Genotoxicological and physiological effects of glyphosate and its metabolite, aminomethylphosphonic acid, on the freshwater invertebrate Lymnaea stagnalis

Aminomethylphosphonic acid (AMPA) is the main metabolite in the degradation of glyphosate, a broad-spectrum herbicide, and it is more toxic and persistent in the environment than the glyphosate itself. Owing to their extensive use, both chemicals pose a serious risk to aquatic ecosystems. Here, we explored the genotoxicological and physiological effects of glyphosate, AMPA, and the mixed solution in the proportion 1:1 in Lymnaea stagnalis, a freshwater gastropod snail. To do this, adult individuals were exposed to increasing nominal concentrations (0.0125, 0.025, 0.050, 0.100, 0.250, 0.500 µg/mL) in all three treatments once a week for four weeks. The genotoxicological effects were estimated as genomic damage, as defined by the number of micronuclei and nuclear buds observed in hemocytes, while the physiological effects were estimated as the effects on somatic growth and egg production. Exposure to glyphosate, AMPA, and the mixed solution caused genomic damage, as measured in increased frequency of micronuclei and nuclear buds and in adverse effects on somatic growth and egg production. Our findings suggest the need for more research into the harmful and synergistic effects of glyphosate and AMPA and of pesticides and their metabolites in general.

Accumulation and histopathological effects of cadmium on the great pond snail Lymnaea stagnalis Linnaeus, 1758 (Gastropoda: Pulmonata)

Toxic metal ions are an important stress factor for a living organism. In this study, accumulation and histopathological changes in foot, mantle and hepatopancreas of great pond snail, Lymnaea stagnalis exposed to different Cadmium (Cd) concentrations in laboratory conditions were investigated. Great pond snails were exposed to sublethal concentrations of 7.92 μg/L, 15.85 μg/L, 31.7 μg/L and 63.4 μg/L Cd. At the end of 7, 14, 21 and 28 days, snail foot, mantle and hepatopancreas were removed to investigate and determine Cd accumulation and histopathological alterations by light microscopy. Cd levels determined in hepatopancreas were higher than those measured from the foot and the mantle of studied specimens. A positive correlation was found between Cd levels in tissues and exposure days. As a result of Cd application, we observed increase in the number of mucosit, pigment and protein cells and desquamation in the epithelium in the foot, atrophy in muscle fibrils, connective tissue cells and increase in the lipid vacuoles in the mantle, increase in the lipid vacuoles and amoebocyte in the hepatopancreas. The severity of the alterations resulting from Cd increased with dose-time dependent.

Preliminary Study of Multiple Stress Response Reactions in the Pond Snail Lymnaea stagnalis Exposed to Trace Metals and a Thiocarbamate Fungicide at Environmentally Relevant Concentrations

Gastropod mollusks have achieved an eminent importance as biological indicators of environmental quality. In the present study, we applied a multibiomarker approach to evaluate its applicability for the pond snail Lymnaea stagnalis, exposed to common industrial and agricultural pollutants at environmentally relevant concentrations. The snails were exposed to copper (Cu²⁺, 10 µg L^-1), zinc (Zn²⁺, 130 µg L^-1), cadmium (Cd²⁺, 15 µg L^-1), or the thiocarbamate fungicide "Tattoo" (91 µg L^-1) during 14 days. Metal treatment and exposure to "Tattoo" caused variable patterns of increase or decrease of metal levels in the digestive gland, with a clear accumulation of only Cd and Zn after respective metal exposure. Treatment with Cu and "Tattoo" caused an increase of cytochrome P450-related EROD activity. Glutathione S-transferase was inhibited by exposure to Cu, Zn, and "Tattoo." Treatment with the "Tattoo" led to an inhibition of cholinesterase activity, whereas Cu and Cd increased its activity. Caspase-3 activity was enhanced by up to 3.3 times in all treatments. A nearly uniform inhibitory effect for oxidative stress response parameters was observed in all kinds of exposure, revealing an inhibition of superoxide dismutase (Mn-SOD) activity, a depression of glutathione (GSH and GSSG) and of protein carbonyl levels. Pollutant-specific effects were observed for the catalase activity, superoxide anion production, and lipid peroxidation levels. Due to the high response sensitivity of Lymnaea stagnalis to chemical impacts, we suggest our study as a contribution for biomarker studies with this species under field conditions.

Acute and Chronic Toxicity of Cobalt to Freshwater Organisms: Using a Species Sensitivity Distribution Approach to Establish International Water Quality Standards

Water quality standards for cobalt (Co) have not been developed for the European Union or United States. The objective of the present study was to produce freshwater Co toxicity data that could be used by both the European Union and the United States to develop appropriate regulatory standards (i.e., environmental quality standards or predicted-no-effect concentrations in Europe and ambient water quality criteria or state water quality standards in the United States). Eleven species, including algae, an aquatic plant, and several invertebrate and fish species, were used in the performance of acute and chronic Co toxicity tests. Acute median lethal or median effective concentration (LC50 or EC50) values ranged from 90.1 µg Co/L for duckweed (Lemna minor) to 157 000 µg Co/L for midges (Chironomus tentans). Chronic 10% effect concentration (EC10) values ranged from 4.9 µg Co/L for duckweed to 2170 µg Co/L for rainbow trout (Oncorhynchus mykiss). Chronic 20% effect concentration (EC20) values ranged from 11.1 µg Co/L for water flea (Ceriodaphnia dubia) to 2495 µg Co/L for O. mykiss. Results indicated that invertebrate and algae/plant species are more sensitive to chronic Co exposures than fish. Acute-to-chronic ratios (derived as acute LC50s divided by chronic EC20s) were lowest for juvenile O. mykiss (0.6) and highest for the snail Lymnaea stagnalis (2670). Following the European-based approach and using EC10 values, species sensitivity distributions (SSDs) were developed and a median hazardous concentration for 5% of the organisms of 1.80 µg Co/L was derived. Chronic EC20 values were used, also in an SSD approach, to derive a US Environmental Protection Agency-style final chronic value of 7.13 µg Co/L. Environ Toxicol Chem 2020;39:799-811. © 2020 SETAC.

Accumulation of polybrominated diphenyl ethers and microbiome response in the great pond snail Lymnaea stagnalis with exposure to nylon (polyamide) microplastics

Microplastics attract widespread attention, including for their potential to transport toxic chemicals in the form of plasticisers and associated hydrophobic organic chemicals, such as polybrominated diphenyl ethers (PBDEs). The aims of this study were to investigate how nylon (polyamide) microplastics may affect PBDE accumulation in snails, and the acute effects of nylon particles and PBDEs on survival, weight change and inherent microbiome diversity and community composition of the pond snail Lymnaea stagnalis. Snails were exposed for 96 h to BDEs-47, 99, 100 and 153 in the presence and absence of 1% w/w nylon microplastics in quartz sand sediment. No mortality was observed over the exposure period. Snails not exposed to microplastics lost significantly more weight compared to those exposed to microplastics. Increasing PBDE concentration in the sediment resulted in an increased PBDE body burden in the snails, however microplastics did not significantly influence total PBDE uptake. Based on individual congeners, uptake of BDE 47 by snails was significantly reduced in the presence of microplastics. The diversity and composition of the snail microbiome was not significantly altered by the presence of PBDEs nor by the microplastics, singly or combined. Significant effects on a few individual operational taxonomic units (OTUs) occurred when comparing the highest PBDE concentration with the control treatment, but in the absence of microplastics only. Overall within these acute experiments, only subtle effects on weight loss and slight microbiome alterations occurred. These results therefore highlight that L. stagnalis are resilient to acute exposures to microplastics and PBDEs, and that microplastics are unlikely to influence HOC accumulation or the microbiome of this species over short timescales.

Physiological and pharmacological characterization of a molluscan neuronal efflux transporter; evidence for age-related transporter impairment

Plasma membrane efflux transporters play crucial roles in the removal and release of both harmful and beneficial substances from the interior of cells and tissue types in virtually every extant species. They contribute to the clearance of a broad spectrum of exogenous and endogenous toxicants and harmful metabolites, including the reactive lipid aldehyde byproducts of lipid peroxidation that are a hallmark of cellular ageing. Here, we tested whether declining transporter functionality may contribute to functional decline in a snail model of neuronal ageing. Through measuring the removal of 5(6)-carboxyfluorescein, a known substrate for membrane efflux transporters, we provide, for the first time, physiological evidence for the existence of probenecid-, MK571- and glutathione-sensitive efflux transporters in (gastropod) neurons and demonstrate that their functionality declines with age. Our data support the idea that waning cellular detoxification capacity might be a significant factor in the escalation of (lipo-)toxicity observed in neuronal ageing.

