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The distribution of the subtropical Asian clam (Corbicula fluminea (O.F. Müller, 1774)), one of the world’s most invasive freshwater molluscs, is reportedly constrained by a lower thermal tolerance limit of 2 °C. Although its occurrence in north temperate regions is typically restricted to artificially heated waterbodies, the species has been found to overwinter in unheated lakes and rivers. In laboratory experiments, we compared the cold tolerance of populations from several geographically distinct sites spanning 35°N to 46°N in eastern North America. Each population contained individuals that fully recovered from 2 months of continuous exposure to near-freezing (1 °C) conditions, contrary to published accounts of C. fluminea’s thermal ecology. Survivorship increased with body size and was enhanced by prior acclimation to a low temperature (10 °C) compared with a higher one (18 °C). When acclimated to 10 °C, clams from northern populations exhibited greater survivorship (55.0% ± 16.1%) than those from southern populations (26.7% ± 19.2%). However, one southern population demonstrated survivorship as great as that of the most tolerant northern population, suggesting that its clams could overwinter in unheated northern waterbodies. Differences among populations indicate either that contemporary evolution has occurred or that developmental plasticity shapes future acclimation responses.

Biological invasions are common among freshwater molluscs, with the North American planorbid gastropod Gyraulus parvus being reported from Europe (Germany) by the 1970s. It has since spread across Central and Western Europe, mostly living in artificial and highly modified habitats. However, considerable conchological and anatomical similarity exists between it and the native European G. laevis. Using four other European and one North American Gyraulus species as outgroups, separate phylogenetic analyses using mitochondrial and nuclear DNA sequences show that G. parvus and G. laevis are in fact part of the same species-level clade, with the former having nomenclatural priority. However, the structure within the mitochondrial tree suggests a North American origin of the invasive populations. It also makes it possible to track down the distribution of both races. Although native and non-native races in Europe tend to possess some differences in conchology and ecology, the degree of overlap makes it impossible to accurately distinguish between them without the DNA barcode data. Our results change the outlook on the conservation of the rare native race. While interspecific competition among snail species is rare, invasion on an intraspecific level may represent a serious threat for native populations.

Molluscs are among the most diverse and widespread animal groups in freshwater habitats. Unfortunately, like most freshwater taxa, they are decreasing dramatically and are now among the most threatened animals on Earth, with many species already extinct or on the brink of extinction. Here, we review our current knowledge on the biodiversity and conservation of freshwater molluscs using the concept of knowledge shortfalls. We focus on seven previously proposed key shortfalls to review and analyse existing knowledge gaps relating to (1) taxonomy, the Linnean Shortfall; (2) distribution, the Wallacean Shortfall; (3) abundance and population dynamics, the Prestonian Shortfall: (4) evolution, the Darwinian Shortfall; (5) abiotic tolerances, the Hutchinsonian Shortfall; (6) traits, the Raunkiaeran Shortfall; and (7) biotic interactions, the Eltonian Shortfall. In addition, we address a new shortfall, which relates to the application and effectiveness of conservation measures, including assessments, methods, funding, and policies, the Ostromian Shortfall. Based on our review, we provide recommendations and suggest pathways to overcome these existing shortfalls. This work also introduces the articles in this special issue of Hydrobiologia, which represent key contributions to the First International Freshwater Mollusk Conservation Society Meeting held in Verbania, Italy, in 2018.

Acknowledgements The authors acknowledge the two anonymous reviewers for their useful comments that improved the manuscript. Financial support for the excavations in Neumark‐Nord 2 was provided by the Lausitzer Mitteldeutsche Braunkohlengesellschaft mbH, the Landesamt fur Denkmalpflege und Archaologie Sachsen‐Anhalt (Harald Meller, Susanne Friederich), the Romisch‐Germanisches Zentralmuseum Mainz, the Leids Universiteits Fonds ‘Campagne voor Leiden’ program and the Netherlands Organization for Scientific Research (N.W.O.).

The first in-depth revision of a lacustrine freshwater mollusc fauna of the Serbian Lake System (SLS) is carried out. We describe and discuss well-preserved faunas from two localities in central and southern Serbia (Mađere and Medoševac), along with the reinvestigation of type material of several species described in the late nineteenth and early twentieth centuries. Our revision yields 14 species of gastropods, with the families Hydrobiidae (six species) and Planorbidae (four species) being most abundant, along with one species each of Neritidae, Melanopsidae, Bithyniidae and Bulinidae, as well as two dreissenid bivalve species. Three of the hydrobiid gastropods are new to science, Prososthenia milosevici sp. nov., Prososthenia? naissensis sp. nov., and Prososthenia rundici sp. nov., and so is the bivalve Trigonipraxis madjerensis sp. nov. The present study results in 12 lectotype designations, 10 new generic combinations, and 10 new junior synonyms. About four-fifths (81.3%) of the species are endemic to the SLS, which is slightly higher than the overall SLS endemism (71.4%). The composition at the genus and family level overlaps strongly with the slightly older faunas of the Dinaride Lake System in Croatia and Bosnia and Herzegovina, as well as that of the late Miocene Lake Pannon. Its stratigraphically intermediate position and geographical proximity suggest that the SLS was a stepping stone for many of the mollusc lineages, some of which are found only in those systems.

