Control of common freshwater predatory fish, Channa punctatus, through Nerium indicum leaf extracts

The diethyl ether, chloroform, acetone and methanol extract of Nerium indicum leaf were evaluated for their piscicidal activity against common freshwater air breathing predatory fish Channa punctatus. The rank of order of toxicity (LC50) of the leaf extract was, diethyl ether extract (17.34 mg/l)>acetone (40.01 mg/l)>chloroform (40.61 mg/l)>and methanol (106.37 mg/l). There was a significant negative correlation between LC50 values and exposure periods. Thus increase in exposure period, LC50 decreases from 17.34 mg/l (24 h) to >13.58 mg/l (96 h) in the diethyl ether extract. Similar trends were also observed in acetone, chloroform and methanol extracts. Exposure of sub-lethal doses (40% and 80% of LC50) of the diethyl ether extract of N. indicum leaf (which has maximum piscicidal activity) for 24 or 96 h caused significant alteration in the level of total protein, total free amino acid, nucleic acid, glycogen, pyruvate, lactate and activity of enzyme protease, phosphatases, alanine aminotransferase, aspartate aminotransferase and acetylcholinesterase in liver and muscle tissue. The alterations in all the above biochemical parameters were significantly (P<0.05) time and dose dependent. There was a significant recovery in all the above biochemical parameters, in both liver and muscle tissues of fish after the seventh day of the withdrawal of treatment. Thus, the leaf extracts of N. indicum have potent piscicidal activity against fish C. punctatus and also significantly affect both aerobic and anaerobic pathway of respiration in fish.     

Toxic effect of stem bark and leaf of Euphorbia hirta plant against freshwater vector snail Lymnaea acuminata

The aqueous stem bark and leaf extracts of plant Euphorbia hirta (family-Euphorbiaceae) have potent molluscicidal activity. Sub-lethal doses (40% and 80% of LC50) of aqueous stem bark and leaf extracts of this plant also significantly (P<0.05) alter the levels of total protein, total free amino acid, nucleic acids (DNA and RNA) and the activity of enzyme protease and acid and alkaline phosphatase in various tissues of the vector snail Lymnaea acuminata in time and dose dependent manner. Euphorbia hirta (family-Euphorbiaceae) commonly known as Dudhi, is a common medicinal plant of India, which is used in variety of diseases i.e. cough, asthma, colic, dysentery, genito urinary diseases.     

Molluscicidal activity of Ferula asafoetida, Syzygium aromaticum and Carum carvi and their active components against the snail Lymnaea acuminata

The molluscicidal activity of dried root latex powder of Ferula asafoetida, flower-bud powder of Syzygium aromaticum and seed powder of Carum carvi against the snail Lymnaea acuminata was studied. The molluscicidal activity of all the three plant products was found to be both time and concentration dependent. The toxicity of S. aromaticum flower-bud powder (96 h LC(50):51.98 mg/l) was more pronounced than that of root latex powder of F. asafoetida (96 h LC(50):82.71 mg/l) and seed powder of C. carvi (96 h LC(50):140.58 mg/l). Ethanol extract was more toxic than other organic extracts. The ethanol extract of S. aromaticum (24h LC(50):83.53 mg/l) was more effective than that of F. asafoetida (24h LC(50):132.31 mg/l) and C. carvi (24h LC(50):130.61 mg/l) in killing the test animals. The 96 h LC(50) of column purified fraction of seed powder of C. carvi was 5.40 mg/l whereas those of flower-bud powder of S. aromaticum and dried root latex powder of F. asafoetida were 7.87 and 9.67 mg/l, respectively. The product of F. asafoetida, S. aromaticum and C. carvi may be used as potent molluscicides.     

