Effects of dietary Cd and Cu on feeding and growth rates of the landsnail Helix engaddensis

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.

Dose-dependent effects of lead and cadmium and the influence of soil properties on their uptake by Helix aspersa: an ecotoxicity test approach

Three soil types with different physicochemical properties were selected to evaluate their effect on lead and cadmium bioavailability and toxicity in the land snail Helix aspersa. In 28-day ecotoxicity tests, H. aspersa juveniles were exposed to increasing concentrations of Pb or Cd. EC50s, concentrations reducing snail growth by 50%, differed between the soils and so did Cd and Pb uptake in the snails. For lead, EC50s were 2397-6357 mg Pb/kg dry soil, while they ranged between 327 and 910 mg Cd/kg dry soil for cadmium. Toxicity and metal uptake were highest on the soil with the lowest pH, organic matter content and Cation Exchange Capacity (CEC). Growth reduction was correlated with metal accumulation levels in the snails' soft body, and differences in toxicity between the soils decreased when EC50s were expressed on the basis of internal metal concentrations in the snails. These results confirm the effect of soil properties; pH, CEC, OM content, on the uptake and growth effect of Pb and Cd in H. aspersa, indicating the importance of properly characterizing soils when assessing the environmental risk of metal contaminated sites.

Physiological and behavioral responses of land molluscs as biomarkers for pollution impact assessment: A review

Environmental pollution caused by human activities is a global public health concern. This review discusses the impact of different types of pollutants such as pesticides, metals, nanoparticles and others on land molluscs. These molluscs are of great interest as good model organisms for studying biomarker responses in ecotoxicological monitoring programs. Several biomarkers are utilized to characterize and quantify the exposure and harmful impacts of various pollutants. In this review, we have identified physiological and behavioral endpoints (feeding, growth, avoidance, mucus secretion, locomotion and reproductive behavior) for the diagnosis of environmental pollution. The present review displays that all types of pollutants can disturb physiological and behavioral endpoints of gastropods, and these impacts depend on the matrix, exposure time and route as well as the type and concentration of the pollutants in the environment. We have also confirmed that terrestrial gastropods particularly snails as sentinel species could be used as potential bioindicator organisms for environmental quality assessment and thus for predicting potential hazards to human health.

Common mechanisms activated in the tissues of aquatic and terrestrial animal models after TiO2 nanoparticles exposure

Titanium dioxide nanoparticles (TiO₂-NPs) are among the most popular manufactured and widely used nanoparticles. They are released into the environment, affecting terrestrial and aquatic ecosystems, with unexpected consequences to organisms and human health. The present study investigates the mediated toxicity imposed to the freshwater fish species, zebrafish (Danio rerio) and the prussian carp (Carassius gibelio), and to the terrestrial land snail Cornu aspersum, after their exposure to sublethal concentrations of TiO₂-NPs. Oxidative, proteolytic, genotoxic and apoptotic parameters in fish liver and gills, as well as on snail hemocytes were studied and the swimming performance was estimated in order to (a) estimate and suggest the most susceptible animal, and (b) propose a common battery of biomarkers as the most suitable indicator for biomonitoring studies against TiO₂-NPs. Our in vivo experiments demonstrated that NPs induced detrimental effects on animal physiology and swimming behavior, while no general pattern was observed in species and tissues responsiveness. Generally, TiO₂-NPs seemed to activate a group of molecules that are common for aquatic as well as terrestrial animals, implying the existence of a conserved mechanism. It seems that after exposure to TiO₂-NPs, a common mechanism is activated that involves the stimulation of immune system with the production of ROS, damage of lysosomal membrane, protein carbonylation, lipid peroxidation, DNA damage, following proteolysis by ubiquitin and finally apoptosis. Thus, the simultaneous use of the latter biomarkers could be suggested as a reliable multi parameter approach for biomonitoring of aquatic and terrestrial ecosystems against TiO₂-NPs.

