Bioaccumulation of endosulfan (Thiodan insecticide) in the tissues of Louisiana crayfish, Procambarus clarkii

The bioaccumulation potential of endosulfan was determined by constantly exposing male and female adult crayfish, Procambarus clarkii to 100 ppb Thiodan insecticide for 8 wks. The crayfish were removed at 2 wk intervals and the uptake by tissues (whole-body) was determined by electron capture gas-chromatography. The same number of pre-exposed crayfish (100 ppb Thiodan) were transferred to endosulfan-free water after 8 wks, and insecticide loss (depuration) was similarly quantitated. The maximum amount of insecticide and its metabolites detected after 8 wks were 197 ppb endosulfan II, 18 ppb endosulfan I and 3 ppb endosulfan sulfate. During the first 4 wks of depuration, endosulfan loss from cryfish tissues occurred rapidly, and only 3 ppb endosulfan I remained. No endosulfan II and sulfate were detected beyond 4 wks. The residues in male vs female were not significant statistically. Bioaccumulation factor (BF) for endosulfan II for crayfish tissues was 1.97, which is considerably lower than for other aquatic invertebrates (26 for scallop, Chlamys opercularis and 600 for mussel, Mytilus edulis. The presence of endosulfan sulfate in the tissues cannot be considered as 'detoxification' which is as toxic as the parent compound.     

Toxicity of fipronil and its enantiomers to marine and freshwater non-targets

Fipronil is a phenylpyrazole insecticide used in agricultural and domestic settings for controlling various insect pests in crops, lawns, and residential structures. Fipronil is chiral; however, it is released into the environment as a racemic mixture of two enantiomers. In this study, the acute toxicity of the (S,+) and (R,-) enantiomers and the racemic mixture of fipronil were assessed using Simulium vittatum IS-7 (black fly), Xenopus laevis (African clawed frog), Procambarus clarkii (crayfish), Palaemonetes pugio (grass shrimp), Mercenaria mercenaria (hardshell clam), and Dunaliella tertiolecta (phytoplankton). Results showed that S. vittatum IS-7 was the most sensitive freshwater species to the racemic mixture of fipronil (LC50 = 0.65 microg/L) while P. pugio was the most sensitive marine species (LC50 = 0.32 microg/L). Procambarus clarkii were significantly more sensitive to the (S,+) enantiomer while larval P. pugio were significantly more sensitive to the (R,-) enantiomer. Enantioselective toxicity was not observed in the other organisms tested. Increased mortality and minimal recovery was observed in all species tested for recovery from fipronil exposure. These results indicate that the most toxic isomer of fipronil is organism-specific and that enantioselective toxicity may be more common in crustaceans than in other aquatic organisms.     

Population-level effects of the neem insecticide, Neemix, on Daphnia pulex

Although natural insecticides from the neem tree are generally perceived as less harmful to the environment than synthetic insecticides, new evidence indicates that these products may pose a risk to certain nontarget organisms. In this paper, acute and chronic effects of commercial neem insecticides on the aquatic invertebrate, Daphnia pulex were examined. The acute toxicity of two commercial neem insecticides, Neemix, Azatin and the experimental insecticide, RH-9999 to D. pulex was investigated using traditional 48 hr concentration-mortality estimates. Neemix and Azatin were equitoxic with LC50's of 0.68 and 0.57 ppm; RH-9999 was significantly less toxic with an LC50 of 13 ppm. A 10 d population growth study was conducted for Neemix and a Neemix formulation blank (Neemix devoid of the active ingredients) to determine whether the active ingredients of Neemix and/or components of the formulation were responsible for toxicity. D. pulex populations went to extinction after exposure to a Neemix concentration of 0.45 ppm azadirachtin (equivalent to the acute LC7). Neemix No Observable Effect Concentration (NOEC) and Lowest Observable Effect Concentration (LOEC) values for population growth were 0.045 and 0.15 ppm azadirachtin, respectively. The mean number of offspring per surviving female (Ro) declined in a concentration-dependent manner after exposure to Neemix with no offspring being produced after exposure to 0.45 ppm. Neemix NOEC and LOEC values for reproduction were 0.045 and 0.15 ppm, respectively. The formulation blank caused no mortality in the individuals used to start the population growth study but reduced reproduction and population growth accounting for 47% of the toxicity caused by Neemix at a concentration of 0.15 ppm. Thus, the formulation contributes substantially to the toxicity of Neemix but neem components are also toxic to D. pulex. Because the NOEC for population growth and reproduction were higher than the estimated environmental concentration of 0.035 ppm (a measure developed for forest pest mananagement), Neemix should pose little risk to populations of D. pulex.     