The effect of water temperature on early-life development, growth and survival of the freshwater mussel, Hyriopsis bialata, was studied under controlled conditions. Gravid female mussels carrying gastrula embryos or early glochidia larvae were reared at 4 temperatures (25, 28, 31 and 34 °C) until they released mature glochidia; glochidia were then allowed to develop into juveniles. The highest survival rate of glochidia released from mussels carrying gastrula embryos was at 25 °C (91.4%), while survival for glochidia released from mussels carrying early glochidia larvae ranged from 83.2–91.3%. Average larval development time for gravid females carrying gastrula embryos or early glochidia larvae was between 5.0 and 9.2 days and 2.6–3.6 days, respectively. The survival of glochidia cultured to early juveniles in artificial medium was high in gravid mussels with gastrula embryos originally reared at 25 °C (93.9%) or 28 °C (93.6%), but was markedly decreased when originally reared at 31 °C (49.6%), while survival rates of those in gravid mussels with early glochidia larvae originally reared at 25, 28 or 31 °C were 92.3, 90.2 and 87.7%, respectively. The average transformation period from glochidia to early juvenile was 8–11 days, regardless of the temperature. Juveniles were reared for 1 month, and survival and length were measured. For glochidia released from gravid females with gastrula embryos, survival (85.7%) and length (0.49 ± 0.05 mm) were highest when originally reared at 25 °C, and both measures were significantly decreased at 28 and 31 °C. For glochidia released from gravid females carrying early glochidia larvae, survival (82.2%) and length (0.45 ± 0.06 mm) were highest when originally reared at 28 °C and lower when reared at 25 or 31 °C. Our results indicate that the optimal water temperature for culturing gravid female mussels carrying gastrula embryos or early glochidia larvae was 25 and 28 °C, respectively. These temperatures allowed high juvenile survival and growth.

Invasions of non-native species are major threats for freshwater ecosystems. One of the most invasive freshwater mussels in Europe is the Asian Sinanodonta woodiana (Chinese pond mussel). It occurs in the same waterbodies as the endangered native species Anodonta cygnea and Anodonta anatina with unknown consequences for them. Thus, the analysis about the host–parasite relationship between the larvae of S. woodiana and host fish species in Europe is important to assess impacts on the native mussels regarding their competition for hosts. In this study, host suitability of ten different fish species (native and non-native to Europe) for the glochidia of S. woodiana was analyzed by simultaneous infestation of the fish. All fish species were identified as suitable hosts but differed significantly in initial infestation rate as well as duration and rate of juvenile mussel excystment. Surprisingly, the glochidia developed successfully on Rhodeus amarus (bitterling), which cannot use S. woodiana for its own reproduction, and which is an unsuitable host for native anodontines. Compared to both native Anodonta, S. woodiana glochidia developed more successfully resulting in a higher number of excysted juvenile mussels at similar larval exposure. Metamorphosis was also faster on all tested fish species. These factors, together with the faster growth and higher number of offspring in S. woodiana likely contribute to a competitive advantage over native anodontines. The great likelihood of spreading this mussel on a large number of different possible host fish species deserves attention in fisheries management and stocking programs.

First records of invasive bivalve freshwater mollusc species Mytilopsis leucophaeata (Conrad, 1831) and Corbicula fluminalis (O. F. Müller, 1774) in Georgia are reported. No native or alien extant dreissenid species have ever been recorded form this region so far. A finding of C. fluminalis in Georgia is also a new record for the country though this species inhabits the rivers of adjacent Azerbaijan. Apart from two mentioned bivalve molluscs three non-indigenous gastropod species are registered from Georgia: freshwater Ferrisia californica (Rowell, 1863) and Physella acuta (Draparnaud, 1805) and land snail Eobania vermiculata (O. F. Müller, 1774).

Human fascioliasis is a freshwater snail borne, zoonotic disease caused by Fasciola liver flukes which are widely spread throughout Pakistan and has recently proved to be endemic in humans of the Punjab province. To verify whether fasciolids are also affecting humans outside this province, studies were conducted in four communities comprising rural and urban areas of Mardan district, Khyber Pakhtunkha province, northern Pakistan. Activities comprised two surveys, a coprological one to look for Fasciola infection and another to get information on potential human infection sources and risk factors by means of a questionnaire. Out of 540 subjects of all ages surveyed, only 4 children (0.74%) were found positive for Fasciola eggs: two 9- and 13-year old boys and two 7- and 16-year old girls. Burden per child ranged 73–146 eggs per gram of faeces (epg), with an average of 106 ± 15.4 epg. Based on the egg size, the infection was diagnosed to be caused by F. hepatica. Serum analyses showed eosinophilia and elevated enzyme values in liver function tests. The Mardan area fits well to all transmission and epidemiological requirements of F. hepatica, namely the presence of infected livestock reservoirs throughout, the appropriate climatic factors (mainly monthly temperature variation along the year), and the existence of adequate freshwater collections. The existence of the specific lymnaeid snail vector species for F. hepatica transmission was reported in the neighbouring Swat valley time ago. Results show that human fascioliasis may be widespread in Pakistan and that both F. hepatica and F. gigantica may be involved.

Freshwater mollusc diversity has repeatedly been found to peak in lowland stagnant waters, which are highly exposed to human-made degradation and the spread of non-native species. Despite the increasing loss of these habitats, little is known about the main predictors of their mollusc diversity patterns. Therefore, we aimed to determine the environmental drivers of mollusc assemblage variation between and within sites by sampling 62 water bodies in the Dyje River floodplain (south-eastern Czechia). We measured 14 environmental variables, categorized as site-specific or plot-specific. Species richness and abundances were analysed by GLM and GEE; species compositional variance was assessed by NMDS and db-RDA ordinations. Mollusc species richness, ranging between 0 and 15 species per site, and abundance sharply decreased towards high trophy sites, with the chlorophyll-a concentration and water pH highly correlated with species counts. Species compositional variation was driven mainly by water trophy and the quality of organic detritus. Site heterogeneity turned out to significantly control local assemblages of molluscs, while the presence of individual species seemed to be filtered by site trophy and the shoreline length. Thus, to maintain high regional diversity of aquatic molluscs in lowland agricultural landscapes, the presence of low trophy sites seems to be essential.