Physiological traits of land snails Theba pisana as simple endpoints to assess the exposure to some pollutants

In the current study, the toxicity bioassay of three pollutants abamectin (ABM), thiamethoxam (TMX), and acrylamide (ACR) against land snails Theba pisana was measured. Also, the ecotoxicological effects of dietary exposure to sublethal concentration (1/20 LC₅₀) of these pollutants for 2-week exposure and 1-week recovery on some physiological endpoints evaluated as feeding activity, growth response, and carbonic anhydrase activity as a marker in charge of shell formation and seromucoid level as a marker in charge of mucus synthesis of the snails were studied. The results exhibited that the 48-h LC₅₀ values were 0.91, 313.8, and 45.7 μg/g dry food for ABM, TMX, and ACR, respectively. The sublethal concentrations of these pollutants in the diet after 2-week exposure were found to reduce the food consumption and inhibit growth rate of the snails. Also, the data illustrated that carbonic anhydrase activity was significantly decreased. On the other hand, there was a significant increase in the seromucoid level as a marker responsible for mucus synthesis in ABM- and TMX-exposed snails, while ACR showed significantly decreased level when compared to control. After 1-week recovery, the tested endpoints of treated snails were slightly repaired but still less than that of the untreated animals. The overall outcome of this investigation suggests the utility of this animal as a good bioindicator organism for ABM, TMX, and ACR exposure in pollution monitoring studies.

Short-term effects of very low dose cadmium feeding on copper, manganese and iron homeostasis: A gastropod perspective

The available information on the interplay between low-dose cadmium intake and copper, manganese, and iron homeostasis in invertebrates is limited. We have currently studied the accumulation of these trace metals in the hepatopancreas of adult snails, Cantareus aspersus, following 14 and 28 days of exposure to low doses of dietary cadmium, up to 1 mg/kg dw (dry weight). The cadmium dose, but not the duration of exposure, had a significant effect on hepatopancreas copper deposition, the values being significantly elevated compared to controls. A significant peak in manganese levels at 14 days was found in snails administered the lowest cadmium dose. These increases occurred even in the absence of cadmium increase in the hepatopancreas. Our data suggest that low dose cadmium feeding can produce a transient disturbance in hepatopancreas copper and manganese homeostasis. Such responses may serve as early biomarkers of physiological changes occurring during the initial stages of cadmium intoxication.

Bioaccumulation of cadmium in soil organisms - With focus on wood ash application

Harvesting whole-tree biomass for biofuel combustion intensifies removal of nutrients from the ecosystem. This can be partly amended by applying ash from the combustion back to the system and thus recycle the nutrients. However, besides being rich in inorganic nutrients, ash also contains trace amounts of heavy metals. Due to the risk of toxic effects and trophic transfer of heavy metals, especially cadmium, legislation usually restricts the use of ash as a soil amendment. In order to provide researchers and governmental agencies with a tool to assess the risk of cadmium bioaccumulation in specific soil systems after ash application, we review: 1) the properties of ash; 2) the chemical and toxic properties of cadmium; 3) the key factors affecting cadmium bioavailability, cadmium uptake-, storage- and elimination-abilities in soil organisms and the risk of cadmium accumulation and biomagnification in the soil food web; 4) how ash impact on soil can change the risk of cadmium bioaccumulation. We conclude that for assessing the risk of cadmium bioaccumulation for specific sites, it is necessary to consider both the type and composition of ash, the soil conditions and organism composition on the site. On a general basis, we conclude that granulated ashes low in cadmium content, applied to low pH soils with high organic matter content, in systems with low abundances of earthworms, isopods and gastropods, will have a low risk of cadmium accumulation.

Insights into the toxicity of iron oxides nanoparticles in land snails

The use of manufactured nanoparticles (NPs) is spreading rapidly across technology and medicine fields, posing concerns about their consequence on ecosystems and human health. The present study aims to assess the biological responses triggered by iron oxide NPs (IONPs) and iron oxide NPs incorporated into zeolite (IONPZ) in relation to oxidative stress on the land snail Helix aspersa in order to investigate its use as a biomarker for terrestrial environments. Morphology and structure of both NPs were characterized. Snail food was supplemented with a range of concentrations of IONPs and IONPZ and values of the hemocyte lysosomal membranes' destabilization by 50% were estimated by the neutral red retention (NRRT50) assay. Subsequently, snails were fed with NPs concentrations equal to half of the NRRT50 values, 0.05 mg L^-1 for IONPs and 1 mg L^-1 for IONPZ, for 1, 5, 10 and 20 days. Both effectors induced oxidative stress in snails' hemocytes compared to untreated animals. The latter was detected by NRRT changes, reactive oxygen species (ROS) production, lipid peroxidation estimation, DNA integrity loss, measurement of protein carbonyl content by an enzyme-linked immunoabsorbent assay (ELISA), determination of ubiquitin conjugates and cleaved caspases conjugates levels. The results showed that the simultaneous use of the parameters tested could constitute possible reliable biomarkers for the evaluation of NPs toxicity. However, more research is required in order to enlighten the disposal and toxic impact of iron oxide NPs on the environment to ensure their safe use in the future.