Biochemical stress response in freshwater fish Channa punctatus induced by aqueous extracts of Euphorbia tirucalli plant

Piscicidal activities of aqueous extracts of Euphorbia tirucalli were very well established, but their ultimate mode of action on fish metabolism was not yet known. Exposure of fishes over 24h or 96h to sub-lethal doses (40% and 80% of LC(50)) of aqueous extract of E. tirucalli stem-bark and latex, significantly (P<0.05) altered the level of total protein, total free amino acids, nucleic acids, glycogen, pyruvate, lactate and activity of protease, alanine aminotransferase, aspartate aminotransferase, acetylcholinesterase and cytochrome oxidase enzyme in liver and muscle tissues of freshwater fish Channa punctatus. The alterations in all these biochemical parameters were significantly (P<0.05) time- and dose-dependent. After 7d of withdrawal of treatment of 80% of LC(50) of E. tirucalli extracts shows that there was a partial recovery in the levels of glycogen but nearly complete recovery in total protein, total free amino acids, pyruvate, lactate, nucleic acids level and activity of protease, aspartate aminotransferase, alanine aminotransferase, acetylcholinesterase and cytochrome oxidase enzyme in both the tissues of fish. Thus aqueous extracts of E. tirucalli adversely affect respiratory pathway of fish and cause energy crisis during stress by suppressing ATP production. The reversibility of the action of the aqueous extracts would be an additional advantage in their use.     

Molluscicidal activity of Sapindus mukorossi and Terminalia chebula against the freshwater snail Lymnaea acuminata

The molluscicidal activity of Sapindus mukorossi and Terminalia chebula fruit powder against the vector snail Lymnaea acuminata was time and concentration dependent. The molluscicidal activity of T. chebula fruit powder (96 h LC(50):93.59 mg L(-1)) was more pronounced than that of S. mukorossi fruit powder (96 h LC(50):119.57 mg L(-1)). Ethanolic extracts of S. mukorossi and T. chebula fruit powder were more toxic than their other organic solvent extracts. The molluscicidal activity of ethanolic extract of S. mukorossi fruit powder (24h LC(50):2.75 mg L(-1)) was more effective than the ethanolic extract of T. chebula fruit powder (24h LC(50):124.06 mg L(-1)). The 96 h LC(50) of column-purified fraction of S. mukorossi fruit powder was 5.43 mg L(-1) whereas those of T. chebula fruit powder was 7.49 mg L(-1). Column, thin layer and high performance liquid chromatography analysis demonstrates that the active molluscicidal component in S. mukorossi and T. chebula is saponin (96 h LC(50):1.31 mg L(-1)) and tannic acid (96 h LC(50):1.64 mg L(-1)), respectively. These plants may be used as potent source of molluscicides against the snail L. acuminata.     

Mortality response and LC50 values for juvenile and adult crayfish, Procambarus clarkii exposed to Thiodan (insecticide), Treflan, MSMA, Oust (herbicides) and Cutrine-Plus (algicide)

Toxicities of three herbicides (Treflan, MSMA and Oust), an algicide (Cutrine-plus) and an insecticide (Thiodan) to juvenile (3.0-3.4 cm) and adult (9.0-10.0 cm) crayfish, Procambarus clarkii, were determined by 96 h static bioassays. Freshly prepared 0.01% and 1.0% aqueous stock solutions of these pesticides were diluted to desired concentrations. Mortalities were recorded each day up to 96 h. Aged tap-water was used for preparing all test solutions. Per cent mortalities were analyzed for linear regression and LC(50) values were computed by probit analysis. LC(50) values for juvenile P.clarkii in the descending order of toxicity were: 24 ppb Thiodan, 13 ppm Treflan, 101 ppm MSMA, 461 ppm Cutrine-plus, 12,174 ppm Oust; and for adults these values were: 423 ppb Thiodan, 26 ppm Treflan, 1019 ppm MSMA and 2945 ppm Cutrine-plus. No LC(50) values for adult crayfish could be computed for Oust herbicide which caused no mortalities up to 60,000 ppm concentration. Comparing the overall toxicities of these pesticides, Thiodan was the most toxic to all crayfish; followed by Treflan, MSMA, Cutrine-plus and Oust. Oust was more than 1/2 million times less toxic than Thiodan to juvenile crayfish. Published LC(50) values indicate that freshwater crayfish are more tolerant than marine decapods, Crangon septemspinosa and Mysidopsis bahia, to Thiodan insecticide and Treflan herbicide.     

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.     