The effects of bayluscide and malathion on the survival of Schistosoma mansoni miracidia

Laboratory experiments were conducted to assess the toxic effects of bayluscide and malathion against Schistosoma mansoni miracidia. The results indicate that survival of miracidia varied with times of exposure and concentrations of tested chemicals. Statistical analyses reveal that LC5, LC50 and LC95 for bayluscide were 0.04 ppm, 0.06 ppm and 0.12 ppm after 2 hours of exposure; 0.02 ppm, 0.03 ppm and 0.06 ppm after 4 hours of exposure; and 0.01 ppm, 0.02 ppm and 0.04 ppm after 6 hours of exposure respectively. These data indicate that bayluscide is much more toxic to the first stage larvae of schistosomes than to snail intermediate hosts cited in the literature. Application of lower concentrations of molluscicide in the transmission sites is thus expected to curtail the survival of miracidia; therefore controlling schistosomiasis at relatively low costs. Such applications also reduce the risk of toxicity to non target organisms present in the aquatic environment. Statistical analysis of the results of tests using malathion gave LC5, LC50 and LC95 values of 83.38 ppm, 153.11 ppm and 245.85 ppm after 2 hours of exposure; and 76.86 ppm, 116.48 ppm and 172.04 ppm after 4 hours of exposure respectively. These data indicate that the use of malathion as an insecticide in tropical ecosystems may also affect the survival and viability of schistosome miracidia. Such uses could help reducing the risk of schistosomiasis transmission in these particular locations.     

A freshwater shrimp (Paratya compressa improvisa) as a sensitive test organism to pesticides

The susceptibility of 2-week-old individuals of the freshwater shrimp, Paratya compressa improvisa, to five kinds of insecticide and five kinds of herbicide was examined in comparison with that of two species of Cladocera, Daphnia magna and Moina macrocopa. The shrimp was especially sensitive to two organophosphorus insecticides. The 48-h LC50 values for fenitrothion and fenthion to the shrimp were 1.15 and 1.04 microg litre(-1) (mean value, n=2), in contrast with 37.8 and 35.3 microg litre(-1) in the case of M. macrocopa, and more than 50 microg litre(-1) with D. magna. The shrimp also showed the higher susceptibility to other insecticides, diazinon, carbaryl (NAC) and BPMC, apart from D. magna to diazinon and NAC. The shrimp also showed higher susceptibility to herbicides. The 48-h LC50 values of CNP, benthiocarb, oxadiazon, butachlor, and symetryne to the shrimp were two to eight times lower than those of two species of Cladocera, except for the LC50 value of oxadiazon to M. macrocopa, which was very slightly higher. However, the shrimp showed a somewhat lower susceptibility to heavy metals than the two species of Cladocera, especially to copper, and to cadmium and zinc in comparison with D. magna. A bioassay using the shrimp with river water, collected from the river adjacent to the paddy field, showed clearly the high mortality of the shrimp following the aerial spraying with pesticides.     

Investigation of acute toxicity of fenitrothion on peppered corydoras (Corydoras paleatus) (Jenyns, 1842)

Fenitrothion, as an organophosphothionate insecticide, is a contact insecticide and selective acaricide, also used as a vector control agent for malaria in public health programs. A 96 h LC50 value of fenitrothion, a potential toxic pollutant contaminating aquatic ecosystems, was determined on the adult peppered corydoras (Corydoras paleatus). The experiments were repeated three times. The static test method of acute toxicity test was used. Water temperature was regulated at 23 +/- 1 degrees C. In addition, behavioral changes at each fenitrothion concentration were observed for the individual fish. Data obtained from acute toxicity tests were evaluated using the Probit Analysis Statistical Method. The 96 h LC50 value for peppered corydoras was estimated as 3.51 mg/l.     

