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Pierre-marie Badot - One of the best experts on this subject based on the ideXlab platform.
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Metal distribution and metallothionein induction after cadmium exposure in the terrestrial snail Helix Aspersa (Gastropoda, Pulmonata).
Environmental Toxicology and Chemistry, 2008Co-Authors: Florian Hispard, Renaud Scheifler, Annette De Vaufleury, Pierre-marie Badot, Dietmar Schuler, Reinhard DallingerAbstract:The aim of the present work was to study the effect of Cd2+ exposure on metallothionein (MT) induction and on the distribution of metals (Cd, Cu, and Zn) in the terrestrial pulmonate Helix Aspersa. In particular, the soluble and nonsoluble pools of the accumulated metals and their tissue distribution in uncontaminated and contaminated edible snails were investigated after a two-week exposure to Cd2+. In the soluble cytosolic pool of the midgut gland of H. Aspersa, three metal-specific putative MT isoforms were separated following a fractionation protocol with diethylaminoethyl cellulose, size-exclusion chromatography, ultrafiltration, and reversed-phase high-performance liquid chromatography (RP-HPLC). Interestingly, one of the above isoforms seems to bind both Cd and Cu, which may in addition mobilize, after induction by Cd2+, some of the intracellular Cu and, thus, perhaps increase the Cu pool in the cytosolic fraction. The cDNA and its translated amino acid sequence of a Cd2+-binding MT isoform from the snail midgut gland was characterized and attributed to one of the putative MT isoforms obtained by RP-HPLC. The amino acid sequence of this Cd-MT isoform of H. Aspersa differed from similar sequences described in other terrestrial pulmonates, such as Helix pomatia or Arianta arbustorum, by only a few amino acids (n = 4 and 8, respectively). That the identified Cd-MT from H. Aspersa is inducible by Cd2+ also was shown, chromatographic evidence aside, by a specific polymerase chain reaction protocol on a cDNA basis, which included a noninducible housekeeping gene as a control.
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Modelling chronic exposure to contaminated soil: a toxicokinetic approach with the terrestrial snail Helix Aspersa.
Environment International, 2006Co-Authors: Frederic Gimbert, Michael Coeurdassier, Renaud Scheifler, Annette De Vaufleury, Francis Douay, Pierre-marie BadotAbstract:To enlarge the possibilities of using organisms of the soil fauna to assess the bioaccumulative potential of chemicals, the kinetic of soil cadmium (Cd) transfer to the terrestrial gastropod Helix Aspersa was investigated under laboratory conditions during a long-term experiment (6 months). During the exposure phase (3 months), juvenile snails were subjected to three different concentrations of Cd spiked in artificial ISO soil (ISO 0, 20 and 100 mg Cd kg(-1)) and to a field soil (ME4) industrially contaminated by 20 mg Cd kg (-1). For both soils, internal steady-state Cd concentrations were reached in the viscera of the snails, the main storage organ for Cd, after 2 weeks of exposure whatever the Cd concentration in soil. The equilibrium concentrations in the viscera were 0.7 (+/-0.1), 11.3 (+/-2.4), 73.3 (+/-4.8) and 6.3 (+/-1.3) mg Cd kg(-1) dry mass for ISO 0, ISO 20, ISO 100 and ME4, respectively. During the depuration phase (3 months), from 0 to 52% of the accumulated Cd in the viscera were removed by excretion or relocation in the foot. However, the snails were not able to depurate down to initial concentrations. Data were modelled by integrating a specific growth rate constant into one-compartment toxicokinetic models. This allowed the calculation of Cd uptake rates that can be used as indicators of metal bioavailability. Since this parameter was found to be lower for snails exposed to the field soil ME4, we concluded that lower Cd bioavailability in this field soil was responsible of the lower transfer to the snails compared to the ISO 20 soil, even though they were polluted to similar extents. Internal validation showed that the toxicokinetic models could be applied for predictive purposes, promising for the development of a bioaccumulation directive for terrestrial environment.
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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.
Environmental Pollution, 2002Co-Authors: Renaud Scheifler, Annette De Vaufleury, M Ben Brahim, J-m Carnus, Pierre-marie BadotAbstract: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.
