Aspersa Snails Research Articles

Release of lungworm larvae from snails in the environment: potential for alternative transmission pathways.

BackgroundGastropod-borne parasites may cause debilitating clinical conditions in animals and humans following the consumption of infected intermediate or paratenic hosts. However, the ingestion of fresh vegetables contaminated by snail mucus and/or water has also been proposed as a source of the infection for some zoonotic metastrongyloids (e.g., Angiostrongylus cantonensis). In the meantime, the feline lungworms Aelurostrongylus abstrusus and Troglostrongylus brevior are increasingly spreading among cat populations, along with their gastropod intermediate hosts. The aim of this study was to assess the potential of alternative transmission pathways for A. abstrusus and T. brevior L3 via the mucus of infected Helix aspersa snails and the water where gastropods died. In addition, the histological examination of snail specimens provided information on the larval localization and inflammatory reactions in the intermediate host.Methodology/Principal FindingsTwenty-four specimens of H. aspersa received ~500 L1 of A. abstrusus and T. brevior, and were assigned to six study groups. Snails were subjected to different mechanical and chemical stimuli throughout 20 days in order to elicit the production of mucus. At the end of the study, gastropods were submerged in tap water and the sediment was observed for lungworm larvae for three consecutive days. Finally, snails were artificially digested and recovered larvae were counted and morphologically and molecularly identified. The anatomical localization of A. abstrusus and T. brevior larvae within snail tissues was investigated by histology. L3 were detected in the snail mucus (i.e., 37 A. abstrusus and 19 T. brevior) and in the sediment of submerged specimens (172 A. abstrusus and 39 T. brevior). Following the artificial digestion of H. aspersa snails, a mean number of 127.8 A. abstrusus and 60.3 T. brevior larvae were recovered. The number of snail sections positive for A. abstrusus was higher than those for T. brevior.ConclusionsResults of this study indicate that A. abstrusus and T. brevior infective L3 are shed in the mucus of H. aspersa or in water where infected gastropods had died submerged. Both elimination pathways may represent alternative route(s) of environmental contamination and source of the infection for these nematodes under field conditions and may significantly affect the epidemiology of feline lungworms. Considering that snails may act as intermediate hosts for other metastrongyloid species, the environmental contamination by mucus-released larvae is discussed in a broader context.

Antimicrobial properties of mucus from the brown garden snail Helix aspersa

Research into naturally occurring antimicrobial substances has yielded effective treatments. One area of interest is peptides and proteins produced by invertebrates as part of their defence system, including the contents of mollusc mucus. Mucus produced by the African giant land snail, Achatina fulica has been reported to contain two proteins with broad-spectrum antibacterial activity. Mucus from the brown garden snail, Helix aspersa, appears to have skin regeneration properties. This study sought to investigate the antimicrobial properties of H. aspersa mucus. Mucus was collected from H. aspersa snails, diluted in phosphate-buffered saline (PBS), with the supernatant tested against a wide range of organisms in a disc-diffusion antimicrobial assay. This was followed with comparative experiments involving A. fulica, including bacteriophage assays. Mucus from both species of snail was passed through a series of protein size separation columns in order to determine the approximate size of the antimicrobial substance. Electrophoresis was also carried out on the H. aspersa mucus. Results indicated that H. aspersa mucus had a strong antibacterial effect against several strains of Pseudomonas aeruginosa and a weak effect against Staphylococcus aureus. Mucus from A. fulica also inhibited the growth of S. aureus, but the broad spectrum of activity reported by other workers was not observed. Antimicrobial activity was not caused by bacteriophage. Size separation experiments indicated that the antimicrobial substance(s) in H. aspersa were between 30 and 100 kDa. Electrophoresis revealed two proteins in this region (30–40 kDa and 50–60 kDa). These do not correspond with antimicrobial proteins previously reported in A. fulica. This study found one or more novel antimicrobial agents in H. aspersa mucus, with a strong effect against P. aeruginosa.

