Acute LC50 Research Articles

Free silver ion as the main cause of acute and chronic toxicity of silver nanoparticles to cladocerans.

We investigated the interspecific variation of silver nanoparticle (SNP) sensitivity in common cladocerans (Daphnia magna, D.galeata, and Bosmina longirostris) and the exact cause of both acute and chronic toxicity focusing on the form of silver (NPs and ions). Materials tested were non-surface-coated silver nanocolloids (SNCs) and AgNO3. The results of the acute toxicity tests support the theory that the effects of SNPs on aquatic organisms is mainly due to Ag(+) released from SNPs. Among the three cladocerans, D.galeata was more sensitive to silver (as Ag(+)) than both D.magna and B.longirostris. Moreover, the chronic toxicity of SNCs was also derived from dissolved silver (especially Ag(+)). SNCs (as total silver concentration) showed far lower chronic compared with acute toxicity to daphnids because the amount of dissolved silver decreased in the presence of prey algae. The chronic end-point values (EC10 values for net reproductive rate and the probability of survival to maturation) did not differ largely from acute ones (48-h EC50 obtained from acute toxicity tests and 48-h LC50 estimated by the biotic ligand model) when the values were calculated based on Ag(+) concentration. The α value (concentration at which intrinsic population growth rate is decreased to zero) estimated by a power function model was a reliable parameter for assessing the chronic toxicity of silver.

Developmental toxicity, acute toxicity and mutagenicity testing in freshwater snails Biomphalaria glabrata (Mollusca: Gastropoda) exposed to chromium and water samples

A protocol combining acute toxicity, developmental toxicity and mutagenicity analysis in freshwater snail Biomphalaria glabrata for application in ecotoxicological studies is described. For acute toxicity testing, LC50 and EC50 values were determined; dominant lethal mutations induction was the endpoint for mutagenicity analysis. Reference toxicant potassium dichromate (K2Cr2O7) was used to characterize B. glabrata sensitivity for toxicity and cyclophosphamide to mutagenicity testing purposes. Compared to other relevant freshwater species, B. glabrata showed high sensitivity: the lowest EC50 value was obtained with embryos at veliger stage (5.76mg/L). To assess the model applicability for environmental studies, influent and effluent water samples from a wastewater treatment plant were evaluated. Gastropod sensitivity was assessed in comparison to the standardized bioassay with Daphnia similis exposed to the same water samples. Sampling sites identified as toxic to daphnids were also detected by snails, showing a qualitatively similar sensitivity suggesting that B. glabrata is a suitable test species for freshwater monitoring. Holding procedures and protocols implemented for toxicity and developmental bioassays showed to be in compliance with international standards for intra-laboratory precision. Thereby, we are proposing this system for application in ecotoxicological studies.

Innovative Biocontrolling Method of Dengue Fever Vector, Aedes aegypti (Diptera: Culicidae)

The control of mosquitoes is an important public health concern around the world. The activity of petroleum ether extracts of Dodonaea viscose, Lantana camara and Ruta chaliphenses have been investigated towards larval development of Aedes aegypti. The plant extracts exhibits variable biological activity against Ae. aegypti. The greatest effect was observed with Dodonaea viscose and Lantana camara. They showed acute LC50 (2days) of 126.2, 136.9 and chronic LC50 (10 days) of 64.6 and 68.5 ppm, respectively. Larvae suffered chronic toxicities leading to 97.8% mortality using Dodonaea viscose and 95.6% using Lantana camara. Egg hatchability was significantly reduced in Dodonaea viscose and Lantana camara concentrations. All extracts concentrations of Dodonaea viscose and Lantana camara as well as higher extract concentration of Ruta chaliphenses caused significant high hindrance of subsequent larval development and consequently reduced both pupation and adult mergence. Drastic retardation of development was shown using Dodonaea viscose extracts (17.3, 7.4%) and Lantana camara extracts (19.3, 9.0%) from larval stage managed to pupal and adult stages, when reared in very low concentration (100 ppm) of the extracts. Ruta chaliphense was only more effective at higher concentrations. Hence, application of these extracts to Ae. aegypti mosquito breeding sites can be used as an innovative valuable alternative to the existing synthetic pesticides for the control of Ae. aegypti.