The Effect of Persistent Heavy Metal Exposure on Some Antioxidant Enzyme Activities and Lipid Peroxidation of the Freshwater snail, Lymnaea natalensis

This study investigated the effect of persistent heavy metal exposure on the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) of the freshwater snail, Lymnaea natalensis. Malondialdehyde (MDA) levels were also measured as an index of lipid peroxidation. The snails were exposed to cadmium, copper, lead and mercury for a total of 28 days at 0.1 mg/L, 0.1 mg/L, 0.2 mg/L and 0.1 mg/L respectively. Samples were collected at 1, 7, 14, 21 and 28 days intervals. Analysis of SOD showed significant initial increases in enzyme activity following exposure to copper, lead and mercury, while cadmium exposures caused increases from Day 14 onwards. Copper, cadmium and lead caused significant initial increases in CAT activity and mercury caused an increase only on Day 28. Copper caused a significant increase in GPx activity on Day 28 while MDA levels diminished significantly at Days 7-28. Similarly, cadmium caused significant increases of GPx activity on Day 28 whereas MDA levels were significantly reduced. Lead also caused a significant increase in GPx activity on Days 14-28 whilst no significant changes occurred in MDA levels. Mercury exposures caused significant increases in GPx activity on Days 7 and 21, whilst MDA levels were significantly reduced on Days 7 and 14. These findings suggest that persistent exposure of snails to heavy metals induces the antioxidant defence system, and decreases lipid peroxidation.

The allelochemical tannic acid affects the locomotion and feeding behaviour of the pond snail, Lymnaea stagnalis, by inhibiting peripheral pathways

(1) The effect of tannic acid (TA), a dominant component of plant allelochemicals, was investigated on the locomotion and feeding of the pond snail, Lymnaea stagnalis. The effect of TA on the neuronal background underlying feeding activity was also analysed. (2) TA affected the spontaneous locomotion and of juvenile snails in a concentration-dependent way. Low (10 μM) TA concentration resulted in an increased (sliding or swimming) activity compared to the control; meanwhile, high (100 μM) TA concentration inhibited the locomotion of the animals. (3) Low (10 μM) TA concentration increased the frequency of sucrose-evoked feeding of intact animals, whereas high (100 μM) TA concentration resulted in significantly longer feeding latency and decreased feeding rate. The feeding changes proved to be partially irreversible, since after 48 h maintained in clear water, the animals tested in 100 μM TA previously still showed lower feeding rate in sucrose. (4) Electrophysiological experiments on semi-intact preparations showed that application of 100 μM TA to the lip area inhibited the fictive feeding pattern of central neurons, the cellular response to sucrose. (5) On isolated CNS preparation, 100 μM TA applied in the bathing solution, however, failed to inhibit the activation of the central feeding (CPG) interneurons following application of extracellular dopamine. Our results suggest that TA affects both afferent and efferent peripheral functions in Lymnaea. TA reduces feeding activity by primarily blocking feeding sensory pathways, and its negative effect on locomotion may imply sensory pathways and/or ciliary activity.

Species-Specific (Hyalella azteca and Lymnea stagnalis) Dietary Accumulation of Gold Nano-particles Associated with Periphyton

Ecological effects of gold nano-particles (AuNP) are examined due to growing use in consumer and industrial materials. This study investigated uptake and movement of AuNPs through an aquatic food chain. Simple (single-species) and diverse (multi-species) periphyton communities were exposed to AuNP (0, 100, 500 µg L^-1 treatments). AuNP quickly aggregated and precipitated from the water column, suggesting it is an insignificant route of AuNP exposure even at elevated concentrations. Gold was measured in 100 and 500 µg L^-1 periphyton treatments. Gold accumulation was similar between periphyton treatments, suggesting physical processes were important for AuNP basal accumulation. Hyalella azteca and Lymnea stagnalis whole body tissue analysis indicated gold accumulation may be attributed to different feeding mechanisms, general versus selective grazing, respectively. Results suggest trophic transfer of AuNP is organism specific and aggregation properties of AuNP are important when considering fate of nano-particles in the environment and movement through aquatic food webs.

The Use of Mechanistic Population Models in Metal Risk Assessment: Combined Effects of Copper and Food Source on Lymnaea stagnalis Populations

Environmental risk assessment (ERA) of chemicals aims to protect populations, communities, and ecosystems. Population models are considered more frequent in ERA because they can bridge the gap between the individual and the population level. Lymnaea stagnalis (the great pond snail) is an organism that is particularly sensitive to various metals, including copper (Cu). In addition, the sensitivity of this species to Cu differs between food sources. The first goal of the present study was to investigate whether we could explain the variability in sensitivity between food sources (lettuce and fish flakes) at the individual level with a dynamic energy budget (DEB) model. By adapting an existing DEB model and calibrating it with Cu toxicity data, thereby combining information from 3 studies and 2 endpoints (growth and reproduction), we put forward inhibition of energy assimilation as the most plausible physiological mode of action (PMoA) of Cu. Furthermore, the variation in Cu sensitivity between both food sources was considerably lower at the PMoA level than at the individual level. Higher Cu sensitivity at individual level under conditions of lower food quality or availability appears to emerge from first DEB principles when inhibition of assimilation is the PMoA. This supports the idea that DEB explained Cu sensitivity variation between food sources. Our second goal was to investigate whether this food source effect propagated to the population level. By incorporating DEB in an individual-based model (IBM), population-level effects were predicted. Based on our simulations, the food source effect was still present at the population level, albeit less prominently. Finally, we compared predicted population-level effect concentration, x% (ECx) values with individual-level ECx values for different studies. Using the DEB-IBM, the range of effect concentrations decreased significantly: at the individual level, the difference in chronic EC10 values between studies was a factor of 70 (1.13-78 µg dissolved Cu/L), whereas at the population level the difference was a factor of 15 (2.9-44.6 µg dissolved Cu/L). To improve interstudy comparability, a bioavailability correction for differences in water chemistry was performed with a biotic ligand model. This further decreased the variation, down to a factor of 7.4. Applying the population model in combination with a bioavailability correction thus significantly decreased the variability of chronic effect concentrations of Cu for L. stagnalis. Overall, the results of the present study illustrate the potential usefulness of transitioning to a more modeling-based environmental risk assessment. Environ Toxicol Chem 2019;00:1-16. © 2019 SETAC.

Parental diet affects embryogenesis of the great pond snail (Lymnaea stagnalis) exposed to cadmium, pyraclostrobin, and tributyltin

Diet quality has a strong impact on life-history traits, but it is not usually considered as a factor in toxicity tests. The purpose of the present study was to evaluate how diets differing in nutritional content affect sensitivity to cadmium, pyraclostrobin, and tributyltin in Lymnaea stagnalis offspring. Three groups were fed a different diet each: lettuce, high-caloric pellets, or a combination of both. Snails fed pellets and both diets had similar growth; however, snails fed lettuce showed lower growth until the fourth month. Egg masses were collected from adult snails fed each diet and exposed to 3 concentrations of either cadmium, pyraclostrobin, or tributyltin. We quantified time to hatch, hatching success, and the developmental stages of embryos. We measured fecundity in adults and total lipids, carbohydrates, and proteins in adult snails and egg masses. Adult snails fed different diets produced a similar number of egg masses, but the number of eggs per egg mass in snails fed pellets was lower than for snails fed the other 2 diets. We found that adult snails fed pellets had a higher lipid content compared to snails fed the other 2 diets. However, egg masses from parental snails fed pellets did not hatch, including those from the controls. Interestingly, egg masses exposed to the lowest concentration of tributyltin had low hatching success. These observations on offspring performance suggest that there are important diet effects that can strongly influence responses that could be diet- and chemical-dependent. Environ Toxicol Chem 2018;37:2428-2438. © 2018 SETAC.

The effects of fluoxetine on attachment and righting behaviours in marine (Gibbula unbilicalis) and freshwater (Lymnea stagnalis) gastropods

Recent studies have highlighted that antidepressants such as the selective serotonin reuptake inhibitors (SSRIs) entering aquatic systems through wastewater discharges might impact organisms at environmentally relevant concentrations. In this study, two snail species (Gibbula unbilicalis and Lymnea stagnalis) representing the marine and freshwater environments were exposed to a large range of fluoxetine concentrations (1 ng L^-1-1 mg L^-1) and two distinct behaviours (foot detachment and righting time) were recorded. Fluoxetine significantly caused foot detachment only at the higher of the concentrations (1 mg L^-1) in both species during the course of this short term 1.5 h and 4 h exposures. In this study, lowest observed effect concentrations (LOECs) for foot detachment fell repeatedly within the range for other gastropod snails exposed to fluoxetine. Fluoxetine effected righting times in a concentration dependant manner but only significantly within G. unbilicalis in the highest concentration. Reviewing existing data on the effects of antidepressants on a range of endpoints in gastropod molluscs reveals wide variability of results. The importance of publishing 'negative' and/or non-dramatic results to aid risk assessment are discussed along with the variability between antidepressants, model species, experimental designs and endpoints.