Development of the feline lungworms Aelurostrongylus abstrusus and Troglostrongylus brevior in Helix aspersa snails

Aelurostrongylus abstrusus (Strongylida, Angiostrongylidae) and Troglostrongylus brevior (Strongylida, Crenosomatidae) are regarded as important lungworm species of domestic felids, with the latter considered an emerging threat in the Mediterranean region. The present study aimed to assess their concurrent development in the mollusc Helix aspersa (Pulmonata, Helicidae). Thirty snails were infested with 100 first-stage larvae (L1) of A. abstrusus and T. brevior, isolated from a naturally infested kitten. Larval development was checked by digesting five specimens at 2, 6 and 11 days post infestation. Larvae retrieved were morphologically described and their identification was confirmed by specific PCR and sequencing. All H. aspersa snails were positive for A. abstrusus and T. brevior, whose larval stages were simultaneously detected at each time point. In addition, snails were exposed to outdoor conditions and examined after overwintering, testing positive up to 120 days post infestation. Data herein presented suggest that A. abstrusus and T. brevior develop in H. aspersa snails and may eventually co-infest cats. Data on the morphology of both parasitic species in H. aspersa provide additional information on their development and identification, to better understand the population dynamics of these lungworms in receptive snails and paratenic hosts.

Parasitic infections in mixed system-based heliciculture farms: dynamics and key epidemiological factors

Heliciculture is an excellent alternative to obtain edible snails but its viability is seriously threatened by pathogens. A parasitological survey was conducted in 3 mixed system-based heliciculture farms in Galicia (NW Spain), with the species Tetrahymena rostrata, Tetrahymena limacis, Tetratrichomonas limacis, Cryptobia helicogenae, Brachylaima aspersae (metacercariae and sporocysts), Alloionema appendiculatum, Nemhelix bakeri, and Riccardoella limacum being commonly found infecting Helix aspersa aspersa (petit-gris) snails. With the exception of C. helicogenae, N. bakeri, and B. aspersae sporocysts, all species were also detected in Helix aspersa maxima (gros-gris) snails, although generally with lower parameters. Most monoxenous infections, and consequently multiple parasitism, exhibited a rising trend during the first 2 months of intensive mating, with tendencies being slowed down or even reversed during the third month as a result of accumulated mortality and a sampling-derived reduction in host density. No parasites were vertically transmitted and infections were initially acquired from invading gastropod and micromammal reservoirs during fattening. Finally, artificial hibernation reduced significantly the prevalence of most species. These results confirm the importance of parasites in heliciculture and emphasize the need to prevent the entry of wild reservoirs into the farms and to rapidly remove the carcasses of dead snails from the reproduction units and fattening pens.

The Biochemistry of hemolymph and the concentration of some heavy metals in the exoskeleton of the Helix aspersa snail in two localitites in Kosovo

The concentration of Pb, Cd, Zn and Fe in the soil, their bioaccumulation in the exoskeleton of the Helix aspersa snail, as well as the concentration of total proteins and hemocyanin in its hemolymph was researched.Snails of the (N=24) sample group were collected in the close vicinity of the “Sharrcem“ Hani i Elezit (N=24) cement factory whereas, those of the (N=24) control group were taken in the village of Zhur near Prizren. The weight of the snails was approximately the same.The analysis of heavy metals was done with the Perkin Elmer – ICP OES Optima 2100 DV equipment whereas, the concentration of hemocyanin has been indirectly measured through copper with the sodium diethyldithiocarbamate.The research results show that compared to the location of Zhur, the concentration of lead, cadmium, iron and zinc (ppm) in the soil samples and the exoskeleton of snails from the contaminated location (Sharrcem) snails, are 2–6.5 times higher whereas, the quantity of total proteins (P<0.01) and the hemocyanin, (P<0.05) ) in their hemolymph, is significantly lower.The preliminary analysis of the results show that the biochemistry of the hemolymph depends on the accumulation level of heavy metals in the orgranism, while exoskeleton of the snail Helix aspersa has a higher capacity for the accumulation of Zn (about 5–20 times more than its concentration on the soil), but not for the Pb, Cd and Fe.

