Effects of copper on the survival, hatching, and reproduction of a pulmonate snail (Physa acuta)

Chronic and transgenerational effects of silver nanoparticles in freshwater gastropod Lymnaea stagnalis

Traditional ecotoxicological studies prove to be focused mainly on single-generation, multigenerational research in ecotoxicological testing is needed to improve the predictive approaches in ecological risk assessment. Silver nanoparticles (AgNPs) have been increasingly detected in aquatic environments due to their extensive use in consumer products. We investigated the transgenerational effects of AgNPs on the life traits of freshwater model gastropods Lymnaea stagnalis for two generations. The reversibility of the effects of using recovery experiments was also performed. Results showed that AgNPs induced high Ag bioaccumulation in the whole soft tissues of parental L. stagnalis after 21 days of exposure. The increased ROS production and reduced condition index and fecundity were found after exposure to AgNPs at 500 μg/L. These results highlight that under AgNPs exposure, adult gastropods might allocate more resources to resist oxidative stress rather than to growth or reproduction. Furthermore, the Ag accumulation and ROS production of egg clutches were significantly related to parental exposure duration and concentrations. On the other hand, isolated eggs exposure demonstrated biological effects were persistent in terms of the next generation. For example, after transfer to a clean medium, similar Ag bioaccumulation and ROS production were observed from eggs which parents were pre-exposed to 50 and 500 μg/L AgNPs. Current explicit consideration of offspring performance adds value to existing toxicity testing protocols. Parental exposure duration has important implications for offspring effects, and parental exposure can cause transgenerational changes in resistance that have significant implications for toxicity testing and adaptive responses. These effects across generations point out the need for multigenerational tests to assess the environmental risk of MNPs in aquatic organisms.

Short and long-term phytoremediation capacity of aquatic plants in Cu-polluted environments

Freshwater ecosystems face numerous threats from human populations, including heavy metal contamination. Phytoremediation, the use of plants to remediate contaminated soils and sediments, is an effective and low-cost means of removing chemical contaminants, including heavy metals, from polluted environments. However, key questions remain unanswered in the application of this technology in aquatic environments, such as the long-term fate of pollutants following plant uptake. In this study, using two common wetland plant species (duckweed and tape grass), we first examined the capacity of plants to remove copper (Cu) from polluted water. Next, we evaluated the leaching potential of plant tissues following decomposition and how it is affected by a simulated freeze-thaw cycle. Using phytoremediated water and leachates from senesced plants we assessed phytoremediation success and Cu leaching potential by conducting standard toxicity assays using pond snails (Physa acuta), a species with known Cu sensitivity. We found that duckweed outperformed tape grass as a phytoremediator at low Cu concentrations. In addition, for plants grown in low concentrations of Cu, leaching from decaying plant material did not negatively impact snail survival, while at high concentrations of Cu, leaching did result in toxicity. Lastly, we found that a simulated freeze-thaw cycle increased the release of Cu from plant tissue in the presence of high Cu concentrations only, resulting in reduced snail survival. Our results indicate that in moderately Cu-polluted environments, some aquatic plants can remove contaminants without a long-term risk of leaching. In contrast, phytoremediation in highly polluted environments will likely require removal of plant tissue to prevent leaching of previously accumulated metals. Land managers must not only consider plant species and degree of contamination, but also geographic location, as freeze-thaw cycles may enhance plant decomposition and increase the likelihood of contaminant leaching following phytoremediation efforts in aquatic ecosystems.

Evaluation of the developmental toxicity of solvents, metals, drugs, and industrial chemicals using a freshwater snail (Biomphalaria glabrata) assay

A freshwater snail assay was employed to assess the embryotoxicity of solvents including acetone, methanol, ethanol, isopropanol, dimethyl-sulfoxide, glycerin, metals/metalloids including mercuric chloride (HgCl₂), cadmium chloride (CdCl₂,), antimony salts Sb⁺³ and Sb⁺⁵, drugs including colchicine, hydroxyurea, cyclophosphamide, an industrial chemical sodium azide (SA), an anionic surfactant dodecyl sodium sulfate-(DSS), H₂O₂ and sodium chloride (NaCl). The assay consists of exposing Biomphalaria glabrata egg masses (EM) to the substances for 96-hr and following up embryo/snail development for lethality, abnormal morphology (teratogenicity), and day of hatching up to day 10 or 14 after spawning. Based upon concentration-response relationships, LC_50%s (embryolethality), EC_50%s (teratogenicity) and IC_50%s (hatching retardation) and 95%CIs were determined for tested chemicals. The LOECs indicated that HgCl₂ (37 nM) and CdCl₂ (140 nM) are potent embryotoxic agents in snails. Teratogenic indices (TI = LC₅₀/EC₅₀) for almost all tested chemicals were lower than or close to unity suggesting that these compounds were not teratogenic in this assay. The snail assay may be adequately performed in a cost-effective standardized protocol which enables testing a number of environmental chemicals over a broad concentration range. The snail assay needs to undergo further validation to be recognized for an internationally harmonized hazard identification in ecotoxicity risk assessment.