Diet quality affects chemical tolerance in the freshwater snail Lymnaea stagnalis

Organisms generally select high-quality diets to obtain maximal energy while devoting the least amount of time and energy. Diets, however, can vary in natural systems. In ecotoxicological testing, the effect of diet type on organismal responses to toxicants has not been explored despite the potential for dietary effects to influence toxicological endpoints. We first evaluated diet quality using growth rate and sensitivity to the fungicide pyraclostrobin of Lymnaea stagnalis fed lettuce (common laboratory diet), turtle pellets (high nutrient composition), and a combination diet of both food items. We also measured the macronutrient content of snails raised on the multiple diets to determine how diet may have impacted energy allocation patterns. Finally, we evaluated whether snails discernibly preferred a particular diet. Snails fed high-nutrient and combination diets grew larger overall than snails fed a lettuce-only diet. Snails fed the high-nutrient and combination diets, both juvenile and adult, were significantly more tolerant to pyraclostrobin than snails fed lettuce. When measured for macronutrient content, snails raised on high-nutrient and combination diets had significantly higher carbohydrate content than snails fed lettuce. Despite the strong effects of diet type, snails did not exhibit a clear diet choice in preference trials. Dietary composition clearly influences growth rate, sensitivity, and macronutrient content of Lymnaea stagnalis. These results suggest that the nutritional environment has potentially strong impacts on toxicant sensitivity. Environ Toxicol Chem 2018;37:1158-1167. © 2017 SETAC.

Combining Factors That Individually Enhance Memory in Lymnaea

When applied individually, thermal stress (1 hour at 30 °C) and (-)epicatechin (a flavonol found in green tea, e.g.) each enhance long-term memory formation following operant conditioning of Lymnaea aerial respiratory behavior. Snails demonstrate enhanced long-term memory formation when trained in epicatechin-treated pond water or when placed in 30 °C pond water for 1 hour, 1 hour prior to training in pond water. We ask here whether the combined application of epicatechin + thermal stress enhances long-term memory retention length beyond the maximal lengths of the individual factors alone. We report that the applied combination of epicatechin + thermal stress has a synergistic memory-enhancing effect; that is, when the two are applied in combination, memory persists longer than when either is applied alone. We then ask whether quercetin, a heat shock protein blocker, will affect the memory enhancement produced by the combined treatment of thermal stress and epicatechin. We report that quercetin does not decrease the memory enhancement of epicatechin, but it does decrease the memory enhancement by thermal stress; and it also decreases the memory persistence of snails exposed to both treatments in combination.

Studies on acute and chronic toxicity of cadmium to freshwater snail Lymnaea acuminata (Lamarck) with special reference to behavioral and hematological changes

Molluscs have long been regarded as promising bioindicator and biomonitoring subjects for heavy metals as molluscs are highly tolerant to heavy metals and exhibit high accumulation in their body. In spite of several previous studies about the impact of cadmium on molluscs, little information exists in literatures concerning the toxic effects of cadmium on Lymnaea acuminata, especially pertaining to behavioral and hematological changes as these are considered effective bioindicators and biomonitoring variables for detecting heavy metals in polluted water bodies. In the present study, the median lethal concentrations of cadmium chloride to snail, Lymnaea acuminata, were estimated to be 9.66, 7.69, 6.26, and 5.54 mg/L at 24, 48, 72, and 96 h, respectively. For behavioral studies, variable test concentrations of cadmium from 0.00 to 10 mg/L were used. The clumping tendency, crawling activity, and touch reflex in the exposed snails were gradually decreased with higher concentrations at 72 and 96 h. For measuring the hemocyte numbers in the circulating hemolymph of snail during chronic cadmium exposure, two sublethal doses of cadmium (10 and 20% 96-h LC₅₀-0.55 and 1.11 mg/L, respectively) were used. A significant variation (p < 0.05) from the control at all exposure times (7, 14, 21, and 28 days) was recorded at 1.11 mg/L concentration. The total count of circulating hemocytes was significantly reduced (p < 0.05) compared to the controls at both concentrations of cadmium exposure at all time periods except 14 and 21 days exposure at 0.55 mg/L where values were non-significantly increased. In comparison between two sublethal doses, blood cells were significantly (p < 0.05) lowered at 1.11 mg/L cadmium treatment. Considering the behavioral and hematological data, it seems possible to forecast the physiological state of snails in cadmium-contaminated water bodies and these findings can be used in determining the safe disposal level of cadmium in aquatic ecosystem.

No effect of insect repellents on the behaviour of Lymnaea stagnalis at environmentally relevant concentrations

Insect repellents are widely applied to various materials and to both human and animal skin to deter mosquitoes and ticks. The most common deterrent compounds applied are DEET, EBAAP and icaridin (picaridin, Bayrepel). Due to their extensive application, these repellents are frequently detected in surface waters in considerable concentrations. As these compounds are designed to alter invertebrates' behaviour rather than to intoxicate them, we hypothesised that insect repellents have the potential to modify the natural behaviour of non-target invertebrates in natural freshwater bodies. To test this, we used a well-established laboratory assay designed to quantify the odour-mediated foraging behaviour of freshwater gastropods and the great pond snail Lymnaea stagnalis (Linnaeus, 1758) as a model organism to test for potential deterrent effects of insect repellents on aquatic snails. Using a wide concentration range from the picogramme per litre to microgramme per litre range (and by far exceeding the range of concentrations reported from natural waters), we found no evidence for a deterrent effect of either of the three repellents on foraging L. stagnalis. Our data and other recent studies give no indication for undesirable behavioural alterations by common insect repellents in surface waters.

Effect of progesterone and its synthetic analogs on reproduction and embryonic development of a freshwater invertebrate model

The presence of a mixture of progestogens at ng/L concentration levels in surface waters is a worldwide problem. Only a few studies explore the effect of progestogen treatment in a mixture as opposed to individual chemicals to shed light on how non-target species respond to these contaminants. In the present study, we used an invertebrate model species, Lymnaea stagnalis, exposed to a mixture of four progestogens (progesterone, levonorgestrel, drospirenone, and gestodene) in 10ng/L concentration for 3 weeks. Data at both physiological and cellular/molecular level were analyzed using the ELISA technique, stereomicroscopy combined with time lapse software, and capillary microsampling combined with mass spectrometry. The treatment of adult Lymnaeas caused reduced egg production, and low quality egg mass on the first week, compared to the control. Starting from the second week, the egg production, and the quality of egg mass were similar in both groups. At the end of the third week, the egg production and the vitellogenin-like protein content of the hepatopancreas were significantly elevated in the treated group. At the cellular level, accelerated cell proliferation was observed during early embryogenesis in the treated group. The investigation of metabolomic changes resulted significantly elevated hexose utilization in the single-cell zygote cytoplasm, and elevated adenylate energy charge in the egg albumen. These changes suggested that treated snails provided more hexose in the eggs in order to improve offspring viability. Our study contributes to the knowledge of physiological effect of equi-concentration progestogen mixture at environmentally relevant dose on non-target aquatic species.

Silver nanoparticles alter learning and memory formation in an aquatic organism, Lymnaea stagnalis

We tested the effect of silver nanoparticles (AgNPs) on the ability of the pond snail, Lymnaea stagnalis, to learn and form long-term memory (LTM) following operant conditioning of aerial respiration. We hypothesized that the AgNPs would act as a stressor and prevent learning and LTM formation. We tested snails exposed for either 72 h or only during training and testing for memory (i.e. 0.5 h) and found no difference between those treatments. We found that at a low concentration of AgNPs (5 μg/L) neither learning and nor memory formation were altered. When we increased the concentration of AgNPs (10 μg/L) we found that memory formation was enhanced. Finally, at a higher concentration (50 μg/L) memory formation was blocked. To determine if the disassociation of Ag⁺ from the AgNPs caused the effects on memory we performed similar experiments with AgNO₃ and found similar concentration-dependent results. Finally, we found that snails perceive the AgNPs differently from Ag+ as there was context specific memory. That is, snails trained in AgNPs did not show memory when tested in Ag⁺ and vice-versa. We believe that changes in memory formation may be a more sensitive determination of AgNPs on aquatic organisms than the determination of a LC₅₀.

Immune responses in the aquatic gastropod Lymnaea stagnalis under short-term exposure to pharmaceuticals of concern for immune systems: Diclofenac, cyclophosphamide and cyclosporine A

This is a pioneering study in the ecotoxicological assessment of immunotoxic effects of the three selected drugs of concern to a freshwater gastropod species. Lymnaea stagnalis was exposed in the laboratory for 3 days to three drugs used for immune systems: diclofenac (nonsteroidal anti-inflammatory drug), cyclophosphamide (anti-cancer immunosuppressive drug) or cyclosporine A (anti-xenograft immunosuppressive drug). Exposure ranges included environmental realistic (1-10μgL^-1) and therapeutic concentrations (100-1000μgL^-1). At the end of exposure times, the immune parameters of individual snails were measured: hemocyte density and viability, hemocyte phagocytosis capacity and hemocyte-related oxidative activities (basal and NADPH-oxidase stimulated with zymosan particles). Diclofenac and cyclosporine A induced immune responses, although the effects were not strong. No immunosuppression was observed. Such subtle immunomodulations bring further interrogations regarding their long-term immunotoxicity and possible resulting tradeoffs with life-history traits. On the other hand, the prodrug cyclophosphamide did not induce significant immune responses. Since metabolism pathways differ greatly between vertebrates and invertebrates, this study also suggests that relevant vertebrate metabolites should be included in the immunotoxicity assessment of pharmaceuticals in non-target invertebrate species. Finally, the possible interactive effects of these pharmaceuticals sharing similar modes of action or effects features should also be explored.