This work evaluated the molluscicidal activity of the essential oil of the Zingiber officinale Roscoe rhizomes in with of the Biomphalaria glabrata species. The essential oil was isolated q...

Summary Freshwater snails serve as one of trematodes’ intermediate hosts. Previous studies on trematode larval stages in the Philippines have largely focused on species with public health importance. This study sought to investigate the prevalence of cercarial morphotypes in several freshwater snail species found in different habitat types (rice field, irrigation canals, and residential area) in selected agricultural areas in Los Baños and Bay in Laguna. Cercarial emergence was induced through exposure to artificial light. A total of 2,720 freshwater snails were collected and were represented by seven species, namely, Melanoides tuberculata Muller 1774 (n = 1229), Radix quadrasi von Moellendorf (n = 630), Tarebia granifera Lamarck, 1816 (n = 417), Pomacea canaliculata Lamarck 1819 (n = 257), Vivipara angularis philippinensis Nevill (n = 18), Stenomelania sp. (n = 104), Thiara scabra Muller 1774 (n = 65). A 2.57 % over-all prevalence was recorded; the infected snail species were M. tuberculata (2.21 %), R. quadrasi (0.21 %), T. granifera (0.11 %). Four cercarial morphotypes, namely, Parapleurolophocercous cercaria (1.80 %), Virgulate xiphidiocercaria (0.26 %), Megaluruous cercaria (0.29 %), and Echinostome cercaria (0.22 %) were recovered from the infected snail species. Prevalence of cercarial infection was significantly different (p < 0.05) among habitat types.

Glycogen is a primary metabolic reserve in bivalves and can be suitable for the evaluation of bivalve condition and health status, but the use of glycogen as a diagnostic tool in aquaculture and biomonitoring is still relatively rare. A tissue biopsy combined with a simplified phenol-sulfuric acid method was used in this study to evaluate the inter- and intraindividual variation in the glycogen concentrations among several tissues (foot, mantle, gills, adductor muscle) of the unionid bivalve, the duck mussel Anodonta anatina. This short report documents that individual bivalves differ in the spatial distribution of glycogen among tissues. Sampling of different types of tissues can cause distinct results in the evaluation of energetic reserves at the individual level. At the same time, spatial variability in glycogen content has the potential to provide a more detailed evaluation of physiological conditions based on tissue-specific glycogen storage. The results obtained and the simplified methodology provide a new opportunity for researching the energetic reserves and health status of freshwater mussels in various applications.

This is the first review of life cycles of trematodes with parthenitae and larvae in freshwater gastropods from forest biocoenoses of Ukrainian Polissia. Altogether 26 trematode species from 14 families were found circulating in 13 ways in molluscs from reservoirs connected with forest ecosystems of the region. Three-host life cycle is typical of 18 trematode species, two-host life cycle has found in 7 species, and four-host cycles has found in one species. Alaria alata Goeze, 1782, has three-host (Shults, 1972) and four-host cycles. Opisthioglyphe ranae (Froehlich, 1791) can change three-host life cycle to two-host cycle replacing the second intermediate host (Niewiadomska et al., 2006) with the definitive host. Species with primary two-host life cycle belong to Notocotylidae Lühe, 1909, Paramphistomidae Fischoeder, 1901 and Fasciolidae Railliet, 1758 families. Trematodes with three-host cycle have variable second intermediate hosts, including invertebrates and aquatic or amphibious vertebrates. Definitive hosts of trematodes are always vertebrates from different taxonomic groups. The greatest diversity of life cycles is typical for trematodes of birds. Trematodes in the forest biocoenoses of Ukrainian Polissia infect birds in six ways, mammals in three, amphibians in four, and reptiles in one way. The following species have epizootic significance: Liorchis scotiae (Willmott, 1950); Parafasciolopsis fasciolaemorpha Ejsmont, 1932; Notocotylus seineti Fuhrmann, 1919; Catatropis verrucosa (Frölich, 1789) Odhner, 1905; Cotylurus cornutus (Rudolphi, 1808); Echinostoma revolutum (Fröhlich, 1802) Dietz, 1909; Echinoparyphium aconiatum Dietz, 1909; Echinoparyphium recurvatum (Linstow, 1873); Hypoderaeum conoideum (Bloch, 1782) Dietz, 1909; Paracoenogonimus ovatus Kasturada, 1914; Alaria alata Goeze, 1782.

Echinostome metacercariae were investigated in freshwater snails from 26 districts in 7 provinces of upper northern Thailand. The species identification was carried out based on the morphologies of the metacercariae and adult flukes harvested from experimental hamsters, and on nucleotide sequences of internal transcribed spacer 2 (ITS2) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (nad1) genes. Twenty-four out of 26 districts were found to be infected with echinostome metacercariae in freshwater snails with the prevalence of 40.4%. The metacercariae were found in all 6 species of snails, including Filopaludina martensi martensi (21.9%), Filopaludina doliaris (50.8%), F. sumatrensis polygramma (61.3%), Bithynia siamensis siamensis (14.5%), Bithynia pulchella (38.0%), and Anenthome helena (4.9%). The echinostome metacercariae found in these snails were identified as Echinostoma revolutum (37-collar-spined) and Echinostoma macrorchis (45-collar-spined) morphologically and molecularly. The 2-week-old adult flukes of E. revolutum revealed unique features of the cirrus sac extending to middle of the ventral sucker and smooth testes. E. macrorchis adults revealed the cirrus sac close to the right lateral margin of the ventral sucker and 2 large and elliptical testes with slight indentations and pointed posterior end of the posterior testis. The ITS2 and nad1 sequences confirmed the species identification of E. revolutum, and the sequences of E. macrorchis have been deposited for the first time in Gen-Bank. The presence of the life cycle of E. macrorchis is a new record in Thailand and the snail F. doliaris as their second intermediate host seems to be new among the literature.

