Bithynia Tentaculata Research Articles

Assessing whether a thermoluminescence peak at ∼100 °C in calcitic opercula can be used to monitor thermal reproducibility

The opercula of the gastropod Bithynia tentaculata is composed of calcite and exhibits three main thermoluminescence peaks at ∼100, 280 and 360 °C when heated at 0.5 °C.s−1. The two higher temperature peaks can be used for geological and archaeological dating, whilst the lower temperature peak has a lifetime of hours and is only seen after laboratory irradiation. This study explores whether this lower temperature TL peak can be used to assess the reproducibility of laboratory heating of opercula. As found in previous studies, the TL peak at ∼100 °C is seen to consist of at least two signals which have different lifetimes at room temperature. By fixing the interval between irradiation and measurement of the TL signal, the impact of these different lifetimes on the temperature at which the TL peak occurs (Tm) can be reduced, and replicate measurements on a single operculum using the same radiation dose yield values of Tm within 1 °C. Comparison of different opercula shows variation in Tm of 9 °C when heating at 5 °C.s−1, interpreted as primarily arising from variation in thermal lag between the hotplate and the different samples assessed. Reducing the heating rate to 0.5 °C.s−1 reduces the variation in Tm between opercula to 2 °C. Imaging the TL emission from opercula using an EMCCD shows spatial variation in heating, and also demonstrates the reduction in variability that can be achieved by using a slower heating rate. Thus, monitoring the position of the TL peak at ∼100 °C can be used to assess thermal reproducibility of TL measurements on calcitic opercula.

Chasing snails: Automating the processing of EMCCD images of luminescence from opercula

Opercula of the gastropod Bithynia tentaculata are composed of calcite, and are typically 2–4 mm in length. They emit a thermoluminescence (TL) signal that can be used for dose reconstruction, and spatially resolved TL data from them can be obtained using an electron multiplying charge coupled device (EMCCD). However, when multiple measurements are made of the same sample with imaging detectors such as the EMCCD, registering the different images is crucial so that when regions of interest (ROI) are defined they consistently relate to the same part of the specimen. Previous work on opercula has undertaken this registration by hand, but this is prohibitively time consuming and is also potentially prone to human error. An automated registration process is described, and its use is illustrated using a dose recovery experiment. Without registration more than half of the regions of interest defined across the operculum failed the recycling test, and for those ROIs which did pass recycling the dose recovery ratio varied from 0.7 to 1.2. After registration more than 97% of ROIs passed recycling and all these ROIs gave dose recovery ratios within two sigma of unity. The automated registration process described here has potential for application to other types of solid sample such as rock slices provided they are not perfectly circular.

Trematode species diversity in the faucet snail, Bithynia tentaculata at the western edge of its native distribution, in Ireland.

Trematodes and their snail hosts have developed intimate parasite-host associations, with snails supporting a diverse and often species-specific trematode fauna. In the faucet snail, Bithynia tentaculata (Caenogastropoda, Littorinimorpha), a unique trematode fauna has been recorded recently. However, knowledge of the exact species identity, phylogenetic relationships, and geographical distribution remains limited as many of the species belong to groups with unclear or controversial taxonomical assignment. To contribute to our knowledge of the trematodes, we investigated the trematode fauna of B. tentaculata by examining a total of 556 snails from lakes in County Galway, Ireland. Using an integrative taxonomic approach including DNA sequence data analyses (28S rRNA gene, ITS1-5.8S-ITS2, ITS2, cox1, nad1) and morphological tools (taxonomical drawings and measurements), we identified nine trematode species of seven families, with seven species occurring as cercariae (Cyathocotyle prussica, Lecithodendrium linstowi, Lecithodendrium sp., Asymphylodora progenetica, Sphaerostoma bramae, Metorchis xanthosomus, and Notocotylus sp.) and three species occurring as metacercariae (A. progenetica, Parasymphylodora parasquamosa, and Sphaeridiotrema sp.). Except for S. bramae, all are new species records for Ireland and provide the most western distribution of these trematodes in Europe. The trematode species recorded are known to use a wide range of definitive hosts and have a wide geographical distribution; among them are species members of genera that are zoonotic (Metorchis) and pathogenic to wildlife (Cyathocotyle, Sphaeridiotrema, and Notocotylus). There remains an ongoing need for precise identification of the trematode species to ensure that wider ecological contexts are correctly understood and biodiversity and disease threats can be accurately evaluated.