Transgenerational endpoints provide increased sensitivity and insight into multigenerational responses of Lymnaea stagnalis exposed to cadmium

Ecotoxicology provides data to inform environmental management. Many testing protocols do not consider offspring fitness and toxicant sensitivity. Cadmium (Cd) is a well-studied and ubiquitous toxicant but little is known about the effects on offspring of exposed parents (transgenerational effects). This study had three objectives: to identify endpoints related to offspring performance; to determine whether parental effects would manifest as a change in Cd tolerance in offspring and how parental exposure duration influenced the manifestation of parental effects. Adult snails were exposed to Cd 0, 25, 50, 100, 200 and 400 μg Cd/L for eight weeks. There were effects on adult endpoints (e.g., growth, reproduction) but only at the highest concentrations (>100 μg/L). Alternatively, we observed significant transgenerational effects at all Cd concentrations. Surprisingly, we found increased Cd tolerance in hatchlings from all parental Cd exposure concentrations even though eggs and hatchlings were in Cd-free conditions for 6 weeks. Explicit consideration of offspring performance adds value to current toxicity testing protocols. Parental exposure duration has important implications for offspring effects and that contaminant concentrations that are not directly toxic to parents can cause transgenerational changes in resistance that have significant implications for toxicity testing and adaptive responses.

Structure-dependent effects of amyloid-β on long-term memory in Lymnaea stagnalis

Amyloid‐β (Aβ) peptides are implicated in the causation of memory loss, neuronal impairment, and neurodegeneration in Alzheimer's disease. Our recent work revealed that Aβ 1–42 and Aβ 25–35 inhibit long‐term memory (LTM) recall in Lymnaea stagnalis (pond snail) in the absence of cell death. Here, we report the characterization of the active species prepared under different conditions, describe which Aβ species is present in brain tissue during the behavioral recall time point and relate the sequence and structure of the oligomeric species to the resulting neuronal properties and effect on LTM. Our results suggest that oligomers are the key toxic Aβ1–42 structures, which likely affect LTM through synaptic plasticity pathways, and that Aβ 1–42 and Aβ 25–35 cannot be used as interchangeable peptides.

Embryonic exposure to model naphthenic acids delays growth and hatching in the pond snail Lymnaea stagnalis

Naphthenic acids (NAs), a class of structurally diverse carboxylic acids with often complex ring structures and large aliphatic tail groups, are important by-products of many petrochemical processes including the oil sands mining activity of Northern Alberta. While it is evident that NAs have both acute and chronic harmful effects on many organisms, many aspects of their toxicity remain to be clarified. Particularly, while substantive data sets have been collected on NA toxicity in aquatic prokaryote and vertebrate model systems, to date, nothing is known about the toxic effects of these compounds on the embryonic development of aquatic invertebrate taxa, including freshwater mollusks. This study examines under laboratory conditions the toxicity of NAs extracted from oil sands process water (OSPW) and the low-molecular weight model NAs cyclohexylsuccinic acid (CHSA), cyclohexanebutyric acid (CHBA), and 4-tert-butylcyclohexane carboxylic acid (4-TBCA) on embryonic development of the snail Lymnaea stagnalis, a common freshwater gastropod with a broad Palearctic distribution. Evidence is provided for concentration-dependent teratogenic effects of both OSPW-derived and model NAs with remarkably similar nominal threshold concentrations between 15 and 20 mg/L and 28d EC₅₀ of 31 mg/L. In addition, the data provide evidence for substantial toxicokinetic differences between CHSA, CHBA and 4-TBCA. Together, our study introduces Lymnaea stagnalis embryonic development as an effective model to assay NA-toxicity and identifies molecular architecture as a potentially important toxicokinetic parameter in the toxicity of low-molecular weight NA in embryonic development of aquatic gastropods.

Sub-lethal cadmium exposure increases phytochelatin concentrations in the aquatic snail Lymnaea stagnalis

Phytochelatins are metal-binding metabolites found in almost all plant species and some animal groups, including nematodes and annelids, where they can play an important role in detoxifying metals such as cadmium. Species from several other taxa contain a phytochelatin synthase (PCS) gene orthologue, including molluscs, indicating they may have the potential to synthesize phytochelatins. However, the presence of a gene alone does not demonstrate that it plays a functional role in metal detoxification. In the present study, we show that the aquatic snail Lymnaea stagnalis produced both penta- and heptapeptide phytochelatins (i.e. phytochelatin-2 and phytochelatin-3), and their levels increased in response to sub-lethal levels of cadmium.

Peptides from puff adder Bitis arietans venom, novel inhibitors of nicotinic acetylcholine receptors

Phospholipase A₂ (named bitanarin) possessing capability to block nicotinic acetylcholine receptors (nAChRs) was isolated earlier (Vulfius et al., 2011) from puff adder Bitis arietans venom. Further studies indicated that low molecular weight fractions of puff adder venom inhibit nAChRs as well. In this paper, we report on isolation from this venom and characterization of three novel peptides called baptides 1, 2 and 3 that reversibly block nAChRs. To isolate the peptides, the venom of B. arietans was fractionated by gel-filtration and reversed phase chromatography. The amino acid sequences of peptides were established by de novo sequencing using MALDI mass spectrometry. Baptide 1 comprised 7, baptides 2 and 3-10 amino acid residues, the latter being acetylated at the N-terminus. This is the first indication for the presence of such post-translational modification in snake venom proteins. None of the peptides contain cysteine residues. For biological activity studies the peptides were prepared by solid phase peptide synthesis. Baptide 3 and 2 blocked acetylcholine-elicited currents in isolated Lymnaea stagnalis neurons with IC₅₀ of about 50 μM and 250 μM, respectively. In addition baptide 2 blocked acetylcholine-induced currents in muscle nAChR heterologously expressed in Xenopus oocytes with IC₅₀ of about 3 μM. The peptides did not compete with radioactive α-bungarotoxin for binding to Torpedo and α7 nAChRs at concentration up to 200 μM that suggests non-competitive mode of inhibition. Calcium imaging studies on α7 and muscle nAChRs heterologously expressed in mouse neuroblastoma Neuro2a cells showed that on α7 receptor baptide 2 inhibited acetylcholine-induced increasing intracellular calcium concentration with IC₅₀ of 20.6 ± 3.93 μM. On both α7 and muscle nAChRs the suppression of maximal response to acetylcholine by about 50% was observed at baptide 2 concentration of 25 μM, the value being close to IC₅₀ on α7 nAChR. These data are in accord with non-competitive inhibition as follows from α-bungarotoxin binding experiments. The described peptides are the shortest peptides without disulfide bridges isolated from animal venom and capable to inhibit nAChR by non-competitive way.

Accumulation and detoxication responses of the gastropod Lymnaea stagnalis to single and combined exposures to natural (cyanobacteria) and anthropogenic (the herbicide RoundUp(®) Flash) stressors

Freshwater gastropods are increasingly exposed to multiple stressors in the field such as the herbicide glyphosate in Roundup formulations and cyanobacterial blooms either producing or not producing microcystins (MCs), potentially leading to interacting effects. Here, the responses of Lymnaea stagnalis to a 21-day exposure to non-MC or MC-producing (33μgL(-1)) Planktothrix agardhii alone or in combination with the commercial formulation RoundUp(®) Flash at a concentration of 1μgL(-1) glyphosate, followed by 14days of depuration, were studied via i) accumulation of free and bound MCs in tissues, and ii) activities of anti-oxidant (catalase CAT) and biotransformation (glutathione-S-transferase GST) enzymes. During the intoxication, the cyanobacterial exposure induced an early increase of CAT activity, independently of the MC content, probably related to the production of secondary cyanobacterial metabolites. The GST activity was induced by RoundUp(®) Flash alone or in combination with non MC-producing cyanobacteria, but was inhibited by MC-producing cyanobacteria with or without RoundUp(®) Flash. Moreover, MC accumulation in L. stagnalis was 3.2 times increased when snails were concomitantly exposed to MC-producing cyanobacteria with RoundUp(®), suggesting interacting effects of MCs on biotransformation processes. The potent inhibition of detoxication systems by MCs and RoundUp(®) Flash was reversible during the depuration, during which CAT and GST activities were significantly higher in snails previously exposed to MC-producing cyanobacteria with or without RoundUp(®) Flash than in other conditions, probably related to the oxidative stress caused by accumulated MCs remaining in tissues.

