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Snails are effective bioindicators due to their prolific distribution, high level of endemism, and capacity to accumulate contaminants. Freshwater snails have unique ecological niches which are imperiled by land‐use change and the introduction of hazardous chemicals. To assess how environmental alterations affect gastropods, lab‐based studies are needed to characterize the toxicity of specific stressors. This can help guide policy decisions and remediation efforts. The aim of this research was to characterize acute toxicity of nickel (Ni) on endemic snails (Somatogyrus georgianus [Walker, 1904], Elimia cahawbensis [Lea, 1861], and Elimia spp.) and measure the accumulation of Ni and mineral elements including calcium (Ca), magnesium, potassium, and sodium (Na). Snails were exposed to six concentrations (25–800 µg/L) of Ni for 96 h. Among the studied snail species, E. cahawbensis was the most sensitive to Ni, with the lowest lethal concentration where 50% of the organisms died (LC50) at 88.88 µg/L Ni after 96 h. The LC50 at 96 h for S. georgianus was 167.78 µg/L Ni, and 393.13 μg/L Ni for Elimia spp. Except for Elimia spp., mortality of the other two snail species corresponded to the whole‐body uptake of Ni. Nickel exposure also influenced Ca and Na uptake for Elimia spp. All three endemic species are potential candidate species for evaluating localized effects of human activities, and the present study provides a first step in characterizing how snails would be affected by environmental alterations. More research could further characterize potential effects of other human stressors on these endemic snail species. Future research into subindividual responses and routes of exposure can further elucidate variations in species sensitivity. Environ Toxicol Chem 2024;00:1–11. © 2024 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Aquatic invasive species are a significant threat to global freshwater biodiversity. This study focuses on the banded mystery snail, Callinina georgiana, an invasive species in the Adirondack region of northern New York—an important section of the New York Great Lakes Basin. This project aims to explore the genetic connectivity of C. georgiana within its invasive range using a combination of mitochondrial and nuclear markers.Sampling was conducted in the Raquette River and adjacent waterways, with a total of 229 snails collected from 16 distinct populations distributed across eight different waterbodies. Also included were two populations from the species' native range in the southern U.S.A. DNA was extracted, and a 710‐bp fragment of the mitochondrial DNA marker cytochrome c oxidase 1 and a 351‐bp fragment of nuclear marker histone‐3 were amplified. Population genetic analyses including haplotype patterning, AMOVA and genetic diversity estimates, neutrality tests and tests for isolation by distance were performed to assess connectivity patterns.Results showed moderate to high levels of genetic admixture within the snail's invasive range as indicated by the lack of geographic patterning of haplotypes and low to moderate levels of genetic differentiation across multiple sites. Demographic analyses combined with high numbers of private haplotypes indicate historic population expansion. Interestingly, a case of mitonuclear discordance was detected for native and invasive populations as evident by incongruent haplotype patterns for the cytochrome c oxidase 1 and histone‐3 markers.Callinina georgiana exhibits a high level of genetic connectivity in its invasive range. The presence of dams does not significantly affect apparent gene flow, indicating that anthropogenic activities, such as boat traffic might be key in dispersing the snails across this fragmented freshwater system.This study offers new insights into the dispersal and genetic structure of an invasive freshwater snail. It highlights the importance of considering anthropogenic factors when confronting complex patterns of genetic diversity. The findings are significant for biodiversity conservation and provide a basis for developing strategies to manage and contain the spread of aquatic invasive species such as C. georgiana, especially in regions with high human activity. [ABSTRACT FROM AUTHOR]

The genus Pseudamnicola Paulucci, 1878, is commonly found throughout the Mediterranean region. The genus displays considerable levels of endemism, accompanied by notable systematic and taxonomic ambiguity. However, the application of molecular data has proven highly effective in clarifying taxonomy and unveiling the diversity of cryptic species within the genus. Therefore, we employed all cytochrome c oxidase subunit I sequence data available and generated new ones from Greece to infer the phylogeny of the genus throughout its Mediterranean range and estimate the divergence times as well as the ancestral area of diversification. Our phylogenetic and time‐estimate analyses demonstrate that with 36 to 38 extant Pseudamnicola species and genetic divergences across species ranging from 0.5% to 11.9% on average, the genus underwent relatively recent diversification during late Miocene (6.53 Ma), and the primary speciation events occurred during Plio‐Pleistocene. The Italian Peninsula and Islands and the Ionian Drainages as defined by the Freshwater Ecoregions of the World are the ancestral regions of the genus following two different dispersal routes. Our study contributes to deepening our understanding of Pseudamnicola phylogeny by using data from throughout its range for the first time. This phylogeny provides evidence and confirms previous studies that relatively recent habitat isolation, followed by founder and dispersal events, has been one of the primary reasons for the evolution of the genus Pseudamnicola in the Mediterranean basin. [ABSTRACT FROM AUTHOR]

Schistosoma mansoni is a parasitic flatworm that causes the major neglected tropical disease schistosomiasis. The miracidium is the first larval stage of the life cycle. It swims and infects a freshwater snail, transforms into a mother sporocyst, where its stem cells generate daughter sporocysts that give rise to human-infective cercariae larvae. To understand the miracidium at cellular and molecular levels, we created a whole-body atlas of its ~365 cells. Single-cell RNA sequencing identified 19 transcriptionally distinct cell clusters. In situ hybridisation of tissue-specific genes revealed that 93% of the cells in the larva are somatic (57% neural, 19% muscle, 13% epidermal or tegument, 2% parenchyma, and 2% protonephridia) and 7% are stem. Whereas neurons represent the most diverse somatic cell types, trajectory analysis of the two main stem cell populations indicates that one of them is the origin of the tegument lineage and the other likely contains pluripotent cells. Furthermore, unlike the somatic cells, each of these stem populations shows sex-biased transcriptional signatures suggesting a cell-type-specific gene dosage compensation for sex chromosomelinked loci. The miracidium represents a simple developmental stage with which to gain a fundamental understanding of the molecular biology and spatial architecture of schistosome cells. [ABSTRACT FROM AUTHOR]

Three new populations of the invasive New Zealand mud snail, Potamopyrgus antipodarum, have been discovered in central Chile, increasing the documented records in the country to 23. Only females were observed in the present study. Significant differences in shell length and fecundity were found among populations. The size of the snails was less than 6 mm, while fecundity varied from 0 to 45 offspring per snail. A significant correlation was found between adult shell length and brood size in one of the three populations discovered. In these localities, Potamopyrgus antipodarum coexists with native and possibly other invasive gastropods. [ABSTRACT FROM AUTHOR]

Genetic drift, gene flow, and natural selection commonly influence population genetic diversity. In populations of self‐compatible hermaphrodites, the mating system (e.g., self‐fertilization) further reduces individual heterozygosity. Furthermore, selfing, as a form of inbreeding, significantly impacts genetic drift by reducing effective population size (Ne). This can potentially accelerate genetic drift, particularly in small populations where self‐fertilization is likely during founder events. To investigate the roles of genetic drift and contemporary mating system in populations of the freshwater snail Lymnaea stagnalis, we examined their effective population sizes (Ne) and Tajima's D values, which reflect genetic drift over extended time periods, as well as estimates of within‐population selfing rates and pairwise relatedness reflecting contemporary mating system. We used 4054 SNP markers obtained using restriction site associated DNA (RAD) sequencing from individuals in five snail populations originating from geographically closely located ponds. We found strong population genetic structure and differences in genetic diversity among populations. Covariation between genetic diversity and Ne estimates and Tajima's D values suggested drift being an important determinant of genetic diversity and structure in these populations. However, this effect was independent of the contemporary mating system, as indicated by the similarity of selfing rates and relatedness estimates among populations. Thus, founder events (possibly including historical inbreeding) and/or drift due to small sizes of L. stagnalis populations are likely to explain their genetic structure and limit within‐population genetic diversity. [ABSTRACT FROM AUTHOR]

