Juvenile Snails Research Articles

Burrowing behaviour of the juvenile rapa whelk Rapana venosa (Valenciennes, 1846) reared under laboratory conditions: A protective behaviour

Juvenile Rapana venosa are vulnerable immediately after metamorphosis. The high mortality rate of juveniles seriously limits the development of the aquaculture industry. A number of gastropods use burrowing as an environmental adaptation. R. venosa is a widespread gastropod species, but little is known about its ecology, especially its burrowing behaviour. Here, we studied the obvious burrowing behaviour of juvenile R. venosa. Our results showed that the size of the juvenile snail, grain size of the sediment, dissolved oxygen and water temperature significantly affect the burrowing behaviour of juveniles. Large juveniles have a strong burrowing capacity. The shortest burrowing time occurred in sediment of small grain size. When dissolved oxygen was high (8 mg/L), juveniles displayed obvious burrowing behaviour, and as the dissolved oxygen decreased, the juveniles reduced their burrowing behaviour. Low or high temperatures (≤15 or 30°C, respectively) significantly increased the burrowing rate and depth. Moreover, small snails (shell height <2.5 cm) exhibited obvious shell and tissue detachment (an abnormal phenomenon) when the water temperature was low (5°C). Small snails could reduce shell and tissue detachment and mortality rate by submerging themselves in sand (diameter: 0.50–1.00 mm), indicating that burrowing was a kind of protective behaviour that enables juvenile R. venosa to adapt to the environment. Our results add to the body of knowledge on snail responses to particular environmental factors and allow a better understanding of the species’ needs in its natural environment and can be used to improve commercial breeding strategies for R. venosa.

An assessment of the molluscicidal potential of Cucurbita maxima seed extracts on Biomphalaria pfeifferi and Bulinus globosus snails

Reports of snails’ resistance to niclosamide appeared recently and finding new molluscicides becomes necessary. We investigated the molluscicidal effects of Cucurbita maxima seed extracts on Biomphalaria pfeifferi, and Bulinus globosus snails under laboratory conditions. For B. pfeifferi, we tested seed extracts on juvenile and adult snails while only adult B. globosus were available for testing. Snails were exposed to water and crude ethanol extracts for 72 h and significant concentration-dependent mortality rates were observed. The number of B. pfeifferi juveniles collected was not enough for a comprehensive investigation against both solvents. We, therefore, tested them against water extracts only. A lethal concentration of 0.02 mg/mL killed 50% of the snails (LC50) for both water and ethanol extracts on adult B. pfeifferi snails. Our results suggest that pumpkin seed extracts have a significant molluscicidal effect on B. pfeifferi and B. globosus snails. The LC50 values for all the extracts in B. pfeifferi and B. globosus snails are within the threshold set for potential molluscicides by the World Health Organisation. We propose that C.maxima seed extracts be considered as potential molluscicidal agents in Schistosomiasis transmission control.

Effect of Herbicides Used in Horticulture (2,4-D, Glyphosate and Nicosulfuron) on Snails &amp;lt;i&amp;gt;Achatina fulica&amp;lt;/i&amp;gt; (Bowdich, 1720)

2,4-Dichlorophenoxyacetic (2,4-D), glyphosate, and nicosulfuron, because of their modes of action and selectivity, are the most widely used herbicides in Ivorian horticulture. Fuels toxicity was the reason of many debates in the world because of their massive and uncontrolled use. They are frequently blamed for the reduction of soil fertility and terrestrial biodiversity observed in agricultural areas. In view of the debates raised by their toxicities, the use of these herbicides requires the greatest caution and clear information on the real risk incurred by the edaphic fauna by conducting ecotoxicity studies. The present study aims to evaluate the effect of 2,4-D, glyphosate and nicosulfuron herbicides on the growth and reproduction of Achatina fulica snails in microcosm. To do this, we treated each plot on which snail microcosms were placed with 2,4-D, glyphosate or nicosulfuron herbicides according to the manufacturer’s recommendations. The results showed for all the herbicides used, that after 28 days of exposure, the growth of juvenile snails was slowed down. The number of eggs laid per pair was reduced in adult snails. The egg hatchability test revealed a reduction in egg hatchability. In addition, each effect was dependent on the herbicide used. Thus, toxicity was found to be greater according to the following order: nicosulfuron ? glyphosate ? 2,4-D. From the results obtained, we concluded that 2,4-D, glyphosate, and nicosulfuron treatments under field conditions are a potential threat to the sustainability of snail species and therefore to soil life. The intensity of the effect depends on the toxicity of the herbicides used.

