrating the efficacy of fipronil at eliminating colonies. Taken together, these results, indicate that low-dose fipronil eliminated R. s. kyushuensis colonies faster than insect growth regulators; therefore, it is expected to be useful when trying to conserve historical wooden buildings.

Influence of humidity, rainfall, and fipronil toxicity on rice leaffolder (Cnaphalocrocis medinalis)

Influence of humidity, rainfall, and fipronil toxicity on rice leaffolder (Cnaphalocrocis medinalis)

Perturbation of metabonome of embryo/larvae zebrafish after exposure to fipronil.

The escalating demand for fipronil by the increasing insects' resistance to synthetic pyrethroids placed a burden on aquatic vertebrates. Although awareness regarding the toxicity of fipronil to fish is arising, the integral alteration caused by fipronil remains unexplored. Here, we investigated on the development toxicity of fipronil and the metabolic physiology perturbation at 120h post fertilization through GC-MS metabolomics on zebrafish embryo. We observed that fipronil dose-dependently induced malformations including uninflated swim bladder and bent spine. Further, the "omic" technique hit 26 differential metabolites after exposure to fipronil and five significant signaling pathways. We speculated that changes in primary bile acid synthesis pathway and the content of saturated fatty acid in the chemical-related group indicated the liver toxicity. Pathway of Aminoacyl-tRNA biosynthesis changed by fipronil may relate to the macromolecular synthesis. Concurrently, methane metabolism pathway was also identified while the role in zebrafish needs further determination. Overall, this study revealed several new signaling pathways in fipronil-treated zebrafish embryo/larval.

Developmental effects of fipronil on Japanese Medaka (Oryzias latipes) embryos

Pesticides in urban runoff are a major source of pollutants in aquatic ecosystems. Fipronil, a phenylpyrazole insecticide, found in structural pest control products, turf grass control, and home pet flea medication, has recently increased in use and is commonly detected in urban runoff. However, little is known about the effects of fipronil on aquatic organisms at early developmental stages. Here, we evaluated toxicity of fipronil to embryos of Japanese Medaka (Oryzias latipes, Qurt strain) using a high-throughput 96-well plate toxicity test. Male and female embryos (<6 h post fertilization) were exposed to concentrations of fipronil ranging from 0.1 to 910 μg L−1 for 14 days or until hatching. Embryos were subjected to gross and microscopic examinations of developmental adverse effects as well as transcriptome analysis using RNA-seq. Results indicated a positive dose-response in reduced hatching success, increased gross deformity (tail curvature) at a lowest-observed-effect concentration (LOEC) of 200 μg L−1 and delayed hatching (∼1 day at the highest concentration, LOEC = 600 μg L−1). The transcriptome analysis indicated that fipronil exposure enhanced expression of titin and telethonin, which are responsible for muscle development. It is therefore possible that the formation of a tail curvature is due to asymmetrical overgrowth of muscle. Our results indicate that sub-lethal effects occur in embryonic stages of an aquatic vertebrate following exposure to high concentrations of fipronil, although no adverse effects at the highest published environmentally relevant concentration (6.3 μg L−1) were observed.

Citotoxicity of Fipronil on Hepatocytes Isolated from Rat and Effects of Its Biotransformation

The aim of this study was to characterize the mechanism of toxicity of fipronil on hepatocytes isolated from the rat and the effect of its biotransformation on the toxicological potential. The toxicity of fipronil was assessed by monitoring the oxygen consumption and mitochondrial membrane potential, intracellular ATP concentration, Ca2+ homeostasis and cell viability. The cell viability was evaluated by trypan blue exclusion in hepatocytes that were isolated from the normal rats and by the release of the enzymes alanine transaminase and aspartate transaminase in hepatocytes that were isolated from the normal rats or proadifen-pretreated rats. Fipronil reduced mitochondrial respiration in the cells that were energized with glutamate plus malate in a dose-dependent manner and dissipated the mitochondrial membrane potential that was accompanied by a reduction in ATP concentration and a disruption of intracellular Ca2+ homeostasis. The cell viability was affected by fipronil with higher potency in hepatocytes that were isolated from the normal rats, which indicated that the metabolism of this insecticide increased its toxicological potential. The results of this study indicated that the toxicity of fipronil to the hepatocytes was related to the inhibition of mitochondrial activity, which led to decreased ATP synthesis and a consequent alteration in intracellular Ca2+ homeostasis and ultimately resulted in cell death.