The immune system of snails is highly sensitive to pollutants, which can suppress its immune response. We investigated the effects of exposure to the glyphosate-based herbicide Roundup® Original on the snail Biomphalaria glabrata infected by the platyhelminth Echinostoma paraensei by evaluating changes in the snail's internal defense system. Four cohorts were studied: control group, infected snails, snails treated with Roundup®, and snails infected and treated with Roundup®. The hemocyte viability was assessed, morphological differentiation of cells was observed and flow cytometry was performed to determine the morphology, viability and the lectin expression profiles. The frequencies of dead hemocytes were lower in the infected group and higher in both pesticide treated groups. Three cell types were identified: blast-like cells, hyalinocytes and granulocytes. The highest number of all types of hemocytes, as well as the highest number of dead cells, were observed in the infected, pesticide-treated group. The association between infection and herbicide exposure greatly increased the frequency of dead hemocytes, suggesting that this condition impairs the internal defense system of B. glabrata making the snails more vulnerable to parasitic infections.

Human cercarial dermatitis is a parasitic disease that causes an allergic reaction in the skin (swimmer's itch) as a consequence of contact with cercariae of bird schistosomes present in water, mainly of the genus Trichobilharzia Skrjabin et Zakarow, 1920. The main objective of the study was to confirm the presence of the zoonotic disease agent following reports of human infections in recreational water in Slovakia. We identified two species of freshwater snails at Kosice Lake, Radix auricularia (Linnaeus, 1758) and Physa acuta (Draparnaud, 1805). Trematode infections were observed only in R. auricularia. Of the 62 snails collected, 11 (17.7%) were infected with 5 different species of larval stages of trematodes. The blood fluke Trichobilharzia franki was found in 2 (3.2%) of the examined snails. The present record provides the first evidence that T. franki from the pulmonate snail R. auricularia represents a source of human cercarial dermatitis in recreational water in Slovakia. Our finding complements the easternmost records of both swimmer's itch and the confirmed occurrence of a bird schistosome in a waterbody in Europe. The present work suggests that the health risks associated with trichobilharziasis need to be further studied by detailed monitoring of the occurrence of the major causative agent of human cercarial dermatitis, T. franki.

Background Schistosomiasis is a common parasitic disease designated as a neglected tropical disease by the World Health Organization. Schistosomiasis mansoni is a form of the disease that is caused by the digenean trematode Schistosoma mansoni, transmitted through Biomphalaria spp. as an intermediate host. Biomphalaria was introduced to Hong Kong, China in aquatic plants shipments coming from Brazil and the snail rapidly established its habitats in southern China. Earlier studies of Biomphalaria spp. introduced to southern China identified the snails as Biomphalaria straminea, one of the susceptible species implicated in S. mansoni transmission in South America. However, recent molecular investigations also indicated the presence of another South American species, B. kuhniana, which is refractory to infection. As such, it is important to identify accurately the species currently distributed in southern China, especially with emerging reports of active S. mansoni infections in Chinese workers returning from Africa. Methods We combined morphological and molecular taxonomy tools to precisely identify Biomphalaria spp. distributed in Guangdong Province, southern China. In order to clearly understand the molecular profile of the species, we constructed a phylogeny using mtDNA data (COI and 16S rRNA sequences) from six populations of Biomphalaria spp. from Shenzhen City in Guangdong Province. In addition, we examined the external morphology of the shell and internal anatomy of the reproductive organs. Results Both morphological and molecular evidences indicated a close affinity between Biomphalaria spp. populations from Guangdong and B. straminea from Brazil. The shell morphology was roughly identical in all the populations collected with rounded whorls on one side and subangulated on the other, a smooth periphery, an egg-shaped aperture bowed to one side, and a deep umbilicus. The shape and number of prostate diverticula (ranged from 11.67 to 17.67) in Guangdong populations supports its close affinity to B. straminea rather than B. kuhniana. Molecular analysis did not conflict with morphological analysis. Little genetic differentiation was observed within Biomphalaria populations collected. Phylogenetic analysis of COI and 16S rRNA haplotypes from snails collected and B. straminea sequences from Brazil and China using Bayesian inference revealed that Guangdong populations were clustered in one clade with B. straminea from Hong Kong of China and B. straminea from Brazil indicating their close affinity to each other. Conclusions Data obtained in the current study clearly show that the populations of Biomphalaria spp. investigated are B. straminea, and we assume that those snails were either introduced via passive dispersal from Hong Kong of China or as a result of multiple introduction routes from Brazil. Electronic supplementary material The online version of this article (10.1186/s40249-018-0505-5) contains supplementary material, which is available to authorized users.

Controlling of Biomphalaria alexandrina snails by plant molluscicides is the cornerstone in treating schistosomiasis in Egypt. The objective of this study is, to evaluate the molluscicidal activity of the aqueous leaves extract of Anagallis arvensis against B. alexandrina snails. The present results showed that this aqueous extract was lethal for B. alexandrina snails at (LC50 37.9 mg/l; LC90 48.3 mg/l), and caused reduction in survival; reproductive rates and hormonal activity (testosterone (T) and 17β-estradiol (E)) of these snails. Histopathological changes occurred in the hermaphrodite glands of snails exposed to the sub lethal concentrations of this aqueous extract are detected, where, there were degeneration in both eggs and sperms and there were losses of connective tissues between acini. The present investigation revealed that this plant had a genotoxic effect especially with its concentration (LC10 and LC25), where, the length of olive tail moment was significantly increased than control group. These observations prove the potent molluscicidal activity of aqueous leaves extract of A. arvensis against the intermediate hosts of Schistosoma mansoni and provide natural biodegradable resources for snails' molluscicidal agents.