Sublethal effects of the chitin synthesis inhibitor, hexaflumuron, in the cotton mirid bug, Apolygus lucorum (Meyer-Dür)

Hexaflumuron is a type of benzoylphenylurea insecticide which is highly toxic for many insects. Sublethal doses of hexaflumuron have been shown to significantly affect insect growth and development. However, the action mechanism of hexaflumuron is not well understood. In the present study, first instar Apolygus lucorum nymphs were exposed to sublethal doses of hexaflumuron based on the estimated 120h acute LC50 valve of 20.53mg/ml. We found that exposure to sublethal hexaflumuron doses resulted in a significant increase in development time and reduced the weights of fifth instar A. lucorum nymphs. We also measured trehalose, which is a primary blood sugar in insects, and the enzyme trehalase that is involved in energy metabolism. Trehalose content in first instar nymphs significantly increased following hexaflumuron treatment while the glucose content, soluble trehalase activity and expression levels of ALTre-1 mRNA decreased significantly. However, no significant changes in membrane-bound trehalase activity and ALTre-2 mRNA expression were observed. In addition, these decreases or increases could be correlated to increases in treatment time or concentration of hexaflumuron, respectively. The present findings indicated that sublethal doses of hexaflumuron could interfere the normal carbohydrate metabolism by depressing the expression of ALTre-1 in A. lucorum, which provide valuable information on the physiology and molecular mechanisms for the toxicity of hexaflumuron.

Lethal and Sublethal Effects of Imidacloprid, After Chronic Exposure, On the Insect Model Drosophila melanogaster

Neonicotinoids are subjected to vigilance because of environmental contaminations and deleterious effects on bees. Imidacloprid (IMI) is one of the most representative insecticides of this family. At chronic exposure, concentration-effect relationships are non linear. An insect model should allow a better description of this toxicity. We compared the lethal concentration 50% (LC50) of IMI for a Drosophila-field strain, after acute and chronic exposure. Relative to the acute LC50, the chronic LC50 was lowered by a factor of 29 for males (1.3 mM/45 μM), 52 for larvae (157 μM/3 μM) and more than 172 for females (>3.1 mM/18 μM). Chronic exposure also revealed significant lethal and sublethal effects, at concentrations 3-5 orders of magnitude lower than the chronic LC50. Mean mortalities reached 28% (at 3.91 nM) and 27% (at 39.1 nM) for females and males, respectively. Fecundity decreased of 16% at 1.96 nM. Mating increased of 30% at 0.391 nM. The LOEC (lowest observed effect concentration: 0.391 nM) was 46 000 times lower than the chronic LC50 for males; it was 115 000 times lower than the chronic LC50 for females. This study illuminates effects that neonicotinoids can induce at very low concentrations. This is of particular interest for nontarget insects and for insect dependent species.

Environmental and Toxicological Impacts of Glyphosate with Its Formulating Adjuvant

Environmental and toxicological characteristics of formulated pesticides may substantially differ from those of their active ingredients or other components alone. This phenomenon is demonstrated in the case of the herbicide active ingredient glyphosate. Due to its extensive application, this active ingredient was found in surface and ground water samples collected in Bekes Country, Hungary, in the concentration range of 0.54–0.98 ng/ml. The occurrence of glyphosate appeared to be somewhat higher at areas under intensive agriculture, industrial activities and public road services, but the compound was detected at areas under organic (ecological) farming or natural grasslands, indicating environmental mobility. Increased toxicity of the formulated herbicide product Roundup compared to that of glyphosate was observed on the indicator aquatic organism Daphnia magna Straus. Acute LC50 values of Roundup and its formulating adjuvant polyethoxylated tallowamine (POEA) exceeded 20 and 3.1 mg/ml, respectively, while that of glyphosate (as isopropyl salt) was found to be substantially lower (690-900 mg/ml) showing good agreement with literature data. Cytotoxicity of Roundup, POEA and glyphosate has been determined on the neuroectodermal cell line, NE-4C measured both by cell viability test and holographic microscopy. Acute toxicity (LC50) of Roundup, POEA and glyphosate on NE-4C cells was found to be 0.013±0.002%, 0.017±0.009% and 6.46±2.25%, respectively (in equivalents of diluted Roundup solution), corresponding to 0.022±0.003 and 53.1±18.5 mg/ml for POEA and glyphosate, respectively, indicating no statistical difference between Roundup and POEA and 2.5 orders of magnitude difference between these and glyphosate. The same order of cellular toxicity seen in average cell area has been indicated under quantitative cell visualization. The results indicate that toxicity of the formulated herbicide is caused by the formulating agent, but in some parameters toxicological synergy occurs between POEA and glyphosate.