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.

Bioaccumulation and tissue distribution of Pb and Cd and growth effects in the green garden snail, Cantareus apertus (Born, 1778), after dietary exposure to the metals alone and in combination

The present study was aimed at determining bioaccumulation and cell and tissue distribution of Pb and Cd in the green garden snail, Cantareus apertus (Born, 1778), exposed to different nominal dietary concentrations of Pb (25, 100 and 2500 mg Pb/kg), Cd (5, 10 and 100 mg Cd/kg) and their combination (25mg Pb+10 mg Cd/kg and 2500 mg Pb+100 mg Cd/kg) for 1 and 8 wk. Pb and Cd were bioaccumulated in the digestive gland in a dose-dependent manner and the degree of effects on growth was related to the level of exposure, though metal-metal interactions were observed after treatment with mixtures of Pb and Cd. The present results are absolutely comparable to those obtained in other terrestrial pulmonates in other regions and therefore they absolutely support that C. apertus is suitable as biomonitor for the assessment of the Pb and Cd levels and their biological effects in soil ecosystems in Northern Africa.

Effects of sewage sludge amendment on snail growth and trace metal transfer in the soil-plant-snail food chain

Cu, Zn, Pb, and Cd concentrations in a soil plant (Lactuca sativa) continuum were measured after sewage sludge amendment. The effects of sewage sludge on growth and trace metal bioaccumulation in snails (Cantareus aspersus) were investigated in a laboratory experiment specifically designed to identify contamination sources (e.g., soil and leaves). Application of sewage sludge increased trace metal concentrations in topsoil. However, except Zn, metal concentrations in lettuce leaves did not reflect those in soil. Lettuce leaves were the main source of Zn, Cu, and Cd in exposed snails. Bioaccumulation of Pb suggested its immediate transfer to snails via the soil. No apparent toxic effects of trace metal accumulation were observed in snails. Moreover, snail growth was significantly stimulated at high rates of sludge application. This hormesis effect may be due to the enhanced nutritional content of lettuce leaves exposed to sewage sludge.

Food utilization and growth of cutworm Spodoptera litura Fabricius larvae exposed to nickel, and its effect on reproductive potential

Food utilization and growth of the 5th and 6th instar Spodoptera litura Fabricius larvae, and its effect on reproduction potential was evaluated by feeding larvae diets with different doses of Ni for 3 generations. Dose-dependent relationships between Ni levels and food consumption and growth were variable with different larval developmental period and Ni exposure duration. RCR, AD and RGR of the 6th instar larvae were much more affected by Ni exposure than those of 5th instar larvae, and the effects were strongest in the 3rd generation. It was found that RCR was significantly stimulated after 1 and 20 mg kg(-1) Ni exposure, while AD was significantly inhibited after 1, 5, 10 and 40 mg kg(-1) Ni exposure. However, lower levels of Ni (≤5 mg kg(-1)) significantly increased and higher levels of Ni (≥10 mg kg(-1)) significantly decreased RGR. In 3 successive generations, 10 mg kg(-1) Ni significantly increased the ECI and ECD of the 5th instar larvae, and 5 mg kg(-1) Ni significantly increased the ECD of the 6th instar larvae. However, ECD were all significantly inhibited with 20 mg kg(-1) Ni exposure. Results also revealed that durations of larvae were shortened at low levels of Ni, but extended at high levels of Ni. Fecundity was inhibited by the highest Ni doses in each generation, while improved by low Ni doses in the 3rd generation. Hatching rates in all treatments were significantly decreased in a Ni dose-dependent manner. Study indicated that effects of Ni on these parameters were predominant with the increasing Ni exposure period.

Effects of organic pollutants on Eobania vermiculata measured with five biomarkers

In the present study, the effect of organic pollution on land snails Eobania vermiculata was investigated. Five pollution biomarkers (neutral red retention assay, morphometry of lysosomes and neutral lipids, acetylcholinesterase activity and metallothioneins content), were applied on tissues of the land snails. The results showed intense differentiations between the snails treated with organic pollutants and the control ones, as indicated by the results obtained. Statistically significant correlations among the results obtained emphasize the usefulness of these biomarkers.