Comparative study on the susceptibility of freshwater species to copper-based pesticides

Copper compounds have been intentionally introduced into water bodies as aquatic plant herbicides, algicides and molluscicides. Copper-based fertilizers and fungicides have been widely used in agriculture as well. Despite the fact that copper is an essential element for all biota, elevated concentrations of this metal have been shown to affect a variety of aquatic organisms. Nonetheless, comparative studies on the susceptibility of different freshwater species to copper compounds have seldom been performed. This study was conducted to compare toxicity of copper-based pesticides (copper oxychloride, cuprous oxide and copper sulfate) to different freshwater target (Raphidocelis subcapitata, a planktonic alga and Biomphalaria glabrata, a snail) and non-target (Daphnia similis, a planktonic crustacean and Danio rerio, a fish) organisms. Test water parameters were as follows: pH = 7.4 +/- 0.1; hardness 44 +/- 1 mg/l as CaCO3; DO 8-9 mg/l at the beginning and > 4 mg/l at the end; temperature, fish and snails 25 +/- 1 degrees C, Daphnia 20 +/- 2 degrees C, algae 24 +/- 1 degrees C. D. similis (immobilization), 48-h EC50s (95% CLs) ranging from 0.013 (0.011-0.016) to 0.043 (0.033-0.057) mg Cu/l, and R. subcapitata (growth inhibition), 96-h IC50s from 0.071 (0.045-0.099) to 0.137 (0.090-0.174) mg Cu/l, were the most susceptible species. B. glabrata (lethality), 48-h LC50s from 0.179 (0.102-0.270) to 0.854 (0.553-1.457) mg Cu/l, and D. rerio (lethality), 48-h LC50s 0.063 (0.045-0.089), 0.192 (0.133-0.272) and 0.714 (0.494-1.016) mg Cu/l, were less susceptible than Daphnia to copper-based pesticides. Findings from the present study therefore suggest that increased levels of copper in water bodies is likely to adversely affect a variety of aquatic species.     

Toxicity of the mosquito control insecticide phenothrin to three life stages of the grass shrimp (Palaemonetes pugio)

Phenothrin is a synthetic pyrethroid used as a contact insecticide in mosquito control programs. This study compared the toxicity of phenothrin to adult, larval and embryonic grass shrimp (Palaemonetes pugio) and examined oxidative stress responses in adult and larval grass shrimp. The adult 24-h LC50 was 0.341 μg/L (95 % confidence intervals 0.282–0.412) and the 96-h LC50 was 0.161 μg/L (95 % CI 0.128–0.203 μg/L). The larval 24-h LC50 was 0.50 μg/L (95 % CI 0.441–0.568) and the 96-h LC50 was 0.154 μg/L (95 % CI 0.139–0.170 μg/L). In the presence of sediment, the 24-h LC50 was 6.30 μg/L (95 % CI 5.00–7.44 μg/L) for adults and 0.771 μg/L (95 % CI 0.630–0.944) for larvae. The sublethal biomarkers glutathione and lipid peroxidase (LPx) were examined after 96-h phenothrin exposure at five concentrations, and there were no statistically significant differences in these levels in adults or larvae compared to controls. There was a significant downward trend in larval LPx levels. This research confirms that phenothrin is highly toxic to grass shrimp and suggests that both adult and larval grass shrimp are appropriate life stages for risk assessments.     

Investigation of acute toxicity of chlorpyrifos-methyl on Nile tilapia (Oreochromis niloticus L.) larvae

Chlorpyrifos-methyl, a wide-spectrum organophosphorus insecticide and potential toxic pollutant contaminating aquatic ecosystems, was investigated for acute toxicity. Larvae of the freshwater fish Nile tilapia (Oreochromis niloticus L.) were selected for the bioassay experiments. The experiments were repeated three times and the 96 h LC50 was determined for the larvae. The static test method for assessing acute toxicity was used. Water temperature was maintained at 25+/-1 degrees C. In addition, behavioral changes at each chlorpyrifos-methyl concentration were observed for the individual fish. Data obtained from the chlorpyrifos-methyl acute toxicity tests were evaluated using Finney's probit analysis statistical method. The 96 h LC50 value for Nile tilapia larvae was calculated to be 1.57 mg/l.     