Characterization and response of antioxidant systems in the tissues of the freshwater pond snail (Lymnaea stagnalis) during acute copper exposure

The response of enzymatic (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX and glutathione reductase, GR) and non-enzymatic responses (glutathione, GSH, oxidized glutathione, GSSG and GSH/GSSG) against acute Cu toxicity (2-90μg/mL for 48h) in different tissues of Lymnaea stagnalis were measured. Incubation conditions for enzymatic activity measurements were optimized for L. stagnalis tissues. Three examined tissues, the hepatopancreas, the foot muscle and the mantle, exhibited variable responses in antioxidant parameters as a function of Cu concentrations. The most responsive antioxidant enzymes were GPX and CAT while GR appeared less sensitive. In general antioxidant enzymes at higher Cu concentrations though GSH levels at lower Cu concentrations exhibited the greatest changes in hepatopancreas and foot muscle, respectively. All antioxidant enzymes except GR increased after exposure to the highest Cu concentration in mantle. Total and reduced GSH increased in hepatopancreas but decreased with GSH/GSSG ratios at all Cu concentrations in foot muscle. The present results show that antioxidants respond to acute Cu exposure at concentrations as low as 2μg Cu/L in adult L. stagnalis with variable responses in different tissues. Antioxidants both including enzymatic and non-enzymatic parameters may account, in part, for the high tolerance to acute metal exposure observed in adult L. stagnalis and could form suited biomarkers to evaluate the metal exposure and toxicity in aquatic environment even at relatively low level short term exposure.

The effect of pH on chronic aquatic nickel toxicity is dependent on the pH itself: Extending the chronic nickel bioavailability models

The environmental quality standard for Ni in the European Commission's Water Framework Directive is bioavailability based. Although some of the available chronic Ni bioavailability models are validated only for pH ≤ 8.2, a considerable fraction of European surface waters has a pH > 8.2. Therefore, the authors investigated the effect of a change in pH from 8.2 to 8.7 on chronic Ni toxicity in 3 invertebrate (Daphnia magna, Lymnaea stagnalis, and Brachionus calyciflorus) and 2 plant species (Pseudokirchneriella subcapitata and Lemna minor). Nickel toxicity was almost always significantly higher at pH 8.7 than at pH 8.2. To test whether the existing chronic Ni bioavailability models developed for pH ≤ 8.2 can be used at higher pH levels, Ni toxicity at pH 8.7 was predicted based on Ni toxicity observed at pH 8.2. This resulted in a consistent underestimation of toxicity. The results suggest that the effect of pH on Ni(2+) toxicity is dependent on the pH itself: the slope of the pH effect is steeper above than below pH 8.2 for species for which a species-specific bioavailability model exists. Therefore, the existing chronic Ni bioavailability models were modified to allow predictions of chronic Ni toxicity to invertebrates and plants in the pH range of 8.2 to 8.7 by applying a pH slope (SpH ) dependent on the pH of the target water. These modified Ni bioavailability models resulted in more accurate predictions of Ni toxicity to all 5 species (within 2-fold error), without the bias observed using the bioavailability models developed for pH ≤ 8.2. The results of the present study can decrease the uncertainty in implementing the bioavailability-based environmental quality standard under the Water Framework Directive for high-pH regions in Europe.

Pesticide Mixture Toxicity in Surface Water Extracts in Snails (Lymnaea stagnalis) by an in Vitro Acetylcholinesterase Inhibition Assay and Metabolomics

Many chemicals in use end up in the aquatic environment. The toxicity of water samples can be tested with bioassays, but a metabolomic approach has the advantage that multiple end points can be measured simultaneously and the affected metabolic pathways can be revealed. A current challenge in metabolomics is the study of mixture effects. This study aims at investigating the toxicity of an environmental extract and its most abundant chemicals identified by target chemical analysis of >100 organic micropollutants and effect-directed analysis (EDA) using the acetylcholinesterase (AChE) bioassay and metabolomics. Surface water from an agricultural area was sampled with a large volume solid phase extraction (LVSPE) device using three cartridges containing neutral, anionic, and cationic sorbents able to trap several pollutants classes like pharmaceuticals, pesticides, PAHs, PCBs, and perfluorinated surfactants. Targeted chemical analysis and AChE bioassay were performed on the cartridge extracts. The extract of the neutral sorbent cartridge contained most of the targeted chemicals, mainly imidacloprid, thiacloprid, and pirimicarb, and was the most potent AChE inhibitor. Using an EDA approach, other AChE inhibiting candidates were identified in the neutral extract, such as carbendazim and esprocarb. Additionally, a metabolomics experiment on the central nervous system (CNS) of the freshwater snail Lymnaea stagnalis was conducted. The snails were exposed to the extract, the three most abundant chemicals individually, and a mixture of these. The extract disturbed more metabolic pathways than the three most abundant chemicals individually, indicating the contribution of other chemicals. Most pathways perturbed by the extract exposure overlapped with those related to exposure to neonicotinoids, like the polyamine metabolism involved in CNS injuries. Metabolomics for the straightforward comparison between a complex mixture and single compound toxicity is still challenging but, compared to traditional biotesting, is a promising tool due to its increased sensitivity.

[ENGAGEMENT OF SEROTONIN-MODULATING ANTICONSOLIDATION PROTEIN IN REGULATION OF EMBRYOGENESIS OF LYMNEAE STAGNALIS AND LEWIS SARCOMA IN HYBRID MICE Fl C57B2/6 X DBA]

The article concerns study of the effects of a novel serotonin-modulating anticonsolidation protein (SMAP) being in a linear relationship with serotonin level, on embryogenesis of Lymneae stagnalis and Lewis sarcoma in hybrid mice Fl C57B2/6 X DBA. Inhibition of embryogenesis of Lymneae stagnalis on the stage of four blastomers and late blastula, lack of changes on the stage of trochofora and acceleration of metamorphosis under the effects of SMAP in a dose-dependent manner was observed. Short-term retardation (during the first 10 days) of development of Lewis sarcoma in mice and survival of 25% of transferring animals under high doses of SMAP was revealed. Cytostatic activity for high doses of SMAP and their effects on the duration of single phases of the cell cycle is proposed.

Energetic endpoints provide early indicators of life history effects in a freshwater gastropod exposed to the fungicide, pyraclostrobin

Organismal energetics provide important insights into the effects of environmental toxicants. We aimed to determine the effects of pyraclostrobin on Lymnaea stagnalis by examining energy allocation patterns and life history traits. Juvenile snails exposed to pyraclostrobin decreased feeding rate and increased apparent avoidance behaviors at environmentally relevant concentrations. In adults, we found that sublethal concentrations of pyraclostrobin did not affect reproductive output, however, there were significant effects on developmental endpoints with longer time to hatch and decreased hatching success in pyraclostrobin-exposed egg masses. Further, there were apparent differences in developmental effects depending on whether mothers were also exposed to pyraclostrobin suggesting this chemical can exert intergenerational effects. Pyraclostrobin also affected protein and carbohydrate content of eggs in mothers that were exposed to pyraclostrobin. Significant effects on macronutrient content of eggs occurred at lower concentrations than effects on gross endpoints such as hatching success and time to hatch suggesting potential value for these endpoints as early indicators of ecologically relevant stress. These results provide important insight into the effects of a common fungicide on important endpoints for organismal energetics and life history.

Dietary Uptake of Cu Sorbed to Hydrous Iron Oxide is Linked to Cellular Toxicity and Feeding Inhibition in a Benthic Grazer

Whereas feeding inhibition caused by exposure to contaminants has been extensively documented, the underlying mechanism(s) are less well understood. For this study, the behavior of several key feeding processes, including ingestion rate and assimilation efficiency, that affect the dietary uptake of Cu were evaluated in the benthic grazer Lymnaea stagnalis following 4-5 h exposures to Cu adsorbed to synthetic hydrous ferric oxide (Cu-HFO). The particles were mixed with a cultured alga to create algal mats with Cu exposures spanning nearly 3 orders of magnitude at variable or constant Fe concentrations, thereby allowing first order and interactive effects of Cu and Fe to be evaluated. Results showed that Cu influx rates and ingestion rates decreased as Cu exposures of the algal mat mixture exceeded 10(4) nmol/g. Ingestion rate appeared to exert primary control on the Cu influx rate. Lysosomal destabilization rates increased directly with Cu influx rates. At the highest Cu exposure where the incidence of lysosomal membrane damage was greatest (51%), the ingestion rate was suppressed 80%. The findings suggested that feeding inhibition was a stress response emanating from excessive uptake of dietary Cu and cellular toxicity.