The concentrations of organochlorine and organophosphorus pesticides were determined in surface sediments and freshwater molluscs (Melanoides scabra and Melanoides tuberculata) from Tighra Reservoi...

In spite of considerable progress made in the prevention and control of schistosomiasis and other snail-borne diseases, transmission has intensified in some endemic areas as a result of land-use and climate changes. We used decision tree models and multivariate analysis to identify factors affecting the occurrence and abundance of medically important freshwater snail intermediate hosts in the Omo-Gibe river basin, Ethiopia. The models were based on a dataset of 140 samples collected from lakes, wetlands, rivers, dam reservoir shores and irrigation canals. A total of 1866 freshwater snails belonging to four genera and seven species were collected. Biomphalaria pfeifferi, Lymnaea natalensis and Bulinus globosus had fair to moderate predictive performance based on Kappa statistics (ĸ > 0.2), indicating that these species have clear environmental requirements within the habitat gradient studied. The most important variables influencing the abundance and occurrence of snail species were the presence of predator and competitor, canopy cover, type of water body, waste dumping and water pH. In conclusion, snail species occurred less frequently and in smaller numbers in water bodies with minimal human disturbances. Therefore, preventing human disturbance in water bodies may enhance aquatic biodiversity, thereby increasing the abundance of snail predators and competitors. Preventing the pollution of these ecosystems is essential to maintain their ecological integrity and sustain the ecosystem services they provide to local communities.

In this review, we are discussing South Asian schistosomiasis; more specifically species which are responsible for schistosomiasis in India or South Asia –Schistosoma indicum, S. spindale, S. nasale, S. incognitum, S. gimvicum (S.haematobium), Bivitellobilharzia nairi, Orientobilharzia bomfordi, O. dattai, O. turkestanicum and O.harinasutai, their survival strategies such as mild pathology to the host, producing low egg number and utilizing fresh water snails (Indoplanorbis exustus and Lymnaea luteola) in stagnant water bodies like ponds, lakes, ditches, low laying areas, marshy lands and rice fields. Presently, correct identification of blood fluke species, their immature stages, male schistosomes and their intermediate host details like strain variations, susceptibilities, ecologies are not well studied. Species like B. nairi, O. bomfordi, O. harinasutai (Lymnaea rubiginosa intermediate host for O.harinasutai in Thailand) are also not well studied. Moreover, snail species like Oncomalania spp are not from South Asia, but species of Tricula or Neotricula are reported from this geography, which gives indications of S. mekongi like blood fluke presence in the area. Although in humans, cercarial dermatitis is rampant in rural population with occasional reporting of schistosome eggs in stools, human schistosomiasis is considered absent from this region, despite finding a foci (now dead) of urinary schistosomiasis in Gimvi village of Ratnagiri district, Maharashtra, India. There is great difficulty in diagnosing the infection in man and animals due to low egg production, hence development of a single step antigen detection test is the need of the hour. Interestingly, lethal effect of praziquantel was seen against S.haematobium and S.mansoni. However, this drug failed to cause significant reduction of S. incognitum and S. spindale experimentally suggesting some differences in the biology of two groups of the schistosomes. Triclabendazole showed adulticidal effect at a dose rate of 20 mg/kg body against female schistosome worms, but at lower dose (10 mg/kg body wt) of the drug, a dose that is used in treating bovine fascioliasis, it is providing chances of drug resistance of the persisting schistosomes against triclabendazole. Though the South Asian institutes have all the facilities to tackle issues related to existing schistosomes, it is recommended to develop an international collaboration by establishing an international centre on schistosomiasis in India.

A new large population of the Asian clam Corbicula fluminea (O. F. Müller, 1774) was found within a reach (ca 210 km long) of one of the largest European rivers, the Vistula. The largest population and the largest individuals were found at the outlet of a channel collecting heated water from the cooling process at the Połaniec power station and adjacent parts of the river. In the northern part of the study area, bivalves occurred at the channel margins, in groyne fields, and in the shallows of sand banks or sandbars. The clams were less numerous in places where the river was regulated with straightened banks and stone ripraps. Twenty-five other taxa of mollusks were found altogether at the sampling stations where Corbicula was observed, including other non-indigenous mollusk species.

Several non-native trematodes hosted by the invasive Eurasian faucet snail, Bithynia tentaculata, have been causing die-offs of waterfowl in the Midwestern United States and Canada for several decades. Because of the potential implications of these die-offs on waterfowl in non-native settings, it is necessary to better understand the trematodes that cause the die-offs. Here, we studied the spatio-temporal dynamics of two trematodes, Cyathocotyle bushiensis and Sphaeridiotrema spp., known to infect waterfowl in northern Minnesota, USA, via their intermediate host, the faucet snail (Bithynia tentaculata). We studied prevalence (% of snails infected within a sample) and intensity (mean number of parasites per infected snail within a sample) of faucet snail infection with these two trematodes in small lakes, large lakes, ponds, and rivers in northern Minnesota in the spring, summer, and fall of 2011–2013. We tested whether parasite prevalence and infection intensity could be explained spatially (as a function of the abundance of faucet snails, average snail size, water depth, and proximity to known waterfowl groups) and temporally (across years and seasons) using generalized estimating equation models. The spatial and temporal patterns we observed varied within and among waterbodies. For both parasite species, parasite prevalence and intensity of infection were consistently higher in samples with larger snails and in deeper portions of the waterbodies. In Lake Winnibigoshish, prevalence was lower farther from the large waterfowl groups we observed, but the abundance of snails in a sample had no effect on prevalence or intensity of infection. Our findings help improve understanding of this multi-species system, but also illustrate the complexity of modeling the spatial and temporal dynamics of infections in waterbodies that are so variable in size, shape, waterfowl use, and function., Graphical abstract Image 1, Highlights • Non-native trematodes hosted by snails cause waterfowl mortality in N. America. • Bithynia tentaculata had higher trematode prevalence and intensity in deep areas. • Snail size and distance to waterfowl related to infection, snail abundance did not. • Trematode infection varied among years and seasons, but not consistently.