Wastewater treatment plant contaminant profiles affect macroinvertebrate sludge degradation

Disposal of the overwhelming amounts of excess wastewater treatment plant (WWTP) sludge is an increasing financial and environmental problem, and new methods to reduce the amount of excess sludge are therefore required. In the natural environment, interactions between multiple macroinvertebrate detritivores mediate the degradation of organic matter. Macroinvertebrates may thus also be able to degrade WWTP sludge, but may meanwhile be impacted by the associated contaminants. Therefore, the aim of the present study was to examine if WWTPs contaminant concentrations and profiles affect the biotic interactions and macroinvertebrate mediated degradation of sludge. Assessing degradation of sludge from three WWTPs differing in contaminant profile by (combinations of) three macroinvertebrate detritovore taxa, revealed that macroinvertebrate enhanced sludge degradation was WWTP and taxa combination specific. Yet, taxa combinations only had an additional positive effect on sludge degradation when compared to single taxa in sludge with a higher contaminant load. This was confirmed by the results of a Cu-spiked sludge degradation experiment, indicating a possible effect of biotic interactions. It was concluded that macroinvertebrates are a potential tool for the reduction of excess WWTP sludge, and that using multispecies assemblages of detritivorous macroinvertebrates may increase the resilience of this additional treatment step.

Consequences of artificial light at night on behavior, reproduction, and development of Lymnaea stagnalis

Light is an important zeitgeber that regulates many behavioral and physiological processes in animals. These processes may become disturbed due to the changes in natural patterns of light and dark via the introduction of artificial light at night (ALAN). The present study was designed to determine the effect of possible consequences of ALAN on reproduction, hatching success, developmental success, growth rate, feeding rate, mortality rate, and locomotor activity of the simultaneous hermaphrodite pond snail Lymnaea stagnalis. Snails were exposed to different light intensities at night that simulate actual ALAN measurements from the snail's night environment. The data revealed that exposure to ALAN at a low level significantly affected the cumulative number of laid eggs. At the same time, snails exposed to ALAN laid smaller eggs than those laid under normal light-dark cycles. Additionally, high light-intensity of ALAN delayed development and hatching of eggs of L. stagnalis while it showed no effect on hatching percentage. Furthermore, ALAN increased both the feeding and growth rates but did not lead to mortality. The results also show that snails exposed to dark conditions at night travel longer distances and do so faster than those exposed to ALAN. In light of these findings, it is clear that ALAN may have an influence on snails and their abundance in an environment, possibly disturbing ecological stability.

Aquatic Contamination in Lugano Lake (Lugano Lake Ecological Reserve, Buenos Aires, Argentina) Cause Negative Effects on the Reproduction and Juvenile Survival of the Native Gastropod Biomphalaria straminea

Lugano Lake is located in an Ecological Reserve of Buenos Aires City. Biomonitoring of its water quality is essential due to its importance as a place for recreation and protection of native species. Biomphalaria straminea is a native hermaphrodite aquatic gastropod that inhabits different freshwater bodies of Argentina and was recently selected as a potential bioindicator. We propose this study as a first approach to assessing specific organisms’ use in biomonitoring of urban wild reserves, and the usefulness of reproduction assays. B. straminea survival, behavior, reproduction success and offspring survival after the exposure to water samples from Lugano Lake (L1, L2, and L3) were evaluated. Temperature, pH, conductivity and dissolved oxygen were registered in situ. Samples were transported to the laboratory and chemical analysis and bioassays were performed using 20 snails per site. A control group with tap water was added. Egg masses were separated, exposed individually and observed daily using a stereoscopic microscope. After hatching, juveniles were placed in tap water and offspring survival was registered at the first, second, third and fourth months after the beginning of the assay. High levels of conductivity, turbidity and nutrients were obtained. Ammonium and nitrite were higher than the guideline level for the protection of aquatic life. During the bioassay 20% of the snails (L2 and L3) showed abnormally protruding of the head-food region. The number of eggs and embryonated eggs per mass did not differ between treatments. Egg masses exposed to water samples from the lake presented overlapping and abnormal eggs and arrested embryos. Besides, low % of hatching (L1: 33%, L2: 42%, and L3: 16%) and juvenile survival after the first (L1:14%; L2:78%) and second month (L1: 60%) were noted. In the control group, 85% of hatching and 100%–90% of survival were observed. Our results suggests the presence of pollutant in the lake. B. straminea seems to be a sensitive local species. Biomphalaria spp. reproduction assays can provide a valuable endpoint for toxicity and risk assessments and a usefulness tool for biomonitoring water quality.