Single versus combined exposure of Hyalella azteca to zinc contaminated sediment and food

The amphipod Hyalella azteca was exposed for 28 d to different combinations of Zn contaminated sediment and food. Sediment exposure (+clean food) resulted in increased Zn body burdens, increased mortality and decreased body mass when the molar concentrations of simultaneously extracted Zn were greater than the molar concentration of Acid Volatile Sulfide (SEM(Zn)-AVS>0), suggesting that dissolved Zn was a dominant route of exposure. No adverse effect was noted in the food exposure (+clean sediment), suggesting selective feeding or regulation. Combined exposure (sediment+food) significantly increased adverse effects in comparison with sediment exposure, indicating contribution of dietary Zn to toxicity and bioaccumulation. The observed enhanced toxicity also supports the assumption on the presence of an avoidance/selective feeding reaction of the amphipods in the single sediment or food exposures. During 14 d post-exposure in clean medium, the organisms from the same combined exposure history received two feeding regimes, i.e. clean food and Zn spiked food. Elevated Zn bioaccumulation and reduced reproduction were noted in amphipods that were offered Zn spiked food compared to the respective organisms that were fed clean food. This was explained by the failure of avoidance/selective feeding behavior in the absence of an alternative food source (sediment), forcing the amphipods to take up Zn while feeding. Increasing Zn body burdens rejected the assumption that Zn uptake from food was regulated by H. azteca. Our results show that the selective feeding behavior should be accounted for when assessing ecological effects of Zn or other contaminants, especially when contaminated food is a potential exposure route.

Effects of organic contaminants in reactive oxygen species, protein carbonylation and DNA damage on digestive gland and haemolymph of land snails

The present study focused on early responses of land snails Eobania vermiculata to organic environmental contaminants, by investigating the use of a newly-established method for the measurement of protein carbonylation as a new biomarker of terrestrial pollution, as well as by measuring the ROS production and the DNA damage. Land snails were exposed to different concentrations of chlorpyrifos, parathion-methyl or PAHs in vivo or in vitro in the laboratory. The susceptibility of exposed snails was increased in relation to oxidative stress induced by contaminants tested. A statistically significant increase in ROS production, protein carbonylation and DNA damage was revealed in the snails treated with pollutants, compared to the untreated ones. The results indicated the effectiveness of measuring ROS production and DNA damage and reinforce the application of the present ELISA method in organic terrestrial pollution biomonitoring studies.

In vivo and in vitro effects of metals in reactive oxygen species production, protein carbonylation, and DNA damage in land snails Eobania vermiculata

Heavy metals are known to induce oxidative damage by way of enhancement of intracellular reactive oxygen species (ROS) production, which often preludes the onset of alterations, such as protein carbonylation and DNA damage. In this study, our aim was to examine the early responses of land snails Eobania vermiculata to environmental contaminants by investigating the use of a modified enzyme-linked immunosorbent assay (ELISA) assay for the measurement of protein carbonylation as a new biomarker of terrestrial pollution as well as by measuring ROS production and DNA damage. Land snails were treated with heavy metals-cadmium, lead, or copper-in vivo (15 or 40 ppm) for 25 days or in vitro (0.5, 5, 50 or 500 μM) for 30 min in the laboratory, and the previously mentioned biomarkers were determined in digestive gland and haemolymph of the treated animals. A statistically significant increase in ROS production, protein carbonylation, and DNA damage was shown in the snails treated with pollutants compared with the untreated snails. The results indicate the effectiveness of measuring ROS production and DNA damage, as well as using the present ELISA method, as sensitive tools of terrestrial pollution biomonitoring studies. Statistically significant correlations among the previously mentioned techniques further enhance their role as promising biomarkers in terrestrial pollution studies.