Eemian paleoenvironment based on the freshwater malacofauna and isotope record (Piła site; north-western Poland)

This article presents the results of malacological and isotope studies on lacustrine sediments from the Eemian interglacial site in the Piła (north-western Poland). Twenty species of molluscs were found in the analysed sediments. Changes in the taxonomic composition and the quantitative structure of malacofauna in the profile allowed distinguishing five types of assemblages corresponding to different phases of the lake's evolution. Ratios of oxygen and carbon isotopes (δ18O and δ13C) reflecting changes in the lake water composition were measured in shells of two predominating snail species, Valvata piscinalis (Müller, 1774) and Bithynia tentaculata (Linnaeus, 1758), and in opercula of Bithynia tentaculata. Significant variability in isotope contents was noted for shells in individual profile sections and between analysed taxa. The results of malacological and isotope studies were supplemented with lithological, stratigraphical and palynological data. On this basis, the sediments age was determined (optimal and suboptimal phases of the Eemian interglacial). Environmental changes of paleolake have been also reconstructed. The analysed sediments were initially deposited in the coastal, periodically drained zone of the reservoir. The younger part of the sequence represents the shallow part of the littoral zone of the permanent water body. The malacological and isotope data also allowed distinguishing two phases of increased water level in the reservoir, and changes in its trophic state probably generated by climatic factors.

DNA Barcoding and Distribution of Gastropods and Malacostracans in the Lower Danube Region

This survey reports the spatial distribution of gastropods belonging to Caenogastropoda, Architaenioglossa, Littorinimorpha, Cycloneritida and Hygrophila orders, and malacostracans from Amphipoda and Mysida orders in the lower sector of the Danube River, Romania, using DNA barcoding based on the cytochrome C oxidase I (COI) gene sequence. Sampling was performed for eight locations of Danube Delta branches and Bechet area during three consecutive years (2019–2021). Molecular identification of sixteen gastropods and twelve crustacean individuals was confirmed to the species level, providing the first molecular identification of gastropods from the Lower Danube sector. Phylogenetic analysis showed that species of gastropods and crustaceans clustered in monophyletic groups. Among gastropods, Microcolpia daudebartii acicularis, Viviparus viviparus, Bithynia tentaculata, Physa fontinalis, Ampullaceana lagotis and Planorbarius corneus were identified in Chilia and Sulina branches; and the Bechet area was populated by Holandriana holandrii, Theodoxus transversalis and Gyraulus parvus. The amphipods and mysids were present along the three main Danube branches. The calculated density of these species revealed an abundant community of crustacean Chelicorophium robustum on Sulina branch, and Dikerogammarus haemobaphes and D. villosus in extended areas of the Danube Delta. The presence of these invertebrates along Danube River was reported in relation to the sediment type and water depth.

Supplement to the knowledge of aquatic molluscs of greenhouses in the Czech Republic

This study expands and supplements the knowledge of aquatic molluscs of selected public greenhouses, especially in zoological and botanical gardens, in the Czech Republic. In total, 14 freshwater species were found at 23 sites situated mostly in botanical and zoological gardens. Freshwater molluscs were divided into four groups: species occurring in the Czech Republic only in greenhouses, non-native species living also in the wild, native species and alien genotypes of native species. The most frequent mollusc of greenhouses was Physella acuta (Draparnaud). Melanoides tuberculata (O. F. Müller) and Helisoma cf. duryi (Wetherby) of the first group were other very common and widespread greenhouse species. On the other hand Marisa cornuarietis (Linnaeus), Bithynia tentaculata (Linnaeus), Lymnaea stagnalis (Linnaeus), Gyraulus crista (Linnaeus) and Ferrissia californica (Rowell) were found at only one studied site.