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transfer of cadmium from plant leaves and vegetable flour to the snail Helix Aspersa bioaccumulation and effects
Ecotoxicology and Environmental Safety, 2002Co-Authors: Renaud Scheifler, Gomotde A Vaufleury, Pierre-marie BadotAbstract: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.
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dose dependent growth inhibition and bioaccumulation of hexavalent chromium in land snail Helix Aspersa Aspersa
Environmental Toxicology and Chemistry, 2000Co-Authors: Michael Cœurdassier, Annette De Vaufleury, Pierre-marie BadotAbstract:The toxicity of Cr6+ was determined in a laboratory environment in the snail Helix Aspersa Aspersa. The effects on growth were evaluated on animals reared in controlled conditions at the age of one month that had been exposed for 28 d to increasing doses of Cr6+ mixed in with their food. Two experimental groups were set up with concentrations of chromium in the feed of 250 to 1,250 μg/g (test 1) and 100 to 800 μg/g (test 2). Growth inhibition was dose dependent, and the mean EC50 calculated at four weeks for tests 1 and 2 were, respectively, 354.7 and 298.8 μg/g and for the EC10 195.3 and 160.9 μg/g. The levels of Cr6+ bioaccumulated in the foot and the viscera of the snails were dose dependent in both types of tissues. The highest concentrations occurred in the viscera, the levels being 0.79 μg/g in the controls and reaching 3,067 μg/g in the animals exposed to the maximum contamination (1,250 μg/g). These high levels of bioaccumulation in addition to the lower concentrations of Cr6+ excreted in the feces than those present in the food suggest that chromium is not physiologically regulated by Helix Aspersa. The results provide added support for the use of snails as a model to determine the toxicity of substances in laboratory biotests by measuring the effects on growth and by assessing bioaccumulation.
Ronald Chase - One of the best experts on this subject based on the ideXlab platform.
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sensory innervation of the ovotestis in the snail Helix Aspersa
The Journal of Experimental Biology, 2003Co-Authors: Tomasz Antkowiak, Ronald ChaseAbstract:Because oviposition in the land snail Helix Aspersa is a metabolically expensive process coupled to a high fixed cost, one expects oviposition to occur only when the clutch size surpasses a minimum value at which the reproductive benefit exceeds the cost. We propose that neural innervation of the gonad allows H. Aspersa to monitor oocyte production and ensure an adequate supply of gametes prior to ovulation. The ovotestis is innervated by a branch of the intestinal nerve in which the majority of axon fibres measure <0.2 microm in diameter. We found a strong positive correlation between the number of mature oocytes in the ovotestis and the frequency of spontaneous afferent spikes in the nerve branch. Tactile stimulation of the ovotestis resulted in a 20-fold increase in afferent spikes and an efferent reflex directed towards the ovotestis and the pericardium. Afferent activity also increased 10-fold after an experimentally induced increase in the volume of the ovotestis. These results suggest that the growing oocytes expand the walls of the acini and trigger action potentials in the mechanosensitive nerve terminals that lie within the acinar walls. We hypothesize that the resulting tonic signal is permissive for ovulation. In addition, a phasic sensory signal may occur during ovulation to trigger CNS motor output related to oviposition.
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determinants of paternity in the garden snail Helix Aspersa
Behavioral Ecology and Sociobiology, 2002Co-Authors: David W Rogers, Ronald ChaseAbstract:Despite the likely importance of post-copulatory sexual selection in simultaneous hermaphrodites, the factors influencing sperm competition in these organisms are generally unknown. We have investigated the effects of dart-shooting, mating order, and several other predictors on the proportion of offspring fathered by penultimate (P n -1) and ultimate (P n ) sperm donors in multiply mated garden snails, Helix Aspersa. While paternity ratios were biased towards the penultimate donor (mean P n -1=0.61), the magnitude of this advantage was dependent upon which of the two donors successfully darted the recipient. Mean P n -values increased from 0.17 when the recipient was hit by the penultimate donor to 0.39 when it was hit by the ultimate donor. Furthermore, the effect of the dart was more pronounced in the clutches of smaller recipients. From these results, and observations of live sperm in the storage organs, we propose a novel mechanism to explain the detected pattern of sperm utilization in helicid snails. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00265-002-0519-6.