Introduction of the land snail Eobania vermiculata as a bioindicator organism of terrestrial pollution using a battery of biomarkers

The present study aimed to enrich the group of sentinel organisms of terrestrial pollution biomonitoring, by investigating the efficacy of the land snail Eobania vermiculata. For this reason, a package of biomarkers was performed on land snails E. vermiculata collected from polluted areas in the field or treated with heavy metals in the laboratory. The biomarkers used were neutral red lysosomal retention assay of the haemocytes, acetylcholinesterase activity in the digestive gland and the haemolymph, and metallothionein content of the digestive gland. Moreover, the morphometric changes in the lysosomal system and the morphometric alterations of the neutral lipids were also investigated. In addition, the content of cadmium, lead and copper was evaluated in the digestive gland of the snails. The results revealed appreciable alterations in the biomarker values both in field- and laboratory-conditions, accompanied by significant correlations among the biomarkers. Therefore, this exploratory study suggests the utility of E. vermiculata as a sentinel organism for biomonitoring the biologic impact of terrestrial pollution, and supports the package's efficacy of the selected biomarkers.

Feeding and growth responses of the snail Theba pisana to dietary metal exposure

The effects of dietary exposure to copper (Cu), lead (Pb), and zinc (Zn) on feeding activities, growth response, and mortality of Theba pisana snails were studied in 5-week feeding tests. Snails were fed on an artificial diet containing the following Cu, Pb, or Zn concentrations: 0, 50, 100, 500, 1000, 5000, 10,000, and 15,000 μg/g dry food. At the end of 5 weeks, the food consumption rate was decreased with increasinges in both metal concentrations and time of exposure. The estimated concentrations of metals that reduces food consumption to 50% (EC₅₀) after 5 weeks were 56, 118, and 18 μg/g dry food for Cu, Pb, and Zn, respectively. All tested metals in the diet were found to inhibit growth of the snails in a dose-dependent manner. The toxic effect on growth of the tested metals could be arranged in the order Cu > Zn > Pb. The cumulative percentage mortality among snails fed a Cu- or Zn-contaminated diet was 73.3% and the respective value for a Pb-contaminated diet was 13.3%. There was a positive correlation between growth coefficient and food consumption for all tested metals.

Bioaccumulation of copper and toxic effects on feeding, growth, fecundity and development of pond snail Lymnaea luteola L

We studied the bioaccumulation and the toxic effects of Cu on survival, number of eggs and eggmasses laying, embryo development, growth, and food consumption in an Indian pond snail, Lymnaea luteola L. exposed for 7 weeks. Copper caused loss of chemoreception, locomotion and inhibited food consumption significantly during 7 weeks of exposure. Food consumption in Cu exposed snails significantly decreased and at 56 and 100 μg L(-1), snail stopped feeding activity. Mean number of eggmasses or eggs significantly decreased in Cu concentrations during the 7 week study. The percentage hatching decreased in Cu concentrations but there was more than 95% hatched in control in 10-11 days after spawning. Egg development was completely inhibited at 100 μg L(-1), while abnormal embryonic development observed at 32 and 56 μg L(-1) of Cu. The Cu concentration in tissues increased in Cu treated snails and bioaccumulation factor ranged from 2.3 to 18.7. Snail growth at 5.6 and 10 μg L(-1) was reduced by 6.2% and 16.9%, respectively. The study revealed that snail embryos and adults could be used as in vivo test models for ecotoxicological studies. Findings of present study are helpful for advancing water quality guidelines for protecting aquatic biota.

