Juvenile Snails Research Articles

Low specific conductivity limits growth and survival of the New Zealand mud snail from the Upper Owens River, California

The New Zealand mud snail (NZMS), Potamopyrgus antipodarum (Gray), is an invasive species of aquatic snail that is becoming widespread in inland and coastal waters of the western United States. The New Zealand mud snail can have significant impacts on stream ecosystems, as they may consume a large fraction of available algae production and compete with and displace native invertebrates. Even though the distribution of this species is expanding, the habitat conditions conducive to invasion are incompletely understood. Surveys following the NZMS invasion in the Upper Owens River, California, indicated that the snail may be excluded from waters where dissolved solute content is low, so experimental studies were undertaken to evaluate survival and growth as a function of varied specific conductivity (SC) and calcium availability. Juvenile snails were collected from the Upper Owens River and reared in dilutions of natural river water adjusted to 10, 50, 100, 200 and 300 μS · cm−1 SC. Experiments were also conducted with newborn clones raised in river water dilutions ranging from 25 to 200 μS · cm−1 to examine mortality and growth at this sensitive stage of development. In addition, calcium-free artificial river water was prepared at 200 μS · cm−1 to test for the independent effect of limitation of this mineral ion required for shell-building. Significant reductions in survival and growth occurred among treatments diluting river water from 300 to 50 μS · cm−1. No growth was found at or below 25 μS · cm−1. Growth was also inhibited in calcium-free artificial water compared to natural river water with the same SC, showing that lack of this mineral impedes development. These results suggest that many streams in the range of 25–200 μS · cm−1 cannot support productive NZMS populations and that nuisance invasions may be most prevalent in waters above 200 μS · cm−1 where sufficient dissolved mineral content is present for growth.

Density effects of native and exotic snails on growth in juvenile apple snails Pomacea paludosa (Gastropoda: Ampullariidae): a laboratory experiment

Pomacea paludosa (native Florida apple snail) is found in wetlands in the southeastern United States. Pomacea insularum is an exotic apple snail which has invaded wetlands in Florida and co-occurs with P. paludosa. The effect of changes in density on growth in native juvenile snails was studied by manipulating native juvenile density, native adult density and exotic adult density in a set of laboratory experiments. Growth decreased when native juvenile densities (without adults) increased from four to eight snails per 38-l aquarium. The presence of adults of either species decreased juvenile growth and also decreased juvenile survival. One exotic adult had the equivalent effect of three to four native adults. Based on the response of native juveniles to exotic adults, populations of the native apple snail P. paludosa could be negatively impacted by expansion of the exotic snail P. insularum.

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

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

A photogrammetric methodology for size measurements: application to the study of weight–shell diameter relationship in juvenile Cantareus aspersus snails

A photogrammetric methodology is proposed to measure the diameter of snail shells on digital pictures. Digital photographs were taken of juvenile Cantereus aspersus snails. AutoCAD image analysis software was used for the measurements and the results were contrasted with data obtained using a digital caliper in the same snails to compare the accuracy of both methods. The snails were individually weighed and the shell diameter was measured once a week, for a total of 7 weeks. After the third week, there were no significant differences between both methods, whereas in the first 2 weeks the measurements obtained with a digital caliper scored larger diameters than the photogrammetric measurements. This is probably due to the difficulty to define the end of the shell with the caliper, whereas the photogrammetric analysis does not involve any risk for the snail. To test the reproducibility and repeatability of both methodologies seven snails were measured five times by three different examiners. Using the variance components analysis, the repeatability was 4.8% of the total variation for the photogrammetric methodology and 6.9% for the conventional methodology, while the reproducibility was 0.0% and 2.7% for the photogrammetric and conventional methodology, respectively. These findings indicate that the photogrammetric methodology can be used with confidence to measure the diameter of snail shells. The great advantage of this method is the ability to magnify the images to make more precise measurements from snails of any size, which is especially useful in the early stages of development. The growth data were used to construct a model for live weight (LW) estimation based on shell diameter. The snails showed high growth rates both in terms of shell diameter and LW. The shell diameters showed a low individual variation (16.2% CV) and were normally distributed, whereas the LWs showed greater variability (36.8% CV) and were not normally distributed. The best model for estimating LW from shell diameter in juvenile snails is the multiplicative model, with a high determination coefficient (96%).