Estimating growth, size-dependent mortality, and tag loss in a mark-recapture study: demography of wavy turban snails in Southern California, USA

Tagging studies are often used to measure survival and growth in wild populations. However, issues such as low returns of tagged animals, tag loss, and handling mortality can affect the precision and accuracy of demographic estimates if not accounted for. We conducted a mark-recapture study to measure the survival and growth of juvenile and adult wavy turban snails Megastraea undosa. Our study highlights several methodological advances, including a method for estimating a single growth function by analyzing the joint changes in length and weight of tagged animals; a simple method for estimating rates of tag loss when some animals are double tagged; and a way to estimate handling mortality by comparing encounter histories of animals immediately after tagging and after several weeks in the field. Tag loss was moderate (≈15% over a 100 d period) and handling mortality was substantial during the fall (≈55%), but negligible during the spring. If we did not account for tag loss and handling mortality, our estimate of survival would have been severely underestimated (≈46% lower over a 100 d period). After accounting for such effects, our study revealed that survival probably increased sharply with body size, but survival did not differ among seasons. These snails are slow-growing, mature after approximately 6 yr, and can routinely grow to &gt;10 yr old. There is an emerging fishery for this species, and because our results suggest that the oldest snails have a very high reproductive value, measures that protect these large individuals are likely to be beneficial for the resilience of these populations.

A Mystery Tale: Nickel Is Fickle When Snails Fail-Investigating the Variability in Ni Toxicity to the Great Pond Snail.

Dissolved Ni concentrations inhibiting the growth of juvenile great pond snails (Lymnaea stagnalis) have been documented to vary from about 1 to 200 µg L-1 Ni. This variability makes L. stagnalis either a moderately sensitive or the most sensitive freshwater species to chronic Ni exposure tested to date. Given the role of sensitive species in environmental risk assessment frameworks, it is particularly important to understand this variability, i.e., to characterize the factors that modulate Ni toxicity and that may confound toxicity test outcomes when uncontrolled. In the present study, we tested if this variability was due to analytical (growth calculation: biomass versus growth rate), environmental (water quality), lab-specific practices, and/or snail population differences among earlier studies. Specifically, we reanalyzed previously published Ni toxicity data and conducted additional measurements of Ni aqueous speciation, short-term Ni uptake, and chronic Ni toxicity with test waters and snail cultures used in previous studies. Corrections for Ni bioavailability and growth calculations explained a large degree of variability in the published literature. However, a residual 16-fold difference remained puzzling between 2 studies: Niyogi et al. (2014) (low ECxs) and Crémazy et al. (2018) (high ECxs). Indeed, differences in metal bioavailability due to water chemistry, lab-specific practices, and snail population sensitivity could not explain the large variation in Ni toxicity in these 2 very similar studies. Other potentially important toxicity-modifying factors were not directly evaluated in the present work: test duration, diet, snail holding conditions, and snail age at onset of testing. The present analysis highlights the need for further studies to elucidate 1) the mechanisms of growth inhibition in Ni-exposed L. stagnalis and 2) the important abiotic and biotic factors affecting this biological response. Until these processes are understood, substantial uncertainties will remain about inclusion of this species in Ni environmental risk assessment. Integr Environ Assess Manag 2020;16:983-997. © 2020 SETAC.