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dart receipt promotes sperm storage in the garden snail Helix Aspersa
Behavioral Ecology and Sociobiology, 2001Co-Authors: David W Rogers, Ronald ChaseAbstract:During courtship, many helicid snails attempt to pierce the body walls of their mating partners with mucus-coated calcareous darts. The mucus covering the dart induces conformational changes in the female reproductive tract of the recipient, closing off the entrance to the gametolytic bursa copulatrix. We have tested the effect of dart receipt on the number of sperm stored by once-mated snails, Helix Aspersa. Snails that were hit by darts stored significantly more sperm than did snails that were missed. Additionally, the effect of the dart was stronger in smaller animals and the number of sperm stored decreased with the shell volume of the recipient. Although larger animals produced larger spermatophores, dart-shooting success was not related to the number of sperm transferred. These data suggest a role for dart-shooting in post-copulatory sexual selection.
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changes in the reproductive system of the snail Helix Aspersa caused by mucus from the love dart
The Journal of Experimental Biology, 1998Co-Authors: Joris M Koene, Ronald ChaseAbstract:The function of the love dart in certain species of terrestrial snails is unknown. In Helix Aspersa, the dart is a sharp calcareous structure that is used to pierce the partner's skin during courtship. When expelled, the dart is covered with a thick mucus. The hypothesis tested here is that the mucus contains a biologically active substance. Extracts of the digitiform glands that produce this mucus were applied to parts of the reproductive system in vitro. The extracts triggered an initial reconfiguration of the copulatory canal that caused the bursa tract diverticulum to become more accessible to the spermatophore. The reconfiguration of the copulatory canal also closed off the tract leading to the bursa copulatrix, a sperm-digesting organ. A few minutes after the initial contraction, the peristaltic contractions in the diverticulum became significantly more frequent. This latter effect continued for at least 1 h, provided that the mucus extract remained in the saline bath. The minimum effective dosage was less than the 2.2 mg of mucus transferred with the dart. Sperm competition is expected in Helix Aspersa since multiple matings occur before eggs are laid. By influencing the female organs involved in the processing of foreign sperm, the dart shooter may increase the chance that his sperm will fertilise eggs.
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the love dart of Helix Aspersa muller is not a gift of calcium
Journal of Molluscan Studies, 1998Co-Authors: Joris M Koene, Ronald ChaseAbstract:The phenomenon of dart shooting in several species of land snails has still not been explained. We were interested in whether the dart can function as a nuptial gift of calcium, as previously proposed. Donating calcium would increase the fitness of the offspring and thereby result in a higher reproductive success for the donor. We confirmed in Helix Aspersa that the developing embryo takes up calcium from the egg shell for the formation of its embryonic shell. However, other results from behavioural observations and calcium measurements in various reproductive structures do not support the calcium hypothesis. We found that the dart penetrated the skin in 91.7% of the shootings, but it was internalized by the recipient in only 6.3% of the shootings. The amount of calcium in one dart is roughly equal to that of one egg, and thus it would not contribute significantly to an average clutch of 59 eggs. The spermatophore contains virtually no calcium, and therefore it is unlikely that the dart signals a donation of calcium with the sperm. The dart is also unlikely to influence egg laying since dart shooting does not predict either the latency or the productivity of egg laying in the shooter or the recipient. We conclude that the love dart of Helix Aspersa is not a gift of calcium. Instead, we suggest that it is a vehicle to introduce a substance into the partner to influence the fate of the donated sperm.
Annette De Vaufleury - One of the best experts on this subject based on the ideXlab platform.
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Metal distribution and metallothionein induction after cadmium exposure in the terrestrial snail Helix Aspersa (Gastropoda, Pulmonata).