Toxicity of the mosquito control insecticide phenothrin to three life stages of the grass shrimp (Palaemonetes pugio)

Phenothrin is a synthetic pyrethroid used as a contact insecticide in mosquito control programs. This study compared the toxicity of phenothrin to adult, larval and embryonic grass shrimp (Palaemonetes pugio) and examined oxidative stress responses in adult and larval grass shrimp. The adult 24-h LC50 was 0.341 μg/L (95 % confidence intervals 0.282-0.412) and the 96-h LC50 was 0.161 μg/L (95 % CI 0.128-0.203 μg/L). The larval 24-h LC50 was 0.50 μg/L (95 % CI 0.441-0.568) and the 96-h LC50 was 0.154 μg/L (95 % CI 0.139-0.170 μg/L). In the presence of sediment, the 24-h LC50 was 6.30 μg/L (95 % CI 5.00-7.44 μg/L) for adults and 0.771 μg/L (95 % CI 0.630-0.944) for larvae. The sublethal biomarkers glutathione and lipid peroxidase (LPx) were examined after 96-h phenothrin exposure at five concentrations, and there were no statistically significant differences in these levels in adults or larvae compared to controls. There was a significant downward trend in larval LPx levels. This research confirms that phenothrin is highly toxic to grass shrimp and suggests that both adult and larval grass shrimp are appropriate life stages for risk assessments.     

Evaluation of copper effects upon Girardia tigrina freshwater planarians based on a set of biomarkers

Copper is a common environmental contaminant, which is particularly toxic to living organisms when in high concentrations. To monitor environmental contamination by Cu2+ and other heavy metals, well characterized bioindicator organisms and standardized assays are needed. As a first step toward this end, we have analysed Cu2+ effects upon Girardia tigrina freshwater planarians, based on the assessment of mobility, regeneration performance, micronucleus (MN) frequency in regenerating animals, and reproductive performance. These four biomarkers provided complementary information on Cu2+ toxicity, teratogenicity, mutagenicity and chronic (>96 h of exposure) effects, respectively. The LC50 was calculated for newborn, adult and regenerating planarians, and values of 12+/-0.02 mg l(-1), 42+/-0.08 mg l(-1), 48+/-0.13 mg l(-1), respectively, were obtained after 96 h of exposure. Mobility, for intact adults, and time of regeneration and MN frequency, for regenerating animals, were significantly affected by Cu2+ concentrations as low as 0.10 mg l(-1). MN assay for regenerating G. tigrina neoblasts showed higher sensitivities than MN assays performed with other bioindicator freshwater organisms, such as moluscs or fish. Chronic exposure effects were clearly evidenced by assessment of reproductive performance, with significant reduction in fecundity and fertility rates upon exposure to Cu2+ concentrations as low as 0.05 mg l(-1). Therefore, G. tigrina can be regarded as a useful bioindicator species for the detection and evaluation of Cu2+ effects upon freshwater invertebrates, allowing insights on the effects of Cu2+ (and possibly other heavy metals) in a freshwater environment.     

Field and laboratory investigations on the effects of road salt (NaCl) on stream macroinvertebrate communities

Field and laboratory experiments were conducted to examine the effects of road salt (NaCI) on stream macroinvertebrates. Field studies investigated leaf litter processing rates and functional feeding group composition at locations upstream and downstream from point source salt inputs in two Michigan, USA streams. Laboratory studies determined the effects of increasing NaCl concentrations on aquatic invertebrate drift, behavior, and survival. Field studies revealed that leaves were processed faster at upstream reference sites than at locations downstream from road salt point source inputs. However, it was sediment loading that resulted in partial or complete burial of leaf packs, that affected invertebrate activity and confounded normal leaf pack colonization. There were no significant differences that could be attributed to road salt between upstream and downstream locations in the diversity and composition of invertebrate functional feeding groups. Laboratory drift and acute exposure studies demonstrated that drift of Gammarus (Amphipoda) may be affected by NaCl at concentrations greater than 5000 mg/l for a 24-h period. This amphipod and two species of limnephilid caddisflies exhibited a dose response to salt treatments with 96-h LC50 values of 7700 and 3526 mg NaCl/l, respectively. Most other invertebrate species and individuals were unaffected by NaCl concentrations up to 10,000 mg/l for 24 and 96 h, respectively.     