Effect of fipronil on energy metabolism in the perfused rat liver

Fipronil is an insecticide used to control pests in animals and plants that can causes hepatotoxicity in animals and humans, and it is hepatically metabolized to fipronil sulfone by cytochrome P-450. The present study aimed to characterize the effects of fipronil (10–50μM) on energy metabolism in isolated perfused rat livers. In fed animals, there was increased glucose and lactate release from glycogen catabolism, indicating the stimulation of glycogenolysis and glycolysis. In the livers of fasted animals, fipronil inhibited glucose and urea production from exogenous l-alanine, whereas ammonia and lactate production were increased. In addition, fipronil at 50μM concentration inhibited the oxygen uptake and increased the cytosolic NADH/NAD+ ratio under glycolytic conditions. The metabolic alterations were found both in livers from normal or proadifen-pretreated rats revealing that fipronil and its reactive metabolites contributed for the observed activity. The effects on oxygen uptake indicated that the possible mechanism of toxicity of fipronil involves impairment on mitochondrial respiratory activity, and therefore, interference with energy metabolism. The inhibitory effects on oxygen uptake observed at the highest concentration of 50μM was abolished by pretreatment of the rats with proadifen indicating that the metabolites of fipronil, including fipronil sulfone, acted predominantly as inhibitors of respiratory chain. The hepatoxicity of both the parent compound and its reactive metabolites was corroborated by the increase in the activity of lactate dehydrogenase in the effluent perfusate in livers from normal or proadifen-pretreated rats.

Fipronil promotes motor and behavioral changes in honey bees (Apis mellifera) and affects the development of colonies exposed to sublethal doses.

Bees play a crucial role in pollination and generate honey and other hive products; therefore, their worldwide decline is cause for concern. New broad-spectrum systemic insecticides such as fipronil can harm bees and their use has been discussed as a potential threat to bees' survival. In the present study, the authors evaluate the in vitro toxicity of fipronil and note behavioral and motor activity changes in Africanized adult Apis mellifera that ingest or come into contact with lethal or sublethal doses of fipronil. The effects of sublethal doses on brood viability, population growth, behavior, and the expression of the defensin 1 gene in adult bees were studied in colonies fed with contaminated sugar syrup (8 µg fipronil L(-1) ). Fipronil is highly toxic to bees triggering agitation, seizures, tremors, and paralysis. Bees that are exposed to a lethal or sublethal doses showed reduced motor activity. The number of eggs that hatched, the area occupied by worker eggs, and the number of larvae and pupae that developed were reduced, adult bees showed lethargy, and colonies were abandoned when they were exposed to sublethal doses of fipronil. No change was seen in the bees' expression of defensin 1. The authors conclude that fipronil is highly toxic to honey bees and even sublethal doses may negatively affect the development and maintenance of colonies.

Cross-resistance between fipronil and lindane in Rhipicephalus (Boophilus) microplus

The southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini), is one of the most damaging parasites of cattle in tropical and subtropical regions. Several chemical groups have been used for its control, including cyclodienes (lindane and dieldrin). In Uruguay and Brazil these products were used at the beginning of the 1960s and during a few years. Fipronil and lindane act on the same target site. In both countries, southern cattle tick resistance to fipronil has sometimes developed quickly after only a few acaricide treatments (three to seven). The objective of the present study was to determine cross-resistance between fipronil and lindane in southern cattle ticks from Uruguay and Brazil. Initially, the FAO's (Food and Agricultural Organization) larval packet test with lindane was applied to a fipronil-resistant strain and to susceptible field populations. Mozo and POA strains were used as the susceptible controls. A larval immersion test was used to assess fipronil toxicity. Of fifteen fipronil-resistant field populations that were tested with lindane, eleven were lindane-resistant and three were susceptible. The last three populations had incipient resistance to fipronil. Finally, cross-resistance between fipronil and lindane in the southern cattle tick is reported in this study for the first time.