In this study, the effects of the heavy metal cadmium on the stress protein HSP70 are investigated in freshwater mollusks Biomphalaria glabrata . Adult snails were exposed for 96 h to CdCl 2 at concentrations ranging from 0.09 to 0.7 mg L −1 (LC 50/96 h =0.34 (0.30–0.37). Time and concentration-dependent increases in the expression of HSP70 were observed at sub-lethal levels in the immunoblotting assay. Further, an increased survival to a lethal heat shock was observed in animals pre-exposed to a nonlethal concentration of cadmium, evidencing the induction of acquired tolerance. The present study demonstrated the inducibility of B. glabrata HSP70 by cadmium, a relevant environmental contaminant, at non-lethal levels, providing evidences that the assessment of HSP70 in B. glabrata can be regarded as a suitable biomarker for ecotoxicological studies.

Freshwater samples and gastropod mollusks (Pomacea canaliculata) were collected at 5 sampling stations located along the lower Río de la Plata basin, Argentina, to assess the extent of tributyltin (TBT) contamination. Determined data revealed the presence of TBT and some of its breakdown products (dibutyltin: DBT, and monobutyltin: MBT) in all freshwater samples and also in soft tissues of P. canaliculata gastropods. Chronic bioassays (6 months) were performed using female gastropods that had been reared under laboratory conditions and exposed to a similar TBT concentration than the value determined in freshwater samples (1 µg L−1). The aims of this study were to evaluate the extent of TBT accumulation, the tissue distribution, and the effects on selected biomarkers (activity of superoxide dismutasa: SOD, activity of catalase: CAT, levels of total glutathione: t-GSH, lipid peroxidation, and activity of acetylcholinesterase: AChE). Gonads presented the highest accumulation, followed by the cephalopedal region, albumin gland, and finally hepatopancreas. Both metabolites, DBT and MBT, were also found. All exposed female animals presented development of a penis reflecting the potential of TBT as an endocrine disrupting chemical for this gastropod species. Results on the selected biomarkers confirmed additional adverse effects induced by TBT. An increase in CAT activity and changes in t-GSH levels are indicative of alterations on the cellular redox status. The inhibition of AChE could reflect signs of neurotoxicity. Altogether, these results reveal a negative impact on the health of this gastropod population. Fil: Martínez, María L.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina Fil: Piol, María Natalia. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Sbarbati Nudelman, Norma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina Fil: Verrengia Guerrero, Noemí Rosario. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina

The effects of invasive alien species (IAS) on host–affiliate relationships are often subtle and remain unnoticed or insufficiently quantified. The global decline of freshwater unionid mussel species has been attributed to many causes, but little is known about the interactions of IAS, with their complex life cycle, which includes an obligatory parasitic stage (the glochidium) that develops on fishes. The capacity of a European freshwater mussel, Anodonta anatina, to develop on its widespread fish host, Squalius cephalus was tested experimentally, after previous infestations by the IAS, Sinanodonta (Anodonta) woodiana. The initial attachment of glochidia, the length of the parasitic period, and the metamorphosis success rate of A. anatina glochidia were compared among treatments of different priming infestation intensities. The metamorphosis success rate of the native A. anatina glochidia was strongly reduced (Wilcoxon Signed-Rank Test, P < 0.001) and declined by 42.1 and 45.4% on fish hosts that were previously exposed to S. woodiana by single and multiple priming infestations, respectively, in comparison with the control group. Such cross-resistance is expected to decrease significantly the quality of the host resources available to native mussels. This study provides the first evidence of the host-mediated adverse impact of invasive S. woodiana on native mussel species. These results also highlight the importance of potential competition for hosts between threatened groups of affiliate species and their invasive counterparts, which should be reflected in conservation strategies., Czech Science Foundation, Grant/Award Number: 13-05872S, info:eu-repo/semantics/publishedVersion

Because biological invasions may cause loss of biodiversity, accurate predictions are necessary for implementing effective restrictions aimed at specific high-risk taxa. The majority of freshwater macroinvertebrate invaders are molluscs and crustaceans. The pet trade has been considered one of the main pathways for new introductions of such species. Risk assessment is usually focused on traded ornamental species whereas, despite their potential importance, incidental “hitchhiking” molluscs are usually given only minimal consideration. We surveyed the Czech Republic, which is one of the leading markets for aquarium species in the European Union (EU), and found 41 freshwater mollusc species (25 ornamental gastropods, 6 ornamental clams, and 10 “hitchhiking” gastropods) representing 13 families. We extrapolated data from the Czech Republic and, using Climatch v. 1.0, matched the climate in each species’ native range to the entire territory of the EU. We also assessed the risk associated with each species by FI-ISK. “Hitchhiking” gastropods were found to be significantly more hazardous and with higher potential to become established within the EU than were ornamental gastropods and bivalves. Many “hitchhikers” may be easily overlooked due to their small size and cryptic coloration or shape. Thus, they easily can be accidentally imported in association with aquarium plants. Therefore, we recommend here to disinfect imported ornamental plants to eradicate these unwanted faunal assemblages.