The effects of radionuclides on animal behavior

Concomitant with the expansion of the nuclear industry, the concentrations of several pollutants, radioactive or otherwise, including uranium, caesium, cadmium and cobalt, have increased over the last few decades. These elemental pollutants do exist in the environment and are a threat to many organisms. Behavior represents the integration of all the anatomical adaptations and physiological processes that occur within an organism. Compared to other biological endpoints, the effects of pollutants on animal behavior have been the focus of only a few studies. However, behavioral changes appear to be ideal for assessing the effects of pollutants on animal populations, because behavior links physiological functions with ecological processes. The alteration of behavioral responses can have severe implications for survival of individuals and of population of some species. Behavioral disruptions may derive from several underlying mechanisms: disruption of neuro-sensorial activity and of endocrines, or oxidative and metabolic disruptions. In this review, we presented an overview of the current literature in which the effects of radioactive pollutants on behavior in humans, rodents, fish and wildlife species are addressed. When possible, we have also indicated the potential underlying mechanisms of the behavioral alterations and parameters measured. In fried, chronic uranium contamination is associated with behavior alterations and mental disorders in humans, and cognitive deficits in rats. Comparative studies on depleted and enriched uranium effects in rats showed that chemical and radiological activities of this metal induced negative effects on several behavioral parameters and also produced brain oxidative stress. Uranium exposure also modifies feeding behavior of bivalves and reproductive behavior of fish. Studies of the effects of the Chernobyl accident shows that chronic irradiation to 137Cs induces both nervous system diseases and mental disorders in humans leading to increased suicides, as well as modification of preferred nesting sites, reduced hatching success and fecundity in birds that live in the Chernobyl zone. No significant effect from caesium exposure was shown in laboratory experiments with rats, but few studies were conducted. Data on radioactive cadmium are not available in the literature, but the effects of its metallic form have been well studied. Cadmium induces mental retardation and psychomotor alterations in exposed populations and increases anxiety in rats, leading to depression. Cadmium exposure also results in well-documented effects on feeding and burrowing behavior in several invertebrate species (crustaceans, gastropods, annelids, bivalves) and on different kinds of fish behavior (swimming activity, fast-start response, antipredatory behavior). Cobalt induces memory deficits in humans and may be involved in Alzheimer's disease; gamma irradiation by cobalt also decreases fecundity and alters mating behavior in insects. Collectively, data are lacking or are meagre on radionuclide pollutants, and a better knowledge of their actions on the cellular and molecular mechanisms that control animal behavior is needed.

Bioaccumulation and toxic effects of cadmium on feeding and growth of an Indian pond snail Lymnaea luteola L. under laboratory conditions

Effects of dissolved cadmium exposure on the survival, feeding, growth rates and accumulation in Indian pond snails Lymnaea luteola L. were examined for a period of 7 weeks. The concentrations of cadmium tested were 0, 10, 32, 100, 320, 560, and 1000 microg l(-1). Cadmium exposure significantly inhibited the feeding and growth rates. At higher Cd concentrations snails refused to consume food offered as plant Marsilia sp. leaves. Cadmium mainly accumulated in soft tissues in a dose-dependent manner. After 4 and 7 weeks of exposure, the no observed effect concentration (NOEC) of Cd was 10 microg l(-1) and the lowest observed effect concentration (LOEC) was 32 microg l(-1). Reduction of growth (decrease in wet weight) was noticed followed by a high mortality in higher Cd concentrations. Significant reduction in food consumption and growth rates was found at 32 microg l(-1) and above Cd concentration. A significant relationship between Cd exposure and growth and feeding rates was noticed. The results obtained with these key aquatic organisms in the food chains complement those obtained with other aquatic organisms and gastropod snails. The findings of the present study and those of earlier studies suggested that Indian pond snail L. luteola are useful test organisms for ecotoxicology bioassays.

Responses of abalone Haliotis diversicolor to sublethal exposure of waterborne and dietary silver and cadmium

In this study, we examined the chronic waterborne and dietary exposure of silver (Ag) and cadmium (Cd) to the abalone Haliotis diversicolor using various endpoints such as growth and feeding rates, metal body burden, subcellular distribution, and metallothionein (MT) concentration over a period of 7 weeks of exposure. The growth and feeding rates of abalones were inhibited during the early stage of exposure to different extents, but then recovered to nearly the control levels. A large portion of Ag was redistributed to organelles and metal-rich granules from the cellular debris fraction, whereas cellular debris and metallothionein-like protein were the dominant pools for the storage of Cd, which remained comparable during the exposure period. The MT concentrations were significantly elevated (in a dose-dependent manner) within the first 2 weeks of exposure, after which the MT concentrations started to decrease. All these results implied that abalones respond rapidly to metal exposure, but apparently developed subsequent acclimation.

The potential role of cAMP as a pollution biomarker of terrestrial environments using the land snail Eobania vermiculata: correlation with lysosomal membrane stability

The present study investigates the role of the signal transduction molecule cAMP, and the lysosomal membrane stability (LMS), as biomarkers of terrestrial environmental pollution using the land snail Eobania vermiculata. Snails were exposed to different concentrations of heavy metals (Cd, Pb and Cu) and organic pollutants (chlorpyrifos, parathion-methyl and PAHs) in laboratory conditions for 25 days. In addition, snails were collected from various sites located at different distances away from two polluted areas in northern Greece (the road Agiou Dimitriou in Thessaloniki city and a lignite power station in the district of Kozani). The results of the current investigation showed significantly increased levels of cAMP in the digestive gland of snails, as well as decreased LMS values in all experimental groups compared to control animals. In support of our data, cAMP levels were significantly negatively correlated with the conventional biomarker LMS, thus encouraging the use of cAMP as a new potential stress index in terrestrial pollution biomonitoring studies.