Sensitivities of Australian and New Zealand amphipods to copper and zinc in waters and metal-spiked sediments

The sensitivities of eight benthic amphipods, Chaetocorophium cf. lucasi, Corophium colo, Grandidierella japonica, Hyale crassicornis, Hyale longicornis, Melita awa, Melita matilda and Melita plumulosa, to copper and zinc in water-only and whole-sediment toxicity tests were compared. Whole-sediment tests used copper- (1300 mg/kg) and zinc- (4000 mg/kg) spiked sediments after equilibration for sufficient time to produce pore water and overlying water concentrations below the lowest observable effect concentrations of water-only exposures. Survival of adults (after 10 d) and juveniles (after 96 h), and the metal concentrations in the body tissues of adults, were determined at the end of the tests. Two epibenthic amphipods from the genus Melita were the most sensitive species to aqueous copper and zinc, with a 96-h LC50 value of 120 microg Cu/l for both M. awa and M. plumulosa juveniles, and a 96-h LC50 value of 640 microg Zn/l for juveniles of M. plumulosa. Juvenile amphipods (7-d old) were more sensitive than adult amphipods (>30-d old) in both water-only and whole-sediment tests, with adult-LC50/juvenile-LC50 ratios in water-only tests ranging from 1.2 to l.5 for copper and 1 to 1.4 for zinc. All species except C. colo, C. cf. lucasi and M. matilda were sensitive to the copper-spiked sediment, with survival between 14% and 74% of controls. Similarly, all species except C. colo and G. japonica, showed a response to the zinc-spiked sediment (26-81% of control survival). The epibenthic amphipods were more sensitive than the infaunal tube-dwelling amphipods and are recommended as test species.     

In vivo evaluation of three biomarkers in the mosquitofish (Gambusia yucatana) exposed to pesticides

In this study, the acute toxicity and the in vivo effects of commercial chlorpyrifos, carbofuran and glyphosate formulations on cholinesterase (ChE), glutathione S-transferase (GST) and lactate dehydrogenase (LDH) activities of the mosquitofish (Gambusia yucatana) were investigated. In a first phase of the study, head and muscle ChE were characterized with different substrates (acetylthiocholine iodide, s-butyrylthiocholine iodide and propionylthiocholine iodide) and the selective inhibitors eserine hemisulfate, 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide (BW284C51), and N,N'-diisopropylphosphorodiamic acid (iso-OMPA). The results obtained suggest that the enzyme present in both head and muscle of G. yucatana is mainly acetylcholinesterase (AChE). Acute toxicity was evaluated by exposing fish to several concentrations of single pesticides and of a mixture of chlorpyrifos/glyphosate. LC50 values were determined after 96 h of exposure, except in the case of carbofuran for which LC50 was calculated after 24 h since almost all the fish died within this period. LC50 values were 0.085 mg/l for chlorpyrifos, 17.79 mg/l for glyphosate, 0.636 mg/l for carbofuran and 0.011 mg/l for the chlorpyrifos/glyphosate mixture. A Toxic Unit approach was used to compare the toxicity of chlorpyrifos and glyphosate when occurring in a mixture with their toxicities as single compounds. Synergistic effects of chlorpyrifos and glyphosate when present in a mixture were found. At the end of each bioassay (24 h for carbofuran, 96 for the other substances/mixture), effects on biomarkers were analyzed. Muscle LDH activity was not altered by any of the three pesticides tested. Gill GST activity was significantly inhibited (40%) by carbofuran after 24 h of exposure to concentrations equal or higher than 0.06 mg/l. ChE muscle and head activity were significantly inhibited (50% and 30%, respectively) by carbofuran at concentrations equal or higher than 0.25 mg/l. Chlorpyrifos induced a significant inhibition of both muscle and head ChE (80% and 50%, respectively) after 96 h of exposure to concentrations equal or higher than 0.05 mg/l. Carbofuran did not induce significant alterations of fish ChE. The ChE EC50 determined for chlorpyrifos/glyphosate mixture (0.070 mg/l) was higher than the correspondent value calculated for chlorpyrifos alone (0.011 mg/l) suggesting an antagonistic effect of glyphosate on ChE inhibition by chlorpyrifos. ChE activity of G. yucatana seems to be a good biomarker to diagnose the exposure of wild populations of this species exposed to anticholinesterase pesticides.     