Diversity of European lissorchiid trematodes from fish and snail hosts with comments on the validity of the genus Parasymphylodora Szidat, 1943.

Genetic markers, DNA sequences and karyotypes, of some European lissorchiid species from their intermediate and final hosts were obtained to clarify controversial data about their life cycles and taxonomy, and to reveal phylogenetic affinities. The life cycles of three species have been confirmed for the first time based on molecular data. Comparative analysis of internal transcribed spacer 2 (ITS2) and partial 28S rDNA sequences has undoubtedly proven that cercariaeum of type-species of the genus Asymphylodora, Asymphylodora tincae, develops in pulmonate snails, Anisus vortex and Stagnicola palustris, but not in the genus Bithynia. The faucet snail, Bithynia tentaculata, serves as the first intermediate host for Parasymphylodora (=Asymphylodora) markewitschi and Parasymphylodora parasquamosa; adults of both species were isolated from the common rudd, Scardinius erythrophthalmus. It has also been confirmed that B. tentaculata serves as the second intermediate host for P. parasquamosa. Phylogenetic analysis supports the validity of the genus Parasymphylodora. Two species, Parasymphylodora markewitschi and P. parasquamosa, with cercariaeum belonging to the Parasquamosum group, are closely related and are being recovered as a well-defined evolutionary lineage in phylogenetic trees. A significant divergence between Parasymphylodora spp. and Asymphylodora spp. was revealed. The diploid chromosome set of P. markewitschi is composed of 14 chromosomes and does not show similarities with karyotypes of other lissorchiid species. Asymphylodora progenetica and Asymphylodora tincae share the basal diploid value of the family, 2n = 20, and reveal very close morphology of the corresponding chromosome pairs. Karyotypic similarities of these species are in accordance with molecular phylogenetic data. Thus, the available molecular and cytogenetic data support the assignment of P. markewitschi and P. parasquamosa to a separate genus, meanwhile, the assignment of A. progenetica to the genus Parasymphylodora was not justified.

Evaluating the Life-History Responses of Adult Invasive (Bithynia tentaculata) and Native (Physa gyrina) Snails Exposed to a Cu-Based Pesticide (EarthTec® QZ)

The faucet snail, Bithynia tentaculata, is an invasive snail that facilitates outbreaks of waterfowl disease in the Upper Mississippi River of the United States. In response, there is interest in identifying strategies that mitigate its population and spread. In this study we assessed the effects of a copper (Cu) molluscicide, EarthTec® QZ, at three concentrations (0, 0.1 and 0.6mg/L Cu) on adult B. tentaculata and a coexisting native species, Physa gyrina. We found that in the 0.6mg/L Cu treatment, ~ 68% of B. tentaculata snails remained alive after a 4-day exposure whereas all P. gyrina snails died. In contrast, a majority of both snail species remained alive and active after 4 days in the control and 0.1mg/L Cu treatments. Although B. tentaculata demonstrated higher survivorship, it bioaccumulated more Cu than P. gyrina. Additionally, examination of B. tentaculata individuals revealed that females tended to exhibit higher mortality than males.

Freezing mortality of faucet snails, Bithynia tentaculata: a viable method for equipment decontamination to reduce aquatic invasive species spread

Freezing mortality of faucet snails, Bithynia tentaculata: a viable method for equipment decontamination to reduce aquatic invasive species spread

Changes of malacofauna in a small lowland river in eastern Poland

In 2016, the species composition and the structure of the dominance of molluscs in the Muchawka River (left-bank tributary of the Liwiec River) were assessed. The occurrence of 19 species of molluscs were recorded, including 11 species of snails and 8 species of mussels. The eudominant was Pisidium casertanum, which, only in the last two sites, constituted 43.1% of all molluscs. Two other species of molluscs from the Sphaeriidae family were also eudominants – Pisidium subtruncatum (22.8%) and Sphaerium corneum (10.3%). Snails were most frequently represented by the dominant Bithynia tentaculata, constituting 5.4% of all molluscs, and the subdominant Bathyomphalus contortus at 2.8%. Sixteen years after the first malacological analysis, an increase in species richness and differences in the dominance of molluscs were found in the Muchawka River. Clams from the Sphaeriidae family invariably dominated but with a different species composition. The disappearance of the protected Anodonta cygnea and Sphaerium rivicola has been noted, and the occurrence of the protected Unio crassus has also been noted.