Cloning, genomic organization and expression of two glycosyl hydrolase family 10 (GHF10) genes from golden apple snail (Pomacea canaliculata)

Two cellulase cDNAs (GHF10-Pc1 and GHF10-Pc3) belonging to glycoside hydrolase family 10 (GHF10) were successfully isolated and characterized from stomach tissue of golden apple snail (Pomacea canaliculata), a kind of herbivorous mollusca. Sequencing analysis revealed full-length cDNAs of 1300 and 1277 bp in length, respectively. The open reading frame (ORF) of cellulase cDNA was 1188 and 1191 bp, encoding 395 and 396 amino acid, respectively. Sequence alignment revealed that GHF10-Pc1 and GHF10-Pc3 shared high identity with glycosyl hydrolase family 10 (GHF10) and had an overall similarity of 98 and 82% to those of Ampullaria crossean cellulase EGX. A neighbour-joining tree showed a clear differentiation between each species and also indicated that GHF10-Pc1 and GHF10-Pc3 from P. canaliculata and A. crossean EGX are closely related phylogenetically. The genomic organization of cellulase GHF10-Pc1 and GHF10-Pc3 genes was also investigated. The GHF10-Pc1 and GHF10-Pc3 genes spanned over 4937 and 4512 bp, respectively. Both genes contained 9 exons interrupted by eight introns. The result verified the endogenous origin of the GHF10-Pc1 and GHF10-Pc3 genes. Analysis of RNA by RT-PCR from several ages of P. canaliculata revealed that neither gene was expressed in eggs. GHF10-Pc1 was also expressed in 1- and 10-day-old juvenile snails whereas GHF10-Pc3 was expressed only in 1-day-old juvenile snails. The result showed that two GHF10-Pc transcripts were developmentally expressed.

The population dynamics of the mediterranean snails Cernuella virgata, Cochlicella acuta (Hygromiidae) and Theba pisana (Helicidae) in pasture - cereal rotations in South Australia: a 20-year study

The snails Cernuella virgata, Cochlicella acuta and Theba pisana are introduced pests of grain crops and pastures in southern Australia. The population dynamics of these three species of snail were studied for 20 years in two adjacent fields where they coexisted on a farm on the Yorke Peninsula in South Australia. The fields were used for pasture–cereal rotations. Surveys were conducted in autumn and spring each year, coinciding respectively with the start of the breeding season and peak abundance of snails (mostly juveniles). Populations varied greatly in abundance between years and between species, but snails were generally most common in spring, in wet years, especially those with wet autumns and wet springs. Rainfall early in a particular year (i.e. at sowing of crops in autumn) can thus be used to predict the likelihood of heavy snail infestations later in spring (i.e. at harvest). In contrast, the abundance of adult snails in autumn was a poor predictor of the subsequent abundance of juvenile snails in spring, especially in crops. There were no significant correlations, at field scale, between the average abundance of the three species of snail in spring, in either pastures or crops. However, at a sampling scale of 0.25 m2, there were consistent, negative relationships between the abundance of all three snail species. Such patterns may reflect either competitive interactions between snails or subtle differences in micro-habitat choice. Patterns in the abundance of snails (e.g. large numbers near field edges) were suggestive of occasional invasion from dense populations in adjacent fields.

Embryonic shell formation in the snail Biomphalaria glabrata: a comparison between scanning electron microscopy (SEM) and synchrotron radiation micro computer tomography (SRµCT)

Embryos of different developmental stages and newly hatched juveniles of the freshwater snail Biomphalaria glabrata were investigated by synchrotron radiation micro computer tomography (SRµCT). Because this method is sensitive for objects with a high X-ray density, it is ideally suited to study mineralized tissues without the need for dissection of the sample, i.e. removal of the soft tissue. This is a clear advantage over scanning electron microscopy (SEM). However, the resolution is inferior to SEM (about 1–2 µm compared to a few nm). After the measurement, computer-processed handling (virtual turning, cutting and measuring) of the object is possible. The development of the calcified shell in embryos before hatching (age 60, 72, 96 and 120 h after oviposition) was investigated and both methods were compared. While it was not possible to find a calcified shell in 60 h old embryos, the shell in 72 h old embryos was almost fully mineralized. By SRµCT, the weight of the calcified shell was estimated to 0.64, 9.59 and 30.3 µg for embryos of 72, 96 and 120 h. All juvenile snails, of 5 days and 4 weeks after hatching, contained concretions in the stomach, mostly consisting of calcium phosphate.