Toxicity of the mosquito control pesticide Scourge to adult and larval grass shrimp (Palaemonetes pugio)

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 microg/L (95% confidence interval (CI): 0.46-0.60 microg/L), and for larval shrimp was 0.35 microg/L (95% CI: 0.28-0.42 microg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 microg/L (95% CI: 4.52-6.55 microg/L), and for larval shrimp of 2.15 microg/L (95% CI: 1.35-3.43 microg/L). For Scourge, the 96-h aqueous LC50 for adult shrimp was 2.08 microg/L (95% CI: 1.70-2.54 microg/L), and for larval shrimp was 0.36 microg/L (95% CI: 0.24-0.55 microg/L). The 24-h sediment test yielded an LC50 value of 16.12 microg/L (95% CI: 14.79-17.57 microg/L) for adult shrimp, and 14.16 microg/L (95% CI: 12.21-16.43 microg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge are 0.37 microg/L (adult), 0.07 microg/L (larvae) for the 96-h aqueous test, and 2.90 microg/L (adult), 2.6 microg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge.     

Toxicity of the pyrethroid pesticide fenvalerate to freshwater catfish clarias gariepinus: Lethality,biochemical effects and role of dietary ascorbic acid

Static bioassays were made in the laboratory to determine lethal concentration of the pyrethroid pesticide fenvalerate [(RS)-alpha-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] for the freshwater catfish Clarias gariepinus and effects of sublethal concentrations of the pesticide on some biochemical parameters of the fish. For exposure periods of 24 to 96 h, LC₅₀ values of fenvalerate ranged from 5.83–4.76 μ g/L and 4.24–2.94 μ g/L, respectively for water and acetone soluble fenvalerate. Two sublethal concentrations of fenvalerate were used in the bioassays for biochemical parameters: 2.1 μ g/L for 24 h and 1.4 μ g/L for 96 h exposure, both concentrations representing 50% of LC₅₀ value of acetone soluble fenvalerate for the respective exposure period. Hepatosomatic index, liver glycogen, alkaline phosphatase of liver and ascorbic acid of blood, liver, and kidney decreased while haemoglobin (Hb) %, plasma glucose levels and acid phosphatase level of liver increased after 24 h exposure to 2.1 μ g/L fenvalerate. Longer exposure (96 h) to even a lower concentration (1.4 μ g/L) of fenvalerate resulted in reduction of all the parameters (except Hb %) tested as compared with control. Fish previously fed for 60 days with a diet supplemented by a high level of ascorbic acid (100 mg/100 g diet) could reverse most of the effects caused by 24 h exposure to 2.1 μ g/L fenvalerate. A lower level of ascorbic acid (50 mg/ 100 g diet) supplement could not influence these effects of fenvalerate. Even the higher dose of ascorbic acid supplementation (100 mg/100 g diet) could not relieve the stress parameters, except for Hb% and HSI, when the pesticide was applied at 1.4 μ g/L for a longer time period (96 h).     

Water quality and fish size affect toxicity of endosulfan, an organochlorine pesticide, to rainbow trout