Copper uptake and depuration by juvenile and adult Florida apple snails (Pomacea paludosa)

The present study characterized copper (Cu) uptake and depuration by juvenile and adult Florida apple snails (Pomacea paludosa) from water, soil, and diet. During a 28-day uptake period, juvenile apple snails were exposed to aqueous Cu and adult apple snails were exposed to Cu-contaminated soil, water, and food. In the follow-up 14-day depuration period, both juvenile and adult apple snails were held in laboratory freshwater with background Cu concentrations<4 microg/l. For juvenile apple snails, whole body Cu concentrations increased with time and reached a plateau after 14 days. The data followed Michaelis-Menten kinetics rather than a one compartment first order kinetics model. The mean Cu bioconcentration factor (BCF) for juvenile apple snails was 1493 and the depuration half-life was 10.5-13.8 days. For adult snails, dietary uptake of Cu resulted in higher bioaccumulation factors (BAFs) compared to uptake from soil. Most of the accumulated Cu was located in soft tissue (about 60% in the viscera and 40% in the foot). The shell contained <1% of the total accumulated copper. Soft tissue is usually consumed by predators of the apple snail. Therefore, the results of the present study show that Cu transfer through the food chain to the apple snail may lead to potential risk to its predators.

Long-term responses of snails exposed to cadmium-contaminated soils in a partial life-cycle experiment

Juvenile snails were exposed during their growth period to Cd-contaminated field and artificial soils and then transferred to uncontaminated soil to assess the sequels of previous exposure on adult reproduction. Growth modelling highlighted growth inhibitions of 5% and 10% after 70 and 84 days of exposure to 20 and 100 mg Cd kg(-1) in artificial soils, respectively. Growth disruption was accompanied by a decrease in the clutch number and a 4-week delay in the egg-laying cycle. Although it was also contaminated at 20 mg Cd kg(-1), the contaminated field soil did not lead to detectable effects in snails, suggesting a lower Cd bioavailability confirmed by the bioaccumulation analysis. We demonstrated that the 28-day growth test, as advised by the ISO-guideline, may not be sufficient to assess sublethal toxic effects of realistically contaminated soils. For this purpose, a life cycle experimental set-up is proposed, allowing a thorough assessment of toxicity during successive life stages.

Digestive cell turnover in digestive gland epithelium of slugs experimentally exposed to a mixture of cadmium and kerosene

Slugs, Arion ater (L), have been proposed as sentinel organisms to assess soil health. In slugs under the influence of pollutants, digestive cell loss and the concomitant increase of excretory cells of the digestive gland have been described. The aim of the present work was to determine up to what extent digestive cell loss affects biomarkers and whether the affectation is reversible after exposure to a mixture of metal and organic pollutants. Slugs were dosed with a mixture of cadmium and kerosene in the food for 27 days. Apart from chemical analyses, the volume density of black silver deposits (Vv(BSD)) after autometallography, and acyl-CoA oxidase (AOX) activity were used as biomarkers of exposure to metals and organic compounds, respectively. As effect biomarkers, changes in the volume density of the cell types that constitute the digestive gland epithelium were calculated. Proliferating cells were identified by means of bromodeoxyuridine (BrdU) immunohistochemistry. Results revealed that the mixture of pollutants provoked an increase in Vv(BSD) and AOX activity and a decrease in the number of digestive cells. These changes had no effect in the digestive gland accumulation capacity or in the effect and exposure biomarkers employed. BrdU-labelling showed that exposure to pollutants provoked an enhanced digestive cell proliferation.