Juvenile snails, adult appetites: contrasting resource consumption between two species of applesnails (Pomacea)

Research on aquatic snails usually examines consumption of periphyton, but emergence of large, invasive aquatic snails that prefer macrophytes has necessitated a new understanding about snail herbivory. Ample research exists detailing invasive potential of certain species of applesnails, such as Pomacea canaliculata, to successfully invade aquatic ecosystems. However, very few studies examine differences in resource utilization between different size-classes within species, or between closely-related species. To quantify these potential differences, we compared per mass resource consumption at two life history stages by P. canaliculata and a lesser-known species recently identified in Texas (USA), Pomacea insularum. We presented adult and juvenile snails with whole and reconstituted forms of Lactuca sativa longifolia (romaine lettuce), Myriophyllum spp. (watermilfoil), and Eichhornia crassipes (water hyacinth). In addition, we added chemical extracts to reconstituted watermilfoil and water hyacinth to test if extracts deterred consumption. Addition of periphyton to reconstituted watermilfoil allowed us to examine supplementary structure and chemistry. Juveniles seemed to prefer reconstituted resources. All snails, regardless of life-history stage, avoided water hyacinth in either form. Chemical extracts from both water hyacinth and watermilfoil deterred consumption by all snails. When presented with reconstituted watermilfoil containing additional periphyton, juvenile P. insularum consumed more resource with additional periphyton. In contrast, periphyton presence did not produce a noticeable effect on P. canaliculata consumption. Overall, juveniles of both species consumed considerably more by mass than their respective adult counterparts. Through increased numbers and difficult detection, juvenile applesnails could feasibly consume a greater proportion of plant biomass than adult applesnails and this may partially underlie the success of global applesnail invasions.

Size-dependent distribution and feeding habits of Terebralia palustris in mangrove habitats of Gazi Bay, Kenya

The gastropod Terebralia palustris often dominates the surface of muddy to sandy substrates of intertidal mudflats and mangrove forests, where they clearly destabilize the sediment. In the present study, it was investigated whether and to what extent the behaviour of juvenile and adult snails differs among habitats (mudflat vs. mangrove stand) in a Sonneratia alba mangal at Gazi Bay, Kenya. For this purpose we: (1) examined their distribution along three land–sea transects; and (2) applied stable isotope analysis to determine the feeding patterns of different-sized snails from the mangrove and mudflat habitats. Additionally, we investigated if these gastropods exert an impact on microphytobenthic (diatom) biomass, and whether this is size-dependent. The latter objective was met by either enclosing or excluding different-sized snails from experimental cages on the intertidal mudflat and the subsequent assessment of a change in pigment concentration of the sediment surface. In agreement with several previous studies conducted in other mangroves and geographical locations, a spatial segregation was demonstrated between juveniles (more common on the mudflat) and adults (more common in the mangrove forest). On the intertidal mudflat juveniles avoided sediment patches characterized by highly saline water in intertidal pools and a high mud content, while adults tended to dwell on substrates covered by a high amount of leaf litter. Stable carbon isotope analysis of the foot tissue of snails sampled from the S. alba stand and the mudflat indicated a transition in food source when a shell length of 51 mm is reached. Considering the δ 13C value of juveniles, it seems they might be selecting for microphytobenthos, which might explain their preference for the mudflat. The diet of size classes found in both habitats did not differ significantly, although juveniles inhabiting the mangrove forest were slightly more depleted in 13C compared to those residing on the mudflat. Assuming juveniles feed on benthic microalgae and considering the lower microalgal biomass inside the mangrove forest, this may be a consequence of a higher contribution of other, more 13C depleted organic carbon sources, like phytoplankton, to their diet. Experimental results indicate a negative, but insignificant, impact on benthic diatom biomass by juveniles (due to grazing) and adults (due to physical disturbance). This finding seems to be in agreement with the results of the stable carbon isotope analysis, strongly suggesting the selective feeding of juvenile T. palustris on benthic diatoms.

Expression of MAP/ERK kinase cascade corresponds to the ability to develop food aversion in terrestrial snail at different stages of ontogenesis

The mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) cascade plays an important role in gene expression regulation during memory formation in both vertebrates and invertebrates. MAPK/ERK regulates gene expression through phosphorylation of transcription factors binding to the regulatory elements SRE and CRE of target genes. Previously we reported that juvenile snails Helix lucorum differ from adult animals in a spectrum of transcription factors binding to DNA regulatory elements SRE and AP-1. In this study we analyzed the expression and activation of MAPK/ERK in CNS of H. lucorum during formation of the conditioned avoidance reflex at different stages of postnatal ontogenesis. Under conditions of learning, juvenile snails (aged 2–3 months) possessing immature mechanisms of avoidance reflex plasticity showed dramatically low level of phosphorylation and, correspondingly, low activation of MAPK/ERK in comparison to adult animals. Beside this, the MAPK/ERK cascade was not activated after 10 and 60 min after learning in juvenile snails in contrast to adults, while basal expression level of this kinase was similar in juveniles and adults. Low activation of MAPK/ERK cascade can cause a deficiency in phosphorylation of downstream transcription factors binding to SRE and thereby influence the expression of early response genes (particularly, of the family AP-1) and late response genes necessary for cellular and synaptic plasticity. These observations suggest that the MAPK/ERK regulatory cascade plays an essential role in the formation of conditioned avoidance reflexes in Helix. Low activation of this cascade might be one of the reasons for deficiency of long-term memory formation during avoidance learning in juvenile animals.

Studying the effect of exposure of the snail Helix aspersa to the purified Bt toxin, Cry1Ab

The present study was intended to assess the effect of the Bt toxin, Cry1Ab, on the snail, Helix aspersa. We studied hatchability of eggs as well as growth and survival of the juvenile snails . The eggs were exposed to purified Bacillus thuringiensis Cry1Ab toxin mixed in with soil in 0, 11, 22, 44 or 88 mg Bt kg −1. To check the growth and survival of the juvenile snails, we conducted two different sets of experiments. In the first experiment, the snails were exposed to soil mixed with Bt toxin in 0, 5.5, 11, 22 or 44 mg Bt kg −1 concentrations. In the second experiment, the snails were fed a diet with pure Bt toxin at 0, 11, 44 or 88 mg Bt kg −1 dry weight. We found that Bt toxin has no negative effect on H. aspersa during the observed life stages.

Short-term climate change and the extinction of the snail Rhachistia aldabrae (Gastropoda: Pulmonata)

The only known population of the Aldabra banded snail Rhachistia aldabrae declined through the late twentieth century, leading to its extinction in the late 1990s. This occurred within a stable habitat and its extinction is attributable to decreasing rainfall on Aldabra atoll, associated with regional changes in rainfall patterns in the late twentieth and early twenty-first century. It is proposed that the extinction of this species is a direct result of decreasing rainfall leading to increased mortality of juvenile snails.

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

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

A Studies on Chemical Control of S. mansoni Intermediate Host

This study was conducted to screen different snail species to determine their susceptibility for different parasitic infections and also to determine LC50 and LC90 values. The screening of snail species infected with Schistosome parasite and mean number of cercariae shed by individual infected snail was 184+12. The experiment on relationship of snail size and dose of Niclosamide showed that juvenile snails were more susceptible to chemical when compared with adult snails. A series of seven experiments indicated that concentration of 0.067 and 0.109 mg L(-1) were required to kill 50 and 90% snails, respectively in an exposure period of 24 h and no death occurred in recovery period.

Oviposition and Hatchling Diet of a Snail-eating Snake Pareas iwasakii (Colubridae: Pareatinae)

ABSTRACT Pareas iwasakii, a rare pareatine snake endemic to Japan, is considered a dietary specialist on land snails. I observed the oviposition and hatchling diet of this species in captivity. One female laid six eggs on 30 September, and one of these eggs hatched on 26 November 2004. The hatchling fed on the soft body of juvenile land snails, leaving empty shells, most likely by extracting the former from the latter using its mandibles as do the adult snakes. This observation suggests that the dietary habits of P. iwasakii do not exhibit ontogenetic changes.

Effects of backwashing on the prosobranch snail Potamopyrgus jenkinsi Smith in granular activated carbon (GAC) adsorbers

Granular activated carbon (GAC) adsorbers are often the penultimate stage of surface water treatment and provide ideal habitats for invertebrates. Proliferation of chlorine-resistant invertebrates in GAC adsorbers may lead to their efflux into distribution systems, possibly resulting in contamination of customers’ tap water. GAC adsorber sampling and laboratory experiments were undertaken to determine the effects of routine backwashing on GAC adsorber populations of the chlorine-resistant snail Potamopyrgus jenkinsi at a water treatment works. GAC adsorber sampling results suggested that routine backwashing altered the spatial distribution of snails, but not their overall abundance. In small-scale glass columns 40–50% of the smallest (0.3–0.6 mm shell height) juvenile snails were removed by a GAC backwash bed expansion of 30–40%; however, bed expansions of greater than 20% were not possible in the GAC adsorbers.