The acute toxicity of endosulfan in juvenile rainbow trout (Oncorhynchus mykiss, 10.61+/-1.69 g) was evaluated in glass aquaria under static conditions. Nominal concentrations of endosulfan in the toxicity test ranged from 1.3 microg l(-1) to 29 microg l(-1). The concentrations of endosulfan that killed 50% of the rainbow trout within 24-h (24-h LC50), 48-h LC50, 72-h LC50, and 96-h LC50 were 19.78, 8.89, 5.28, and 1.75 microg l(-1), respectively. None of the unexposed control fish died, and the first fish died 4 h after exposure to 26.3 microg l(-1) of endosulfan. Survival of fish was significantly increased with increasing fish size and decreased with decreased fish size at the same temperature (p<0.001). Temperature also had a significant effect on survival of fish. Alkalinity at levels above 20 mg l(-1) as CaCO3 significantly increased survival of fish at 19.78 microg l(-1) of endosulfan. Increasing alkalinity from 20 mg l(-1) as CaCO3 to 42 or higher concentrations tested in this study (121 mg l(-1) as CaCO3) significantly increased survival of fish (p<0.01). Total hardness ranging from 55 mg l(-1) as CaCO3 to 126 mg l(-1) as CaCO3 did not affect survival of fish exposed to endosulfan. Endosulfan toxicity was found to be irreversible when fish were exposed to minimum concentrations of endosulfan tested. Histologically, fish gills had lamellar edema, separation of epithelium from lamellae, lamellar fusion, and swelling of the epithelial cells. Melanomacrophage centers were scattered throughout the trunk kidney, head kidney, and spleen. The liver of endosulfan-exposed fish had severe focal necrosis. None of these lesions were seen in unexposed control fish. Results indicate that alkalinity, temperature, and fish size affect endosulfan toxicity of rainbow trout.     

Full life-cycle toxicity assessment using rotifer resting egg production: implications for ecological risk assessment

The majority of standardized toxicity tests incorporate only a fraction of the test organism's life-cycle. However, in natural ecosystems, organisms may be exposed at various times during their life-cycle or throughout their life-cycle. Thus, ecotoxicological data from standardized toxicity tests is of limited ecological relevance. Existing standardized toxicity tests using the freshwater rotifer Brachionus calyciflorus utilize 24-h survival or 48-h asexual reproduction as endpoints, despite evidence that sexual reproduction is more sensitive. A 96-h B. calyciflorus resting egg toxicity test was developed and used to estimate the toxicity of pentachlorophenol (PCP) and copper. Results were compared to a variety of acute and sublethal endpoints for both toxicants. The B. calyciflorus 96-h resting egg production NOEC for PCP of 10 micrograms/l was 20 times lower than the 48-h asexual reproduction no observed effect concentration (NOEC) and 120 times lower than the 24-h acute lethal concentration 50%. The 96-h resting egg production NOEC for copper of 2.8 micrograms/l was 7 times lower than the 48-h asexual reproduction NOEC and nine times lower than the 24-h acute LC50. Resting egg production was a more sensitive indicator of toxicity than several other sublethal endpoints as well. These results indicate that partial life-cycle toxicity tests are not sufficiently sensitive to detect ecologically relevant adverse effects.     

Toxicokinetics,toxicity and lethal body residues of two chlorophenols in the oligochaete worm,Lumbriculus variegatus,in different sediments

Bioavailability, toxicokinetics and toxicity (LC(50)) of water- and sediment-associated 2,4,5-trichlorophenol (2,4,5-TCP) and pentachlorophenol (PCP) were measured in Lumbriculus variegatus Müller in a set of experiments. The critical body residue approach was applied by measuring also the lethal body residues (LBR(50)). Freshwater and three different sediments with various sediment organic carbon (SOC) concentrations were used as exposure media. SOC decreased the bioavailability of both chlorophenols, and the uptake rates decreased by 81% and 91% for 2,4,5-TCP and PCP, respectively, in the sediment with a SOC of 6.9% compared to those in sediment with a SOC of 0.5%. SOC appeared to be an important factor controlling the bioavailability as after the carbon normalisation the difference between the sediments was much smaller. The 96-h LC(50) values for instance for PCP were 145.3 microg/l in freshwater, and 6.8 and 8.1 microg/g dry weight in sediments with SOC concentrations of 0.5% and 2.4%, respectively. The LBR(50) values, were practically the same in freshwater and sediments: between 1.0 and 1.6 and from 0.4 to 0.9 micromol/g wet weight for 2,4,5-TCP and PCP, respectively, demonstrating the usefulness of this method for accurate, and more comparable, measurement of toxicity of chemicals with the same mode of toxic action in varying conditions. L. variegatus expressed a dose-response sediment avoidance behaviour but the PCP tissue concentrations were not affected by this behaviour.