Comparative Toxicity of Endosulfan and Fipronil Insecticides: Utilizing In Vivo and In Vitro Data

Background: Endosulfan, an organochlorine compound, and fipronil, a phenylpyrazole, are insecticides with a common mechanism of toxicity. They interfere with Cl- influx by binding to the gamma-aminobutyric acid receptor (GABAAR) and blocking the inhibitory actions of GABAA. In vivo they cause neurotoxicity, hepatotoxicity, developmental toxicity, and can alter endocrine and immune systems. The thyroid is a target of fipronil toxicity. Human exposure occurs via food residues, skin contact and/or air dispersion. They are environmentally persistent and bioaccumulate in food chains. Method: Compare in vivo data with in vitro results from the U.S. Environmental Protection Agency (USEPA) Toxicology Forecaster (ToxCast) high-throughput screening assays and zebrafish models to assess their usefulness in predicting toxicity. Results: Fipronil’s in vivo toxicity occurred at lower doses than endosulfan for similar effects. ToxCast was a weak predictor of liver toxicity and estrogen receptor interaction. Missing is evidence of “true actives” for fipronil ToxCast assays with the thyroid receptor and for either compound with GABAAR or androgen receptors. Zebrafish models were good predictors of endosulfan and fipronil neurotoxicity in mammalian in vivo studies. Conclusion: ToxCast assays do not provide support for in vivo neurotoxicity or endocrine disruption where zebrafishs are good predictors of both parameters.

English

Pesticide use in the modern agriculture, animal husbandry and public health practices has increased enormously. Pesticides affect man, environment and wild life including birds. Pesticides including fungicides, herbicides and insecticides are the major class of chemicals deliberately released into the environment because of their indiscriminate use in various agricultural practices. Pesticides are present in air, soil and water which leave their residue in food chain causing deleterious effect on the health status of man and animals including poultry. After ingestion, they get into blood stream lodging themselves in various tissues causing adverse effects on health and production of livestock and poultry resulting in substantial economic losses. Fipronil was discovered and developed by Rhone-Poulenc between 1985- 1987 and placed in the market in 1993. It is the member of new and relatively small class of pesticides, the phenyl pyrazoles, which are principally chemicals with an herbicidal effect. According to data obtained from metabolic studies showed that there was potential for bioaccumulation of the Fipronil in fatty tissues, fish, fibre crops and food crops. Limited investigations have been carried on effect of fipronil in health of animals and man. Therefore present study was designed to study the effect of fipronil toxicity in white leghorn cockerels. Twenty white leg horn male chickens of one month old weighing about 150 to 200 g were procured and kept at Instructional Poultry Farm Nagla, Pantnagar. The birds in poultry shed in deep litter system under standard managemental conditions. They were randomly divided into four groups of 5 birds each. After one week of adaptation period, different doses of Fipronil were administered orally through feed at 1, 5 and 10 ppm levels to groups G1, G2 and G3 respectively for 100 days daily. The birds of group &ldquo;C&rdquo; served as control. After every 20 days blood was taken from each bird for study of different parameters. The experiment was conducted for a period of 100 days. All the hematological parameters viz. hemoglobin, packed cell volume, total erythrocyte count and differential leucocyte count were performed on the day of blood collection as per the standard method. Hematological parameters showed significant decrease leading to anemia and significant decrease in total leucocyte count leading to suppression in cell mediated immune response in different doses of fipronil treated birds in comparison to birds of control group. &nbsp; Key words: Fipronil toxicity, white leghorn cockerels, haematological parameters.

Acute toxicity and sublethal effects of fipronil on detoxification enzymes in juvenile zebrafish (Danio rerio)

The acute toxicity of fipronil and its sublethal effects on detoxification enzymes (carboxylesterases (CarEs), glutathione S-transferases (GSTs), and 7-ethoxycoumarin O-deethylase (ECOD)) in zebrafish (Danio rerio) were investigated. The results indicated that the 24-h LC50 of fipronil for zebrafish was 220.4μg/L (95% CI: 173.7–272.4μg/L). Sublethal concentrations of fipronil did not cause significant changes in CarEs activities. In the liver and muscle tissues, GST activities at the tested concentrations did not significantly differ from those in the control. In the brain and gill tissues, GST activities at a concentration of 4μg/L were significantly lower than those at a concentration of 2μg/L. The results suggest that CarEs and GSTs were not suitable biomarkers for fipronil effects in D. rerio. A significant induction in the ECOD activities in the brain, gill, liver, and muscle tissues was observed compared with the control. Moreover, the dose-dependent responses of the ECOD activity were observed after treatment with sublethal concentrations of fipronil in the range of 2–20μg/L. The results suggested that ECOD could be a suitable biomarker of fipronil effects in D. rerio.