Effects of five insecticides used in apple orchards on Hyaliodes vitripennis (Say) (Hemiptera: Miridae)

Azinphos-methyl, carbaryl, dimethoate, phosmet and phosalone were used in apple orchards to manage apple aphid, apple maggot, woolly apple aphid and leaf eating caterpillars. Among the five insecticides evaluated, dimethoate, carbaryl and azinphosmethyl were the most toxic to the nymphs and adults of Hyaliodes vitripennis (Say) from two regions. Phosalone was the least toxic. Nymphs were more resistant than the adults. While the LC50 for dimethoate was 130 ppm for nymphs, it was 3 ppm for adults from St. Jean-Baptiste-de-Rouville. There were also significant differences in the level of resistance between the two regions where the H. vitripennis were collected. At St. Alexandre the LC50 for phosalone on nymphs was 19,250 ppm whereas, at St. Jean-Baptiste-de-Rouville it was 160,000 ppm.     

Ecological risk assessment of neem-based pesticides

A tiered process was used to evaluate the risks of pure azadirachtin (AZA) and two neem-based insecticides (Neemix and Bioneem) on six aquatic animals [crayfish (Procambarus clarkii), white shrimp (Penaeus setiferus), grass shrimp (Palaemonetes pugio), blue crabs (Callinectes sapidus), water fleas (Daphnia pulex), and mosquito larvae (Culex quinquefasciatus)] through short term acute toxicity tests. The risk was calculated using the level of concern endpoints (Q values) and relative hazard index (RHI) for acute and chronic exposure scenarios. The Q values of Neemix, Bioneem, and pure AZA derived from acute exposure tests indicated that D. pulex is the only sensitive species to the test pesticides. Furthermore, the RHI values of Neemix and Bioneem for D. pulex were above the critical limit of 10 indicating that these pesticides may pose a moderate hazard to this species and related crustaceans in acute exposure scenarios. The RHI values of the two pesticides and pure AZA were all below the critical limit of 10 for P. clarkii, P. setiferus, P. pugio, C. sapidus, and C. quinquefasciatus. The aquatic risk assessment process showed that the risk values of tested pesticides did not exceed the criteria, and therefore, no ecological hazard is likely to result from their use.     

Investigation of acute toxicity and the effect of 2,4-D (2,4-dichlorophenoxyacetic acid) herbicide on the behavior of the common carp (Cyprinus carpio L., 1758; Pisces,Cyprinidae)

A 96-h LC(50) values of 2,4-D [(2,4-dichlorophenoxy)acetic acid], a common contaminating agricultural herbicide, were determined on the adult common carp (Cyprinus carpio L., 1758; Pisces, Cyprinidae). The study was conducted in two stages using 130 carp. The data obtained were statistically evaluated by the use of the EPA computer program based on Finney's Probit Analysis Method and a 96-h LC(50) value for C. carpio L., 1758 was found to be 63.24 mg/l in a static bioassay test system. 95% lower and upper confidence limits for the LC(50) were 55.03 and 71.92 mg/l, respectively. Water temperature was 17+/-1 degrees C. Behavioral changes of the above mentioned species were examined for various herbicide concentrations.     

Comparison of in vitro and in vivo acute fish toxicity in relation to toxicant mode of action

Acute toxicity to fish hepatoma cell line PLHC-1 and to juvenile rainbow trout was examined for 18 plant protection products. The main objective was to explore whether hepatoma cells could be used to predict acute toxicity in fish taking into account the mode of toxic action and compound properties. Acute fish toxicity was determined using the OECD guideline test 203 and compared to predicted baseline LC50 of acute fish toxicity calculated with a quantitative structure-activity relationship (QSAR) derived for guppy fish. Cytotoxicity was determined through the inhibition of neutral red uptake (NR(50)) into lysosomes and compared to predicted baseline cytotoxicity derived for goldfish GFS cells. In general, NR50 values were higher by a factor ranging from 3 to 3000 than the corresponding acute LC50. A weak correlation between NR50 and LC50 values was found (log/log: r2=0.62). Also the lipophilicity (log K(ow)) was not a good predictor for cytotoxicity (r2=0.43) and lethality (r2=0.57) of these pesticides. The neutral red assay is detecting general baseline toxicity only. Comparing LC50 data to QSAR results, the compounds can be classified to act as narcotics or reactive compounds with a specific mode of toxic action in fish. The results indicate that limitation of the neutral red assay in predicting acute fish toxicity. A promising alternative might be the assessment of toxicity in a set of in vitro systems addressing also cell-specific functions which are related to the mode of toxic action of the compound.     