Evaluation of the Genotoxicity of Chlorpyrifos in Common Indus Valley Toad, <i>Bufo stomaticus</i> Using Alkaline Single-Cell Gel Electrophoresis (Comet) Assay

Chlorpyrifos is a commonly used pesticide of organophosphate group, which causes toxicological effects in non-target organisms especially fish and frogs. In the present study, the genotoxicity of sublethal concentrations of chlorpyrifos was observed in the erythrocytes of common Indus valley toad, Bufo stomaticus, using the Alkaline Single-Cell Gel Electrophoresis (Comet) assay. In the first step, acute toxicity of chlorpyrifos was evaluated by exposing the tadpoles to high concentrations of the pesticide. The acute LC50 value of chlorpyrifos, calculated by Trimmed Spearman-Karber (TSK) in static bioassay, was found to be 930.0 μg/L. On the basis of acute LC50 value, the tadpoles were exposed to three sublethal concentrations (155, 233 and 465 μg/L) of chlorpyrifos for 96 h. Blood cells were collected at every 24 h interval and were subjected to the Alkaline Single-Cell Gel Electrophoresis assay. The observed DNA damage was concentration and time-dependent, and those levels of DNA damage in between the tested concentrations and times were significantly different (p Bufo stomaticus.

Chlorpropham and phenisopham: phototransformation and ecotoxicity of carbamates in the aquatic environment

In this study, a comparison of two carbamic pesticides, chlorpropham and phenisopham, was carried out in terms of both photodegradability and ecotoxicity. The photochemical behaviour of the two pesticides was investigated under environmental-like conditions (aqueous media, UVB or solar irradiation). The photochemical kinetic parameters were calculated by irradiating 5 × 10(-5) M solutions (H₂O-CH₃CN, 9 : 1 v/v) using UVB lamps. For chlorpropham and phenisopham similar half-life times (39.0 and 55.0 min) were determined. Irradiation by sunlight leads to longer degradation half-life times (about 3 months), while it is possible to observe the formation of the same photoproducts. The well-known dechlorination reaction to a hydroxyphenylcarbamate was observed for chlorpropham. Phenisopham undergoes photo-Fries reaction to give rearranged products (hydroxybenzamides) and fragmentation products (hydroxyphenylcarbamate and N-ethylaniline). Acute and chronic toxicity tests of pesticides and their photoproducts were performed on organisms from two levels of the freshwater aquatic chain, the anostraca crustacean Thamnocephalus platyurus, the rotifer Brachionus calyciflorus and the alga Pseudokirchneriella subcapitata. The acute results showed that chlorpropham had median lethal concentrations for the crustacean T. platyurus and the rotifer B. calyciflorus of 10.16 and 35.19 mg L(-1), respectively, and phenisopham did not show any acute toxicity as the derivatives up to 10 mg L(-1). The only exception was N-ethylaniline which exhibited an acute LC₅₀ value of 0.46 mg L(-1). Phenisopham was the most toxic in the long term exposure while its five derivatives showed lower chronic potential for rotifers and algae. The same trend was observed for chlorpropham except for rotifers.