Discrete observations of the spatial distributions of the Helix aspersa snail in an outdoor system

O. Gonzalez, G. Perez Camargo, M. Membiela, D. Frezza, N. Bartoloni, and C. Vieites. 2009. Discrete observations of the Helix aspersa land snails’ spatial distribution in an outdoor system. Cien. Inv. Agr. 36(1):123-130. In this study, adult Helix apersa land snails with previously established periodicity were observed at three densities in their fi nishing stage in order to contribute to the body of knowledge about spatial distribution and certain behavior patterns in an outdoor system. From November 8 to December 18, 2006, snails that were in their fi nal fattening phase were grouped at three densities (50 snailm ², 100 snailm ², 200 snailm ²) and randomly placed in nine cubicles, with three replicates of each density. Twelve observations of the snail behavior were made between 12 am and 1 pm. The categories selected as “discrete acts” include: observing the snails in the shelters, on Swiss chard leaves (Beta vulgaris), adhered to the netting, on the balanced feed, on the water supply tray, and on the ground. A statistical analysis employing marginal and partial frequency tests was completed on the density x category x time interactions. It was concluded that around midday, the majority of the snails remained in the artifi cial shelters and on the Swiss chard monoculture leaves. In addition, differences were not detected for the rest of the categories in regard to the spatial distribution of the individuals in the three densities analyzed. If lower densities than the ones most commonly employed in studies (200 snailm ²) are used in an open outdoor system in the fattening stage, the individuals will use the available space in a similar way, thereby exhibiting similar behavior patterns.

Effects of subchronic digestive exposure to organic or inorganic cadmium on biomarkers in rat tissues

In an experimental food chain, Wistar rats were fed cadmium (Cd) in an inorganic (CdCl 2) or organic (mainly associated with metallothionein from Helix aspersa snail viscera) form. After 1 month of exposure to 100 μg inorganic Cd g −1 in food, an induction of metallothionein was observed in all target tissues. In liver, glutathione peroxidase (GSH-Px) activity decreased and alanine aminotransferase (ALAT) activity increased, suggesting that Cd causes hepatotoxicity. However, lipid peroxidation as well as catalase and caspase 3 (a marker of apoptosis) activities were not modified. At a rather low exposure (2.5 μg Cd g −1), metallothionein level in the kidney was found to be the most sensitive biomarker of exposure for both Cd forms. In the small intestine of rats ingesting inorganic Cd, metallothionein expression was significantly higher than that observed for rats fed organic Cd. Present results allowed proposing a simple design to assess the effect of a chemical in a trophic transfer approach.

Seasonal modulation of free radical metabolism in estivating land snails Helix aspersa

We investigated the regulation of free radical metabolism in Helix aspersa snails during a cycle of 20-day estivation and 24-h arousal in summer in comparison with estivation/arousal in winter-snails. In winter-snails (J. Exp. Biol. 206, 675–685, 2003), we had already observed an increase in the selenium-dependent glutathione-peroxidase (Se-GPX) activity in foot muscle and hepatopancreas and in the contents of hepatopancreas GSH-equivalents (GSH-eq=GSH+2 GSSG) during estivation compared with 24-h aroused snails. Summer-estivation prompted a 3.6-fold increase in Se-GPX activity in hepatopancreas, though not in foot muscle. Total-superoxide dismutase and catalase activities in hepatopancreas decreased (by 30–40%) during summer-estivation; however, no changes occurred in the activities of glutathione reductase, glutathione S-transferase and glucose-6-phosphate dehydrogenase in the two organs. GSH-eq levels were increased (by 54%) in foot muscle during estivation, but were unchanged in hepatopancreas. In contrast with winter-snails, oxidative stress markers (lipid peroxidation, carbonyl protein, and the GSSG/GSH-eq ratio) were unaltered during estivation/arousal in summer. These results demonstrate that seasonality modulates not only the absolute activities/levels of antioxidants (enzymes and GSH-eq) in H. aspersa, but also the regulatory process that controls the snail's antioxidant capacity during estivation/arousal. These results suggest that H. aspersa has an “internal clock” controlling the regulation of free radical metabolism in the different seasons.