A study on the lethal toxicity of aminocarb to freshwater crayfish and its in vivo metabolism

Adult crayfish (Orconetes limosus) were exposed to 0.1, 1.0, 5.0, 10.0, 25.0, 30.0, 40.0, 50.0 and 60.0 ppm of aminocarb in water at 15 degrees C under laboratory conditions for 144 h. No apparent behavioral changes were observed in crayfish exposed to 0.1, 1.0 and 5.0 ppm of aminocarb during the experiment. Symptoms of acute toxicity were apparent at concentrations greater than or equal to 10 ppm, and mortality occurred at and above 25 ppm. The LC50, 96 h, to adult crayfish was about 33 ppm. The parent compound and its metabolites, MA (4-methylamino-m-tolyl N-methylcarbamate) and AM (4-amino-M-tolyl N-methylcarbamate), were detected in crayfish 96 h after exposure to various concentrations of aminocarb. The primary metabolite detected was MA which accounted for 75% to 95% of the body residue. The highest total residue (Aminocarb + MA + AM) was 40 ppm detected in crayfish exposed to 60 ppm of aminocarb for 96 h.     

Effects of the insect growth regulator (S)-methoprene on survival and reproduction of the freshwater cladoceran Moina macrocopa

This study examines the acute and chronic effects of the insecticide (S)-methoprene on the survival and reproduction of the freshwater cladoceran Moina macrocopa. In laboratory toxicity tests, the 24- and 48-h LC50 values for (S)-methoprene were 0.51 and 0.34 mg litre(-1), respectively. Survival, longevity and fecundity were reduced at 0.05 mg litre(-1) and higher concentrations. At 0.005 and 0.01 mg litre(-1), longevity and fecundity increased slightly as compared to control animals. If environmental concentrations of methoprene do not exceed 0.05 mg litre(-1), as is generally the case, application of this insecticide is unlikely to induce detrimental effects on natural cladoceran populations. The stimulatory effect of very low levels of methoprene on reproductive performance is consistent with the hypothesis of a regulatory role of juvenile hormone-like compounds in crustacean reproduction.     

Divergent toxicity of parathion in two freshwater invertebrates, orconectes rusticus and viviparus malleatus

The toxicity of parathion and its metabolite paraoxon was examined in the crayfish Orconectes rusticus and the snail Viviparus malleatus and attempts were made to relate this to parathion uptake and metabolism. The crayfish was found to be very susceptible with all animals tested dying at 0.1 ppb of parathion in 48 hours. The snail was resistant to exposure to 1000 ppm. The absence of lethality even to injected (50 mg/kg) parathion and paraoxon suggests an innate lack of susceptibility. Metabolism of the compounds could not be detected in vitro or in vivo in either species.     

Toxic and sublethal effects of endosulfan and carbaryl on growth and egg production of Moina micrura Kurz (Cladocera: Moinidae)

The toxic and sublethal effects of endosulfan and carbaryl on a cladoceran, Moina micrura, were studied. The dosage-mortality regression lines gave LC(50) values for the pesticides. The cumulative growth and egg production during life were inhibited to 31.8 and 20.7% in endosulfan, and 28.2 and 13.7% in carbaryl-treated animals, respectively. The growth coefficient (K value) and the intrinsic rate of natural increase per day (r value) of control M. micrura were 0.144 and 0.377, respectively; these decreased to 0.121 and 0.346 in carbaryl-, and 0.073 and 0.356 in endosulfan-treated animals, respectively.     