Acephate-induced shortening of developmental duration and early adult emergence in a nontarget insect Drosophila melanogaster

Similar to several environmental monitoring studies, the present study used Drosophila melanogaster as a model nontarget organism to explore the interfering effects of an organophosphate (OP) insecticide acephate on insect life cycle parameters. Acephate, a common OP, is readily available in nature from agricultural sources as an environmental contaminant. Along with target pests, nontarget fruit flies also suffer exposure to such environmental chemical. To evaluate the effects of such exposure, initially, acute LC50 of acephate for third instar larvae was investigated and found to be between 14 and 16 μg/ml. This information yielded the following experimental concentrations (0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 μg/ml) of test chemical for evaluation of effect, if any, on the insect model. Results showed that mean larval duration of insect significantly decreased on treatment with acephate, whereas the mean pupal duration remained unaffected. Interestingly the decreasing trend was seen to persist in case of mean adult emergence, where treated flies emerged significantly earlier in comparison to controls. Thus, the study demonstrated that acephate-induced shortening of developmental time and early emergence in Drosophila melanogaster.

Biochemical and genotoxic response of naphthalene to fingerlings of milkfish Chanos chanos

The present study investigated the acute toxicity, sub-lethal toxicity and biochemical response of naphthalene in fingerlings of milkfish Chanos chanos. The 96 h acute toxicity LC50 values for C. chanos exposed to naphthalene was 5.18 μg l(-1). The estimated no observed effect concentration and lowest observed effect concentration values for naphthalene in C. chanos were 0.42 and 0.69 μg l(-1) respectively for 30 days. The estimated maximum allowable toxicant concentration for naphthalene was 0.53 μg l(-1). Biochemical enzyme markers such as lipid peroxidation, catalase, glutathione S transferase and reduced glutathione were measured in gills and liver tissues of C. chanos exposed to sub-lethal concentrations of naphthalene. Fluctuation in lipid peroxidation and catalase level suggests that naphthalene concentrations play a vital role in induction of oxidative stress in fish. Induction of reduced glutathione level and inhibition of glutathione S-transferase level was observed in naphthalene exposed C. chanos suggesting that there may be enhanced oxidative damage due to free radicals. Increasing concentration increases in number of nuclear abnormalities. The formation of micronuclei and binucleated micronuclei induction by naphthalene confirm its genotoxic potential. The highest levels of DNA damage (% tail length) were observed at 1.24 μg l(-1) of naphthalene. The study suggests that biochemical enzymes, nuclear abnormalities and DNA damage index can serve as a biological marker for naphthalene contamination.

Acute toxicity of 31 different nanoparticles to zebrafish (Danio rerio) tested in adulthood and in early life stages – comparative study

At present, nanoparticles are beginning to influence our lives in many ways and understanding the environmental health and safety aspect of nanomaterials has become a crucial issue. The aim of the work was to assess and compare the acute toxicity of 31 different nanomaterials to fish mature individuals Danio rerio with that to fish early life stages on using evaluation of the 48- and 96- hour LC50 values. A further aim was to evaluate teratogenicity of the nanoparticles tested to fish eggs. The nanoparticles tested were: 8 pure metals, 10 metal oxides, 5 other metal compounds and their mixtures, 2 silicon compounds, 3 calcium compounds, and 3 carbon compounds. Using 48-h and 96-h tests of acute toxicity (according to OECD 203), we evaluated mortality data, LC50 values, occurrence of malformations, as well as hatching time. In our study, 6 kinds of nanoparticles – calcium oxide, copper, copper in the form of oxide and CuZnFe4O4, magnesium oxide, and nickel – caused cumulative mortality. Two kinds of nanoparticles – copper and silver – were toxic for fish with LC50 values of approximately 3 mg/L. We did not observe marked differences between the 48-hour and 96-hour acute toxicity LC50 values, yet the possibility to evaluate hatching time in the 96-h acute fish toxicity test seems to be an advantage against that of the 48-hour toxicity.