Effects of starvation on haemolymphatic glucose levels, glycogen contents and nucleotidase activities in different tissues of Helix aspersa (Müller, 1774) (mollusca, gastropoda)

In the present study, the glucose concentration in the haemolymph and glycogen levels were determined in the various body parts of the Helix aspersa snail after feeding lettuce ad libitum and after various periods of starvation. To characterize the effect of starvation on nucleotidase activity, enzyme assays were performed on membranes of the nervous ganglia and digestive gland. Results demonstrated the maintenance of the haemolymph glucose concentration for up to 30 days of starvation, probably due to the consumption of glycogen from the mantle. In the nervous ganglia, depletion of glycogen occurs progressively during the different periods of starvation. No significant changes were observed on ATP and ADP hydrolysis in the membranes of nervous ganglia and no alterations in Ca2+ -ATPase and Mg2+ -ATPase occurred in the membranes of the digestive gland of H. aspersa during the different periods of starvation. Although there were no changes in the enzyme activities during starvation, they could be modulated by effectors in situ with concomitant changes in products/reactants during starvation.

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Everything you always wanted to know about sexes.

A field method using microcosms to evaluate transfer of Cd, Cu, Ni, Pb and Zn from sewage sludge amended forest soils to Helix aspersa snails

Juvenile Helix aspersa snails exposed in field microcosms were used to assess the transfer of Cd, Cu, Ni, Pb and Zn from forest soils amended with liquid and composted sewage sludge. Zn concentrations and contents were significantly higher in snails exposed to liquid and composted sludge after 5 and 7 weeks of exposure, when compared with control. Trends were less clear for the other metals. Present results show that Zn, among the cocktail of metallic trace elements (MTE) coming from sewage sludge disposal, represents the principal concern for food chain transfer and secondary poisoning risks. The microcosm design used in this experiment was well suited for relatively long-term (about 2 months) active biomonitoring with H. aspersa snails. The snails quickly indicated the variations of MTE concentrations in their immediate environment. Therefore, the present study provides a simple but efficient field tool to evaluate MTE bioavailability and transfer.

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 μg.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.

Transfer and effects of cadmium in an experimental food chain involving the snail Helix aspersa and the predatory carabid beetle Chrysocarabus splendens.

The transfer and the toxic effects of Cd were studied in an experimental food chain involving the snail Helix aspersa as prey organism and one of its natural predators, the carabid beetle Chrysocarabus splendens. Juvenile snails were fed plant-based food enriched with 0, 10, 50 and 100 microg g(-1) of Cd, then were offered as prey to beetle larvae from egg hatching to pupation stage. Cd concentrations in snail tissues increased with increasing Cd concentration in food and with duration of exposure. Bioaccumulation factors ranged from 1.87 to 3.39, showing that H. aspersa snails, even in their early life stages, belong to macroconcentrator species for Cd. No significant reduction of snail consumption by beetles was found in exposed groups. Cd concentrations in beetle larvae remained very low (lower than 1 microg g(-1) for all groups), demonstrating a very effective regulation capacity in beetle larvae. However, Cd concentrations in highest exposed groups were higher than those found in control groups. Cd contents in adult beetles were lower than in larvae, showing a loss of Cd during metamorphosis. Despite the low Cd concentrations found in beetles, their exposure to Cd contaminated snails led to 31% of mortality, which occurred only during pupation and for the highest exposure level. No clear sublethal effects were found. These results showed that snails inhabiting heavily polluted areas may represent a risk of secondary poisoning for predatory invertebrates and provided quantitative data on the transfer of Cd between two compartments of a terrestrial food chain.

Life cycle of Brachylaima mascomai n. sp. (Trematoda: Brachylaimidae), a parasite of rats in the Llobregat delta (Spain).