Metabolomics to Explore Imidacloprid-Induced Toxicity in the Central Nervous System of the Freshwater Snail Lymnaea stagnalis

Modern toxicology is seeking new testing methods to better understand toxicological effects. One of the most concerning chemicals is the neonicotinoid pesticide imidacloprid. Although imidacloprid is designed to target insects, recent studies have shown adverse effects on nontarget species. Metabolomics was applied to investigate imidacloprid-induced sublethal toxicity in the central nervous system of the freshwater snail Lymnaea stagnalis. The snails (n = 10 snails) were exposed for 10 days to increasing imidacloprid concentrations (0.1, 1, 10, and 100 μg/L). The comparison between control and exposure groups highlighted the involvement and perturbation of many biological pathways. The levels of several metabolites belonging to different metabolite classes were significantly changed by imidacloprid exposure. A change in the amino acids and nucleotide metabolites like tryptophan, proline, phenylalanine, uridine, and guanosine was found. Many fatty acids were down-regulated, and the levels of the polyamines, spermidine and putrescine, were found to be increased which is an indication of neuron cell injury. A turnover increase between choline and acetylcholine led us to hypothesize an increase in cholinergic gene expression to overcome imidacloprid binding to the nicotinic acetylcholine receptors. Metabolomics revealed imidacloprid induced metabolic changes at low and environmentally relevant concentration in a nontarget species and generated a novel mechanistic hypothesis.

Genetic variation of Lymnaea stagnalis tolerance to copper: A test of selection hypotheses and its relevance for ecological risk assessment

The use of standardized monospecific testing to assess the ecological risk of chemicals implicitly relies on the strong assumption that intraspecific variation in sensitivity is negligible or irrelevant in this context. In this study, we investigated genetic variation in copper sensitivity of the freshwater snail Lymnaea stagnalis, using lineages stemming from eight natural populations or strains found to be genetically differentiated at neutral markers. Copper-induced mortality varied widely among populations, as did the estimated daily death rate and time to 50% mortality (LT50). Population genetic divergence in copper sensitivity was compared to neutral differentiation using the QST-FST approach. No evidence for homogenizing selection could be detected. This result demonstrates that species-level extrapolations from single population studies are highly unreliable. The study provides a simple example of how evolutionary principles could be incorporated into ecotoxicity testing in order to refine ecological risk assessment.

Molluscicidal activity of Solanum elaeagnifolium seeds against Galba truncatula intermediate host of Fasciola hepatica: Identification of β-solamarine

CONTEXT

The persistence of fascioliasis in many developing countries urges the search for simple, cheap, and effective substances. In this view, plants provide interesting molluscicidal activities thanks to the secondary metabolites they produce. The genus Solanum is known for its potent effect on vector snails.

OBJECTIVE

The molluscicidal activity of Solanum elaeagnifolium Cav. (Solanaceae) seeds against Galba truncatula Müll. (Lymnaeidae), intermediate host of Fasciola hepatica L. (Fasciolidae), was evaluated.

MATERIALS AND METHODS

Solanum elaeagnifolium seeds were powdered and successively extracted using n-hexane, methylene chloride, acetone, and methanol, for 20 h each. After filtration, solvents were evaporated. An acid-base treatment was conducted on seed methanolic extract to isolate total alkaloids and β-solamarine. Total saponins fraction was obtained after successive macerations and evaporations. The molluscicidal activity was evaluated by subjecting snails, in groups of 10, for 48 h to 500 mL of extracts, fractions, and pure product aqueous solutions, each containing amounts, ranging from 1 to 50 mg of plant material in 5 mg increments.

RESULTS

The methanolic extract of seeds, β-solamarine isolated for the first time from this plant and total saponins fraction showed very potent activities on snails, giving respective median lethal concentrations (LC50) of 1.18, 0.49, and 0.94 mg/L. Total alkaloids fraction obtained from the methanolic extract was less active giving an LC50 value of 14.67 mg/L.

DISCUSSION AND CONCLUSION

This study emphasizes that glycoalkaloids and saponins of Solanum elaeagnifolium are potent molluscicidal agents. Seed methanolic extract, β-solamarine, and total saponins fraction may be used as molluscicides.

Neonicotinoid insecticides inhibit cholinergic neurotransmission in a molluscan (Lymnaea stagnalis) nervous system

Neonicotinoids are highly potent and selective systemic insecticides, but their widespread use also has a growing impact on non-target animals and contaminates the environment, including surface waters. We tested the neonicotinoid insecticides commercially available in Hungary (acetamiprid, Mospilan; imidacloprid, Kohinor; thiamethoxam, Actara; clothianidin, Apacs; thiacloprid, Calypso) on cholinergic synapses that exist between the VD4 and RPeD1 neurons in the central nervous system of the pond snail Lymnaea stagnalis. In the concentration range used (0.01-1 mg/ml), neither chemical acted as an acetylcholine (ACh) agonist; instead, both displayed antagonist activity, inhibiting the cholinergic excitatory components of the VD4-RPeD1 connection. Thiacloprid (0.01 mg/ml) blocked almost 90% of excitatory postsynaptic potentials (EPSPs), while the less effective thiamethoxam (0.1 mg/ml) reduced the synaptic responses by about 15%. The ACh-evoked membrane responses of the RPeD1 neuron were similarly inhibited by the neonicotinoids, confirming that the same ACh receptor (AChR) target was involved. We conclude that neonicotinoids act on nicotinergic acetylcholine receptors (nAChRs) in the snail CNS. This has been established previously in the insect CNS; however, our data indicate differences in the background mechanism or the nAChR binding site in the snail. Here, we provide the first results concerning neonicotinoid-related toxic effects on the neuronal connections in the molluscan nervous system. Aquatic animals, including molluscs, are at direct risk while facing contaminated surface waters, and snails may provide a suitable model for further studies of the behavioral/neuronal consequences of intoxication by neonicotinoids.

Ecotoxicity of single-wall carbon nanotubes to freshwater snail Lymnaea luteola L.: Impacts on oxidative stress and genotoxicity

Mammalian studies have raised concerns about the toxicity of carbon nanotubes, but there is very limited data on ecogenotoxicity to aquatic organisms. The aim of this study was to determine eco-geno toxic effects of single walled carbon nanotubes (SWCNTs) in fresh water snail, Lymnea luteola (L. luteola). A static test system was used to expose L. luteola to a freshwater control, 0.05, 0.15, 0.30, 0.46 mg/L SWCNTs for up to 4 days. SWCNTs changed a significant reduction in glutathione, glutathione-S-transferase, and glutathione peroxidase with in hepatopancreas of L. luteola. Lipid peroxidation (LPO) and catalase showed dose- and time-dependent and statistically significant increase in hepatopancreas during SWCNTs exposure compared with control. However, a significant (p < 0.01) induction in DNA damage was observed by the comet assay in hepatopancreas cells treated with SWCNTs. These results demonstrate that SWCNTs are ecogenotoxic to freshwater snail L. luteola. The oxidative stress and comet assay can successfully be used as sensitive tools of aquatic pollution biomonitoring.

Oxidative stress-mediated apoptosis and genotoxicity induced by silver nanoparticles in freshwater snail Lymnea luteola L

Silver is one of the most toxic metals to freshwater aquatic organisms. Limited efforts have been made to study apoptosis and genotoxic potential of silver nanoparticles (AgNPs) in freshwater snail Lymnea luteola L. (L. luteola). Therefore, the present investigation was aimed to study the induction of apoptosis and DNA damage by AgNPs in L. luteola. AgNPs showed molluscicidal activity against L. luteola and three concentrations of AgNPs were selected, the concentration I (4 μg/l), concentration II (12 μg/l), and the concentration III (24 μg/l). Induction of oxidative stress in snail hemolymph was observed by a decrease in reduced glutathione (GSH) and glutathione S-transferase (GST) levels at different concentration of AgNPs, and on the other hand, malondialdehyde (MDA) levels increased at lower concentrations but decreased in higher concentration of AgNPs. Catalase (CAT) activity was also decreased at lower concentrations and increased in higher concentration of AgNPs. Flow cytometry data showed that AgNPs exposed hemocyte cells promote apoptotic and necrotic-mediated cell death when AgNPs concentrations were 12 and 24 μg/l compared to control. DNA damage scores increased with the exposure levels of AgNPs, and dose- and time-dependent effects were observed. A significant positive correlation was observed among reactive oxygen species (ROS) generation, apoptosis, and DNA damage. The study suggests that ROS may be involved in inducing apoptosis and DNA damage in the AgNPs exposed hemocyte cells of L. luteola. This study demonstrates that AgNPs is lethal to freshwater snail L. luteola.

Bioaccumulation and toxicity of CuO nanoparticles by a freshwater invertebrate after waterborne and dietborne exposures

The incidental ingestion of engineered nanoparticles (NPs) can be an important route of uptake for aquatic organisms. Yet, knowledge of dietary bioavailability and toxicity of NPs is scarce. Here we used isotopically modified copper oxide ((65)CuO) NPs to characterize the processes governing their bioaccumulation in a freshwater snail after waterborne and dietborne exposures. Lymnaea stagnalis efficiently accumulated (65)Cu after aqueous and dietary exposures to (65)CuO NPs. Cu assimilation efficiency and feeding rates averaged 83% and 0.61 g g(-1) d(-1) at low exposure concentrations (<100 nmol g(-1)), and declined by nearly 50% above this concentration. We estimated that 80-90% of the bioaccumulated (65)Cu concentration in L. stagnalis originated from the (65)CuO NPs, suggesting that dissolution had a negligible influence on Cu uptake from the NPs under our experimental conditions. The physiological loss of (65)Cu incorporated into tissues after exposures to (65)CuO NPs was rapid over the first days of depuration and not detectable thereafter. As a result, large Cu body concentrations are expected in L. stagnalis after exposure to CuO NPs. To the degree that there is a link between bioaccumulation and toxicity, dietborne exposures to CuO NPs are likely to elicit adverse effects more readily than waterborne exposures.