The freshwater snails and mussels are recognized as ecosystem engineers owing to their ability to influence the ecological processes. We investigated the effect of the snail Filopaludina bengalensis and the mussel Lamellidens marginalis alone and in interaction with the macrophyte Lemna minor on the ecological processes (nutrient dynamics, microbial account, sediment properties and periphytic algal growth) of the freshwater ecosystem through a mesocosm experiment. Both the snail and mussel promoted the growth rate of L. minor; however, the presence of snail negatively influenced the growth of periphyton. The biogeochemical process was affected by the presence of snails and mussels. Macrophyte association further influenced this biogeochemical process. Snail and mussel enhance the growth of heterotrophic bacteria and phosphate solubilising bacteria in the sediment. Likewise, the presence of macrophyte also positively influences the microbial growth. The activities of the benthic fauna like the mussels and the snails can be considered a useful process for the sustenance of the microbes and the macrophytes representing a pattern of bottom-up regulation. [ABSTRACT FROM AUTHOR]

The freshwater snail Bulinus truncatus is an important intermediate host for trematode parasites causing urogenital schistosomiasis, a tropical disease affecting over 150 million people. Despite its medical importance, uncertainty remains about its global distribution and the potential impacts of climate change on its future spread. Here, we investigate the distribution of B. truncatus, combining the outputs of correlative and mechanistic modelling methods to fully capitalize on both experimental and occurrence data of the species and to create a more reliable distribution forecast than ever constructed. We constructed ensemble correlative species distribution models using 273 occurrence points collected from different sources and a combination of climatic and (bio)physical environmental variables. Additionally, a mechanistic thermal suitability model was constructed, parameterized by recent life‐history data obtained through extensive lab‐based snail‐temperature experiments and supplemented with an extensive literature review. Our findings reveal that the current suitable habitat for B. truncatus encompasses the Sahel region, the Middle East, and the Mediterranean segment of Africa, stretching from Southern Europe to Mozambique. Regions identified as suitable by both methods generally coincide with areas exhibiting high urogenital schistosomiasis prevalence. Model projections into the future suggest an overall net increase in suitable area of up to 17%. New suitable habitat is in Southern Europe, the Middle East, and large parts of Central Africa, while suitable habitat will be lost in the Sahel region. The change in snail habitat suitability may substantially increase the risk of urogenital schistosomiasis transmission in parts of Africa and Southern Europe while reducing it in the Sahel region. [ABSTRACT FROM AUTHOR]

We show that the globally invasive, human-infectious flatworm, Haplorchis pumilio, possesses the most physically specialized soldier caste yet documented in trematodes. Soldiers occur in colonies infecting the first intermediate host, the freshwater snail Melanoides tuberculata, and are readily distinguishable from immature and mature reproductive worms. Soldiers possess a pharynx five times absolutely larger than those of immature and mature reproductives, lack a germinal mass, and have a different developmental trajectory than reproductives, indicating that H. pumilio soldiers constitute a reproductively sterile physical caste. Neither immature nor mature reproductives showed aggression in in vitro trials, but soldiers readily attacked heterospecific trematodes that coinfect their host. Ecologically, we calculate that H. pumilio caused ~94% of the competitive deaths in the guild of trematodes infecting its host snail in its invasive range in southern California. Despite being a dominant competitor, H. pumilio soldiers did not attack conspecifics from other colonies. All prior reports documenting division of labor and a trematode soldier caste have involved soldiers that may be able to metamorphose to the reproductive stage and have been from nonhuman-infectious marine species; this study provides clear evidence for an obligately sterile trematode soldier, while extending the phenomenon of a trematode soldier caste to freshwater and to an invasive species of global public health concern. [ABSTRACT FROM AUTHOR]

Background: Biological invasions pose risks to the normal functioning of ecosystems by altering the structure and composition of several communities. Molluscs stand out as an extensively studied group given their long history of introduction by either natural or anthropogenic dispersal events. An alien population of the lymnaeid species Orientogalba viridis was first sighted in 2009 in southern Spain. In its native range (Australasian), this species is one of the main intermediate hosts of Fasciola hepatica, a major worldwide trematode parasite largely affecting humans, domestic animals and wildlife. Methods: We collected field populations of O. viridis from its native (Malaysia) and invaded (Spain) ranges. We performed detailed morphoanatomical drawings of the species and screened for natural infection of parasites. Individuals were molecularly characterized using ITS2 for comparison with existing sequences in a fine phylogeography study. We founded experimental populations at two different conditions (tropical, 26 °C and temperate, 21 °C) to study the life-history traits of exposed and non-exposed individuals to different F. hepatica isolates. Results: We found a 9% natural prevalence of trematode infection (98% similarity with a sequence of Hypoderaeum conoideum [Echinostomatidae]) in the Spanish field population. The haplotypes of O. viridis found in our study from Spain clustered with Australian haplotypes. Experimental infection with F. hepatica was successful in both experimental conditions but higher in tropical (87% prevalence) than in temperate (73%). Overall lifespan, however, was higher in temperate conditions (mean 32.5 ± 7.4 weeks versus 23.3 ± 6.5) and survivorship remained above 70% during the first 20 weeks. In parasite-exposed populations, life expectancy dropped from an overall 37.75 weeks to 11.35 weeks but still doubled the time for initial cercariae shedding. Cercariae shedding started at day 23 post-exposure and peaked between days 53 and 67 with an average of 106 metacercariae per snail. Conclusions: Whether O. viridis will succeed in Europe is unknown, but the odds are for a scenario in which a major snail host of F. hepatica occupy all available habitats of potential transmission foci, ravelling the epidemiology of fasciolosis. This research provides a comprehensive understanding of O. viridis biology, interactions with parasites and potential implications for disease transmission dynamics, offering valuable insights for further research and surveillance. [ABSTRACT FROM AUTHOR]

Growing evidence has suggested a strong link between gut microbiota and host fitness, yet our understanding of the assembly mechanisms governing gut microbiota remains limited. Here, we collected invasive and native freshwater snails coexisting at four independent sites in Guangdong, China. We used high-throughput sequencing to study the assembly processes of their gut microbiota. Our results revealed significant differences in the diversity and composition of gut microbiota between invasive and native snails. Specifically, the gut microbiota of invasive snails exhibited lower alpha diversity and fewer enriched bacteria, with a significant phylogenetic signal identified in the microbes that were enriched or depleted. Both the phylogenetic normalized stochasticity ratio (pNST) and the phylogenetic-bin-based null model analysis (iCAMP) showed that the assembly process of gut microbiota in invasive snails was more deterministic compared with that in native snails, primarily driven by homogeneous selection. The linear mixed-effects model revealed a significant negative correlation between deterministic processes (homogeneous selection) and alpha diversity of snail gut microbiota, especially where phylogenetic diversity explained the most variance. This indicates that homogeneous selection acts as a filter by the host for specific microbial lineages, constraining the diversity of gut microbiota in invasive freshwater snails. Overall, our study suggests that deterministic assembly-mediated lineage filtering is a potential mechanism for maintaining the diversity of gut microbiota in freshwater snails [ABSTRACT FROM AUTHOR]

Since time immemorial, molluscs have been a popular source of food in North East India. Given the historical importance of snail consumption in the region, the current investigation was carried out to assess the nutritional properties of mollusc meat/tissue and shell. Three species of freshwater snails (Cipangopaludina sp. Brotia costula, Filopaludina bengalensis) and the bivalve Lamellidens sp. were identified from five states of North East India. Proximate and elemental analyses of mollusc meat revealed high amounts of nutrients (more crude protein (range 26.75–22.83%) and low fat (3.82–2.70%)) and minerals (especially calcium). Additionally, high levels of polyunsaturated fatty acids were observed (maximum 1.95% in B. costula). [ABSTRACT FROM AUTHOR]