Reproductive performance of laying snails (Archachatina marginata) fed on roughages and different concentrate mixes

BackgroundThis study aims to investigate the reproduction output of Archachatina marginata fed on roughage and concentrate feed with leaf meal-inclusive diets. One hundred fifty points of lay snails weighing between 150 and 170 g were randomly allotted to 5 treatment diets with three replicates, ten snails per replicate, designated as treatment 2 (GNCD) which has groundnut cake, treatment 3 (GLLM) has Gliricidia sepium, treatment 4 (MOLM) has Moringa oleifera, and treatment 5 (LLLM) has Leucaena leucocephala leaf meals as protein source in snail diet and a control (treatment 1) (UPWP) fed on roughage (unripe pawpaw and watermelon peel) in a 12-week feed trial. Feed intake, weight gain, egg lay, egg fertility, hatchability, and gonadosomatic index were measured.ResultsThe result revealed snails fed with UPWP had the least final weight and weight gain which was accompanied by the highest feed intake across the treatments. Average egg laid, hatchability, fertility, embryo mortality, and average juvenile produced by snails on roughage-based diet were significantly the least across the treatments. High gonadosomatic index of snails on leaf meal-based diet accompanied with better reproductive output in laying snails was recorded.ConclusionSnails fed with Leucaena leucocephala-inclusive diet had better egg production, fertility, hatchability, and juvenile snails accompanied with gonadosomatic index across the treatments. Concentrate ration is essential for optimal reproductive output in snails.

Aggregation behavior of juvenile Neptunea cumingii and effects on seed production

Neptunea cumingii is an important nutrition-rich economic species in China. Juveniles of N. cumingii suffer from high mortality at low temperatures, which has proved a limiting factor in raising seedlings in artificial habitats. Previous research has shown that N. cumingii displays aggregation behavior in response to adverse environmental changes. Therefore, we determined the effects of temperature, food, size of juvenile snails, substratum type, and density of juvenile snails on the aggregation behavior of N. cumingii. Results show that, at a low (4°C) or a high (22°C) temperature, juvenile snails adjusted to the inhospitable environment by exhibiting increased aggregation behavior. However, their aggregation behaviors differed at these two temperatures. There was no significant difference in the aggregation rate, but the typical aggregation size was larger at 4°C than at 22°C. At 10°C or 16°C, aggregation behavior of juvenile snails reduced. Aggregation increased in the satiation treatment at 10°C and 16°C. Small-sized juveniles tended to have higher aggregation rates (92.22%) and a larger typical aggregation size. More juveniles were distributed in the bottom of shaded substrata. A larger typical aggregation size or higher density significantly reduced the mortality of juvenile snails at a low temperature (4°C). These results broaden our understanding of gastropod aggregation behavior and can be used to develop and improve commercial breeding strategies and resource recovery for N. cumingii.

Effects of salinity on survival, growth and reproduction of the invasive aquatic snail Pomacea canaliculata (Gastropoda: Ampullariidae)

Pomacea canaliculata, a freshwater snail native to tropical and temperate South America, has become an important invader and agricultural pest throughout tropical and subtropical regions around the world. Colonization of various aquatic habitats by P. canaliculata in coastal regions of South China and its establishment potential in estuaries have raised great concern, yet little is known about the biological response of the snail and its tolerance under saline environments. We first examined the salinity tolerance of P. canaliculata using a total of 30 experimental juvenile snails exposed to eight salinity levels (from 0 to 14 psu in 2 psu steps). Daily survival of the snails was measured for each salinity treatment over 30 days. Based on salinity exposure test, influence of salinity on snail reproduction was investigated for a period of 30 days using 30 adult snails exposed to four salinity treatments (0, 2, 4 and 6 psu). Each salinity test replicated three times. Pomacea canaliculata could tolerate salinity levels ranging from 0 to 6 psu in which probability of survival was greater than 72% during a 30 days exposure. Lethal time leading to 50% mortality (LT50) of the snail declined from 71 days at 0 psu to 27 days at 6 psu. Pomacea canaliculata could ingest and reproduce normally at salinities ranging from 0 to 4 psu. Average mass daily gain, specific growth rate, and the hatching of egg clutches decreased significantly with elevated salinities. Results show a general threshold response of P. canaliculata to salinity. This freshwater snail falls into “2nd degree” euryhaline limnobionts tolerating salinities of 3–8‰.