Environmental Toxicology and Chemistry, 2008Co-Authors: Florian Hispard, Renaud Scheifler, Annette De Vaufleury, Pierre-marie Badot, Dietmar Schuler, Reinhard DallingerAbstract:The aim of the present work was to study the effect of Cd2+ exposure on metallothionein (MT) induction and on the distribution of metals (Cd, Cu, and Zn) in the terrestrial pulmonate Helix Aspersa. In particular, the soluble and nonsoluble pools of the accumulated metals and their tissue distribution in uncontaminated and contaminated edible snails were investigated after a two-week exposure to Cd2+. In the soluble cytosolic pool of the midgut gland of H. Aspersa, three metal-specific putative MT isoforms were separated following a fractionation protocol with diethylaminoethyl cellulose, size-exclusion chromatography, ultrafiltration, and reversed-phase high-performance liquid chromatography (RP-HPLC). Interestingly, one of the above isoforms seems to bind both Cd and Cu, which may in addition mobilize, after induction by Cd2+, some of the intracellular Cu and, thus, perhaps increase the Cu pool in the cytosolic fraction. The cDNA and its translated amino acid sequence of a Cd2+-binding MT isoform from the snail midgut gland was characterized and attributed to one of the putative MT isoforms obtained by RP-HPLC. The amino acid sequence of this Cd-MT isoform of H. Aspersa differed from similar sequences described in other terrestrial pulmonates, such as Helix pomatia or Arianta arbustorum, by only a few amino acids (n = 4 and 8, respectively). That the identified Cd-MT from H. Aspersa is inducible by Cd2+ also was shown, chromatographic evidence aside, by a specific polymerase chain reaction protocol on a cDNA basis, which included a noninducible housekeeping gene as a control.
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Modelling chronic exposure to contaminated soil: a toxicokinetic approach with the terrestrial snail Helix Aspersa.
Environment International, 2006Co-Authors: Frederic Gimbert, Michael Coeurdassier, Renaud Scheifler, Annette De Vaufleury, Francis Douay, Pierre-marie BadotAbstract:To enlarge the possibilities of using organisms of the soil fauna to assess the bioaccumulative potential of chemicals, the kinetic of soil cadmium (Cd) transfer to the terrestrial gastropod Helix Aspersa was investigated under laboratory conditions during a long-term experiment (6 months). During the exposure phase (3 months), juvenile snails were subjected to three different concentrations of Cd spiked in artificial ISO soil (ISO 0, 20 and 100 mg Cd kg(-1)) and to a field soil (ME4) industrially contaminated by 20 mg Cd kg (-1). For both soils, internal steady-state Cd concentrations were reached in the viscera of the snails, the main storage organ for Cd, after 2 weeks of exposure whatever the Cd concentration in soil. The equilibrium concentrations in the viscera were 0.7 (+/-0.1), 11.3 (+/-2.4), 73.3 (+/-4.8) and 6.3 (+/-1.3) mg Cd kg(-1) dry mass for ISO 0, ISO 20, ISO 100 and ME4, respectively. During the depuration phase (3 months), from 0 to 52% of the accumulated Cd in the viscera were removed by excretion or relocation in the foot. However, the snails were not able to depurate down to initial concentrations. Data were modelled by integrating a specific growth rate constant into one-compartment toxicokinetic models. This allowed the calculation of Cd uptake rates that can be used as indicators of metal bioavailability. Since this parameter was found to be lower for snails exposed to the field soil ME4, we concluded that lower Cd bioavailability in this field soil was responsible of the lower transfer to the snails compared to the ISO 20 soil, even though they were polluted to similar extents. Internal validation showed that the toxicokinetic models could be applied for predictive purposes, promising for the development of a bioaccumulation directive for terrestrial environment.
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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.
Environmental Pollution, 2002Co-Authors: Renaud Scheifler, Annette De Vaufleury, M Ben Brahim, J-m Carnus, Pierre-marie BadotAbstract: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.