Heavy metal pollution affects consumption and reproduction of the landsnail Cepaea nemoralis fed on naturally polluted Urtica dioica leaves

This study is one of the very first that investigates the effects of heavy metal pollution on food consumption and reproduction of terrestrial snails under semi-realistic field conditions. Two experiments were carried out using snails (Cepaea nemoralis) and food (Urtica dioica leaves) from different metal polluted locations and one reference location. The first experiment showed that both polluted and reference snails fed on high-metal leaves from a highly polluted location had significantly lower consumption rates than snails consuming leaves from the reference location. In the second experiment, snails from both locations used in the consumption experiment and from two low-polluted locations were kept on native soil and food in order to reproduce. No negative effect of heavy metal pollution on clutch size was found for the snails from the reference location and the low-polluted locations. Snails from the highly polluted location laid no eggs. This suggests that at high levels of metal pollution, reproduction is strongly negatively affected. We suggest that the absence of egg laying by snails from the highly polluted location results from a combination of decreased consumption and an increased demand of energy for the accumulation and detoxification of metals (decreased scope for growth).

Transfer of cadmium from plant leaves and vegetable flour to the snail Helix aspersa: bioaccumulation and effects

Juvenile Helix aspersa snails were exposed for 4 weeks to fresh rape leaves (Brassica napus), contaminated by simulating superficial deposits of increasing concentrations of cadmium (Cd). The Cd concentration in leaves was 0.1 in control and 38.4, 93.1, and 177.2 microg x g(-1) (dry mass) in Cd-treated food. The concentration in snail tissues increased with increasing Cd concentrations in the food. The bioaccumulation factors ranged from 4.8 (control) to 2.4 (highest exposed group), indicating a biomagnification of Cd in this food chain. The growth of the snails treated with Cd was reduced by 17, 24, and 43% respectively, compared to the control group. Comparison of these results with those obtained with snails exposed to similar Cd concentrations in a vegetable flour revealed that accumulation and effects were relatively consistent, demonstrating a comparable bioavailability of Cd in the two diets. Tests using growing H. aspersa snails exposed to metals in flour or fresh leaves can be useful for risk assessment purposes.

Metal accumulation from contaminated food and its effect on growth of juvenile landsnails Helix engaddensis

Metal accumulation by juvenile landsnails, Helix engaddensis, and its effect on growth rate was studied over a 5-week period of exposure and 2 weeks of recovery. An artificial food contaminated with Cu (4-2500 microg x g(-1)), Cd (50-800 microg x g(-1)), Pb, and Zn (20-12500 microg x g(-1)) was used. During the 7 weeks of the experiment, mortality rates were 20, 27, 30, and 38% among snails fed Cu-, Pb-, Zn-, and Cd-contaminated food, respectively. According to the ability to inhibit growth, metals were found to have the following order: Cd > Zn > Cu = Pb. Inhibitory effects of dietary metals started to be significant from the third week of exposure on. Inhibition of growth by Pb and Cu was found to be reversible, and within the first week of recovery, snails erupted their aestivation and resumed feeding and growth to gain weights similar to those of the control groups. Snails fed Cd- or Zn-contaminated food failed to resume growth during the 2 weeks of recovery. This indicates that in the case of Cu and Pb, growth inhibition was mainly due to starvation due to food rejection and aestivation. On the other hand, growth inhibition caused by Cd and Zn may have been resulting from irreversible toxicity. Therefore, snails were assumed to be sensitive to Cd and Zn but tolerant to Cu and Pb. Accumulation of Cu and Pb was significant only at the highest concentrations. At low and medium concentrations, no signs of accumulation were observed, indicating regulation at these concentrations. Cd and Zn accumulation starts at low concentrations but became significant at medium and high levels indicating accumulation of these metals.

Dose-dependent effects of dietary Pb and Zn on feeding and growth rates of the landsnail Helix engaddensis

Dose-dependent effects of dietary lead and zinc on feeding and growth rates of adult Helix engaddensis snails were studied over a 1-month period followed by a 2-week recovery period. Snails were fed on an artificial diet containing the following lead or zinc concentrations= 0, 20, 100, 500, 2500, and 12,500 microg/g dry food. At the end of the 6 weeks, mortality rate among snails fed on Pb-contaminated diet was 18.3% (11/60) and the respective value for Zn-contaminated diet was 50% (30/60). Both metals significantly reduced growth and feeding rates. Snails were found to be sensitive to zinc but tolerant to lead. During the recovery period, snails fed on Zn-contaminated diet failed completely to feed or grow normally, whereas snails fed on Pb-contaminated diet showed signs of slow improvement in terms of feeding and growth rates. The NOEC and LOEC for lead were 100 and 500 microg/g (-1), respectively, while the respective concentrations for zinc were 20 and 100 microg/g (-1).