Patterns of Sphaeridiotrema pseudoglobulus infection in sympatric and allopatric hosts (Bithynia tentaculata) originating from widely separated sites across the USA.

In circumstances where populations of invasive species occur across variable landscapes, interactions among invaders, their parasites, and the surrounding environment may establish local coevolutionary trajectories for the participants. This can generate variable infection patterns when parasites interact with sympatric versus allopatric hosts. Identifying the potential for such patterns within an invasive-species framework is important for better predicting local infection outcomes and their subsequent impacts on the surrounding native community. To begin addressing this question, we exposed an invasive snail (Bithynia tentaculata) from two widely separated sites across the USA (Wisconsin and Montana) to the digenean parasite, Sphaeridiotrema pseudoglobulus, collected from Wisconsin. Parasite exposures generated high infection prevalences in both sympatric and allopatric snails. Furthermore, host survival, host growth, the proportion of patent snails, and the timing of patency did not differ between sympatric and allopatric combinations. Moreover, passaging parasites through snails of different origins had no effect on transmission success to subsequent hosts in the life cycle. However, the number of parasites emerging from snails and the pattern of their release varied based on snail origin. These latter observations suggest the potential for local adaptation in this system, but subsequent research is required to further substantiate this as a key factor underlying infection patterns in the association between S. pseudoglobulus and B. tentaculata.

Rapid flood intensification and environmental response of the Lower Meuse during the Allerød-Younger Dryas climate transition

Lateglacial climatic oscillations exerted profound impacts on the Meuse fluvial system. In the Lower Meuse (southern Netherlands), geomorphological studies in the last decades mainly centred on Lateglacial vegetation evolution, channel pattern changes and river terrace formation. Little information has been reported about the paleohydrology and its relation with the regional climate conditions. This study investigates a sediment core that contains flood sediments deposited from the early Allerød up to the middle Holocene. We conducted grain size analysis, thermogravimetric analysis (organic matter and calcium carbonate content), pollen and macrofossil analysis, and determined the oxygen and carbon stable isotope ratios of biogenic carbonate (opercula of the freshwater gastropod Bithynia tentaculata). The chronology of the core is based on AMS 14C dating and pollen biostratigraphical correlation. The pollen and macrofossil studies reveal that the core site was a lake environment during the Allerød and Younger Dryas periods. The oxygen isotope record in conjunction with organic matter and carbonate content are believed to have captured the intra-Allerød Cold Period (IACP). The synchronous variation of oxygen and carbon isotopes with calcium carbonate content indicates a dominant evaporation effect on carbonate chemistry of the lake environments during the warm Allerød interstadial. End-member modelling decomposes the grain-size distributions into two sandy end members (bed load) and two silty-clayey end members (suspended load). In order to highlight the flood signal, we constructed two flood energy indexes (FEI-1 and FEI-2) that reflect the coarseness of the suspended load and bed load, respectively. Both indexes show a relatively high flood condition during the IACP, followed by a low flood phase in the Late Allerød and quickly intensified flood conditions at the onset of the Younger Dryas. In the second phase of the Younger Dryas, deposition of sandy aeolian sediments to the core site complicates the paleoflood identification using FEI-2 (bed load). This study shows a high sensitivity of the hydrological process and sedimentary environment at the Lower Meuse to the regional climate system.