In Vitro Genotoxicity of Fipronil Sister Chromatid Exchange, Cytokinesis Block Micronucleus Test, and Comet Assay

Fipronil (FP) is a phenylpyrazole pesticide developed by the transnational company Rhône-Poulenc Agro in 1987. Data on the genotoxicity and toxicity of FP are rather inadequate. In this study, we aimed to evaluate the potential genotoxic activity of FP using the single-cell microgel electrophoresis or comet assay, sister chromatid exchanges (SCEs), and micronuclei (MN) in human peripheral blood lymphocytes. In addition, the cytokinesis block proliferation index (CBPI) and proliferation index (PRI) were measured for cytotoxicity. In this study, three different doses of FP were used (0.7, 0.3, 0.1 μg/mL). Mitomycin C (2 μg/mL) and hydrogen peroxide were used as positive controls for SCE MN test systems, and comet assay, respectively. FP induced a statistically significant increase in the MN and SCE frequency and DNA damage in a dose-dependent manner in human peripheral blood lymphocytes (p<0.01, p<0.05, for 0.7 and 0.3 μg/mL, respectively) compared with a negative control. There is no significant difference between 0.1 μg/mL and the negative control for MN frequency, but there is significant difference between all the doses of FP and negative control for SCE frequency, mitotic index, CBPI, and PRI values (p<0.01). Using the alkaline comet assay, we showed that all the doses of the FP induced DNA damage in human peripheral blood lymphocytes in vitro (p<0.05).

Toxicity of the Insecticide Fipronil and Its Degradates to Benthic Macroinvertebrates of Urban Streams

Fipronil is a phenylpyrazole insecticide with increasing urban use. Sixteen urban waterways and municipal wastewater were sampled for fipronil, its environmental degradates, and pyrethroid insecticides. Because findings could not be interpreted with existing data on fipronil degradate toxicity, EC50s and LC50s for fipronil and its sulfide and sulfone derivatives were determined for 14 macroinvertebrate species. Four species were more sensitive than any previously studied, indicating fipronil's toxicity to aquatic life has long been underestimated. The most sensitive species tested, Chironomus dilutus, had a mean 96-h EC50 of 32.5 ng/L for fipronil and 7-10 ng/L for its degradates. Hyalella azteca, a common testing species, was among the least sensitive. The typical northern California creek receiving urban stormwater runoff contains fipronil and degradate concentrations twice the EC50 of C. dilutus, and approximately one-third the EC50 for a stonefly, a caddisfly, and two mayfly species. The present study substantially increases data available on toxicity of fipronil degradates, and demonstrates that fipronil and degradates are common in urban waterways at concentrations posing a risk to a wide variety of stream invertebrates.

Histopathological alterations induced by subacute fipronil toxicity in mice and its amelioration by combination of α-tocopherol and ascorbic acid

Swiss albino female mice were randomly divided into four equal groups comprising 6 animals in each. Group 1 was administered vehicle, corn oil and served as control. Group 2 mice received fipronil @ 10 mg/kg body weight; mice in the group 3 were administered with combination of α-tocopherol and ascorbic acid, each @ 100 mg/kg body weight. Mice of group 4 were treated with α-tocopherol and ascorbic acid, each @ 100 mg/kg body weight, 2 hours before administration of fipronil @ 10 mg/kg body weight. Dosage were administered orally daily by gavage for consecutive 28 days. Mice were sacrificed at the end of 28 days to study gross and histopathological alterations. Grossly, liver of mice treated with fipronil was fragile with change of consistency and showed scattered pale foci. In histopathology, liver of mice treated with fipronil showed severe degenerative changes in heptocytes with presence of large number of necrotic foci, infiltration of mononuclear cells and congestion. In kidney, severe degenerative changes along with necrosis of tubular lining cells and congestion were evident in the fipronil treated mice. Severe emphysema and rupture of alveoli along with congestion was observed in the lung of mice treated with fipronil. Testis also showed depopulation of germs cells and thickening in basal layer of seminiferous tubules in fipronil treated mice. Co-administration of combination of these two vitamins against fipronil restored gross and histological changes in these organs. This study indicated that, subacute exposure of fipronil @ 10 mg/kg bw results in heaptotoxicity and cytotoxicity. Combined administration of antioxidant vitmains exerted protective action and ameliorated histological architecture of major organs.

Antioxidant status in oral subchronic toxicity of fipronil and fluoride co-exposure in buffalo calves

The effects of fipronil and fluoride co-exposure were investigated on antioxidant status of buffalo calves. A total of 24 healthy male buffalo calves divided into 4 groups were treated for 98 consecutive days. Group I, receiving no treatment, served as the control. Animals of groups II and III were orally administered with fipronil at the dosage of 0.5 mg/kg/day and sodium fluoride (NaF) at the dosage of 6.67 mg/kg/day, respectively, for 98 days. Group IV was coadministered with fipronil and NaF at the same dosages as groups II and III. Administration of fipronil alone produced significant elevation in lipid peroxidation (LPO) and decrease in the levels of nonenzymatic antioxidant glutathione (GSH). However, it did not produce any significant effect on the activities of enzymatic antioxidants including glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD). NaF exposure led to enhanced oxidative stress as shown by significant increase in the LPO and SOD activities while GPx and CAT activities and GSH levels were significantly decreased. Co-exposure to fipronil and NaF showed additive effects on LPO, GPx activity, and GSH levels.