The terrestrial triheteroxenous life cycle of Brachylaima mascomai n. sp. (Trematoda: Brachylaimidae) is elucidated. Operculated, assymetric, embryonated eggs (25.4 x 12.7 microm) are passed with feces of the natural (Rattus norvegicus and R. rattus) and experimental (albino and wild mice, albino rats, Apodemus sylvaticus, Mus spretus [Muridae] and the golden gerbil) definitive hosts and ingested by the helicid gastropod Pseudotachea splendida, the only natural and experimental first intermediate host. Microcaudate cercariae harbored in branched sporocysts in the digestive gland emerge from this snail and contact P. splendida, Otala punctata, Theba pisana, and Helix (C.) aspersa snails developing into unencysted infective metacercariae in the kidney. Definitive hosts are infected by ingestion of infected snails; the adult parasites inhabit the small intestine. Chaetotaxic cercarial pattern specific at acetabular (S(II) 8-10 papillae) and cephalic (C(III) 13-15 papillae, H 16 papillae) levels. Three types of cercarial papillae are observed by scanning electron microscopy (SEM) and their arrangement is correlated with chaetotaxy for the first time in trematodes: argentophilic papillae with fingerlike process (cephalic, body, and acetabular levels), argentophilic papillae with opening (2 papillae in the M body level), and nonargentophilic dome-shaped papillae (alternated with argentophilic S(II) papillae on the ventral sucker). SEM detected interlacing network of ridges covering the metacercarial body. Adults with multidigitate tegumentary spines were observed by SEM. Subequal suckers; the acetabulum located in the posterior part of anterior fifth of body. Vitellaria extend from between middle level and anterior margin of anterior testis to between middle level and posterior margin of acetabulum. Uterus almost reaches the intestinal bifurcation.

INFLUENCE OF THE QUINOLIZIDINE ALKALOID CONTENT OF LUPINUS ALBUS (FABACEAE) ON THE FEEDING CHOICE OF HELIX ASPERSA (GASTROPODA: PULMONATA)

Adult Helix aspersa snails were maintained individually for one week in plastic cages with 9 living Lupinus albus plants as their only food. Among these 9 plants, 3 chemotypes bitter, intermediate and sweet which differed in their alkaloid content were equally represented. Each day, the leaf surface grazed and the number of leaves attacked by the snails were recorded for each chemotype and each snail. A consumption/ attack (C/A) ratio was calculated by dividing the surface grazed (C) by the number of attacks (A). The number of attacks and the grazed area were positively correlated for each chemotype during the whole experiment, and the snails ate similar quantities of lupin each day. After 4 and 6 days of experiment, we noticed a rejection of the bitter chemotype in favor of the intermediate and sweet ones respectively. After the 6th day, the surface grazed per attack was significantly higher on the sweet chemotype than on the bitter plants. We hypothesize that rejection of the bitter chemotype might be related to (i) an alkaloids reaction threshold associated with an increase in the amount of alkaloids in the wounded plants and/or (ii) aversive ingestive conditioning.

Neurotoxic esterase in the land snails: In vitro comparative and kinetic studies

Abstract In vitro relative sensitivity of NTE of Helix aspersa and Theba pisana snails to eight organophosphorous compounds were investigated. The most potent inhibitors against NTE of H. aspersa snail were O‐methyl O‐2,5‐dichlorophenyl phenylphosphonate and dimethoate‐oxon with Ki values of 6.01 x 105 and 5.94 x 105 M‐1 min‐1, respectively. In the case of T. pisana, triphenyl phosphite and O‐methyl O‐2,5‐dichlorophenyl phenyl‐phosphonate showed high potency as NTE inhibitors with Ki values of 1.74 x 107 and 4.14 x 106 M‐1 min‐1, respectively. From the results obtained, NTE free of inhibitor had the highest dissociation constant in both snails, where Km value of H. aspersa snail was 180 times smaller than Km value of T. pisana. The lowest Km value of H. aspersa snail was found to be 1.6 x 10‐3 M for EPN‐oxon while the highest value was 1.2 x 10‐2 m for leptophos‐oxon. On the other hand, the lowest Km value of T. pisana snail did account for 2.4 x 10‐3 for dimethoateoxon. Finally it could be concluded that...