Toxicity assessment of 45 pesticides to the epigeic earthworm Eisenia fetida

This study was conducted to investigate comparative toxicity of 45 pesticides, including insecticides, acaricides, fungicides, and herbicides, toward the epigeic earthworm Eisenia fetida. Results from a 48-h filter paper contact test indicated that clothianidin, fenpyroximate, and pyridaben were supertoxic to E. fetida with LC(50) values ranging from 0.28 (0.24-0.35) to 0.72 (0.60-0.94) μg cm(-2), followed by carbaryl, pyridaphenthion, azoxystrobin, cyproconazole, and picoxystrobin with LC(50) values ranging from 2.72 (2.22-0.3.19) to 8.48 (7.38-10.21) μg cm(-2), while the other pesticides ranged from being relatively nontoxic to very toxic to the worms. When tested in artificial soil for 14 d, clothianidin and picoxystrobin showed the highest intrinsic toxicity against E. fetida, and their LC(50) values were 6.06 (5.60-6.77) and 7.22 (5.29-8.68) mg kg(-1), respectively, followed by fenpyroximate with an LC(50) of 75.52 (68.21-86.57) mgkg(-1). However, the herbicides fluoroglycofen, paraquat, and pyraflufen-ethyl exhibited the lowest toxicities with LC(50) values>1000 mg kg(-1). In contrast, the other pesticides exhibited relatively low toxicities with LC(50) values ranging from 133.5 (124.5-150.5) to 895.2 (754.2-1198.0) mg kg(-1). The data presented in this paper provided useful information for evaluating the potential risk of these chemicals to soil invertebrates.     

Toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles

This study evaluates the toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles after 168 h of exposure. The LC(50) of deltamethrin and λ-cyhalothrin at 168 h was calculated as the μg of active ingredient per liter (μg AI/L). According to these values, the LC(50) was 6.26 and 3.94 μg AI/L for deltamethrin and λ-cyhalothrin, respectively. Several enzymes were studied for early signs of intoxication following exposure to the pesticides for 24 h. Glutathione-S-transferase,carboxylesterase, and lactate dehydrogenase were inhibited by λ-cyhalothrin, and both pesticides inhibited acid phosphatase and aspartate aminotransferase. In contrast, acetylcholinesterase was activated by deltamethrin. The results suggest that X. laevis is sensitive to the pyrethroids that were tested, and the enzyme responses suggest that they are potential biomarkers for evaluating the toxic effect of pyrethroids on amphibians in environmental conditions.     

Insecticidal activity of different extracts from Scrophularia canina L. against Culex pipiens molestus Forskal (Diptera, Culicidae)

The insecticidal activity of different extracts (aqueous, methyl alcohol, hexane and petroleum ether) of the aerial part of Scrophularia canina against the second and fourth-instar larvae and adult females of Culex pipiens molestus was investigated. The larvicidal activity of all the extracts was tested in the dose range from 7.8 to 1000 ppm. The highest toxicity was exhibited by the petroleum ether extract against second-instar larvae (48 h LC?? = 23.5 ppm) and by the hexane extract against fourth-instar larvae (48 h LC?? = 23.6 ppm). Methyl alcohol and aqueous extracts did not show any larvicidal activity. Sub-lethal doses of petroleum ether and hexane extracts induced increasing mortalities during 13 days after treatment but did not affect the duration of larval and pupal stages. In persistence tests, the hexane extract retained a satisfactory larvicidal activity after a 10-day period of test solutions incubation. Topical treatment of adult females with doses from 0.25 to 8 μg per mg of female body weight of different extracts showed a similar toxicity for the hexane (24 h LD?? = 1.7 μg mg?1) and petroleum ether (24 h LD?? = 1.8 μg mg?1) extracts which were significantly more toxic than methyl alcohol extract (4.2 μg mg?1). Aqueous extract did not induce adult mortality. The marked mosquitocidal activity of petroleum ether and hexane extracts of the aerial part of S. canina against different life stages of C. pipiens molestus is promising to develop effective alternatives to synthetic insecticides.     