Environmental versus anthropogenic effects on population adaptive divergence in the freshwater snail Lymnaea stagnalis

Repeated pesticide contaminations of lentic freshwater systems located within agricultural landscapes may affect population evolution in non-target organisms, especially in species with a fully aquatic life cycle and low dispersal ability. The issue of evolutionary impact of pollutants is therefore conceptually important for ecotoxicologists. The impact of historical exposure to pesticides on genetic divergence was investigated in the freshwater gastropod Lymnaea stagnalis, using a set of 14 populations from contrasted environments in terms of pesticide and other anthropogenic pressures. The hypothesis of population adaptive divergence was tested on 11 life-history traits, using Q(ST)-F(ST) comparisons. Despite strong neutral differentiation (mean F(ST) = 0.291), five adult traits or parameters were found to be under divergent selection. Conversely, two early expressed traits showed a pattern consistent with uniform selection or trait canalization, and four adult traits appeared to evolve neutrally. Divergent selection patterns were mostly consistent with a habitat effect, opposing pond to ditch and channel populations. Comparatively, pesticide and other human pressures had little correspondence with evolutionary patterns, despite hatching rate impairment associated with global anthropogenic pressure. Globally, analyses revealed high genetic variation both at neutral markers and fitness-related traits in a species used as model in ecotoxicology, providing empirical support for the need to account for genetic and evolutionary components of population response in ecological risk assessment.

Effects of single, binary and tertiary combinations with Jatropha gossypifolia and other plant-derived molluscicides on reproduction and survival of the snail Lymnaea acuminata

The effect of sub-lethal doses (40% and 80% of LC(50)/24h) of plant derived molluscicides of singly, binary (1:1) and tertiary (1:1:1) combinations of the Rutin, Ellagic acid, Betulin and taraxerol with J. gossypifolia latex, leaf and stem bark powder extracts and their active component on the reproduction of freshwater snail Lymnaea acuminata have been studied. It was observed that the J. gossypifolia latex, stem bark, individual leaf and their combinations with other plant derived active molluscicidal components caused a significant reduction in fecundity, hatchability and survival of young snails. It is believed that sub-lethal exposure of these molluscicides on snail reproduction is a complex process involving more than one factor in reducing the reproductive capacity.

Laboratory evaluation of molluscicidal & mosquito larvicidal activities of leaves of Solanum nigrum L

BACKGROUND & OBJECTIVES

Indiscriminate use of synthetic pesticides has created serious problem for the aquatic flora and fauna, and also resulted in appearance of pesticide resistance in vector population. This study was designed to evaluate the biocontrol efficacy of aqueous and solvent extracts of mature leaves of Solanum nigrum L., against fresh water snail Lymnaea acuminata f. rufescens (Gray) (an intermediate host of parasites causing fasciolopsiasis) and larvae of Culex vishnui group (Reuben) (vector of Japanese encephalitis).

METHODS

Aqueous and solvent extracts of fresh, mature, green/shed dried leaves of S. nigrum were tested against adult L. acuminata and larvae of Cx. vishnui group. The lethal concentration was determined and the appropriate lethal concentration at 24 h of benzene extract was also studied on non target organisms such as Daphnia sp, Diplonychus annulatum and Chironomus circumdatus. A qualitative phytochemical analysis was carried out in search of active ingredient and the chemical nature of the active substance was also evaluated by infrared (IR) analysis.

RESULTS

In a 72 h bioassay experiment with the aqueous extract, the highest mortality was recorded in 0.5 and 3 per cent extract against larvae of Cx. vishnui group and L. acuminata, respectivela. In the benzene solvent extract, the maximum mortality was recorded at a concentration of 150 ppm against L. acuminata and at 50 ppm against larvae of Cx. vishnui group with LC 50 values of 55.45 and 11.59 ppm, respectively at 72 h. The log probit analysis (95% confidence level) recorded lowest value at 72 h of exposure. Qualitative phytochemical analysis reported the presence of some biochemical compounds, such as saponin, flavonoids, steroid and tannin. Among these, the toxic compound was detected by IR analysis having Rf=0.87 (showed 66.70% and 76.70% mortality of L. acuminata and larvae of Cx. vishnui group, respectively). IR analysis provided preliminary information about the aliphatic amide nature of the active ingredient.

INTERPRETATION & CONCLUSIONS

The study results provide considerable scope in exploiting local indigenous plant resources for molluscicidal and mosquito larvicidal activities.

Considerations for test design to accommodate energy-budget models in ecotoxicology: a case study for acetone in the pond snail Lymnaea stagnalis

Toxicokinetic-toxicodynamic (TKTD) modeling offers many advantages in the analysis of ecotoxicity test data. Calibration of TKTD models, however, places different demands on test design compared with classical concentration-response approaches. In the present study, useful complementary information is provided regarding test design for TKTD modeling. A case study is presented for the pond snail Lymnaea stagnalis exposed to the narcotic compound acetone, in which the data on all endpoints were analyzed together using a relatively simple TKTD model called DEBkiss. Furthermore, the influence of the data used for calibration on accuracy and precision of model parameters is discussed. The DEBkiss model described toxic effects on survival, growth, and reproduction over time well, within a single integrated analysis. Regarding the parameter estimates (e.g., no-effect concentration), precision rather than accuracy was affected depending on which data set was used for model calibration. In addition, the present study shows that the intrinsic sensitivity of snails to acetone stays the same across different life stages, including the embryonic stage. In fact, the data on egg development allowed for selection of a unique metabolic mode of action for the toxicant. Practical and theoretical considerations for test design to accommodate TKTD modeling are discussed in the hope that this information will aid other researchers to make the best possible use of their test animals.

Sensitivity of freshwater pulmonate snail Lymnaea luteola L., to silver nanoparticles

Toxicity of nanoparticles depends on many factors including size, shape, chemical composition, surface area and surface charge. Silver nanoparticles (AgNPs) are likely to enter the aquatic ecosystems because of their multiple applications and pose a health concern for humans and aquatic species. Therefore, we used a freshwater snail Lymnaea luteola L (L. luteola) to investigate the acute toxicity and genotoxicity of AgNPs in a static-renewal system for 96 h. AgNPs caused molluscicidal activity in L. luteola, with 96-h median lethal concentrations (LC50) (48.10 μg L(-1)). We have observed that AgNPs (36 μg L(-1)) elicited a significant (p<0.01) reduction in glutathione, glutathione-s-transferase and glutathione peroxidase with a concomitant increase in malondialdehyde level and catalase in digestive gland of L. luteola. However, a significant (p<0.01) induction in DNA damage was observed by the alkaline single cell gel electrophoresis in digestive gland cells treated with AgNPs for 24 and 96 h. These results demonstrate that silver nanoparticles are lethal to freshwater snail L. luteola. The oxidative stress biomarkers and comet assay can successfully be used as sensitive tools of aquatic pollution biomonitoring.

Does water chemistry affect the dietary uptake and toxicity of silver nanoparticles by the freshwater snail Lymnaea stagnalis?

Silver nanoparticles (AgNPs) are widely used in many applications and likely released into the aquatic environment. There is increasing evidence that Ag is efficiently delivered to aquatic organisms from AgNPs after aqueous and dietary exposures. Accumulation of AgNPs through the diet can damage digestion and adversely affect growth. It is well recognized that aspects of water quality, such as hardness, affect the bioavailability and toxicity of waterborne Ag. However, the influence of water chemistry on the bioavailability and toxicity of dietborne AgNPs to aquatic invertebrates is largely unknown. Here we characterize for the first time the effects of water hardness and humic acids on the bioaccumulation and toxicity of AgNPs coated with polyvinyl pyrrolidone (PVP) to the freshwater snail Lymnaea stagnalis after dietary exposures. Our results indicate that bioaccumulation and toxicity of Ag from PVP-AgNPs ingested with food are not affected by water hardness and by humic acids, although both could affect interactions with the biological membrane and trigger nanoparticle transformations. Snails efficiently assimilated Ag from the PVP-AgNPs mixed with diatoms (Ag assimilation efficiencies ranged from 82 to 93%). Rate constants of Ag uptake from food were similar across the entire range of water hardness and humic acid concentrations. These results suggest that correcting regulations for water quality could be irrelevant and ineffective where dietary exposure is important.