Effects of different feeding regimes on the growth performance of the giant African land snail Archachatina marginata (Swainson)

Effects of various feeding regimes on the growth performance of the giant African land snail, Archachatina marginata were studied using one hundred and twenty (120 Juvenile snails) weighing 0.66g +1 per snails for a period of 90 days. The treatments were. T1 -Grower starter, T2 - Grower mash, T3 - cocoyam and cassava leaves and T4 - Ripe pawpaw fruits. The Completely Randomized Design was used with four treatments and each replicated three times. The snails were confined in wooden hutch boxes. Data was collected on weekly body weight feed intake, shell length and shell width. Results obtained showed that snails fed with broiler starter diet (T1) had significantly (P&lt;0.05) higher performance in terms of weight gain, feed intake, shell length and the aperture, while pawpaw fruits T4 recorded the least values. The highest values for feed intake was observed in T1 (135.5g) followed by T2 (78.2g), while the least feed intake was observed in T4 (55.7g). Snails fed with T1 recorded the highest weight gain (60.1g) followed by T2 and T3.The lowest weight gain was obtained in T4 (37.9g). Shell length was highest in T1 (20.7mm), closely followed by T2 (19.2mm). The aperture recorded the highest mean values in T1 (20.1mm). The least operculum was recorded in T4 (12.9mm). Therefore, the broiler starter T1 should be used to feed growing snails to improve their performance.&#x0D; Keywords: Snails, Broiler Starter, Grower mesh, Cocoyam leaves, Cassava leaves, Pawpaw fruits, hutch boxes

Assessment of the molluscicidal activity of wormwood (Artemisia dubia, Wallich) leaves ethanolic extract on Oncomelania hupensis quadrasi, Möllendorff

This study assessed the in vitro molluscicidal activity of Artemisia dubia (wormwood) leaf ethanolic extract against adult and juvenile Oncomelania hupensis quadrasi and profiled its qualitative phytochemical content. The plants and snails were collected locally. There were 8 concentrations used for adult and juvenile snails: distilled water and 1% ethanol as negative controls; niclosamide (2 mg/L) as a positive control; and different concentrations of wormwood ethanolic extracts for adult snails including 3.98% (T1), 4.46% (T2), 5% (T3), 5.61% (T4), and 6.30% (T5) and for juvenile snails including 7.94% (T1), 8.91% (T2), 10% (T3), 11.22% (T4), and 12.59% (T5). Each treatment was replicated 5 times with 20 snails per replicate. Results showed that the concentrations that were statistically comparable with niclosamide (2 mg/L) were 6.30% (T5) with 92% mortality for adults and 10% (T3), 11.22% (T4), and 12.59% (T5) for juveniles with 94%, 95%, and 98% mortality, respectively (P > 0.05). The qualitative phytochemical tests for secondary metabolites revealed the presence of tannins, saponins, and terpenoids. Independently or in combination, these secondary metabolites may be responsible for the mortality of the snails. This study indicates the possibility of using wormwood ethanolic extract as a potent and a possible alternative for synthetic molluscicides.

Evaluation of a nanoscale zero-valent iron amendment as a potential tool to reduce mobility, toxicity, and bioaccumulation of arsenic and mercury from wetland sediments.