Relationship between individual metabolic rate and patch departure behaviour: evidence from aquatic gastropods

Individual energy requirements are tightly related to individual resource use and by extension of space‐use patterns and other traits at higher levels of the ecological hierarchy. However, there is still little experimental evidence linking individual energetics and space‐use behaviour. Individual energy requirements scale mainly with body size and temperature, but these do not explain all individual variation. Therefore, studies focused on inter individual variation in resource and space use behaviour can be used to frame foraging dynamics in an energy perspective. We empirically tested the hypothesis of a relationship between individual energetics and patch departure behaviour using as model organisms four small species (body mass ranging from 0.4 to 14 mg AFDW) of aquatic gastropods strongly differing in adult size: Galba truncatula, Bithynia tentaculata, Theodoxus fluviatilis and Ecrobia ventrosa (in descending order of size). Motility tests were performed in controlled microcosm conditions. The tests were designed to classify the specimens as either low motility (not inclined to abandon the patch) or high motility (likely to abandon the patch). The tests entailed measuring the propensity of the individuals to abandon a limited resource patch (2 g DW of conditioned Phragmites australis leaves) within a given amount of time (24 h) when foraging with conspecifics under conditions where competition for food is expected to increase over time due to resource depletion. The individual standard metabolic rate of the tested specimens was measured via open flow respirometry and compared across motility classes at intra‐ and interspecific level. At both levels, we observed that individuals with higher standard metabolic rates were more inclined to abandon the patch. This finding establishes a link between foraging theory and competitive coexistence mechanisms.

Smoked cigarette butt leachate impacts survival and behaviour of freshwater invertebrates

Smoked cigarette filters a. k.a. “butts”, composed of plastic (e.g. cellulose acetate) are one of the world’s most common litter items. In response to concerns about plastic pollution, biodegradable cellulose filters are being promoted as an environmentally safe alternative, however, once smoked, both contain toxins which can leach once discarded. The impacts of biodegradable butts as littered items on the receiving environment, in comparison with conventional butts has not yet been assessed. A freshwater mesocosm experiment was used to test the effects of leachate from smoked cellulose acetate versus smoked cellulose filters at a range of concentrations (0, 0.2, 1 and 5 butts L−1) on the mortality and behaviour of four freshwater invertebrates (Dreissena polymorpha, Polycelis nigra, Planorbis planorbis and Bithynia tentaculata). Leachate derived from 5 butts L−1 of either type of filter caused 60–100% mortality to all species within 5 days. Leachate derived from 1 butt L−1 of either type resulted in adults being less active than those exposed to no or 0.2 butts L−1 leachate. Cigarette butts, therefore, regardless of their perceived degradability can cause mortality and decreased activity of key freshwater invertebrates and should always be disposed of responsibly.

The effects of metaldehyde on non-target aquatic macroinvertebrates: Integrating field and laboratory-based evidence

The use of pesticides has historically helped improve agricultural productivity, although their continued use may have unforeseen effects upon the natural environment when not applied appropriately. Metaldehyde is a commercial pesticide widely used to reduce crop losses resulting from terrestrial mollusc damage. However, following precipitation and runoff it frequently enters waterbodies with largely unknown consequences for aquatic fauna. This study represents one of the first attempts to examine its potential effects on aquatic macroinvertebrate communities at sites known to have experienced elevated metaldehyde concentrations alongside unaffected control sites. In addition, a series of laboratory exposures specifically examined the effects of metaldehyde on the survivorship of non-target aquatic mollusc species. When the entire aquatic macroinvertebrate community and aquatic mollusc community were considered, limited differences were observed between metaldehyde affected and control sites based on field data. Laboratory exposures highlighted that for the molluscs examined, gastropods (Bithynia tentaculata, Planorbis planorbis, Radix balthica and Potamopyrgus antipodarum) had a greater tolerance to metaldehyde than bivalves (Sphaerium corneum and Corbicula fluminea). However, the concentrations required to reduce survivorship of all species were much greater than those ever recorded historically under field conditions. The results suggest that the differences in the community composition recorded between sites exposed to elevated metaldehyde concentrations and control sites were probably due to nutrient loading (N and P from agricultural fertilizers) rather than metaldehyde. However, these results do not negate wider concerns regarding metaldehyde use, particularly issues caused when ingested by vertebrate wildlife, livestock or children and pets in domestic settings.