Trematodes of the family Cyclocoelidae are parasites mainly of the respiratory system of birds and present a cosmopolitan distribution. Although infection with these flukes can result in pathological changes and even bird death, information on their life cycles is scarce and almost entirely based on experimental infection data. Thus, the generation of knowledge on the mollusks that act as natural intermediate hosts of cyclocoelids is necessary and can aid control measures against these air sac trematodes. In the present study, gastropod mollusks collected in an urban stream from Belo Horizonte, Minas Gerais, Brazil, were subjected to the compression technique for the detection of non-emerging larval trematodes. Tailless cercariae with confluent ceca were found in 8/30 (26.7%) specimens of Biomphalaria glabrata and 3/33 (9.1%) specimen of Physella acuta. Samples of the cercariae were subjected to morphological characterization and genetic study (28S, Cox-1, and Nad-1). For comparative purposes, adult trematodes previously collected in the air sac of a common gallinule (Gallinula galeata) found dead in another waterbody from the same region were also characterized. The molecular sequences obtained revealed a high degree of similarity (100% in 28S, 99.2% in Cox-1, and 99.5% in Nad-1) between larval stages found in mollusks and adult parasites found in G. galeata and morphologically identified as Cyclocoelum mutabile. The conspecificity with this widely distributed cyclocoelid was also corroborated by phylogenetic analysis and comparison with isolates of this species previously characterized in Peru and the Czech Republic (99.4–100% and 96.7–97.0% of similarity in Nad-1, respectively). Thus, the integrative analysis carried out in the present work enabled us to identify C. mutabile in mollusks in South America for the first time. The finding of B. glabrata and P. acuta as new intermediate hosts corroborates the importance of freshwater gastropods in the transmission of C. mutabile, as well as the low specificity to the mollusk group, as previously characterized through experimental studies. [ABSTRACT FROM AUTHOR]

Valvata (Cincinna) piscinalis (Müller, 1774) is a widespread and variable Palaearctic freshwater snail species. Some authors have separated more depressed forms with a wider umbilicus as a distinct species, Valvata (Cincinna) ambigua Westerlund, 1873. The latter species was described from Scandinavia and has also been reported from Siberia and Kazakhstan and more recently from Central Europe. We conducted an integrative study of the delimitation and relationships of V. ambigua and V. piscinalis using both morphometric and molecular genetic analyses. Analyses of the morphometric data did not reveal differentiation into distinct clusters. Rather, the shell characteristics used to distinguish V. ambigua and V. piscinalis showed continuous variation. There is little variability in mitochondrial DNA sequences in the V. piscinalis complex. A median-joining network based on cytochrome oxidase sequences showed that the morphological character states supposedly characteristic of V. ambigua and V. piscinalis did not correlate with the genetic relationships of the individuals studied. We therefore consider V. ambigua to be synonymous with V. piscinalis. [ABSTRACT FROM AUTHOR]

As ecosystem disruptors and intermediate hosts for various parasites, freshwater snails have significant socioeconomic impacts on human health, livestock production, and aquaculture. Although traditional molluscicides have been widely used to mitigate these effects, their environmental impact has encouraged research into alternative, biologically based strategies to create safer, more effective molluscicides and diminish the susceptibility of snails to parasites. This review focuses on alterations in glucose metabolism in snails under the multifaceted stressors of parasitic infections, drug exposure, and environmental changes and proposes a novel approach for snail management. Key enzymes within the glycolytic pathway, such as hexokinase and pyruvate kinase; tricarboxylic acid (TCA) cycle; and electron transport chains, such as succinate dehydrogenase and cytochrome c oxidase, are innovative targets for molluscicide development. These targets can affect both snails and parasites and provide an important direction for parasitic disease prevention research. For the first time, this review summarises the reverse TCA cycle and alternative oxidase pathway, which are unique metabolic bypasses in invertebrates that have emerged as suitable targets for the formulation of low-toxicity molluscicides. Additionally, it highlights the importance of other metabolic pathways, including lactate, alanine, glycogenolysis, and pentose phosphate pathways, in snail energy supply, antioxidant stress responses, and drug evasion mechanisms. By analysing the alterations in key metabolic enzymes and their products in stressed snails, this review deepens our understanding of glucose metabolic alterations in snails and provides valuable insights for identifying new pharmacological targets. [ABSTRACT FROM AUTHOR]

Nanotechnology has been used to apply nanoparticle essential elements to enhance the ability of animals to absorb these elements and consequently improve their reproductive performance. High concentrations of nanoparticles (NPs) can directly harm a range of aquatic life forms, ultimately contributing to a decline in biodiversity. Helisoma duryi snails are a good model for studying the toxicological effects of bulk zinc oxide (ZnO‐BPs) and nano zinc oxide (ZnO‐NPs) on freshwater gastropods. This study aimed to compare the toxic effects of ZnO‐BPs and ZnO‐NPs on H. duryi snails and explore how waterborne and dietary exposure influenced the reproductive performance of this snail. ZnO‐BPs and ZnO‐NPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray powder (XRD). This study revealed that the size of ZnO‐BPs and ZnO‐NPs were 154 nm and 11–31 nm, respectively. The results showed that exposure of adult snails to sub‐lethal concentrations of both ZnO forms (bulk and nano) for 24 h/week for 4 weeks markedly changed their reproductive performance in a concentration‐dependent manner, where fecundity was negatively affected by high concentrations. It was concluded that dietary exposure to the lowest tested concentration of ZnO‐NPs (1 ppm) has a positive effect as the number of eggs and egg masses/snails increased and the incubation period decreased. Also, poly‐vitelline eggs (The formation of twins) were observed. ZnO‐NPs at low concentrations positively affect the reproductive performance of snails, especially after dietary exposure. The results revealed that 1 ppm ZnO‐NPs could be supplementary provided to snails to improve their fertility, reduce the developmental time course, increase hatchability percentage, and produce poly‐vitelline eggs. Research Highlights: ZnO‐NPs at low concentrations have positive effects on the reproductive performance of H. duryi snails, especially after dietary exposure.One ppm ZnO‐NPs could be supplementary provided to snails for improving their fertility, reducing the developmental time course, increasing hatchability percentage, and producing poly‐vitelline eggs. [ABSTRACT FROM AUTHOR]

Background: In Europe, avian schistosomes of the genus Trichobilharzia are the most common etiological agents involved in human cercarial dermatitis (swimmer's itch). Manifested by a skin rash, the condition is caused by an allergic reaction to cercariae of nonhuman schistosomes. Humans are an accidental host in this parasite's life cycle, while water snails are the intermediate, and waterfowl are the final hosts. The study aimed to conduct a molecular and phylogenetic analysis of Trichobilharzia species occurring in recreational waters in North-Eastern Poland. Methodology: The study area covered three water bodies (Lake Skanda, Lake Ukiel, and Lake Tyrsko) over the summer of 2021. In total, 747 pulmonate freshwater snails (Radix spp., Lymnaea stagnalis) were collected. Each snail was subjected to 1–2 h of light stimulation to induce cercarial expulsion. The phylogenetic analyses of furcocercariae were based on the partial sequence of the ITS region (ITS1, 5.8S rDNA, ITS2 and 28SrDNA). For Radix spp. phylogenetic analyses were based on the ITS-2 region. Results: The prevalence of the Trichobilharzia species infection in snails was 0.5%. Two out of 478 (0.4%) L. stagnaliswere found to be infected with Trichobilharzia szidati. Moreover, two out of 269 (0.7%) snails of the genus Radix were positive for schistosome cercariae. Both snails were identified as Radix auricularia. One of them was infected with Trichobilharzia franki and the other with Trichobilharzia sp. Conclusions: Molecular identification of avian schistosome species, both at the intermediate and definitive hosts level, constitutes an important source of information on a potential threat and prognosis of local swimmer's itch occurrence, and helps to determine species diversity in a particular area. [ABSTRACT FROM AUTHOR]