Relationship Between Bifenthrin Sediment Toxic Units and Benthic Community Metrics in Urban California Streams

The objective of this study was to use ecologically relevant field measurements for determining the relationship between bifenthrin sediment toxic units (TUs) (environmental concentrations/Hyalella acute LC50 value) and 15 benthic metrics in four urban California streams sampled from 2006 to 2011. Data from the following four California streams were used in the analysis: Kirker Creek (2006, 2007), Pleasant Grove Creek (2006, 2007, and 2008), Arcade Creek (2009, 2010, and 2011), and Salinas streams (2009, 2010, and 2011). The results from univariate analysis of benthic metrics versus bifenthrin TU calculations for the four California streams with multiple-year datasets combined by stream showed that there were either nonsignificant relationships or lack of metric data for 93 % of cases. For 7 % of the data (4 cases) where significant relationships were reported between benthic metrics and bifenthrin TUs, these relationships were ecologically meaningful. Three of these significant direct relationships were an expression of tolerant benthic taxa (either % tolerant taxa or tolerance values, which are similar metrics), which would be expected to increase in a stressed environment. These direct significant tolerance relationships were reported for Kirker Creek, Pleasant Grove Creek, and Arcade Creek. The fourth significant relationship was an inverse relationship between taxa richness and bifenthrin TUs for the 3-year Pleasant Grove Creek dataset. In summary, only a small percent of the benthic metric × bifenthrin TU relationships were significant for the four California streams. Therefore, the general summary conclusion from this analysis is that there is no strong case for showing consistent meaningful relationships between various benthic metrics used to characterize the status of benthic communities and bifenthrin TUs for these four California streams.

Acute toxicity, critical body residues, Michaelis–Menten analysis of bioaccumulation, and ionoregulatory disturbance in response to waterborne nickel in four invertebrates: Chironomus riparius, Lymnaea stagnalis, Lumbriculus variegatus and Daphnia pulex

We investigated the bioaccumulation and acute toxicity (48h or 96h) of Ni in four freshwater invertebrate species in two waters with hardness of 40 (soft water) and 140mgL−1 as CaCO3 (hard water). Sensitivity order (most to least) was Lymnaea stagnalis>Daphnia pulex>Lumbriculus variegatus>Chironomus riparius. In all cases water hardness was protective against acute Ni toxicity with LC50 values 3–3.5× higher in the hard water vs. soft water. In addition, higher water hardness significantly reduced Ni bioaccumulation in these organisms suggesting that competition by Ca and Mg for uptake at the biotic ligand may contribute to higher metal resistance. CBR50 values (Critical Body Residues) were less dependent on water chemistry (i.e. more consistent) than LC50 values within and across species by ~2 fold. These data support one of the main advantages of the Tissue Residue Approach (TRA) where tissue concentrations are generally less variable than exposure concentrations with respect to toxicity. Whole body Ni bioaccumulation followed Michaelis–Menten kinetics in all organisms, with greater hardness tending to decrease Bmax with no consistent effect on Kd. Across species, acute Ni LC50 values tended to increase with both Kd and Bmax values — i.e. more sensitive species exhibited higher binding affinity and lower binding capacity for Ni, but there was no correlation with body size. With respect to biotic ligand modeling, log KNiBL values derived from Ni bioaccumulation correlated well with log KNiBL values derived from toxicity testing. Both whole body Na and Mg levels were disturbed, suggesting that disruption of ionoregulatory homeostasis is a mechanism of acute Ni toxicity. In L. stagnalis, Na depletion was a more sensitive endpoint than mortality, however, the opposite was true for the other organisms. This is the first study to show the relationship between Na and Ni.