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dose dependent growth inhibition and bioaccumulation of hexavalent chromium in land snail Helix Aspersa Aspersa
Environmental Toxicology and Chemistry, 2000Co-Authors: Michael Cœurdassier, Annette De Vaufleury, Pierre-marie BadotAbstract:The toxicity of Cr6+ was determined in a laboratory environment in the snail Helix Aspersa Aspersa. The effects on growth were evaluated on animals reared in controlled conditions at the age of one month that had been exposed for 28 d to increasing doses of Cr6+ mixed in with their food. Two experimental groups were set up with concentrations of chromium in the feed of 250 to 1,250 μg/g (test 1) and 100 to 800 μg/g (test 2). Growth inhibition was dose dependent, and the mean EC50 calculated at four weeks for tests 1 and 2 were, respectively, 354.7 and 298.8 μg/g and for the EC10 195.3 and 160.9 μg/g. The levels of Cr6+ bioaccumulated in the foot and the viscera of the snails were dose dependent in both types of tissues. The highest concentrations occurred in the viscera, the levels being 0.79 μg/g in the controls and reaching 3,067 μg/g in the animals exposed to the maximum contamination (1,250 μg/g). These high levels of bioaccumulation in addition to the lower concentrations of Cr6+ excreted in the feces than those present in the food suggest that chromium is not physiologically regulated by Helix Aspersa. The results provide added support for the use of snails as a model to determine the toxicity of substances in laboratory biotests by measuring the effects on growth and by assessing bioaccumulation.
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standardized growth toxicity testing cu zn pb and pentachlorophenol with Helix Aspersa
Ecotoxicology and Environmental Safety, 2000Co-Authors: Annette De VaufleuryAbstract:Abstract Juvenile Helix Aspersa (1 month, 1 g) were exposed for 4 weeks to food contaminated with copper, zinc, lead, and pentachlorophenol. At concentrations observed in contaminated soils, two essential metals at low levels (Cu and Zn) had a dose-dependent sublethal action on growth. Copper inhibited growth dose-dependently between 1000 and 2000 μg·g−1 (EC50=1200 μg·g−1), whereas zinc had a toxic effect from 4000 μg·g−1 (EC50=5500 μg·g−1) on. Lead, a nonessential metal, had no negative effect on growth, unlike cadmium (EC50=140 μg·g−1), as reported previously. Pentachlorophenol inhibited growth at a concentration of 500 μg·g−1 from the fourth week and 1000 μg·g−1 from the first week on. The results obtained with these key organisms in the food chain (consumers) complement those obtained with other land invertebrates (earthworms, springtails, wood-lice, etc.). The findings of the present study and those of earlier studies indicate that juvenile snails are useful organisms for testing the sublethal toxicity of chemicals acting via the food, i.e., the main route of toxicant uptake in land animals.
Luc Madec - One of the best experts on this subject based on the ideXlab platform.
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spatial genetic pattern in the land mollusc Helix Aspersa inferred from a centre based clustering procedure
Genetics Research, 2006Co-Authors: Annie Guiller, Alain Bellido, Alain Coutelle, Luc MadecAbstract:The present work provides the first broad-scale screening of allozymes in the land snail Helix Aspersa. By using overall information available on the distribution of genetic variation between 102 populations previously investigated, we expect to strengthen our knowledge on the spread of the invasive Aspersa subspecies in the Western Mediterranean. We propose a new approach based on a centre-based clustering procedure to cluster populations into groups following rules of geographical proximity and genetic similarity. Assuming a stepping-stone model of diffusion, we apply a partitioning algorithm which clusters only populations that are geographically contiguous. The algorithm used, which is actually part of leading methods developed for analysing large microarray datasets, is that of the k-means. Its goal is to minimize the within-group variance. The spatial constraint is provided by a list of connections between localities deduced from a Delaunay network. After testing each optimal group for the presence of spatial arrangement in the genetic data, the inferred genetic structure was compared with partitions obtained from other methods published for defining homogeneous groups (i.e. the Monmonier and SAMOVA algorithms). Competing biogeographical scenarios inferred from the k-means procedure were then compared and discussed to shed more light on colonization routes taken by the species.