The systematic review and meta-analysis were conducted to determine the estimates of the prevalence and infection rates of natural and experimental infections of amphistome species in intermediate host snails (IHs) across different continents. A search of peer-reviewed literature on natural and experimental infections of freshwater snails with amphistome species was conducted from four electronic databases from 1984 to 2023. The estimates of the prevalence and/or infection rates were based on 36 eligible peer-reviewed articles, which met the inclusion criteria and reported on natural and experimental infections of amphistome species in freshwater snails. The results showed that a total of 1,67,081 snail species from the peer-reviewed articles were examined for natural infections and 7,659 snail species for experimental infections. The overall pooled prevalence of amphistome infections from naturally infected snails was 2% (95% CI: 0–4), while the overall pooled prevalence of amphistome infections from infections was 40% (95% CI: 18–64). The highest pooled prevalence of natural infection was 3%, which was recorded in Europe (95% CI: 1–7%). The highest overall prevalence of naturally infected amphistome was 6% (95% CI: 0–20%) for Paramphistomum epiclitum. The Americas had the highest pooled prevalence of experimental amphistome infection among freshwater snails (66%; 95% CI: 26–96%). The highest pooled infection rate of 65% (95% CI: 12–100%) was recorded for Paramphistomum cervi in experimental infections. Galba truncatula was the only snail that qualified for meta-analysis for natural infection with Calicophoron daubneyi, with a pooled prevalence of 3% (95% CI: 1–8%). Galba truncatula infected with C. daubneyi and P. cervi, and Bulinus tropicus infected with Calicophoron microbothrium in the experimental infection qualified for the meta-analysis, with an overall infection rate of 66% (95% CI: 34–92%) and 30% (95% CI: 0–74%), respectively. The pooled prevalence of amphistome species infection in the intermediate host (IH) snails based on detection techniques was higher with PCR compared to the dissection and shedding of cercariae. The results from the quality effects model revealed a high heterogeneity and publication bias between studies. This meta-analysis provided valuable insights into the prevalence and infection rates of amphistome species in snail IHs across different geographical regions. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a neglected tropical disease caused by Schistosoma parasites. Schistosoma are obligate parasites of freshwater Biomphalaria and Bulinus snails, thus controlling snail populations is critical to reducing transmission risk. As snails are sensitive to environmental conditions, we expect their distribution is significantly impacted by global change. Here, we used machine learning, remote sensing, and 30 years of snail occurrence records to map the historical and current distribution of forward-transmitting Biomphalaria hosts throughout Brazil. We identified key features influencing the distribution of suitable habitat and determined how Biomphalaria habitat has changed with climate and urbanization over the last three decades. Our models show that climate change has driven broad shifts in snail host range, whereas expansion of urban and peri-urban areas has driven localized increases in habitat suitability. Elucidating change in Biomphalaria distribution—while accounting for non-linearities that are difficult to detect from local case studies—can help inform schistosomiasis control strategies. Schistosomiasis is an emerging urban and peri-urban disease in Brazil and freshwater snails are an obligate host of the causative parasite. Here, the authors investigate the ecological suitability for the three freshwater snail hosts in Brazil and identify changes over time driven by climate and urbanisation. [ABSTRACT FROM AUTHOR]

Physella acuta is a freshwater snail native to North America. Understanding the phylogeography and genetic structure of P. acuta will help elucidate its evolution. In this study, we used mitochondrial (COI and 16S rDNA) and nuclear (ITS1) markers to identify the species and examine its genetic diversity, population structure, and demographic history of P. acuta in Thailand. Phylogenetic and network analyses of P. acuta in Thailand pertained to clade A, which exhibits a global distribution. Analysis of the genetic structure of the population revealed that the majority of pairwise comparisons showed no genetic dissimilarity. An isolation-by-distance test indicates no significant correlation between genetic and geographical distances among P. acuta populations, suggesting that gene flow is not restricted by distance. Demographic history and haplotype network analyses suggest a population expansion of P. acuta, as evidenced by the star-like structure detected in the median-joining network. Based on these results, we concluded that P. acuta in Thailand showed gene flow and recent population expansion. Our findings provide fundamental insights into the genetic variation of P. acuta in Thailand. [ABSTRACT FROM AUTHOR]

The sex ratio is nearly equal in most organisms, while several ecological and evolutionary factors skew the sex ratio. We evaluated the sex ratios of 12 species in the freshwater snail genus Semisulcospira in and around Lake Biwa. We found highly female-biased sex ratios in all 12 species. The sex ratios were nearly equal or slightly female-biased in the smaller shell-size classes, while they were highly female-biased in the larger size classes. We also found that females were significantly larger in most of these species. Further, the species with a larger size difference between the sexes tended to exhibit a more female-biased sex ratio. Considering the general correlation between shell size and age, this pattern can be explained by longer lifespans in females, shaping the observed female-biased sex ratios. We also found that some Semisulcospira species showed female-biased sex ratios in all shell size classes. This pattern suggests that the distinct longevity hypothesis can not solely explain the observed biased sex ratios. We discussed the possible contributions of the sampling errors and selfish genetic elements to the observed biased sex ratios. This study provides essential information to disentangle the mechanisms of the biased sex ratio in the Semisulcospira snails. [ABSTRACT FROM AUTHOR]

The freshwater snail Latia neritoides occurs in certain streams and lakes of New Zealand's North Island. It defends itself against predators with a unique mechanism - the release of sticky, glowing mucus. Two possible origins of this defence mucus had earlier been suggested: the foot and the pneumostome area. After examining the glandular system of the foot in a previous study, in the present study we examined the general morphology of L. neritoides, focusing on the mantle cavity. With the first complete 3D model of L. neritoides now available, it is possible to evaluate previous morphological studies and to give non-specialists a better understanding of the soft part anatomy of this fascinating gastropod. As a by-product of this, we also compared the capabilities of μ-CT and HREM on a methodological level. We characterized the two most common gland types in the mantel cavity (Lmcg1/Lmcg2) on the basis of their ultrastructure. They are present in large numbers and, therefore, regarded as likely candidates for being the producers of one or more components of the defence mucus. This notion was confirmed by histochemical analyses of Lmcg1 and Lmcg2 and other gland types in L. neritoides. [ABSTRACT FROM AUTHOR]

Background: Snail-borne trematodes afflict humans, livestock, and wildlife. Recognizing their zoonotic potential and possible hybridization, a One Health approach is essential for effective control. Given the dearth of knowledge on African trematodes, this study aimed to map snail and trematode diversity, focusing on (i) characterizing gastropod snail species and their trematode parasites, (ii) determining infection rates of snail species as intermediate hosts for medically, veterinary, and ecologically significant trematodes, and (iii) comparing their diversity across endemic regions. Methods: A cross-sectional study conducted in 2021 in Chiredzi and Wedza districts in Zimbabwe, known for high human schistosomiasis prevalence, involved malacological surveys at 56 sites. Trematode infections in snails were detected through shedding experiments and multiplex rapid diagnostic polymerase chain reactions (RD-PCRs). Morphological and molecular analyses were employed to identify snail and trematode species. Results: Among 3209 collected snail specimens, 11 species were identified, including schistosome and fasciolid competent snail species. We report for the first time the invasive exotic snail Tarebia granifera in Zimbabwe, which was highly abundant, mainly in Chiredzi, occurring at 29 out of 35 sites. Shedding experiments on 1303 snails revealed a 2.24% infection rate, with 15 trematode species identified through molecular genotyping. Five species were exclusive to Chiredzi: Bolbophorus sp., Schistosoma mansoni, Schistosoma mattheei, Calicophoron sp., and Uvulifer sp. Eight were exclusive to Wedza, including Trichobilharzia sp., Stephanoprora amurensis, Spirorchid sp., and Echinostoma sp. as well as an unidentified species of the Plagiorchioidea superfamily. One species, Tylodelphys mashonensis, was common to both regions. The RD-PCR screening of 976 non-shedding snails indicated a 35.7% trematode infection rate, including the presence of schistosomes (1.1%) Fasciola nyanzae (0.6%). In Chiredzi, Radix natalensis had the highest trematode infection prevalence (33.3%), while in Wedza, R. natalensis (55.4%) and Bulinus tropicus (53.2%) had the highest infection prevalence. Conclusions: Our xenomonitoring approach unveiled 15 trematode species, including nine new records in Zimbabwe. Schistosoma mansoni persists in the study region despite six mass deworming rounds. The high snail and parasite diversity, including the presence of exotic snail species that can impact endemic species and biomedically important trematodes, underscores the need for increased monitoring. [ABSTRACT FROM AUTHOR]