Sediment pollution in the Elbe estuary and its potential toxicity at different trophic levels

Sediment contamination is one of the most pressing environmental problems in estuaries of industrialized countries and is of special interest to water managers involved in waterway maintenance dredging. In the present study, eight heavy metals (As, Pb, Cd, Cr, Cu, Ni, Hg, and Zn) and 41 organic compounds (pentachlorbenzol (PeCB), hexachlorbenzol (HCB), 7 polychlorinated biphenyls (PCBs), the hexachlorocyclohexanes α-HCH, β-HCH, γ-HCH, 6 dichlorodiphenyltrichloroethane isomers, organochlorine styrene (OCS), octachloronaphthalene (OCN), 15 polycyclic aromatic hydrocarbons (PAHs), and 6 organotin (OT) compounds) were analyzed in surface sediments at 36 sites in the Elbe estuary in 2006. Correlation analysis showed a general decrease in sediment contaminant concentrations from the stations near the port of Hamburg towards the open sea. This decrease was significant (Spearman's rank correlation, p<0.05) with most pollutants. In addition, cluster analysis identified five groups of sites with different sediment contaminant patterns within the Elbe estuary. Worst case toxic risks stemming from sediment-bound organic pollutants were predicted using the Toxic Unit approach, based on estimated pore-water concentrations under equilibrium conditions and acute LC50 values for three standard test organisms of the trophic levels of fish, invertebrates, and algae. The estimated sediment toxicity was significantly higher in the inner part (river-km 630 to 660) compared with the estuarine mouth. Moreover, potential toxicity of organic pollutants estimated for invertebrates and for fish exceeded acute-based effect thresholds at 30 and 24 stations, respectively. Chronic effects for invertebrates are expected at all sites investigated. We conclude that sediment pollution and related potential toxicity in the Elbe estuary may have more influence on the benthos fauna than expected to date.

Hypothermal and hyperthermal acclimation differentially modulate cadmium accumulation and toxicity in the zebrafish

Despite the fact that aquatic organisms are mostly poikilothermic and environmental temperature variations can have considerable impact on chemical toxicity, toxicity studies are mainly performed at the species’ specific standard or optimal temperature. Since the zebrafish is a recommended test species for use in toxicity tests, we investigated the temperature dependence of 96h cadmium accumulation and toxicity in zebrafish acclimated to 18, 26, 30 or 34°C. Zebrafish showed high cadmium tolerance with acute 96h LC50 values of 121.5, 102.4, 124.6 and 126.7μM at 18, 26, 30 and 34°C respectively. Differences in cadmium toxicity at the different temperatures were small and toxicity did not increase with increasing temperature as is often suggested. We did however observe an interesting concentration dependent crossover pattern in which the temperature dependence at the highest exposure concentrations was exactly opposite to the pattern at the lower concentrations. At the highest concentrations the following order of toxicity was observed: 26°C>18°C>30°C>34°C. Possibly, either the warm acclimation provoked a general stress response which protected organisms against future severe stress situations, or resulted in specific defence mechanisms which also provided protection against cadmium exposure. Although at 18°C cadmium accumulation decreased more than would be expected based on the metabolic rate, cadmium toxicity was not proportionately decreased. This increased cadmium sensitivity in the cold was likely due to the combined effect of low temperature and cadmium exposure on sodium loss. This study shows that the temperature dependence of cadmium toxicity results from the combination of altered cadmium accumulation and sensitivity. Inclusion of the temperature effect in the calculation of environmental quality standards may have to be considered to ensure that more sensitive species are also protected at suboptimal temperatures.