Gold mining in the 1800s has led to the contamination of wetlands with introduced mercury (Hg) and geogenic arsenic (As). In situ risk management tools to reduce mobility and toxicity of Hg and As are needed to support natural restoration of impacted ecosystems. Here, we explored whether a nanoscale zero-valent iron (nZVI) slurry injected into two different contaminated wetland sediments can reduce Hg and As mobility to the overlaying water and toxicity to two aquatic invertebrates, burrowing mayflies (Hexagenia spp.) and Chinese mystery snails (Cipangopaludina chinensis). Total water Hg and As concentrations overlying both contaminated sediments were reduced by at least 75% and 88% respectively when treated with nZVI slurry. In the first sediment, juvenile snail survival increased from 75% in the untreated sediment to 100% in all nZVI treatments. The 2% nZVI treatment level was the only one with surviving mayflies (33%) and growth of juvenile snails. No snails or mayflies survived in the second sediment, regardless of nZVI treatment level. However, snails survived longer in this sediment with 4% and 8% nZVI. To improve reactivity of nZVI without increasing nZVI dose, future studies should investigate matrix-supported nZVI for reducing mobility and toxicity of As and Hg in wetland sediments.

Disruptive selection of shell colour in land snails: a mark–recapture study of Euhadra peliomphala simodae

Abstract Many theoretical studies have suggested that disruptive selection plays an important role in phenotypic divergence, but few studies have determined the action of disruptive selection on phenotypic divergence via field studies. This study investigated the effect of disruptive selection on shell colour polymorphism in the Japanese land snail Euhadra peliomphala simodae to determine whether extreme phenotypes of snail shell colour are favoured over intermediate phenotypes. We conducted field surveys on an oceanic island with black, yellow and intermediate-coloured E. p. simodae snails. We captured and marked ~1800 individual snails and monitored their survival over 18 months. We quantified shell colours against images and examined the frequency distribution of shell colour variation. The variation exhibited a bimodal distribution with a far lower frequency of intermediate-coloured snails than of black or yellow snails. The population sizes of the three snail groups fluctuated synchronously with the changing seasons. Bayesian estimates showed lower survival rates for juvenile intermediate-coloured snails than for juvenile black and yellow snails, implying there was disruptive selection associated with shell colour. We suggest this disruptive selection may have resulted in the evolutionary divergence of the snail’s shell colour within the lineage having high shell colour variation.

Native Herbivores Improve Sexual Propagation of Threatened Staghorn Coral Acropora cervicornis

Staghorn coral Acropora cervicornis was once spatially dominant on Caribbean reefs but is now threatened throughout its range. In recent years, advancements in ex-situ sexual propagation of Caribbean corals have increased the viability of this management strategy. Thus, improving culture methods for sexually propagated corals is important to bolster the overall coral restoration portfolio and increase genetic diversity in restored populations. In both natural systems and culture scenarios, algae proliferation negatively impacts coral growth and survival. Growing coral with native herbivores may represent a strategy for increased efficiency. We tested A. cervicornis recruits raised in replicate aquaria with identical densities of juvenile Lithopoma americanum or juvenile Batillaria minima snails plus a no-snail control. Each of three replicates per treatment contained tiles with similar numbers of recently settled, visually healthy, A. cervicornis. Tiles were photographed every three weeks for five months and coral growth, survivability, turf algae cover, and crustose coralline algae (CCA) cover were quantified. Labor time for cleaning was carefully recorded for each treatment. Results indicated improved growth and survival when A. cervicornis recruits were raised with either snail species in comparison to a no-herbivore control. Further, including snails decreased labor and eliminated turf algae cover. Interestingly, L. americanum significantly reduced CCA cover relative to the other treatments. We report some of the highest survival rates observed to date for sexually propagated Atlantic corals. Ultimately, results suggest that rearing sexually propagated A. cervicornis with native herbivores could improve the ability to employ these corals in reef restoration.

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.

Soil copper uptake by land snails: A semi-field experiment with juvenile Cantareus aspersus snails

There is currently limited scientific evidence linking soil copper and land snails, although these invertebrates are important players in terrestrial ecosystems. In the present study, Cantareus aspersus juveniles, were exposed in two successive phases of 30 days each, to soil spiked with increasing concentrations of copper sulfate. Copper concentrated preferentially and in a dose-dependent manner in the hepatopancreas. In the case of specimens previously exposed to Cu-spiked soils, Cu retention kinetics were independent from the effects of a new exposure event. There was no effect on shell growth, but significant mortality was observed at 60 days. The no observed effect concentration and the lowest observed effect concentration for mortality in snails, were ˜ 41 and 54 mg, respectively, per grams dry weight in the hepatopancreas. The results demonstrate, for the first time, that terrestrial gastropods can accumulate soil Cu autonomously from dietary uptake.