Understanding how and why some species or lineages become invasive is critically important for effectively predicting and mitigating biological invasions. Here, we address an important unanswered question in invasion biology: do key life‐history traits of invasive versus native lineages within a species differ in response to key environmental stressors? We focus on the environmental factor of population density, which is a fundamental characteristic of all populations, and investigate how changes in density affect native versus invasive Potamopyrgus antipodarum (New Zealand mudsnail). P. antipodarum has invaded 39 countries and detrimentally affects invaded environments. Previous studies of native and invasive populations and from laboratory experiments have demonstrated that growth and reproduction of P. antipodarum is sensitive to population density, though whether and how this sensitivity varies across native versus invasive lineages remains uncharacterized. We quantified individual growth rate and reproduction in P. antipodarum from multiple distinct native and invasive lineages across three different population density treatments. The growth of native but not invasive lineages decreased as density increased. There was no differential effect of density treatment on embryo production of invasive versus native snails, but a significantly higher proportion of snails were reproductive in high density compared to intermediate density for invasive lineages. In native lineages, there were no significant differences in the relative frequency of reproductive snails across density treatments. While the extent to which these results from our laboratory study can be extrapolated to the more complex natural world remain unclear, our findings are consistent with a scenario where differential sensitivity to population density could help explain why some lineages become successful invaders. Our findings also align with previous studies that show that invasive P. antipodarum lineages exhibit a relatively wide range of tolerance to environmental stressors. [ABSTRACT FROM AUTHOR]

Several species of birds deliberately drop hard food items, such as walnuts and molluscs, from high places to break the shell and eat the content. Although the carrion crow Corvus corone preys on the introduced apple snail Pomacea canaliculata by directly breaking the shells with their beaks in paddy fields in Japan, snails living in ponds are too large and hard for crows to directly break the shells. We found that carrion crows dropped apple snails in and around dried ponds in winter in Marugame, Kagawa, Japan, and conducted detailed observations on their predation behaviour. The crows dropped the snails onto various substrates in and around Hachijo Pond, and the release point was higher when the substrate was wet mud than when it was concrete, rock, or grass. As carrion crows rarely prey on other freshwater snails in Japan, this foraging behaviour has likely developed since the introduction of apple snails in the 1980s. The intense predation by the crows likely reduced the snail density in this reservoir pond. [ABSTRACT FROM AUTHOR]

Predicting climate change‐mediated environmental effects on organisms is difficult because their direction and strength may depend on multiple ecological factors that vary in nature. This is because the effects of environmental factors often interact. One potentially important factor modifying organisms' thermal performance is their resource level.We experimentally examined the dependence of phenotypic responses to heatwaves on resource/food availability in the freshwater snail, Lymnaea stagnalis. We maintained snails at different food levels (unlimited, reduced [50% of expected consumption], no food), and exposed them to either a heatwave temperature (27°C) or a benign temperature (17°C) for 1 week, followed by a post‐heatwave week (17°C). To estimate snail performance, we quantified their metabolic activity (respiration rate), growth rate, fecundity, and immune activity.All examined traits responded to temperature, and changes in fitness‐related traits (growth rate, fecundity) depended on snail resource level. During the heatwave phase, the benefits of the elevated temperature (enhanced growth rate and fecundity) were higher with unlimited than with limited resources. Additionally, during the post‐heatwave phase, the performance of previously heat‐challenged snails reduced most strongly in resource‐limited snails. The high‐temperature treatment negatively affected snail immune activity even under the high food supply, but immune traits recovered after the heatwave. Interestingly, the phenotypic effects of the high temperature were mainly direct rather than driven by increased metabolic activity.Our results indicate that heatwave responses of L. stagnalis snails are sensitive to their resource level. Such condition dependence may have important ecological and evolutionary implications by: (1) making natural populations in low‐quality habitats the most susceptible to heatwaves; and (2) altering climate change‐mediated evolution by modifying the expression of phenotypic variation in thermal performance. By demonstrating condition‐dependent heatwave responses, our study highlights the importance of examining the interactive effects of climate change‐mediated environmental alterations and ecological factors that vary in nature. [ABSTRACT FROM AUTHOR]

Furcocercariae, of the trematodes from the family Diplostomidae, were found in freshwater snails—Radix auricularia, which were collected in a reservoir located on Popov Island (Peter the Great Bay, Sea of Japan). The life cycle was experimentally reproduced for the first time, while morphometric data for the development stages were studied and described for the newly discovered trematode. Moreover, molecular data for nuclear and mitochondrial markers were also obtained. It was determined that the morphometric characteristics of the trematode coincided with the species Diplostomum cf. vanelli, the molecular data analysis validates the species independence. Furthermore, the study highlights the issue of species identification in the Diplostomum genus. [ABSTRACT FROM AUTHOR]

In the formation of helminth fauna, the formation of a high diversity of species, in the circulation of helminths between humans and ruminant domestic animals in nature and in their infection, in the completion of the development stages of biohelminths and their invasion and in the transfer of dangerous helminths from one area to another, their intermediate hosts have a great role. When determining the role of intermediate hosts in the spread of helminths of domestic carnivores, it was found that the intermediate hosts of 12 species of helminths are insects, 7 species are ruminants, 16 species are rodents, 5 species are reptiles and 3 species are earthworms. During the study, it was found that rodents were infected with cysticercoids of the mentioned helminths in 49.3%, reptiles with cysticercoids, procercoids and plerocercoids in 34.7%, snails in 24.7% and insects in 37.3%. Among the intermediate hosts, rodents prevail over other intermediate hosts with 16 species and infection rate of 49.3%. It comes from the ethology of rodents. The scientific-research work carried out in this direction has important theoretical and practical importance. The main direction in the fight against intermediate hosts is to break the chain between transmissible diseases and the agent that transmits them. [ABSTRACT FROM AUTHOR]

Simple Summary: Amphistomes, also known as rumen flukes, are parasites of domestic and wild ruminants and occur globally. Adult parasites are found in the forestomach, and the young flukes are found in the small intestines, causing severe damage. The flukes are transmitted by various species of freshwater snails. While the disease is well documented in domestic ruminants, there are gaps in knowledge pertaining to wild ruminants with regard to the fluke species as well as the snail species which transmit them. Therefore, freshwater snails were surveyed from 19 water points that are frequented by wild ruminants in the Matebeleland region, Zimbabwe. Snails were found at nine sites, and eight species were identified and screened for rumen fluke DNA to determine the fluke species and prevalence of infection. Rumen fluke DNA was detected in 11.9% of the screened snails. Prevalence was high in the West Nicholson locality and in Bulinus globosus snail species. One rumen fluke species, i.e., Calicophoron microbothrium, was confirmed in one snail species and there were also mixed infections with lung fluke parasite, Paragonimus spp., in two snail species. This was the first study documenting the presence of this lung fluke in Zimbabwe. This study aimed at determining the identity of freshwater snails collected from selected water habitats frequented by wildlife as source of drinking water in the Matebeleland region of Zimbabwe and further screening the identified snails for natural infections with amphistomes using PCR. A total of 487 freshwater snails were collected from six areas in the Matebeleland region of Zimbabwe for identification and screening of amphistome infection. Eight freshwater snail species were morphologically identified and Biomphalaria pfeifferi, Bul. tropicus, Bul. truncatus, Bul. globosus, and L. (R.) natalensis were confirmed using the COI gene. Bulinus tropicus and Phy. acuta were the most abundant species at 33.9% (165/487) and 31.2% (155/487), respectively. DNA of amphistome was detected in 11.9% (58/487) of the collected snails. The highest infection rate was detected in Bul. globosus (44.4%). West Nicholson recorded the highest infection rate (33.9%), and infection was not detected in L. (R.) natalensis, Phy. acuta, and Bellamya spp. Amphistome DNA from M. tuberculata was successfully sequenced and identified as Calicophoron microbothrium. An additional band was detected in M. tuberculata, Bul. tropicus, and Bul. trancatus, which showed a 96.42% similarity to Paragonimus sp. sequence in the GenBank. [ABSTRACT FROM AUTHOR]