Factors affecting the food intake, growth and protein utilization in the Helix aspersa snail. Protein content of the diet and animal age

Food intake, growth and protein utilization were studied in the Helix aspersa snail by means of a nutritional balance experiment. This was designed in a 5 x 11 factorial arrangement involving 5 diets of different protein content (10.0, 12.5, 15.0, 17.5 and 20.0%) and 11 animal ages (ranging over 15 to 180 days of age). Dietary protein content and animal age determined food intake and protein utilization. The variations of dry matter and protein intake rates, growth rates, growth efficiency factors and protein retention rates, depending on dietary protein content or animal age were in agreement with what happens in other animals. These results suggest that there is no need to use diets with more than 17.5% of crude protein in these animals.

Land snails as experimental animals: a study of the variability and distribution of individual weights in Helix aspersa snails born from the same clutch

A study was carried out to examine the distribution of individual weights in Helix aspersa snails, the aims being to establish the best estimate of the ponderal growth and also to obtain a model growth curve. Four groups of 20 snails from the same clutch were analysed and kept under experimental conditions from birth up to 6 months. The variability of their individual weights within groups was studied by calculating the coefficients of variation every 15 days. At the same time, the assumed normal distribution of those weights was being tested. The coefficients of variation increased with age and the assumed normal distribution of individual weights had to be rejected. By means of a log transformation of the original data, a model growth curve was constructed, and was used to assess the possibility of estimating age from weight. We finally reached the conclusion that median weight, rather than the mean, would be a better measure of central tendency to use until it is possible to obtain selected populations. The difficulty of estimating age from weight is emphasized.

Linear analysis ofKconduction in snail neuron from impedance determinations

Abstract The complex impedance of a soma cell membrane in an identified, isolated single neuron from Helix aspersa (snail) was measured in the frequency range 0.25 Hz to 100 Hz in order to quantify the electrical properties and kinetics of potassium conduction. Use of a synchronized Fourier-synthesized signal applied as a small perturbation during step current-source stimulation via an external suction capillary and use of an internal microelectrode to record the voltage response permitted rapid (4 sec) acquisition of a 400-point impedance function of frequency. Three types of potassium conductance were distinguishable pharmacologically in complex impedance determinations. The linear kinetic parameters of two types of K conductance, the voltage-sensitive “delayed rectifier” potassium conductance, and the Ca-activated, potassium conductance were obtained by curve fitting model admittance functions of frequency to complex admittances obtained from the reciprocal of measured steady-state impedance data. Time...

Na Conductance Kinetics in the Low-Frequency Impedance of Isolated Snail Neurons

The complex impedance of isolated single neurons of Helix aspersa (snail) was measured at low frequencies (0.25-100 Hz) with a combination of a suction electrode for applying current and a microelectrode for measuring potential response. A repetitive, Fourier-synthesized signal superposed as a small perturbation (0.2 nA rms) on step current clamps was used in conjunction with Fourier transform techniques to obtain high-resolution impedance data 1 s after a step. The membrane capacitance of an 80 Ωm diameter cell, measured in the frequency range 2.5-1000 Hz after suppression of ion conduction, was 1.8 nF and had a constant phase angle of about -69°. The resting (-50 mV) extrapolated zero-frequency resistance, before suppression of conduction in the same cell, of a predominantly Na-conducting membrane was about 5 MΩ. Linear ion-conduction parameters were estimated directly by fitting an admittance model, based on the linearized Hodgkin-Huxley equations with a constant-phase-angle capacitance, to the reciprocal of the impedance data. The natural frequencies of Na activation and inactivation processes for small depolarizations (10-20 mV from rest potential) were determined to be 23-28 Hz (Tm = 7-5.7 ms) and 2.5-1.8 Hz (Th = 64-88 ms), respectively. These values are more than an order greater than the corresponding relaxation times of Na channels in the squid axon.