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spatial analysis of allozyme and microsatellite dna polymorphisms in the land snail Helix Aspersa gastropoda helicidae
Molecular Ecology, 2001Co-Authors: J F Arnaud, Luc Madec, Annie Guiller, Alain BellidoAbstract:The genetic structure of the land snail Helix Aspersa was investigated for 21 populations collected along a road located in the polders of the Bay of Mont-Saint-Michel (Brittany, France), following a sampling scheme the area of which did not exceed 900 m in length. A total of 369 individuals were genotyped for five enzymatic markers and seven microsatellite loci. We used sequential hierarchical F -statistics at different spatial scales and spatial autocorrelation statistics to explore recent historical patterns involved in the observed genetic distribution. Whatever the statistics used, congruent levels of spatial genetic substructuring across loci were demonstrated, excepted for one allozyme locus. Overall spatial genetic arrangement matched in a substantial fashion theoretical predictions based on the limited dispersal power of land snails. Positive autocorrelation over short-distance classes may result from the development of genetically distinct patches of individuals organized in family-structured colonies. Therefore, spatial signatures of average I correlograms can be viewed as the expression of a stepping-stone model of population structure, sometimes involving external migrational events. Overall, the revealed pattern of population subdivision on a microgeographical scale was suggestive of a neighbourhood structure. Finally, microsatellite loci are especially suitable for the detection of small genetic clustering, and combining different classes of markers offers the potential to gain further insight into the description of spatial genetic variability over short temporal and geographical scales.
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evolutionary history of the land snail Helix Aspersa in the western mediterranean preliminary results inferred from mitochondrial dna sequences
Molecular Ecology, 2001Co-Authors: Annie Guiller, Luc Madec, Marieagnes Coutellecvreto, Jean DeunffAbstract:Intraspecific phylogeographic methods provide a means of examining the history of genetic exchange among populations. As part of a study of the history of Helix Aspersa in the Western Mediterranean, we performed a phylogenetic analysis based on partial sequences of the mitochondrial large ribosomal subunit (16S) gene. Our samples include 31 H. a. Aspersa populations from North Africa previously investigated for anatomical and biochemical characters. To clarify subspecific relationships, three individuals of the subspecies H. a. maxima were also studied. The molecular phylogeny inferred agrees largely with previous results, in splitting H. a. Aspersa haplotypes into an eastern and a western group. H. a. maxima haplotypes form a third lineage arising before the H. a. Aspersa groups. Divergence times estimated between the lineages suggest that dispersal during Pleistocene glaciation and vicariance events due to Pliocene geological changes in the western Mediterranean may both have played a significant part in the establishment of the present range of H. Aspersa.
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phenotypic plasticity in reproductive traits importance in the life history of Helix Aspersa mollusca helicidae in a recently colonized habitat
Biological Journal of The Linnean Society, 2000Co-Authors: Luc Madec, Christophe Desbuquois, Marieagnes CoutellecvretoAbstract:Abstract Reproductive traits of the land snail Helix Aspersa Muller were investigated under artificial conditions from two samples, one collected from a population exposed to unpredictable human pressures in its natural environment, i.e. a recently created polders area with intensive agriculture, and the other from a snail farm in which animals were reared under constant conditions defined as «optimal» for growth and reproduction. Results were compared with data collected from natural populations of the same region (Brittany) and from habitats spanning the environmental heterogeneity of the range of the species. A large part of the variation among populations could be explained by different phenotypic covariances between shell size, clutch size and egg size, but not by the number of clutches per snail. Thus, the higher egg production of snails from the polders was related to (i) a strong correlation between clutch size and shell size, shell size being in the upper limit of the overall range for the region concerned; (ii) an uncommonly low egg weight in comparison with the «norm» of Helix Aspersa , this trait seeming to be involved in a trade-off with clutch size. Second clutches were smaller than the first ones, but their eggs were significantly heavier. This difference may be linked to a size-dependent mortality of juveniles during winter which arises in all populations in which hibernation occurs as an adaptation to low temperatures. In addition to the selective regime usually involved for populations of helicid snails from Western Europe, several unpredictable mortality factors occurred in the polders area: herbicide and pesticide treatments (lethal for young snails), human predation (lethal for adults) and burning (lethal for all snails). Life-history patterns of Helix Aspersa are discussed in relation to its ability to successfully colonize a large range of habitats modified by humans, to such an extent that it can become a pest.