Background: Most of trematodes need snails to complete their life cycles. Consequently freshwater snails are served as intermediate hosts of many parasites worldwide. There is a lack of report on snail diversity and parasitic infection in snails in Sirindhorn Reservoir, Ubon Ratchathani province, Thailand. Methods: Mollusk diversity and trematode cercariae infections were investigated in snails from 120 sampling sites surround Sirindhorn Reservoir from April 2018 to June 2018. Mollusk species were identified based on their shell morphology. The presence of cercariae infections in snails was examined by cercarial shedding methods. The interaction between snail species was analyzed by the correlation method. Results: Overall, 2076 mollusks were collected which comprised six species of snails and two species of bivalves. Snail species were identified as Bithynia siamensis goniomphalos, Anentome helena, Filopaludina sumatrensis spiciosa, F. martensi martensi, F. martensi munensis and Pomacea canaliculata. The overall rate of trematode cercariae infection was 1.69% (35/2,076). The cercariae found infecting snails were Cercariaeum cercaria, Virgulate cercaria, Cotylomicrocercous cercaria and Furcocercous cercaria. The most common snails found was the assassin snail, A. helena, which showed the negative relationship among other species interactions. Conclusion: This finding indicated infection with animal’s parasites in snails in this area are common, besides, we found many species of snails in Sirindhorn Reservoir are potentially be the host of parasite in animal and human.

Introduction Freshwater vector snails' distribution, infection with cercariae, preferred habitat and possible trematodiases transmission foci is not well known in Western Kenya. We sought to determine the distribution and prevalence of infection of snails per agro-ecological zone and environmental factors in vector snail habitats. Methods We conducted a cross-sectional survey from March, 2016 - May, 2016, harvested and identified snails using shell morphology, determined their infection with trematode cercariae using microscopy, used descriptive statistics to estimate the prevalence of infection and relationship between snail abundance and environmental factors. Results We sampled a total of 1,678 vector snails from 47 sampling sites of which 42% were Lymnaeid, 23% Biomphalaria, 10% Bulinus, 22% Oncomelaniae and 2% Melanoides. Lower Midland I Ago-Ecological Zones had 44% of the snails and streams from springs had 41% of the snails. Overall, 26.5% (445/1678) (95% CI: 24.4 - 28.6) of the snails shed cercariae. Cercariae were found in 11 (23%) of the sites and in all zones. F. gigantica cercariae were shed by L. natalensis, B. pfeifferi, B. sudanica. Lakeshore had both F. gigantica and S. mansoni cercariae shed by B. sudanica. About 72% (1,202/1,678) of snails were found in water with a pH 6.5 - 7.5. Grass habitat had 54% (912/1,678) of the snails. Conclusion Lymnaeid snails were present in all the zones, while streams from springs and near neutral habitats had most of the snails. Infection with trematode cercariae was noted in all the zones. Trematodiases control should be focused on all zones especially in freshwater streams and lakeshores.

In September 2020, the fauna of mollusks was studied at the Priplotinny Ples Reach of the Kuibyshev Reservoir, the Volga River, Russia. In total, 23 taxa were registered, including four invasive species. Extrapolating of the species richness, taking into account the sampling effort, allowed to assess the estimated species pool according to the Chao 2 algorithm. Bivalve mollusks predominated in the studied area. The mollusks Dreissena (Pontodreissena) bugensis and Dreissena (Dreissena) polymorpha have been found most frequently at the study sites. Both abundance and biomass varied in wide range, as 391 ± 325 ind. m−2 and 256.693 ± 228.355 g m−2, respectively. The complex of dominant species was mainly represented by alien mollusks. The type of bottom sediment was a significant ecological factor (p ≤ 0.05) that determined the distribution of mollusks at the Priplotinny Ples Reach. The water quality of the study area was assessed by bioindication method according to the composition and structure of the mollusk fauna, formed mainly by species of European and European-West Siberian ranges.

Naphthenic acids (NAs), a class of structurally diverse carboxylic acids with often complex ring structures and large aliphatic tail groups, are important by-products of many petrochemical processes including the oil sands mining activity of Northern Alberta. While it is evident that NAs have both acute and chronic harmful effects on many organisms, many aspects of their toxicity remain to be clarified. Particularly, while substantive data sets have been collected on NA toxicity in aquatic prokaryote and vertebrate model systems, to date, nothing is known about the toxic effects of these compounds on the embryonic development of aquatic invertebrate taxa, including freshwater mollusks. This study examines under laboratory conditions the toxicity of NAs extracted from oil sands process water (OSPW) and the low-molecular weight model NAs cyclohexylsuccinic acid (CHSA), cyclohexanebutyric acid (CHBA), and 4-tert-butylcyclohexane carboxylic acid (4-TBCA) on embryonic development of the snail Lymnaea stagnalis, a common freshwater gastropod with a broad Palearctic distribution. Evidence is provided for concentration-dependent teratogenic effects of both OSPW-derived and model NAs with remarkably similar nominal threshold concentrations between 15 and 20 mg/L and 28d EC50 of 31 mg/L. In addition, the data provide evidence for substantial toxicokinetic differences between CHSA, CHBA and 4-TBCA. Together, our study introduces Lymnaea stagnalis embryonic development as an effective model to assay NA-toxicity and identifies molecular architecture as a potentially important toxicokinetic parameter in the toxicity of low-molecular weight NA in embryonic development of aquatic gastropods.