Pomacea canaliculata is widely distributed in the Chinese provinces south of the Yangtze River, causing serious damage to aquatic ecosystems, rice cultivation, and human health. Predicting the potential geographic distributions (PGDs) of P. canaliculata under current and future climate conditions in China is crucial for developing effective early warning measures and facilitating long-term monitoring. In this study, we screened various species distribution models (SDMs), including CTA, GBM, GAM, RF, and XGBOOST, to construct an ensemble model (EM) and then predict suitable habitats for P. canaliculata under current and future climate scenarios (SSP1-26, SSP2-45, SSP3-70, SSP5-85). The EM (AUC = 0.99, TSS = 0.96) yielded predictions that were more precise than those from the individual models. The Annual Mean Temperature (Bio1) and Precipitation of the Warmest Quarter (Bio18) are the most significant environmental variables affecting the PGDs of P. canaliculata. Under current climate conditions, the highly suitable habitats for P. canaliculata are primarily located south of the Yangtze River, collectively accounting for 17.66% of the nation's total area. Unsuitable habitats predominate in higher-latitude regions, collectively covering 66.79% of China's total land area. In future climate scenarios, the total number of suitable habitats for P. canaliculata is projected to expand into higher latitude regions, especially under SSP3-70 and SSP5-85 climate conditions. The 4.1 °C contour of Bio1 and the 366 mm contour of Bio18 determine the northernmost geographical distribution of P. canaliculata. Climate change is likely to increase the risk of P. canaliculata expanding into higher latitudes. [ABSTRACT FROM AUTHOR]

This is the first report on microbial communities associated with the freshwater snail Kamtschaticana kamtschatica inhabiting diverse types of water bodies in Eastern Siberia and the Russian Far East. Using metabarcoding data based on 16S rRNA gene fragments, taxonomic profiling of bacterial communities associated with snails from three water bodies of the Magadan Oblast was carried out. Predominant phyla in the studied bacterial communities were Pseudomonadota, Bacillota, Cyanobacteriota, Actinomycetota, Verrucomicrobiota, Planctomycetota, and Bacteroidota. The highest alpha-diversity, according to the Chao1 index, was revealed in the mollusks from the Orotukan Reservoir. The relative abundance of bacteria of the genera Snowella, Leptolyngbya, Nodosilinea, Arenimonas, and Polaromonas significantly distinguished the mollusks of this habitat from mollusks of the other two water bodies. The greatest similarities in the composition of the microbiota in K. kamtschatica were found for the genus Pseudomonas, which was present in the majority of samples in the amount of more than 1% and was not found in the sediment samples. Obtained data on the diversity and composition of bacterial communities associated with lymnaeid snails are of fundamental importance for the ecology of freshwater mollusks. [ABSTRACT FROM AUTHOR]

Background: Prior research suggests that trematode rediae, a developmental stage of trematode parasites that reproduce clonally within a snail host, show evidence of division of labor (DOL). Single-species infections often have two morphologically distinct groups: small rediae, the 'soldiers', are active, aggressive, and do not appear to reproduce; large rediae, the 'reproductives', are larger, sluggish, and full of offspring. Most data supporting DOL come from trematodes infecting marine snails, while data from freshwater trematodes are more limited and generally do not supported DOL. The shorter lifespan typical of freshwater snails may partially explain this difference: defending a short-lived host at the expense of reproduction likely provides few advantages. Here, we present data from sixty-one colonies spanning twenty species of freshwater trematode exploring morphological and behavioral patterns commonly reported from marine trematodes believed to have DOL. Methods: Trematode rediae were obtained from sixty-one infected snails collected in central Vermont, USA. A portion of the COI gene was sequenced to make tentative species identifications ('COI species'). Samples of rediae were photographed, observed, and measured to look for DOL-associated patterns including a bimodal size distribution, absence of embryos in small rediae, and pronounced appendages and enlarged pharynges (mouthparts) in small rediae. Additional rediae were used to compare activity levels and likelihood to attack heterospecific trematodes in large vs. small rediae. Results: Many of the tests for DOL-associated patterns showed mixed results, even among colonies of the same COI species. However, we note a few consistent patterns. First, small rediae of most colonies appeared capable of reproduction, and we saw no indication (admittedly based on a small sample size and possibly insufficient attack trial methodology) that small rediae were more active or aggressive. This differs from patterns reported from most marine trematodes. Second, the small rediae of most colonies had larger pharynges relative to their body size than large rediae, consistent with marine trematodes. We also observed that colonies of three sampled COI species appear to produce a group of large rediae that have distinctly large pharynges. Conclusions: We conclude that these freshwater species likely do not have a group of specialized non-reproductive soldiers because small rediae of at least some colonies in almost every species do appear to produce embryos. We cannot rule out the possibility that small rediae act as a temporary soldier caste. We are intrigued by the presence of rediae with enlarged pharynges in some species and propose that they may serve an adaptive role, possibly similar to the defensive role of small 'soldier' rediae of marine trematodes. Large-pharynx rediae have been documented in other species previously, and we encourage future efforts to study these large-pharynx rediae. [ABSTRACT FROM AUTHOR]

Abstract Schistosomiasis, a prevalent water-borne disease second only to malaria, significantly impacts impoverished rural communities, primarily in Sub-Saharan Africa where over 90% of the severely affected population resides. The disease, majorly caused by Schistosoma mansoni and S. haematobium parasites, relies on freshwater snails, specifically Biomphalaria and Bulinus species, as crucial intermediate host (IH) snails. Targeted snail control is advisable, however, there is still limited knowledge about the community structure of the two genera especially in East Africa. Utilizing a machine learning approach, we employed random forest to identify key features influencing the distribution of both IH snails in this region. Our results reveal geography and climate as primary factors for Biomphalaria, while Bulinus occurrence is additionally influenced by soil clay content and nitrogen concentration. Favorable climate conditions indicate a high prevalence of IHs in East Africa, while the intricate connection with geography might signify either dispersal limitations or environmental filtering. Predicted probabilities demonstrate non-linear patterns, with Bulinus being more likely to occur than Biomphalaria in the region. This study provides foundational framework insights for targeted schistosomiasis prevention and control strategies in the region, assisting health workers and policymakers in their efforts.

The bioturbation potential of three freshwater operculate snails, Filopaludina bengalensis, Gabbia orcula and Melanoides tuberculata, was compared, using water column depth and sediment surface area as the explanatory variables. Assessment of nutrient fluxes from sediment to overlying water was estimated in glass microcosms, that varied in height (tall, medium, short) and base (narrow, wide), resulting in six habitat conditions. In course of movement and grazing, all the three snail species modified surface architecture of the sediment. Besides, the snails modulated NOXˉ (NO2ˉ-N + NO3ˉ-N), NH4+-N and PO43−-P concentrations and other parameters (TDS, conductivity) of the water column in significantly varying proportions. Snail-induced changes in the rate of nutrient flux were highest for F. bengalensis. Periphytic chlorophyll-a concentration was reduced in all snail-treated microcosms compared to the control. Grazing, scraping and movement of snails on sediment facilitated the release of the nutrients in a species-specific manner depending on sediment surface area and water column depth of the microcosm. Apparently, snails may be useful in mobilizing the sediment content in freshwater lakes and ponds, facilitating ecosystem processes. [ABSTRACT FROM AUTHOR]