Assessment of lethal and sublethal effects by spinetoram on Bombus terrestris

Nowadays the worldwide use of bumblebees as pollinator of several horticultural crops has resulted that they fulfil both an ecological and economical role. Consequently, exposure to pesticides is not unlikely. In general naturalyte insecticides as spinosyns are a major widely applied class because they are more selective than conventional pesticides, however, toxicity of spinosyns A and D (spinosad) has been reported on honeybees and bumblebees. In the field bumblebees can be exposed to pesticides by contact and by the consumption of contaminated food. In this project we assessed the potential hazards of a novel naturalyte insecticide spinetoram consisting of spinosyn J and L. Three different experiments were conducted in the laboratory wherein workers of the bumblebee Bombus terrestris were exposed to different concentrations starting form the maximum field recommended concentration (MFRC) and then different dilutions (1/10-1/10,000). First, via direct contact with wet and dry residues of spinetoram severe worker loss was observed; the respective LC50-72h values were 50 μg/l and 21 μg/l. Typically, intoxicated bees showed symptoms of tremors and paralysis. Second, oral exposure via contaminated sugar water in micro-colonies demonstrated that the MFRC caused 100% worker loss after 4 weeks, whereas this was only 54% with 1/10 of the MFRC after 11 weeks. For worker mortality the calculated acute (72 h) and chronic (11 weeks) LC50 values were 21 μg/l and 2.5 μg/l, respectively. At 1/100 of the MFRC no lethal effects were observed. Next to lethal effects, sublethal effects were evaluated. In the nests exposed to the MFRC and to 1/10 of the MFRC the numbers of drones produced were significantly (P<0.05) reduced when compared with the control group (57  4 drones). However at lower concentrations starting at 1/100 of the MFRC no sublethal effects were seen on the reproduction. Third, we assessed for potential sublethal effects by spinetoram (1/100-1/10,000 of the MFRC) towards foraging behaviour. Here we used the bioassay as developed to assess foraging effects by neonicotinoids (Mommaerts et al., 2010). Here no change in the behaviour of the workers was seen. In conclusion, the highest concentrations of spinetoram (MFRC and 1/10 of the MFRC) caused lethal mortality of exposed workers and this resulted in a loss of progeny. But when compared with spinosad, spinetoram is safer. Interestingly, no negative effects towards foraging behaviour were scored in the laboratory foraging bioassay. However, before making final conclusions about the compatibility of this compound with B. terrestris side-effects should be evaluated under more realistic field conditions with queen-right colonies.

Influence of existing site contamination on sensitivity of Rhinella fernandezae (Anura, Bufonidae) tadpoles to Lorsban®48E formulation of chlorpyrifos

Effects of the widely employed insecticide Lorsban(®)48E formulation of chlorpyrifos (CPF) was studied on Rhinella fernandezae tadpoles, a native species of Argentina, Brazil, Paraguay and Uruguay, under the hypothesis of a differential response of organisms from ponds of two sites with different degree of anthropogenic disturbance: S1 an unpolluted area, and S2 area with high degree of antropogenic disturbance. To collect a representative sample of the genotypic variability of each population, small portions from six clutches were taken randomly from each site when the period of clutching was finished. Embryos and tadpoles were maintained under controlled laboratory conditions. Toxicity tests were conducted under standardized conditions to study acute and chronic lethal (mortality) and sublethal effects (behavior, growth, and abnormalities), within the range of concentrations of 0.010 to 5 mg/L. Chronic effects were assessed with organisms from one of the demes (S1). CPF showed high toxicity on the tadpoles, inducing lethal and sublethal effects at 96 h exposure within a narrow range of concentrations from 0.066 to 0.887 mg/L. Results indicate that R. fernandezae tadpoles are below the 30th percentile in the species sensitivity distribution of existing data. The acute LC50, NOEC, and LOEC values were 0.151, 0.066, and 0.133 mg/L for S1, and 0.293, 0.177, and 0.266 mg/L for S2, respectively. Considering all acute end-points evaluated, the effects of CPF showed no significant differences (p = 0.3484) between the studied populations. CPF has more severe effects at higher concentrations than at higher times of exposure. Contaminants in S2 do not seem to induce local adaptation. Sublethal effects data and measured environmental concentrations indicate potential risk for populations inhabiting agroecosystems.