In Vietnam, especially central Vietnam, patients with fascioliasis are increasingly being reported. Since the fascioliasis is zoonotic, survey on the cattle fascioliasis should be informative for the control of human fascioliasis. In this study, the prevalence of cattle fascioliasis as well as the density of the intermediate host snails, Lymnaea swinhoei and L. viridis, were studied in Thua Thien Hue (TTH) province during 2014–2015. A total of 572 cattle feces were examined from 27 communes in 9 districts. Fasciola eggs were detected in cattle from 24 communes with an average prevalence of 23.4% (134/ 572). The highest prevalence was detected in cattle in the coastal plain terrain (31.0%) followed by plain (25.5%), mountain (21.7%), and low hilly (16.2%) terrains. The highest proportion of heavy infection (>200 EPG) was observed in the coastal plain terrain (36.1%), followed by mountains (20.0%), low hills (13.0%), and plains (8.9%). Low number of heavy infection, as well as relatively low prevalence in low hills and plains were associated with the extensive use of anti-fluke treatments. High number of intermediate host snails in low hilly and plain terrains also indicate high risk of fascioliasis. In this study, the density of Lymnaea snails in the coastal plain terrain was found to be very high (17.3 snails/m2) compared to that in previous studies. This is the first report indicating the recent expansion of cattle fascioliasis in the coastal region in Vietnam.

The Central Murray River Valley in northwest Victoria contains a rich and diverse archaeological history spanning the last 20,000 years, which has the potential to help inform on past human behaviour and subsistence strategies. In particular, freshwater shell middens are important as they can provide information about the local aquatic economy, and the role of these molluscs in the diet of Aboriginal hunter–gatherers. Many of the middens in the region consist of thin temporal horizons while being laterally expansive in size (some measuring up to 400 m in length). These middens are dominated by two aquatic molluscs: the river mussel Alathyria jacksoni and the river snail Notopala sublineata. However whilst it is generally accepted that Alathyria jacksoni was a common human prey species, it is thought that the smaller gastropod Notopala sublineata was collected accidentally as by-catch and was not economically important. To investigate, two spatially and temporally distinct middens from different land-systems spanning the late Pleistocene to the late Holocene were studied to look at the variety and size of mollusc species. To supplement the archaeological record, the potential economic and nutritional quality of the bivalve Alathyria jacksoni was investigated. The nutritional results indicate that while Alathyria are low in fat (but are good sources of omega 3- and 6-fatty acids), they are high in protein and calorific energy (kj), and are excellent sources of magnesium (Mg), Iron (Fe), Sodium (Na) and Zinc (Zn). These results coupled with the modern behavioural ecology of these freshwater molluscs, as well as ethnographic and modern cooking experiments, help identify human foraging and subsistence strategies in this region. Results indicate that despite earlier ideas, the river snail Notopala sublineata was an important economic aquatic resource during the late Pleistocene and Holocene.

Objective To evaluate the predatory potential of the Odonata nymph on freshwater snails that serve as intermediate hosts for Schistosoma species ( Bulinus truncatus and Biomphalaria alexandrina ). Methods Observations on the searching, attacking and devouring of the two snail types with series of laboratory-based predation experiments, whose aims were to determine daily predation rate, differential predation, prey preference considering small-, medium- and large-sized snails were conducted. Results Laboratory evaluation revealed that, the Odonata nymph could kill and consume the two intermediate hosts. The number of snails consumed differed according to the snail type, size and density. The times taken for searching and handling times were dependent on the snail size, type and satiation of the predator. The predation rate varied also with respect to snail type, size and density. This study also evaluated that Odonata nymphs consumed more Bulinus truncatus than Biomphalaria alexandrina per unit time, and that there may be a preference for smaller than larger snails. Conclusions According to our observation, the predator, Hemianax ephippiger nymph may be a suitable biocontrol agent in connection with Schistosoma intermediate hosts.

The freshwater snail Bulinus globosus is an important intermediate host of Schistosoma haematobium, the causative agent of urinary schistosomiasis. This disease is of major health concern, especially in Africa where the majority of cases have been reported. In this study the inter- and intra-genetic diversity and population genetic structure of B. globosus from nine locations in the KwaZulu-Natal province of South Africa was studied using four polymorphic microsatellite loci (BgZ1-BgZ4). Moderate genetic diversity was detected within populations with a mean diversity (HE) of 0.49±0.09. The majority of populations significantly deviated from Hardy-Weinberg equilibrium (p

A central premise of ecological stoichiometry is that consumers maintain relatively fixed elemental composition in their bodies, a process known as elemental homoeostasis. Although nutrient enrichment is a ubiquitous problem facing many freshwater lakes around the world, intraspecific variation in elemental composition of freshwater invertebrates and its relationship with nutrient loading have not been well addressed. Here, we examined carbon:nitrogen:phosphorus (C:N:P) stoichiometry of two widely distributed molluscs, Corbicula fluminea and Bellamya aeruginosa, from several subtropical shallow lakes across a nutrient gradient. Our results showed that these two species exhibited substantial natural intraspecific variation in tissue stoichiometry which can reach or even exceed the values among different freshwater taxa investigated before. Our results suggest that tissue P content presents the greatest variations, followed by N content, and lowest in C content. Tissue P content ranged about three-fold (0.56%-1.65%) and five-fold (0.41%-2.28%) for B. aeruginosa and C fluminea, respectively. Correspondingly, N content ranged from 5.16% to 12.06% and from 6.47 to 11.36%, respectively. Tissue %P, C:P and N:P ratios were strongly correlated with PO43--P and/or chlorophyll-a in the water column. Tissue N and P contents of B. aeruginosa and P content of C. fluminea increased with increasing lake trophic levels (mesotrophic to eutrophic to hypertrophic). These results suggest that the two molluscs can adjust their tissue stoichiometry in relation to nutrient enrichment. Relaxing the assumption of strict homeostasis may help them cope with potential stoichiometric constraints. The results provide additional clues to why these two species are successful invaders and widely distributed. (C) 2016 Elsevier Ltd. All rights reserved.