Effects of acidification on the proteome during early development of Babylonia areolata.

Increases in atmospheric CO 2 partial pressure have lowered seawater pH in marine ecosystems, a process called ocean acidification (OA). The effects of OA during the critical stages of larval development may have disastrous consequences for some marine species, including Babylonia areolata (Link 1807), a commercially important sea snail in China and South East Asia. To investigate how OA affects the proteome of Babylonia areolata, here we used label‐free proteomics to study protein changes in response to acidified (pH 7.6) or ambient seawater (pH 8.1) during three larvae developmental stages of B. areolata, namely, the veliger larvae before attachment (E1), veliger larvae after attachment (E2), and carnivorous juvenile snail (E3). In total, we identified 720 proteins. This result suggested that acidification seriously affects late veliger stage after attachment (E2). Further examination of the roles of differentially expressed proteins, which include glutaredoxin, heat‐shock protein 70, thioredoxin, catalase, cytochrome‐c‐oxidase, peroxiredoxin 6, troponin T, CaM kinase II alpha, proteasome subunit N3 and cathepsin L, will be important for understanding the molecular mechanisms underlying pH reduction.

Extraordinarily long development of the Antarctic gastropod Antarctodomus thielei (Neogastropoda: Buccinoidea)

ABSTRACT Antarctic animals share many traits that are attributed to evolution in a stable, extremely cold climate. Among invertebrates, development is exceptionally slow, making observational studies of development logistically challenging, particularly when conducted under natural conditions in the field. Using multiple deployments to McMurdo Station, Antarctica, we characterized the development, in the field, of an unidentified buccinoidean gastropod species with encapsulated development. Thirteen egg capsules collected at Granite Harbor, McMurdo Sound, Ross Sea, were attached to natural rock and outplanted at a depth of ~25 m at the base of the McMurdo Intake Jetty on 2 December 2007, photographed on 5 October 2011 and 6 September 2012 and then returned to the laboratory on 27 November 2015. In 2015, four capsules were open and empty, five were open and contained a single large hatchling and the remaining four capsules were intact but not open, each containing a single large juvenile snail. To identify the developing embryos, we sequenced mitochondrial cytochrome c oxidase subunit I (COI) from two hatchlings and compared those sequences with those from adults collected near the egg mass, as well as with sequences of other buccinoideans from GenBank. Based on the close match between hatchling and adult COI sequences (hatchling sequences differed from those of an adult at only 2 of 658 nucleotide positions), we identified the embryos as Antarctodomus thielei (Powell, 1958)). The egg mass morphology and development of this species have not been previously described. Our study shows that A. thielei has a development time of more than 8 years, which is the longest measured for any gastropod.

Toxicity Impact on Bioaccumulation of Potentially Toxic Elements in African Giant Land Snail (Archachatina margenata) Treated with Different Soils and Its Ecological Risk Assessment