Importance of toxicokinetics for interspecies variation in sensitivity to chemicals

Interspecies variation in sensitivity to synthetic chemicals can be orders of magnitude large. Species traits causing the variation can be related to toxicokinetics (uptake, distribution, biotransformation, elimination) or toxicodynamics (interaction with biological target sites). We present an approach to systematically measure and model the contribution of uptake, biotransformation, internal distribution, and elimination kinetics toward species sensitivity differences. The aim is to express sensitivity as target tissue specific, internal lethal concentrations. A case study with the pesticides diazinon, imidacloprid, and propiconazole and the aquatic invertebrates Gammarus pulex, Gammarus fossarum, and Lymnaea stagnalis illustrates the approach. L. stagnalis accumulates more pesticides than Gammaridae when measured in whole organisms but less in target tissues such as the nervous system. Toxicokinetics, i.e. biotransformation and distribution, explain the higher tolerance of L. stagnalis to the insecticide diazinon when compared to Gammaridae. L. stagnalis was again more tolerant to the other neurotoxicant imidacloprid; however, the difference in sensitivity could not be explained by toxicokinetics alone, indicating the importance of toxicodynamic differences. Sensitivity to propiconazole was comparable among all species and, when expressed as internal lethal concentrations, falls in the range of baseline toxicity.

Effects of chronic waterborne nickel exposure on growth, ion homeostasis, acid-base balance, and nickel uptake in the freshwater pulmonate snail, Lymnaea stagnalis

The freshwater pulmonate snail, Lymnaea stagnalis, is the most sensitive aquatic organism tested to date for Ni. We undertook a series of experiments to investigate the underlying mechanism(s) for this observed hypersensitivity. Consistent with previous experiments, juvenile snail growth in a 21-day exposure was reduced by 48% relative to the control when exposed to 1.3 μg l(-1) Ni (EC20 less than the lowest concentration tested). Ca(2+) homeostasis was significantly disrupted by Ni exposure as demonstrated by reductions in net Ca(2+) uptake, and reductions in Ca(2+) concentrations in the hemolymph and soft tissues. We also observed reduced soft tissue [Mg(2+)]. Snails underwent a significant alkalosis with hemolymph pH increasing from 8.1 to 8.3 and hemolymph TCO2 increasing from 19 to 22 mM in control versus Ni-exposed snails, respectively. Unlike in previous studies with Co and Pb, snail feeding rates were found to be unaffected by Ni at the end of the exposure. Snails accumulated Ni in the soft tissue in a concentration-dependent manner, and Ni uptake experiments with (63)Ni revealed a biphasic uptake profile - a saturable high affinity component at low exposure concentrations (36-189 nM) and a linear component at the high exposure concentrations (189-1,897 nM). The high affinity transport system had an apparent Km of 89 nM Ni(2+) and Vmax of 2.4 nmol g(-1)h(-1). This equates to a logK of 7.1, significantly higher than logK's (2.6-5.2) for any other aquatic organisms evaluated to date, which will have implications for Biotic Ligand Model development. Finally, pharmacological inhibitors that block Ca(2+) uptake pathways in snails did not inhibit Ni uptake, suggesting that the uptake of Ni does not occur via Ca(2+) uptake pathways. As with Cu and Pb, the exact mechanism for the significant disruption in Ca(2+) homeostasis and reduction in juvenile snail growth remains unknown.

Proteomic Analysis of the Reproductive Organs of the Hermaphroditic Gastropod Lymnaea stagnalis Exposed to Different Endocrine Disrupting Chemicals

Many studies have reported perturbations of mollusc reproduction following exposure to low concentrations (ng/L range) of endocrine disrupting chemicals (EDCs). However, the mechanisms of action of these molecules on molluscs are still poorly understood. Investigation of the modifications of protein expression in organisms exposed to chemicals using proteomic methods can provide a broader and more comprehensive understanding of adverse impacts of pollution on organisms than conventional biochemical biomarkers (e.g., heat-shock proteins, metallothioneins, GST, EROD). In this study we have investigated the impacts of four chemicals, which exhibit different endocrine disrupting properties in vertebrates, on the proteome of the hermaphroditic freshwater pulmonate gastropod Lymnaea stagnalis after 21 days of exposure. Testosterone, tributyltin, chlordecone and cyproterone acetate were chosen as tested compounds as they can induce adverse effects on the reproduction of this snail. The 2D-DIGE method was used to identify proteins whose expression was affected by these compounds. In addition to modifying the expression of proteins involved in the structure and function of the cytoskeleton, chemicals had impacts on the expression of proteins involved in the reproduction of L. stagnalis. Exposure to 19.2 µg/L of chlordecone increased the abundance of ovipostatin, a peptide transmitted during mating through seminal fluid, which reduces oviposition in this species. The expression of yolk ferritin, the vitellogenin equivalent in L. stagnalis, was reduced after exposure to 94.2 ng Sn/L of tributyltin. The identification of yolk ferritin and the modification of its expression in snails exposed to chemicals were refined using western blot analysis. Our results showed that the tested compounds influenced the abundance of yolk ferritin in the reproductive organs. Alteration in proteins involved in reproductive pathways (e.g., ovipostatin and yolk ferritin) could constitute relevant evidence of interaction of EDCs with reproductive pathways that are under the control of the endocrine system of L. stagnalis.

A 4-(o-chlorophenyl)-2-aminothiazole: microwave assisted synthesis, spectral, thermal, XRD and biological studies

A 4-(o-chlorophenyl)-2-aminothiazole (CPAT) has been synthesized by reacting o-chloroacetophenone, iodine and thiourea under microwave irradiation as a green chemistry approach. The reactions proceed selectively and within a couple of minutes giving high yields of the products. The compound was characterized by elemental, spectral (UV-visible, IR, NMR and GC-MS), XRD and thermal analyses. The TG curve of the compound was analyzed to calculate various kinetic parameters (n, E, Z, ΔS and ΔG) by using Coats-Redfern (C.R.), MacCallum-Tanner (M.T.) and Horowitz-Metzger (H.M.) method. The compound was tested for the evaluation of antibacterial activity against B. subtilis and E. coli and antifungal activity against A. niger and C. albicans. The compound was evaluated for their in vitro nematicidal activity on plant parasitic nematode Meloidogyne javanica and molluscicidal activity on fresh water helminthiasis vector snail Lymnea auricularia. The compound is biologically active in very low concentration. X-ray diffraction study suggests a triclinic crystal system for the compound.

Contractile activity of living isolated neurons and its inhibition by cytochalasin B

Contractile activity of damaged neuronal axons of Lymnaea stagnalis and Planorbis corneus vulgaris mollusks and the possibility of inhibiting their retraction by cytochalasin B were studied. In experimental series I (control), the neuronal axons contracted in Ringer's fluid in 90% cases. In series II and III (cytochalasin B in concentrations of 0.02 and 0.2 mM), the percentage of non-contracting neurons was 50 and 70%, respectively. Presumably, the fiber retraction mechanism was involved in the formation of diastasis after nerve cutting and damage to conduction tracts. The nerve diastasis formed at the expense of not only elastic characteristics of the nerve sheath and glia, but also due to nerve fiber retraction. Experiments with cytochalasin B demonstrated that F-actin filaments were involved in the retraction of myelin-free nerve fibers.

Laboratory assessment of the molluscicidal and cercariacidal activities of Balanites aegyptiaca

OBJECTIVE

To assess the molluscicidal and cercariacidal activities of aqueous extracts of Balanites aegyptiaca (B. aegyptiaca) against Ethiopian Biomphalaria pfeifferi (B. pfeifferi), Lymnaea natalensis (L. natalensis) and Schistosoma mansoni (S. mansoni) cercariae.

METHODS

Extracts of seeds, endocarp, mesocarp, and fruit of B. aegyptiaca were tested for their activities against adult B. pfeifferi and L. natalensis. The cercariacidal activity of the seeds of the plant was also evaluated against S. mansoni. Bioassays were carried out following the methods recommended by WHO. Snail mortalities were compared between each plant part and snail species, and LC50 and LC90 values for the plant parts tested were computed. The cercariacidal activity of the plant was assessed by exposing the mice to the cercariae pre-exposed to aqueous extract of B. aegyptiaca seeds.

RESULTS

For the molluscicidal activities of seeds, endocarp, mesocarp and whole fruit, the LC50 values against B. pfeifferi were 56.32, 77.53, 65.51 and 66.63 mg/L, respectively, while the respective LC90 values were 77.70, 120.04, 89.50 and 97.55 mg/L. Similarly, the LC50 values for the seeds, endocarp, mesocarp and whole fruit against L. natalensis were 80.33, 92.61, 83.52 and 87.84 mg/L, respectively, while the respective LC90 values were 102.30, 138.21, 115.42 and 127.69 mg/L. B. pfeifferi were found to be more susceptible to B. aegyptiaca than L. natalensis. S. mansoni cercariae exposed to 15 mg/L of extract of seeds were incapable of infecting mice. The mean egg load of tissue was reduced in mice infected with the cercariae exposed to 5 and 10 mg/L of the extract.

CONCLUSIONS

The aqueous extracts of different parts of B. aegyptiaca exhibited reasonable molluscicidal activity against B. pfeifferi and L. natalensis, as well as cercariacidal activity against S. mansoni cercariae. However, comprehensive laboratory evaluation is recommended prior to field tests of the plant parts since their impact on other aquatic biota is not known.