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microspatial genetic structure in the land snail Helix Aspersa gastropoda helicidae
Heredity, 1999Co-Authors: J F Arnaud, Luc Madec, Alain Bellido, Annie GuillerAbstract:The microspatial genetic structure of allele frequencies at seven isozyme loci was examined for 15 populations of the land snail Helix Aspersa sampled in a village from Brittany (north-western France). Spatial heterogeneity of allele frequencies was highly significant (P < 0.001). Fixation indices reflected nonrandom mating within neighbourhoods and a slight but consistent differentiation between colonies (FST=0.044; P < 0.01). Analyses of gene flow or genetic distances failed to reveal a significant relationship with geographical distance, probably because of the complexity of environmental heterogeneity. However, matrix comparisons between genetic distances and connectivity networks among adjacent colonies (Gabriel-connected graph) yielded a significant correlation in every case, indicating a ‘step-by-step’ relationship between neighbouring localities. Moreover, most of the allozymes were spatially structured and showed (i) a gradual isolation of colonies with increasing geographical distances, and (ii), for some correlogram profiles, a circular gradient illustrating a multidirectional colonization of the village. The probable existence of disperser individuals allowed us to suggest a metapopulation model which would explain the maintenance of such animals in fragmented habitats where anthropogenic disturbances and extinction/recolonization events are commonly observed.
Larry Richmond - One of the best experts on this subject based on the ideXlab platform.
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do the soft tissues of Helix Aspersa serve as a quantitative sentinel of predicted free lead concentrations in soils
Applied Soil Ecology, 2003Co-Authors: Alan Beeby, Larry RichmondAbstract:Previous research suggests that free metal concentrations in soils are the best correlate of the proportion available for uptake, especially by plants. The same may be true for animals which ingest soil, such as earthworms and gastropod molluscs. Using predictions from a simple model proposed by Sauve et al. [Environ. Pollut. (1997) 149] and based on soil pH and total soil concentrations, the relationship between free soil Pb and soft tissue Pb concentrations is evaluated in the garden snail Helix Aspersa. Five replicate adults collected from 23 sites in England and Wales were partitioned into two tissue fractions and the relationship between their Pb concentrations and those of their native soil was examined using simple regression analysis. Levels in both fractions rose with free Pb concentrations, but the terms of each relationship and its level of significance were greatly influenced by the most contaminated soils. Neither tissue fraction served as an effective sentinel of free soil Pb and the regression coefficient was a poor summary statistic across sites with a large range of contamination. The same was true of Pb concentrations in the whole soft tissues. It may be that free ion concentrations are not indicative of metal availability to animals with a range of mechanisms to assimilate nutrients, perhaps because of undescribed environmental and physiological factors governing assimilation or limiting soft tissue concentrations.
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evaluating Helix Aspersa as a sentinel for mapping metal pollution
Ecological Indicators, 2002Co-Authors: Alan Beeby, Larry RichmondAbstract:Abstract The common garden snail has been proposed as a sentinel species for mapping environmental concentrations of toxic metals, since it accumulates high levels in its soft tissues. The capacity of Helix Aspersa to quantify site differences is assessed here from a survey of 23 populations around UK and Wales with a wide range of contamination. Five adult snails were collected from each site during 1 week in 1990. Each replicate snail was partitioned into two soft tissue components (the hepatopancreas and the ‘rest’) and their Pb, Cd, Cu and Zn levels compared with those in the soil (as an integrative long-term measure of exposure) and the leaves of one food plant, Taraxacum (as a measure of recent dietary exposure). Median concentrations in one or both tissue fractions correlated with both soil and vegetation levels for each metal except Cu. Whole soft tissue Zn, Pb and Cd concentrations were also correlated with either soil or Taraxacum or both. However, Cd and Zn levels were not independent of tissue dry weight and there were also interference effects between Pb, Cd and Zn in the ‘rest’ and between Cd and Zn in all fractions. Lead in the hepatopancreas correlated with both soil and dietary sources, and was independent of dry weight. There was some correlation of Cd with Pb in this tissue. Outliers largely determined the relationship between hepatopancreatic Pb and both soil Pb and vegetation Pb. If sites with very high levels in each source were excluded from the analysis, the significant correlation of hepatopancreatic Pb with vegetation and soil concentrations disappear. This study emphasizes that sentinels have to do more than simply rank sites by their tissue concentrations: a prime criterion in their selection should be their capacity to quantify the magnitude of site differences.