ТРЕМАТОДОФАУНА ЧЕРЕВОНОГИХ МОЛЮСКІВ (GASTROPODA) ВЕРХІВ’Я КИЇВСЬКОГО ВОДОСХОВИЩА

Our study aimed to examine the current state of trematodes diversity in Kyiv reservoir. The molluscs under analysis belong to the species living for more than two years. The presence of trematode invasion in molluscs indicates the permanent or periodic presence of infected vertebrate hosts in area. Low mobility of the molluscs contributes to specification of the specific reservoir section visited by the definitive hosts. The species composition and quantitative indicators of invasion of the larval stages (cercariae) of trematodes (Digenea) in six species of Gastropoda in the Dnieper area of the upper site of Kyiv reservoir were studied. In total up to 490 specimens of Gastropoda belonging to subclasses Pulmonata (Lymnaea stagnalis Linnaeus, 1758, Planorbarius corneus Linnaeus, 1758, Stagnicola palustris Muller, 1774) and Prosobranchia (Fagotia acicularis Férussac, 1823, Viviparus viviparus Linnaeus, 1758, Bithynia tentaculata Linnaeus, 1758) were examined. The largest number of trematodes species was found in molluscs L. stagnalis (Lymnaeidae) and B. tentaculata (Bithyniidae) which amounted to seven and three species accordingly. The highest abundance, 150 and upper per mollusc specimen, were Diplostomum spathaceum (Rudolphi, 1819) and Tylodelphys conifer (Mehlis, 1846). Three species of trematodes were recorded in B. tentaculata − Cercaria lophocerca Filippi, 1857, Pleurogenoides medians (Olsson, 1876), Palaeorchis incognitus Szidat, 1943 with an average abundance upper 280 and prevalence 8−17%. Basically, the definitive hosts of the detected species of trematodes are fish, amphibians and waterfowl. Detected cercariae of trematodes D. spathaceum, Sanguinicola intermedia Ejsmont, 1925, Metagonimus yokogawai (Katsurada, 1912), Echinostoma revolutum (Fröhlich, 1802), Echinoparyphium recurvatum (Linstow, 1873) may cause diseases and sometimes death of fish and waterfowl. Some species may be used in medicine.

Biological and geochemical indicators of climatic oscillations during the Last Glacial Termination, the Kaniewo palaeolake (Central Poland)

• Bølling-Allerød complex shows climatic heterogeneity and includes cold events. • Deglaciation passed 3 cold (GS-2a, GI-1d, GS-1) and 2 warm periods (GI-1e, GI-1a-c) • Traces of cold oscillation (GI-1b) within the Allerød were found. This study presents the results and interpretations of biological (floral and faunal) and geochemical (isotopic and chemical element composition) investigations of the Late Glacial and Holocene sediment accumulated in the Kaniewo palaeolake. These data allowed us to determine the indicators of environmental changes in this lake ecosystem, such as zooplankton and vegetation development, trophic state, water temperature, and water level. We documented the three cold periods (Oldest, Older, and Younger Dryas) separated by two warm periods (Bølling, Allerød). Additionally, we found traces of cold oscillations within the Allerød, lasting approximately 150 years, probably the Intra-Allerød-Gerzensee oscillation, recorded in western and southern Europe. Our data show that sediment accumulation began at the end of the Oldest Dryas period before ca. 13,900 yr cal BP. The top of the studied sediments represented the transition from the Late Glacial to the early Holocene (Preboreal period, ca.10,500 yr cal BP). The lithology of the sediments changed from silty sands at the bottom, then calcareous detritus gyttja partially interbedded by lake marl to peat at the top. Organic matter occurring in the deposits reflects algae and terrestrial sources. In the cold periods, small number of both Cladocera individuals and species (e.g. Bosmina (E.) longispina , Chydorus sphaericus , Alona affinis ), corroborate the unfavourable conditions for the development of zooplankton. Cladocera species indicated the initial oligotrophic status of the lake and the subsequent increase in trophic status. Plant and animal macrofossils indicate initial shallow lake ecosystem. Chara meadow developed at the bottom of the lake with a belt of vascular plants ( Carex sp., Hippuris vulgaris , Scirpus sp . ) in the littoral zone of the lake. Rich shallow vegetation was accompanied by animals, such as Mollusca (e.g. Valvata piscinalis, Pisidium obtusale, Bithynia tentaculata ) and Oribatidae sp., Cristatella mucedo , and Plumatella type.

