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.

Histopathological Evaluation of the Curative Effects of EDTA on Lymnaea stagnalis Exposed to Subacute Cadmium

We investigated the therapeutic effects of EDTA application for 14 and 28 days on cadmium (Cd) induced pond snail Lymnaea stagnalis (Linnaeus, 1758). The sublethal concentration of cadmium (63.4 mg/l Cd) caused tissue damages to the snail after an exposure for 28 days.In the groups treated with EDTA, the concentration of Cd in the foot, mantle and hepatopancreas tissues showed significantly decreased during the recovery period. The curative effects of EDTA on Cd-induced damage were assessed using a scoring system. Cadmium exposure led to histopathological changes including increased mucositis, pigment and protein cells, foot epithelium desquamation, muscle fibril damage, connective tissue cell atrophy, and increased lipid vacuoles in the mantle and hepatopancreas. However, these changes were less severe in snails treated with EDTA (2.00 mL/L for 28 day), indicating that EDTA reduces their susceptibility to heavy metal toxicity.

Laboratory Assessment of Molluscicidal Activities of Cannabis sativa, Acacia nilotica, and Tinospora cordifolia Against Snail Host of Fasciola spp

Background: The potential molluscicidal extracts, obtained from indigenous plants Cannabis sativa, Acacia nilotica, and Tinospora cordifolia, were tested for toxicity against freshwater pulmonate snail Lymnaea acuminata, an intermediate host of Fasciola hepatica. The organic extracts had a significant effect on young snails. Materials and Methods: All organic extracts and column-purified fractions gave median lethal concentrations (19-100.05 mg/L; 24 h) that fell well within the threshold level of 100 mg/L, set for a potential molluscicide by the World Health Organization. Results: The toxicity of T. cordifolia stem acetone extract (96 h LC50: 16.08 mg/L) was more pronounced compared with C. sativa leaf ethanol extract (96 h LC50: 16.32 mg/L) and A. nilotica leaf ethanol extract (96 h LC50: 24.78 mg/L). β-caryophyllene, gallic acid, and berberine were characterized and identified as active molluscicidal components. Co-migration of β-caryophyllene (retardation factor [Rf] 0.95), gallic acid (Rf 0.30), and berberine (Rf 0.23) with column-purified parts of Cannabis sativa, Acacia nilotica, and Tinospora cordifolia on thin-layer chromatography demonstrates same Rf value, that is, 0.95, 0.30, and 0.23, respectively. Conclusion: This study indicates that these extracts thus represent potential plant-derived molluscicides that are worthy of further investigations.

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.