Detection of the A302S &lt;I&gt;Rdl&lt;/I&gt; Mutation in Fipronil Bait-Selected Strains of the German Cockroach (Dictyoptera: Blattellidae)

Extensive usage and heavy reliance on insecticides have led to the development of insecticide resistance in the German cockroach, Blattella germanica (L.). Six field-collected strains of B. germanica from Singapore were used to investigate resistance to fipronil and dieldrin. The three strains (Boat Quay, Cavenagh Road, and Ghimmoh Road) with greatest resistance to fipronil were subjected to selection with fipronil bait up to the F5 generation. Synergism assay and molecular detection of a target site mutation were used to elucidate the mechanism of fipronil resistance in these strains. With the exception of the Cavenagh Road strain, all parental strains were susceptible to dieldrin. This strain exhibited resistance to dieldrin and fipronil with resistance ratios of 4.1 and 3.0, respectively. Piperonyl butoxide and S,S,S-tributylphosphorotrithioate were antagonistic toward fipronil toxicity in all strains. Bait selection significantly increased fipronil and dieldrin resistance in the three chosen strains, either in topical bioassay or bait evaluations. There was a significant positive relationship [y = (6,852.69 +/- 1,988.37) x - (708.93 +/- 1,226.28), where x = fipronil toxicity and y = dieldrin toxicity] between dieldrin and fipronil resistance levels, indicating significant cross-resistance between the insecticides. High frequencies of individuals possessing the Rdl gene mutation were found in the F5 generation of the three strains selected with fipronil bait. The synergism assays indicated that monooxygenase and esterase were not involved in fipronil resistance in the strains studied herein. The A302S Rdl mutation was the major mechanism contributing to fipronil and dieldrin resistance in these strains.

Behavior of nursery-box-applied fipronil and its sulfone metabolite in rice paddy fields

The granular insecticide fipronil has been widely applied in rice nursery boxes, both before transplanting (BT) and during at-sowing (AS) treatments to control insect pests at the early stages of rice cultivation in Japan. Although a potential effect of fipronil on paddy ecosystems and downstream aquatic environments has been observed, the environmental effect of this substance in paddy fields remains unsought. Here we investigate the environmental behavior of nursery-box-applied granular fipronil and its sulfone metabolite in paddy water and paddy soils during BT and AS treatments performed in a paddy field in Japan. Although the fipronil concentrations in the paddy water in the AS treatment were significantly lower than those measured in the BT treatment, no significant differences were observed in the paddy soil between the two treatments. Fipronil was mainly found in the 0- to 5-cm surface soil layer of the rice-root zone, where its concentrations were approximately ten times higher than those in the soil of the inter-row zone. The insecticide concentration in the 0- to 1-cm layer of the inter-row zone in the surface soil was approximately 2.5 times higher than that in the 0- to 5-cm layer. The maximum concentrations of fipronil in the 0- to 1-cm surface soil layer ranged from 65.8 to 92.1μg/kg on the first day after rice transplanting (DAT), and the corresponding values in the paddy water ranged from 0.9 to 2.5μg/L. The dissipation of fipronil from the paddy water and paddy soil was described by first-order kinetics. The compound's half-life (DT50) was 0.9–3.1 days in paddy water and 12.3–26.4 days in paddy soil. Compared to the BT treatment, the AS treatment may pose a smaller risk to the paddy water and the adjacent environment. Fipronil sulfone was found in every water and soil sample, with the maximum concentrations ranging from 0.4 to 0.9μg/L in the paddy water and from 9.7 to 59.2μg/kg in the paddy soil on the third DAT. These values gradually decreased over time. Ecotoxicological risk assessments of fipronil products in rice paddies should not only consider the toxicity of fipronil itself but also that of fipronil sulfone because of its relatively high concentrations in paddy water and paddy soil

Haemato-biochemical Responses in Cyprinus carpio (Linnaeus, 1758) Fry Exposed to Sub-lethal Concentration of a Phenylpyrazole Insecticide, Fipronil