This study investigated the concentrations of heavy metals (As, Cd, Cr, Cu, Hg and Pb) in African Giant Land Snail (AGLS) treated with different soil samples dumpsite (A), mining site (B) and control soil (C) (a reserve area where no activities) use in farming AGLS and also to ascertain if they are within permissible limits and its ecological risk assessment on the consumption. Soil samples; at site A, B and C was collected at 0-30 cm depth with the aid of soil auger and were used for AGLS farming, to ascertain whether the potentially toxic elements (PTEs) concentration were within the permissible limits and their ecological risk assessment on AGLS consumption. A total of 54 juvenile snails of similar weights was used for the study. The experiment lasted for six month (182 days), during which the snails were subjected to similar dietary reign and equal quantity of feed. Snail’s morphological characteristics such as Weight, length and diameter of its shell were measured after farming. The soil samples were analysed for PTEs before and after farming, and snail were also analyzed for PTEs after farming for six month using atomic absorptions spectrophotometer (AAS). The ecological health risk from the consumption of these snails was assessed using standard methods and formulas. The result of different soil before and after farming shows a significant different (P&lt;0.05) between the activities sites (dump and mining) and the control site. The concentration of PTEs (As, Cd, Cr, Cu, Hg, and Pb) in snails treated with dump site soil were 3.05, 3.89, 3.60, 2.89, 3.98, and 2.55 mg/kg, and snails treated with mining site soil recorded 2.73, 2.74, 3.91, 4.96, 2.88 and 4.82 mg/kg. The values were greater than the maximum permissible limit of 0.5, 2.0, 0.3, 0.04, 0.1 and 0.1 mg/kg respectively recommended by FAO/WHO compared to the control. The study concludes that snail bioaccumulate toxic elements from the soil used in rearing them which is deleterious to humans when consumed. Also the DIM, HQ, HI on the consumption of snail reared with dumpsite, mining site soils are nearly free of risks, but continuous consumption can lead to bioaccumulation in the food chain.

In vitro molluscicidal activity of wormwood (Artemisia dubia) leaves against Oncomelania hupensis quadrasi

There have been many efforts to eradicate the problem of schistosomiasis. One method is to control the growing snail population. This study aimed to determine the molluscicidal activity of wormwood (Artemisia dubia)leaves methanolic extract against adult and juvenile. Using infusion technique, 80% methanol was used as solvent. There were eight treatments used: distilled water (T0(-)1) and 1% methanol (T0(-)2) as negative controls; 0.0002% (2mg/L) niclosamide (T0(+)) as positive control; and 11.121% (T1), 12.478% (T2), 14% (T3), 15.708% (T4) and 17.625% (T5), which were replicated five times with 10 snails per replicate. Results showed that for adults, the wormwood leaves methanolic extract was not statistically significant with the commercially available molluscicide, although 17.625% (T5) resulted in 82% mortality rate. For juveniles, the different extract concentrations resulted in 98 to 100% mortality, which were comparable to 0.0002% (2mg/L) niclosamide and were considered highly effective based on Reik &amp; Keitz (1954) and European Agency for the Evaluation of Medicinal Products (EMEA). Thus, wormwood leaves methanolic extract has a promising molluscicidal activity against adult snails at a concentration of 17.625%, and at all concentrations for the juvenile snails of O. hupensis quadrasi. The LC50 of the adult and juvenile snails were 14.075% and 10.294%, respectively. Secondary metabolites that were found positive during the qualitative phytochemical analysis with the extract were tannins, saponins, and terpenoids. The mortality of the snails can be attributed to the bioactivity of the secondary metabolites present that may be acting in combination or individually.

Shell damage leads to enhanced memory formation in Lymnaea.

Ecologically relevant stressors alter the ability of the pond snail, Lymnaea stagnalis, to form long-term memory (LTM). Here, we show that an environmentally relevant stressor, shell damage, has a dramatic effect on the enhancement of LTM formation. Damage in the form of a shell clip 24 h before operant conditioning training resulted in long-term memory (LTM) formation following a single 0.5 h training session (TS). Typically, in these snails, two 0.5 h TSs with a 1 h interval between the sessions are required to cause LTM formation. We show here that even with a 72 h interval between shell clip and training, memory enhancement still occurred. The stress associated with shell clip could be mitigated by an ongoing high-Ca2+ pond water environment, an injection of propranolol and a DNA methylation blocker. However, use of an anaesthetic (MgCl2) during the clip or intermittent exposure to the high-Ca2+ pond water environment did not mitigate the stress associated with the shell clip. Shell clip was also sufficient to cause juvenile snails, which neither learn nor form memory, to gain the capacity to form LTM. Together, the experiments demonstrate that shell clipping is an environmentally relevant stressor that can cause enhancement of LTM formation.