Invasive species are a major threat to global biodiversity. Therefore, it is crucial to monitor their presence and expansion within invaded areas and carry out studies to improve our knowledge of their biology and ecology. One of the most effective and spectacular invaders among freshwater snails is the acute bladder snail (Physella acuta) (Draparnaud, 1805). This study aims to update the available data on P. acuta in Morocco and determine the main environmental factors that favor its distribution and expansion in this country. Field surveys were conducted in northern Morocco between 2014 and 2023, with a focus on protected areas such as Ramsar sites, and especially great geographical barriers such as the Middle Atlas Mountains and the Sebou and Moulouya River basins. The gastropods were collected using Surber samplers (20 × 25 cm surface area, 400 µm mesh), together with measurements of the physicochemical parameters of the water and other abiotic factors. The bladder snail is probably the most widespread freshwater snail in Morocco, where the species appears to be highly adaptable and can thrive in different habitats, including degraded ones, showing great plasticity in terms of the physicochemical parameters of the water. The main factor limiting the geographical distribution and abundance of P. acuta in the study area was water velocity and conductivity. However, further studies are required to address the future range of expansion of P. acuta in relation to climate change. Although one of the consequences of climate change is reduced water flow speed, which may promote its range of expansion in Morocco, salinization of streams may also reduce its ability to colonize new environments. [ABSTRACT FROM AUTHOR]

Global climate change, driven by rapid population growth and anthropogenic activities, presents an urgent challenge to aquatic ecosystems. Salinity intrusion threatens water quality and availability for human and wildlife populations. At the same time, due to the demand for pharmaceuticals, these pollutants are increasingly detected in freshwater environments, with acetaminophen being one of the most prevalent. This research analyzed the individual and combined effects of salinity (2.5 g/L) and acetaminophen (488 µg/L) on Physella acuta. Overall, we observed reduced snail movement under elevated salinity and no effects on growth or movement with acetaminophen alone or in combination with salinity. Our results suggest a complex interaction between stressors and physiological responses. Despite the high tolerance of P. acuta to salinity, elevated levels affected its movement. Additionally, there is a need for further research into multiple stressors and their interactions as well as understanding the responses of aquatic organisms to mitigate the impact of pollution and climate change on freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Hermaphrodites exhibit a wide variety of reproductive strategies, yet empirical studies lag behind theories about their evolution. Planorbella trivolvis , a simultaneous hermaphrodite capable of reciprocal copulation and rare self-fertilization, provides a unique model system for studying reproduction. This study assessed sex roles during mating, demonstrating that mating is primarily reciprocal, and investigated the relationship between physical coupling and reproductive output for single copulation events. Snails were isolated before sexual maturity and placed in 10-l aquaria in size-matched groups. Upon copulation, pairs were removed to small cups until they separated; they were then kept isolated and eggs counted until egg production ceased. The frequency of reciprocal copulation (both members of a pair produced egg masses following copulation) was 95% (35/37 productive matings), higher than previously reported. The duration of egg production ranged from 19 to 197 days (mean ± SE = 110.13 ± 6.3 days) with a sharp drop in production of egg masses and eggs per mass occurring between 15 and 20 weeks postmating, consistent with previous estimates of sperm storage. There was no relationship between mating duration and total egg production (a biomarker of sperm availability) or the duration of egg production (a marker of sperm longevity). Further investigation is needed to directly estimate sperm transfer and tease apart the duration of reciprocal physical contact from gamete and accessory protein transfer. [ABSTRACT FROM AUTHOR]

The varied types of detergent are considered as contaminants in the freshwater environment and interfere with the bio-ecology of macroinvertebrates. Based on this proposition, a study was conducted to examine the impact of detergents and acidic bathroom cleaners on the oviposition and embryo development of the invasive snail Physella acuta (Draparnaud, 1805) (Gastropoda: Physidae). Laboratory-based experiments were carried out to observe the oviposition pattern and embryo development under varied concentrations of commercially available detergent and bathroom cleaner. The invasive snail, P. acuta, breeds throughout the year, and its reproduction positively correlates with shell length. The results of this study implied that the fecundity and hatching rate were reduced and varied with detergent and bathroom cleaner concentrations compared to the control group. Among the treatments, the higher doses of bathroom cleaners impaired the embryo development of P. acuta. The results suggest that the colonization and establishment of the invasive snail P. acuta in the new habitats may be affected by detergent contamination of the freshwater habitats. While the present study aims to provide a link between the detergent and oviposition pattern of the freshwater snail, further studies should be carried out to deduce the long-term effects of the detergents on the population dynamics of P. acuta. [ABSTRACT FROM AUTHOR]

Many rivers and streams in Nigeria are habitats of freshwater snails. Many of these snails are edible, whereas others are intermediate hosts of various flatworms. Nine rivers and streams from three towns in Ekiti State, Nigeria, were examined for the presence of freshwater snails. Each freshwater habitat was sampled for snails at the designated sites for 15 min on a monthly basis using a 0.2 mm mesh scoop. The collected snails were transported to the laboratory in pre-labelled plastic containers. Two thousand three hundred and thirty-one (2331) freshwater snails were collected from all habitats. Lanistes libycus had the highest population, 1044 (44.8%). The other species were Melanoides tuberculata 550 (23.6%), Bulinus globosus 401 (17.2%), and Potadoma moerchi 336 (14.4%). Freshwater snails were more abundant at the beginning of the rainy season (March-May) than during heavy rainfall (July-October). The environmental conditions of the study area supported the occurrence of these snail species. Although some species of these snails are edible, others can serve as intermediate hosts for parasitic flatworms, which requires urgent attention. [ABSTRACT FROM AUTHOR]

Schistosomiasis, an NTD, poses public health problems for rural communities. The parameters controlling its intermediate hosts are scarcely studied. 24 human-water contacts were sampled for 12 months to understand the impacts of water parameters on the vector. Sampling was done by monthly handpicking of the snail vector with a net to analyze the water parameters (temperature, dissolved oxygen, conductivity, depth, and rainfall). 546 snails recovered from the water sites showed that Bulinus globosus had the highest occurrence (50.5%), followed by Lanistes varicus (27.7%), and Bulinus truncatus species (3.7%). Ohaukwu LGA recorded the highest occurrence of freshwater snails at 55.3%, while Amovu stream had the highest number of snails with an overall abundance of 35.9%. May had the highest cercariae shedding at 26%, followed by June at 20%. No shedding occurred in September, November, December, and January. The infectivity rate of freshwater snails collected showed a significant difference based on the month (X2=6590.079, p-value=0.006). The study reveals that water physicochemical parameters significantly influence the abundance of intermediate snail hosts, with all parameters positively correlated except for temperature, conductivity, and TDS. This poses a significant public health threat due to vector snails' presence. [ABSTRACT FROM AUTHOR]

Cercariae of Plagiorchis spp. are frequently reported in European freshwater snails, but their true diversity is difficult to estimate due to subtle differences in morphology. We molecularly characterized 67 isolates of Plagiorchis cercariae collected from four lymnaeid snail hosts, Ampullaceana balthica, Ampullaceana lagotis, Radix auricularia and Lymnaea stagnalis in freshwater ecosystems in the Czech Republic and Poland. Based on mitochondrial cox1 and nuclear 28S sequences, ten species or species-level lineages were identified, including the first molecular evidence of P. vespertilionis from snail hosts and two species-level lineages reported for the first time. Previously undescribed species and species-level lineages are characterized morphometrically. We confirm the overlapping spatial distribution of Plagiorchis spp. in their snail hosts from Central Europe with those from Western and sub-Arctic Europe. Our results increase the known diversity of Plagiorchis spp. in Europe to 25 species/lineages in snails, but further research is needed to establish links between life cycle stages and to assess the host specificity of these parasites. [ABSTRACT FROM AUTHOR]