Effects of carbaryl, chlorpyrifos and endosulfan on growth, reproduction and respiration of tropical epigeic earthworm, Perionyx excavatus (Perrier)

Effects of sub-lethal doses of carbaryl (1-Naphthyl-methylcarbamate), chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridinyl-phosphorothioate) and endosulfan (6,7,8,9,10,10-Hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin-3-oxide), respectively a carbamate, an organophosphate and an organochlorine insecticide on growth, reproduction and respiration of the tropical earthworm, Perionyx excavatus (Perrier) were investigated under laboratory conditions. The results showed significant reduction in biomass, production and hatching of cocoon and production of juveniles of the worms exposed to 0.75 to 3.03 mg/kg soil of carbaryl, 0.91 to 3.65 mg/kg soil of chlorpyrifos and 3.75 to 15.0 μg/kg soil of endosulfan corresponding to 12.5 to 50 % of LC(50) value of the respective insecticide for P. excavatus. Endosulfan was found most dangerous among the three insecticides followed by carbaryl and chlorpyrifos. There was no hatching of the worms at endosulfan treatment 5.0 μg/kg soil (25 % LC(50)) or above while the highest dose of carbaryl and chlorpyrifos (50 % of LC(50)) rendered respectively 87.13 and 24.84 % reductions in hatching as compared to control. Chlorpyrifos produced no change in respiration of the worms except at the highest dose, while the worms showed an increase in evolution of CO(2) at all doses of carbaryl and endosulfan. Based on the recommended agricultural dose of each insecticide, it was concluded that application of endosulfan and carbaryl was potentially dangerous to earthworms.     

Quantitative structure-toxicity relationship study of lethal concentration to tadpole (Bufo vulgaris formosus) for organophosphorous pesticides

In the present study more than 1,000 structural parameters of 41 organophosphorus pesticides (OPs) were calculated using the software ChemOffice 8.03 and Dragon 2.1. Then, with multivariate linear regression and best subset regression analyses, different equations were derived to calculate the lethal toxicity, LC(50), for these 41 organophosphorous pesticides found in tadpoles (Bufo vulgaris formosus). An equation was developed for all selected OPs, especially those with relatively low toxicity levels (LC(50)>4.5mM) that accounted for 89.09% of the variability in the toxic effect. The equation indicated that the main contributions to OPs toxicity with tadpoles were the electrostatic contribution qH(+) (maximum net positive H atomic charge), spatial autocorrelation (MATS7 m) and hydrophobicity (lgK(ow)), with the two former being the most important parameters. For OPs with high toxicity, however, different structural parameters were introduced. The following equation was developed with LC(50)<4.5mM. These equations implied that with different levels of toxicity there could have different mechanisms in the tadpole. Furthermore, the results showed that molecular structural parameters had a particular value in modeling chemical reactivity within a homologous series of compounds.     

Effects of a selenium-enriched diet on antioxidant response in adult crayfish (Procambarus clarkii)

Many diets employed in aquaculture are enriched with selenium to improve the diet quality and its conservation. The aim of the study was to investigate the effects of a diet enriched in selenium (1.21 mg kg(-1)) on the antioxidant response of Procambarus clarkii (Girard, 1852). Crayfish fed a diet with lower selenium content (0.30 mg kg(-1)) were the control. Selenium accumulation, enzymatic activities, and total glutathione were evaluated in hepatopancreas of adults of both sexes fed with both diets for 50 days at two experimental times (T(30), T(50) days). Treated females exhibited the highest selenium bioaccumulation during both experimental times, while treated males displayed the highest selenium concentration after 30 days, compared to control crayfish. A sex-related difference was found for the response of the analyzed enzymes in the selenium diet-treated specimens. In fact, superoxide dismutase, glutathione peroxidase and glyoxalase I activities in males were more sensitive compared with females, showing depleted activities in both experimental times. Catalase activity was induced in females (T(50)), while glutathione S-transferase activity was the highest in treated females and the lowest in treated males, compared with own controls. Only glutathione reductase activity and glutathione content showed the same trend in both sexes, which were both lowered in treated specimens, when compared with control crayfish. This result might be due to the effect of selenium toxicity on this freshwater species. Males and females of P. clarkii showed a different susceptibility to the prooxidant effects in a Se-enriched diet.