The present study evaluates the haemato-biochemical responses associated with fipronil exposure [(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinyl-pyrazole-3-carbonitrile] in Cyprinus carpio fry. Fish were exposed to sublethal concentration (1/3rd of LC50) (0.142 mg L−1) for 15 days and corresponding changes in different haemato-biochemical parameters were recorded at the end of experimental period. Significant (P < 0.05) increase in white blood cell counts, blood glucose, serum complement reactive protein and serum cortisol level were noticed, whereas haemoglobin and serum total protein contents were significantly (P < 0.05) decreased. Aspartate amino transferase, catalase and super oxide dismutase activities were significantly (P < 0.05) increased while alkaline phosphatase and malate dehydrogenase activities were significantly (P < 0.05) decreased. Similarly, 47 % inhibition in acetylcholine esterase activity was noticed due to fipronil stress. Results indicated that sublethal exposure of fipronil can induce haemato-biochemical alterations causing stress to C. carpio fry. Thus, haemato-biochemical parameters can be used as biomarkers for the sublethal toxicity of fipronil in the water bodies.

Effects of the insecticide fipronil on reproductive endocrinology in the fathead minnow

Gamma-aminobutyric acid (GABA) and GABA receptors play an important role in neuroendocrine regulation in fish. Disruption of the GABAergic system by environmental contaminants could interfere with normal regulation of the hypothalamic-pituitary-gonadal axis, leading to impaired fish reproduction. The present study used a 21-d fathead minnow (Pimephales promelas) reproduction assay to investigate the reproductive toxicity of fipronil (FIP), a broad-spectrum phenylpyrazole insecticide that acts as a noncompetitive blocker of GABA receptor-gated chloride channels. Continuous exposure up to 5 µg FIP/L had no significant effect on most of the endpoints measured, including fecundity, secondary sexual characteristics, plasma steroid and vitellogenin concentrations, ex vivo steroid production, and targeted gene expression in gonads or brain. The gonad mass, gonadosomatic index, and histological stage of the gonad were all significantly different in females exposed to 0.5 µg FIP/L compared with those exposed to 5.0 µg FIP/L; however, there were no other significant effects on these measurements in the controls or any of the other treatments in either males and females. Overall, the results do not support a hypothesized adverse outcome pathway linking FIP antagonism of the GABA receptor(s) to reproductive impairment in fish.

Supplementation of microbial levan in the diet of Cyprinus carpio fry (Linnaeus, 1758) exposed to sublethal toxicity of fipronil: effect on growth and metabolic responses

A 60-day feeding trial was conducted to study the effect of dietary microbial levan on growth performance and metabolic responses of Cyprinus carpio fry exposed to sublethal dose (1/10th LC₅₀) of fipronil [(±)-5-amino-1-(2,6-dichloro-α,α,α-trifluoro-p-tolyl)-4-trifluoromethylsulfinylpyrazole-3-carbonitrile]. Two hundred and twenty five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L₀P₀ (basal feed + 0 % levan without exposure to pesticide); pesticide control L₀P₁ (basal feed + 0 % levan with exposure to pesticide); L₀.₂₅P₁ (basal feed + 0.25 % levan with exposure to pesticide); L₀.₅₀P₁ (basal feed + 0.50 % levan with exposure to pesticide); and L₀.₇₅P₁ (basal feed + 0.75 % levan with exposure to pesticide). Weight gain% and specific growth rate were significantly higher (p < 0.05) in levan fed groups compared to their non-levan fed counterpart. Highest (p < 0.05) content of ascorbic acid in muscle, liver and brain tissues was observed with higher level of dietary levan. Glucose-6-phosphate dehydrogenase activity decreased with the increasing level of dietary levan in the liver and muscle. Aspartate aminotransferase activity exhibited a second order polynomial relationship with the dietary levan, both in liver (Y = -1.001x² + 5.366x + 5.812, r² = 0.887) and muscle (Y = -0.566x² + 2.833x + 6.506, r² = 0.858) while alanine aminotransferase activity showed third order polynomial relationship both in liver (Y = 1.195x³ - 12.30x² + 35.23x + 9.874, r² = 0.879) and muscle (Y = 0.527x³ - 8.429x² + 31.80x + 8.718, r² = 0.990). Highest (p < 0.05) superoxide dismutase activity in gill was observed in the group fed with 0.75 % levan supplemented diet. Overall results indicated that dietary microbial levan at 0.75 % in C. carpio fry ameliorated the negative effects of fipronil and augmented the growth.