Green and brown stream trophic food chains show specific responses to constant or hump-shaped inputs of copper

The brown food chain (based on decomposers) co-exists in streams with the green food chain (based on primary producers). The two trophic chains perform specific ecosystem functions which may be altered by the effect of contaminants. Copper is a common contaminant with recognized effects on several compartments of the two trophic chains. We applied it in two separate mesocosm experiments, in which we tested the effects of copper after contrasting patterns of contaminant exposure (constant vs hump-shaped). The constant input simulated a chronic contamination (average of 20 μg/L Cu), while the hump-shaped simulated the steady arrival of copper, the occurrence of a peak (reaching ca. 60 μg/L Cu), and its progressive decrease (down to 10-15 μg/L Cu). In the green trophic food chain, copper exposure decreased the total chlorophyll-a as well as the basal fluorescence and the photosynthetic yield. The treatment receiving hump-shaped inputs caused the highest mortality of the green food chain consumer, the snail Radix balthica. In the chronic copper exposure, mortality achieved a maximum of 80% by the end of the experiment but occurred later than that in the hump-shaped treatment. Effects on the brown food chain were not so pronounced; the microbial decomposition rate of leaflitter decreased nearly ca. 50% after 14 days of copper exposure. Effects on decomposition translated into the ingestion performance of detritivores, which decreased in the two copper treatments. Our results provide evidence that copper affected the two trophic food chains. The hump-shaped arrival included a peak of high concentration, which caused lethal effects on the consumers, but also a decreasing limb, which allowed a partial recovery of the algal photosynthetic variables. Our results suggest the need to consider the different compartments and functions performed within the stream trophic web when evaluating the effects of a contaminant in a river ecosystem.

Comparative Assessment of Cadmium and Copper Toxicity to Physa acuta (Draparnaud, 1805)

Cadmium and copper toxicity was investigated using bioassays with neonates of a freshwater gastropod Physa acuta. Mortality, lethal time, and effects on shell length were studied during 28-day chronic exposure experiments. Relative toxicity was assessed from acute and chronic LC values. Copper showed significantly more toxicity at lower concentrations than cadmium ([Formula: see text] < 0.001), causing mortality at the same response levels. Conversely, cadmium affected shell length at lower concentrations than copper, although no significant differences ([Formula: see text] > 0.05) were found in affected shell length between copper and cadmium at the end of the assays. Lethal time (LT[Formula: see text]) was significantly affected by metal concentration ([Formula: see text] < 0.001), with a reduction of 8.28% and 5.90% in time per 0.001 mg/L increase of copper and cadmium, respectively. Physa acuta neonates showed medium to high sensitivity to cadmium and copper compared to other freshwater gastropod species, showing it is a suitable test organism, particularly for chronic ecotoxicological assessment.

Environmental biomonitoring by snails

Background: Bio-indicator systems are vital in terms of monitoring of pollutants around the world. The impact of environmental change can be monitored by employing the responsive behaviour of snails. Heavy metal and organic pollutants affects snail reproduction, mortality, and normal metabolic activities. Various changes like a discontinuity in food intake, growth rate, twitching, and quenching of tentacles, are the biomarkers of the snails for biomonitoring. Different snails can bio-monitor eco-toxicological urban pollution, oil pollutant, terrestrial pollution, pesticide pollutants, mercury contamination, ammonia, chlorinated paraffin in soil, ethanol in water, ocean acidification pollutions. These animals can also make bio-sense about diverse environment spheres, which include the biosphere, lithosphere, anthroposphere, cryosphere, and hydrosphere.Methods: We examined the scientific literature and related articles listed in Pub-med, Google Scholar reporting on biomonitoring potential and biomarkers expression of various snail species and consequently explore the value of snails in the respective field by discussing various outcomes of a number of studies on the pollution biomonitoring and biosensing capabilities.Results: Several terrestrial, freshwater and sea snail species are characterized by the high sense of biomonitoring and biosensing potential. Various biomarkers such as expression of heat shock proteins and metallothioneins in the body are found to be the essential in-vivo biomarkers for pollution biomonitoring.Conclusion: It is observed that snails offer an environment friendly approach for the environmental bio monitoring by expressing their numerous physiological, biochemical, genetical and histological biomarkers in their body. Thus, it proved to be a critical bio monitoring tool and early warning indicators.