Laboratory studies on the capability of &lt;i&gt;Biomphalaria pfeifferi&lt;/i&gt; (Krauss), intermediate host of &lt;i&gt;Schistosoma mansoni&lt;/i&gt; to survive desiccation

Four age groups of Biomphalaria pfeifferi were subjected to laboratory desiccation and allowed to aestivate for 7,14,21 and 28 days before being revived. Also, B. pheifferi specimens harbouring schistosomal infection were also subjected to laboratory desiccation and aestivated for 7, 14, 21 and 28 days. Uninfected specimen aestivated for the same number of days respectively were use for control experiments. All four age group were found to have been able to withstand some period of desiccation. Juvenile snails were found to be better aestivators. Infected counterparts, they could not survive for more than 28 days of the desiccation of their habitat. The Nigerian Journal of Parasitology Vol. 24 2003: 173-178

Epidemiological studies of &lt;i&gt;Fasciola gigantica&lt;/i&gt; infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe

During the period between January 1999 and December 2000, the distribution and seasonal patterns of Fasciola gigantica infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe were determined through monthly coprological examination. Cattle faecal samples were collected from 12 and nine dipping sites in the highveld and lowveld communal grazing areas respectively. Patterns of distribution and seasonal fluctuations of the intermediate host-snail populations and the climatic factors influencing the distribution were also determined by sampling at monthly intervals for a period of 24 months (November 1998 to October 2000) in six dams and six streams in the highveld and in nine dams in the lowveld communal grazing areas. Each site was sampled for relative snail density and the vegetation cover and type, physical and chemical properties of water, and mean monthly rainfall and temperature were recorded. Aquatic vegetation and grass samples 0-1 m from the edges of the snail habitats were collected monthly to determine the presence or absence of F. gigantica metacercariae. Snails collected at the same time were individually checked for the emergence of larval stages of F. gigantica. A total of 16264 (calves 5418; weaners 5461 and adults 5385) faecal samples were collected during the entire period of the study and 2500 (15.4%) of the samples were positive for F. gigantica eggs. Significantly higher prevalences were found in the highveld compared to the lowveld (P < 0.001), for adult cattle than calves (P < 0.01) and in the wet season over the dry season (P < 0.01). Faecal egg output peaked from August/September to March/April for both years of the study. Lymnaea natalensis, the snail intermediate host of F. gigantica was recorded from the study sites with the highveld having a significantly higher abundance of the snail species than the lowveld (P < 0.01). The snail population was low between December and March and started to increase in April reaching a peak in September/October. The number of juvenile snails peaked between April and August. The mean number of snails collected was negatively correlated with rainfall and positively correlated with temperature. Mean number of snails collected was also positively correlated with Potamogeton plant species and negatively correlated with Cyperus plant species. However, none of the L. natalensis collected from the habitats were found shedding Fasciola cercariae. Metacercariae were found on herbage from the fringes of the snail habitats between February and August for both years, with most of the metacercariae concentrated on herbage 0-1 m from the banks of the habitats. Based on the findings of this study, anthelmintic treatment should be administered in December/January to control chronic and mature fasciolosis. A second treatment should be given in April/May to reduce pasture contamination and subsequently snail infection, as this is the time the snail population starts to build up. To control acute fasciolosis due to the immature liver flukes a third treatment should be given in August. The first application of molluscicides to control the snail intermediate hosts can be done in June the time when the snail is harbouring the parasite and a second application in September in order to kill new generations of infected snails

Nitrate impacts on the Florida apple snail, Pomacea paludosa

Nitrate pollution in springs in Florida has been suggested as a possible reason for declining populations of the Florida apple snail, Pomacea paludosa (Say). No correlation was found between snail density and nitrate concentration measured in six Florida springs. In laboratory studies examining short-term acute impacts of nitrate, adult and juvenile snail 96 h LC50 values could not be determined due to low mortality rates despite nitrate concentrations > 500 ppm. Juvenile snail growth was affected with EC50 values of 504 and 622 ppm nitrate, in two trials, respectively. Juvenile survival during the 14 d growth study fell below 50%, but again nitrate levels were very high (> 500 ppm). Given that snails exhibited little to no response to nitrate concentrations orders of magnitude greater than those found in Florida springs, we suggest that other factors, possibly including natural differences in habitat structure or changes in structure related to exotic plant invasions, may help explain the observed declines in apple snail abundance.

Modelling chronic exposure to contaminated soil: A toxicokinetic approach with the terrestrial snail Helix aspersa

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.