P-glycoprotein (P-gp) in the monogonont rotifer, Brachionus koreanus: Molecular characterization and expression in response to pharmaceuticals

P-glycoprotein is involved in the efflux of diverse chemicals, including hydrophobic compounds and pharmaceuticals as a first line of defense. Here, we firstly identified and characterized the P-gp (Bk-P-gp) gene in the rotifer, Brachionus koreanus. Bk-P-gp was highly conserved in genomic organization compared to the human P-gp gene. Messenger RNA expression of Bk-P-gp revealed that it would be regulated by temperature change via 14 heat shock response elements in its promoter region. Bk-P-gp showed a high similarity of motifs/domains compared to those of vertebrates in its amino acid sequences. To check whether Bk-P-gp would be inducible, we exposed B. koreanus to six pharmaceuticals including antibiotics for use in aquaculture and observed dose- and time-dependency on transcripts of Bk-P-gp for 24h over a wide range of concentration. Efflux assay and membrane topology supported its conserved function for transportation of a number of chemicals upon cellular damage. To reveal the effect of pharmaceuticals on the rotifer, we measured survival rate and population growth rate after exposure to six pharmaceuticals. In an acute toxicity test, both NOEC and LC50 values for all the pharmaceuticals were high for 24h. ATP, CBZ, SMX, and TMP markedly inhibited the population growth of B. koreanus after exposure up to 100mg/L for 10 days. In this paper, we demonstrated that various pharmaceuticals can retard growth rate with up-regulation of the P-gp gene as a cellular defense system. This finding provides a better understanding of molecular mechanisms involved in pharmaceutical-mediated cellular damage in B. koreanus.

Proactive Aquatic Ecotoxicological Assessment of Room-Temperature Ionic Liquids

Aquatic environments are being contaminated with a myriad of anthropogenic chemicals, a problem likely to continue due to both unintentional and intentional releases. To protect valuable natural resources, novel chemicals should be shown to be environmentally safe prior to use and potential release into the environment. Such proactive assessment is currently being applied to room-temperature ionic liquids (ILs). Because most ILs are water-soluble, their effects are likely to manifest in aquatic ecosystems. Information on the impacts of ILs on numerous aquatic organisms, focused primarily on acute LC50 and EC50 endpoints, is now available, and trends in toxicity are emerging. Cation structure tends to influence IL toxicity more so than anion structure, and within a cation class, the length of alkyl chain substituents is positively correlated with toxicity. While the effects of ILs on several aquatic organisms have been studied, the challenge for aquatic toxicology is now to predict the effects of ILs in complex natural environments that often include diverse mixtures of organisms, abiotic conditions, and additional stressors. To make robust predictions about ILs will require coupling of ecologically realistic laboratory and field experiments with standard toxicity bioassays and models. Such assessments would likely discourage the development of especially toxic ILs while shifting focus to those that are more environmentally benign. Understanding the broader ecological effects of emerging chemicals, incorporating that information into predictive models, and conveying the conclusions to those who develop, regulate, and use those chemicals, should help avoid future environmental degradation. Keywords: Aquatic toxicology, ecotoxicology, bioassay, mesocosm, interdisciplinary collaboration, Aquatic environments, abiotic conditions, oxygen depletion, thermal extremes, anthropogenic, flow alterations, non-native species, quantitative structure-property relationships (QSPR), physiologically-based pharmacokinetic (PBPK) models, biotic interactions, polychlorinated biphenyl (PCB), ecological risk

Sublethal concentrations of waterborne copper induce cellular stress and cell death in zebrafish embryos and larvae

Copper is an essential ion that forms part of the active sites of many proteins. At the same time, an excess of this metal produces free radicals that are toxic for cells and organisms. Fish have been used extensively to study the effects of metals, including copper, present in food or the environment. It has been shown that different metals induce different adaptive responses in adult fish. However, until now, scant information has been available about the responses that are induced by waterborne copper during early life stages of fish. Here, acute toxicity tests and LC50 curves have been generated for zebrafish larvae exposed to dissolved copper sulphate at different concentrations and for different treatment times. We determined that the larvae incorporate and accumulate copper present in the medium in a concentration-dependent manner, resulting in changes in gene expression. Using a transgenic fish line that expresses enhanced green fluorescent protein (EGFP) under the hsp70 promoter, we monitored tissue-specific stress responses to waterborne copper by following expression of the reporter. Furthermore, TUNEL assays revealed which tissues are more susceptible to cell death after exposure to copper. Our results establish a framework for the analysis of whole-organism management of excess external copper in developing aquatic animals.