Signal Decoding for Glutamate Modulating Egg Laying Oppositely in Caenorhabditis elegans under Varied Environmental Conditions

Animals' ability to sense environmental cues and to integrate this information to control fecundity is vital for continuing the species lineage. In this study, we observed that the sensory neurons Amphid neuron (ASHs and ADLs) differentially regulate egg-laying behavior in Caenorhabditis elegans under varied environmental conditions via distinct neuronal circuits. Under standard culture conditions, ASHs tonically release a small amount of glutamate and inhibit Hermaphrodite specific motor neuron (HSN) activities and egg laying via a highly sensitive Glutamate receptor (GLR)-5 receptor. In contrast, under Cu²⁺ stimulation, ASHs and ADLs may release a large amount of glutamate and inhibit Amphid interneuron (AIA) interneurons via low-sensitivity Glutamate-gated chloride channel (GLC)-3 receptor, thus removing the inhibitory roles of AIAs on HSN activity and egg laying. However, directly measuring the amount of glutamate released by sensory neurons under different conditions and assaying the binding kinetics of receptors with the neurotransmitter are still required to support this study directly.

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Short-term exposure of CuSO₄ evokes hyperactive egg laying

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ASHs inhibit HSNs and egg laying via GLR-5 receptor under no Cu²⁺ treatment

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AIA interneurons suppress HSNs and thus egg laying through ACR-14 signaling

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Under noxious Cu²⁺ treatment, ASHs and ADLs suppress AIAs and augment egg laying

Freshwater alien species Physella acuta (Draparnaud, 1805) - A possible model for bioaccumulation of heavy metals

In this study we focused on Physella acuta, an alien snail species in order to determine their ability of bioaccumulation of heavy metals in their shells, bodies, the difference in accumulation in relation to age classes, and the influence of ecological variables on the community composition and density. On the basis of the results of ecological, toxicological, and experimental analyses we aimed to study the potential invasive features of P. acuta in comparision with the native species Stagnicola palustris. The content of Cu and Zn in the substratum and ammonia in the water was strongly related to the patterns of distribution of P. acuta. The content of Cd, Pb, and Cu in the shell fraction was always significantly lower than in the body fraction. A comparison of accumulation with respect to the size classes of P. acuta indicated that the lowest metal concentration in the body was typical for the largest individuals, except for Zn. Metal content in the bodies of the native species did not differ from the content measured in their analogous group of the largest individuals of P. acuta. The lowest value of bioaccumulation factor (BAF) was found for the large class of specimens of this species for each metal. A distinct decrease in the value of BAF in relation to the size of snails was found for cadmium. A 100% hatching success found in masses collected from pond confirmed the high reproductive potential of P. acuta which can be a factor that promotes its invasive features following its ability to occur in very high densities, but not necessarily the ability of metal accumulation in the body. Physella acuta can be used as a model organism in the studies on the accumulation of heavy metals however, the extend of accumulation can differ among the age classes. Because of the high tolerance of P. acuta to heavy metal pollution, in the future this species can be found in significantly polluted habitats, inhabiting free ecological niches, and occurring in high densities in snail communities.

Azinphos-methyl causes in Planorbarius corneus toxic effects on reproduction, offspring survival and B-esterases depending on the exposure time

This work aimed to study in the freshwater gastropod Planorbarius corneus the effects of acute (2 days) and subchronic (14 days) exposures to an environmental concentration of the organophosphate azinphos-methyl on different reproductive parameters, offspring survival and B-esterase activities in gonads and in the whole organism soft tissue. The acute exposure inhibited only carboxylesterase activity in both tissues while the subchronic exposure also inhibited cholinesterase activity, decreased the number of hatched-eggs and increased offspring lethality (92%). On the other hand, B-esterases in gonads were more effective biomarkers than B-esterases in the whole organism due their inhibition appeared earlier in time (cholinesterase activity) and their activity remained inhibited for a longer time (carboxylesterase activity) when recovery studies were performed. We concluded that B-esterases and reproductive parameters can be used as effect biomarkers of aquatic contamination with azinphos-methyl. Our studies showed that a 14 days exposure to an environmental concentration of azinphos-methyl produced severe signs of toxicity in adult organisms, egg masses and juveniles that could cause negative effects at the population level in contaminated environments.