Purpose: The Government of Indonesia committed to eliminating schistosomiasis by 2025. Collaboratively snail control became one of the crucial strategies to ensure that the prevalence of Schistosoma japonicum in Oncomelania hupensis lindoensis reaches zero by the end of the program. This research investigated the spatial cluster change of S. japonicum transmission foci in Indonesia between 2017 and 2021. Methods: We mapped the snail foci, collected the snails, and calculated the snail density. We also conducted laboratory tests to detect the existence of cercariae in the snails. Identified infected snails were used to calculate the infection rate (IR) or snails' prevalence of schistosome cercariae among freshwater snails. We then analysed the spatial cluster using the Getis-Ord Gi* statistic to identify the hot and cold spots. Results: The 5-year schistosomiasis elimination program successfully declined 18.84% of the snail foci and reduced 40.37% of the infected snail foci. Local spatial autocorrelation of snail density and infection rate identified that in 2017 and 2021, the number of cold spots decreased by 53.91% and 0%, while hot spots increased by 2.63% and 56.1%. The presence of more hot spots suggests a rise in the number of foci with high snail density and infection rates. The implementation of snail control was not optimal, and the parasite transmission through domestic animals still existed, causing the spatial cluster of hot spots to change during this period. Most hotspots have been observed near settlements, primarily in cocoa plantations, developed and deserted rice fields, grassland, and bush wetlands. Conclusion: During the schistosomiasis elimination program, the number of hot spots increased while cold spots decreased, and there were notable changes in the geographical distribution of hot spots, indicating a shift in the clustering pattern of schistosomiasis cases. The findings become essential for policymakers, particularly in selecting priority areas for intervention. In the Discussion section, we demonstrated the selection process based on the existence of hot and cold spots. Furthermore, we proposed that enhancing cross-sector integration is crucial, particularly in connection with the management of S. japonicum transmission through domestic animals. [ABSTRACT FROM AUTHOR]

A new species of pomatiopsid freshwater snail, Fenouilia undata Chen & He, sp. nov., is described from Guangxi, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: shell with low, prosocline, rounded axial ribs and fine spiral striae, broader than high; aperture broader than shell height; radula with lateral teeth have only two or three faint, wavy ridges on inner side. A molecular analysis of partial mitochondrial COI and 16S DNA sequences supports the systematic position of the new taxon. [ABSTRACT FROM AUTHOR]

Schistosomiasis, a prevalent water-borne disease second only to malaria, significantly impacts impoverished rural communities, primarily in Sub-Saharan Africa where over 90% of the severely affected population resides. The disease, majorly caused by Schistosoma mansoni and S. haematobium parasites, relies on freshwater snails, specifically Biomphalaria and Bulinus species, as crucial intermediate host (IH) snails. Targeted snail control is advisable, however, there is still limited knowledge about the community structure of the two genera especially in East Africa. Utilizing a machine learning approach, we employed random forest to identify key features influencing the distribution of both IH snails in this region. Our results reveal geography and climate as primary factors for Biomphalaria, while Bulinus occurrence is additionally influenced by soil clay content and nitrogen concentration. Favorable climate conditions indicate a high prevalence of IHs in East Africa, while the intricate connection with geography might signify either dispersal limitations or environmental filtering. Predicted probabilities demonstrate non-linear patterns, with Bulinus being more likely to occur than Biomphalaria in the region. This study provides foundational framework insights for targeted schistosomiasis prevention and control strategies in the region, assisting health workers and policymakers in their efforts. [ABSTRACT FROM AUTHOR]

Background: The large amphibious freshwater apple snail is an important invasive species in China, but there is currently no method available for their surveillance. The development and popularization of smartphones provide a new platform for research on surveillance technologies for the early detection and effective control of invasive species. Methods: The ASI surveillance system was developed based on the infrastructure of the WeChat platform and Amap. The user can directly enter the game interface through the WeChat port on their mobile phone, and the system automatically obtains their location. The user can then report the location of apple snails. The administrator can audit the reported information, and all information can be exported to Microsoft Excel version 2016 for analysis. The map was generated by ArcGIS 10.2 and was used to characterize the spatial and temporal distribution of apple snails in Jiangsu Province. Results: The architecture of ASI consists of three parts: a mobile terminal, a server terminal and a desktop terminal. We published more than 10 tweets on the official WeChat account of the system to announce it to the public, and a total of 207 users in 2020 and 2021 correctly reported sightings of apple snails. We identified 550 apple snails breeding sites in 2020 and 2021, featuring ponds (81%), parks (17%) and farmland (2%). In addition, most of the locations contained snail eggs, and the reporting times mainly occurred between May and September. Conclusions: The ASI is an effective surveillance system that can be used to identify the breeding locations of apple snails and provides the basis of prevention and control for its dispersal. Its successful development and operation provide new potential avenues for surveillance of other public health issues. [ABSTRACT FROM AUTHOR]

Ramshorn snails from the family Planorbidae are important freshwater snails due to their low trophic level, and some of them act as intermediate hosts for zoonotic trematodes. There are about 250 species from 40 genera of Planorbidae, but only 14 species from 5 genera (Anisus, Biomphalaria, Bulinus, Gyraulus, and Planorbella) have sequenced complete mitochondrial genomes (mitogenomes). In this study, we sequenced and assembled a high-quality mitogenome of a ramshorn snail, Polypylis sp. TS-2018, which represented the first mitogenome of the genus. The mitogenome of Polypylis sp. TS-2018 is 13,749 bp in length, which is shorter than that of most gastropods. It contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA). We compared mitogenome characteristics, selection pressure, and gene rearrangement among all of the available mitogenomes of ramshorn snails. We found that the nonsynonymous and synonymous substitution rates (Ka/Ks) of most PCGs indicated purifying and negative selection, except for atp8 of Anisus, Biomphalaria, and Gyraulus, which indicated positive selection. We observed that transpositions and reverse transpositions occurred on 10 tRNAs and rrnS, which resulted in six gene arrangement types. We reconstructed the phylogenetic trees using the sequences of PCGs and rRNAs and strongly supported the monophyly of each genus, as well as three tribes in Planorbidae. Both the gene rearrangement and phylogenetic results suggested that Polypylis had a close relationship with Anisus and Gyraulus, while Bulinus was the sister group to all of the other genera. Our results provide useful data for further investigation of species identification, population genetics, and phylogenetics among ramshorn snails. [ABSTRACT FROM AUTHOR]

Background: Freshwater snails are not only intermediate hosts for parasites but also an important part of the food chain as they convert plant biomass and humus into animal biomass. However, being widely distributed in freshwater environments, snails are highly affected by human activities, which makes their adaptation to altering environments challenging. The gut microbiome helps animals in their digestion, immune system, growth and adapting to changing environments. The effect of host species on intestinal microbial community has been poorly studied in snails. Methods: In this study, single-molecule real-time sequencing technology (SMRT) was used to obtain full-length 16S rRNA genes to determine the intestinal microbiomes of three species of freshwater snails (SQ: Sinotaia quadrata, BU: Boreoelona ussuriensis, RP: Radix plicatula) with similar feeding habits in a same water environment. Results: Unifrac PCoA (P<0.05), hierarchical cluster and Ternary analyses showed distinct and significant segregation of the intestinal microbiomes of the three hosts. The phyla Cyanobacteria, Proteobacteria, Firmicutes and Planctomycetota dominated snail guts, comprising 93.47%, 86.22%, and 94.34% of the total reads in SQ, BU and RP, respectively. Of these, only 25.26% of OTUs were identified up to species level, while 72.07% of OTUs were identified at the genus level. Although 72.94% of the total bacterial species (566) were common to three snails, significant differences were observed in terms of their abundance (P < 0.05). Several genera can help to determine the phenotype of the intestinal microbiota. In this case, Lelliottia contributed mainly to stress tolerance, biofilm formation, potential pathogenicity, mobile elements and facultatively anaerobic phenotypes in RP. Furthermore, Romboutsia and Clostridium_sensu_stricto_1 contributed to the anaerobic phenotype of SQ and RP, while Pirellula contributed to the aerobic phenotype in SQ. Moreover, PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) predicted 68 GH (glycoside hydrolase) genes, with these including monosaccharide-, disaccharide-, polysaccharide-, and starch-digesting enzyme genes as well as enzymes specific to aquatic plants. Many of the identified pathways were related to Infectious diseases and Xenobiotics biodegradation and metabolism, which expanded the resistance of freshwater snails. Concludes: Lelliottia, Romboutsia, Clostridium_sensu_stricto_l, and Pirellula play an important role in the intestinal microbiota phenotype of the host snails. In general, the host species affects the structure of the gut microbial community, which in turn helps gastropods improve their environmental adaptability, but further study is still needed. [ABSTRACT FROM AUTHOR]