Vodní měkkýši národní přírodní památky Žehuňský rybník (střední Čechy) [Aquatic molluscs of the Žehuňský rybník National Nature Monument (Central Bohemia)

The Žehuňský rybník National Nature Monument (Central Bohemia, Czech Republic) contains a pond (258 ha) with extensive wetlands in its surroundings. Aquatic molluscs of this area were studied in years 2005–2019. Altogether, 34 species were found at 29 sites. Anisus vortex, Planorbis planorbis, Valvata cristata, Stagnicola turricula, Bithynia tentaculata, Bathyomphalus contortus and Planorbarius corneus belonged to the most often recorded species, while 16 species were found at only 1–3 sites. Only old shells of two bivalves (Unio crassus, U. tumidus) were found. Rare and endangered bivalves Sphaerium nucleus and Pisidium pseudosphaerium inhabit large area of the wetlands. One non-native species, Ferrissia californica, was found.

Identification and Determination of the Geographical Distribution of Freshwater Snails in Lorestan, Iran.

Snails are creatures present in various ecosystems that, in addition to being present in human surroundings, some of them are also important in veterinary medicine and medicine as the intermediate hosts of Digenean trematodes. The present study was conducted to identify and determine the geographical distribution of freshwater snails and investigate the relationship of variables, such as season and geographical region, with snail species and dispersion in Lorestan in the west of Iran. A total of 4400 samples of freshwater snails were collected using the multistage sampling method (i.e., stratified, cluster, and randomized) from 110 points in five geographical regions in four seasons and then identified based on their morphological characteristics by diagnostic keys. The ArcGIS software (version 10.3) was used to evaluate the spatial distribution of the freshwater snails. In this study, seven species of freshwater snails were identified in six families belonging to six genera, namely Melanopsis doriae (6.30% of the variation in species), Theodoxus doriae (5.55%), Bithynia tentaculata (43.22%, the dominant species), Physa acuta (24.98%), Lymnaea truncatula (9.75%), Gyraulus euphraticus (8.18%), and Lymnaea gedrosiana (2.02%). The geographic distribution of freshwater snails was recorded across five regions in 22 points per region for every season. The spatial distribution maps showed that the distribution of freshwater snails varies according to region and season (P<0.001). The obtained results revealed the effects of season and geographical region on the distribution and population density of snails in the province. These data can be used for the implementation of control programs against parasitic diseases in the region, including trematodes.

Early Holocene succession of vegetation and molluscs in Lake Jaczno, East-Central Europe

Here we present results of high-resolution palaeoecological studies of the organic deposits accumulated in Lake Jaczno, located in the north-eastern Poland. Plant macrofossils and malacological analyses complimented by radiocarbon dating (AMS) were undertaken to reconstruct Early Holocene succession of the pioneer wetland plants and molluscs in the lake ecosystem. Numerous presence of charcoal pieces (>1 mm) and fungal remains (sclerotia) in the peat layer accumulated on the mineral ground document dry habitat what coincides with warm and dry climate conditions in the early Holocene recorded in this part of Europe. Change to lacustrine environment documented by accumulation of the carbonate gyttja on the highly decomposed peat layer took place ca. 10,500 cal yr BP. The current morphology of Lake Jaczno, in which several basins can be distinguished, suggests that different age of sediments accumulated at the bottom part at our sampling sites might result from different sizes of the buried dead ice blocks, and their heterochronous final melting. The first aquatic plants that appeared in Lake Jaczno were Chara sp., Ceratophyllum demersum and Nymphaea alba. The appearance of Cladium mariscus in Lake Jaczno ca. 9400 cal yr BP was synchronous with the substantial spread of this plant in this region which coincided with increased climate humidity. The first molluscan species that colonized the lake ecosystem were Gyraulus crista and Bithynia tentaculata, species living on macrophytes, and Valvata piscinalis, typical for habitats characterized by a thick layer of plant detritus.