Freshwater Snail Species Research Articles

LIFE CYCLE VARIATION AND HOST-PARASITE INTERACTIONS OF FOUR CONGENERIC SPECIES OF TURTLE ACANTHOCEPHALANS.

Turtle acanthocephalans in the genus Neoechinorhynchus have complex life cycles and are thought to involve an ostracod intermediate host and a turtle definitive host. For Neoechinorhynchus emydis, an additional snail paratenic host is part of its life cycle. However, how snails become infected and whether other species of Neoechinorhynchus can be found in snails remains unclear. This study was conducted to understand the survival, development, and host use of 4 species of turtle acanthocephalans (Neoechinorhynchus chrysemydis, N. emydis, Neoechinorhynchus emyditoides, and Neoechinorhynchus pseudemydis) in their intermediate, paratenic, and definitive hosts. Using eggs recovered from adult acanthocephalans from naturally infected turtle hosts in Oklahoma, experimental infections were conducted in 2 species of ostracods and 1 species of freshwater snail. Ionomes also were generated for these acanthocephalans and their turtle definitive hosts to better understand resource competition. Upon ingestion by ostracods, eggs of all 4 species of acanthocephalans hatched in both ostracod species. However, no further acanthocephalan development occurred in Cypridopsis sp. ostracods, whereas all 4 acanthocephalan species grew and developed into infective juveniles over 28-32 days in Physocypria sp. ostracods. Of the 4 species of acanthocephalans, N. emydis grew faster early in ostracods and was the only species to survive and establish in snail hosts. This finding was supported by the observation of proboscis remnants in the feces of snails that ingested ostracods infected with N. chrysemydis, N. emyditoides, and N. pseudemydis. In contrast, when snails were exposed to eggs of all 4 acanthocephalan species, eggs were passed in the feces, resulting in no infections. The overall ionomic composition of adult acanthocephalans and their turtle hosts suggested that the hosts and parasites share host resources. However, specific elemental differences indicated that turtle acanthocephalans can accumulate heavy metals at concentrations higher than those in their hosts. Results of this study support previous field observations and hypotheses that (1) Physocypria sp. ostracods serve as intermediate hosts for N. chrysemydis, N. emydis, N. emyditoides, and N. pseudemydis; (2) N. emydis uses snail paratenic hosts, but snails are a non-viable route of transmission to turtles for N. chrysemydis, N. emyditoides, and N. pseudemydis; and (3) as adults, these 4 acanthocephalan species utilize their turtle definitive hosts similarly in terms of ionomic composition. This work challenges the traditional view of the acanthocephalan life cycle and sets the stage for future hypotheses.

Assessment of haemolymph parameters of some freshwater snails and mussels collected from a lentic habitat of Bangladesh

ABSTRACT The present study was conducted to determine certain haemolymph parameters of natural populations of two freshwater snails Pila globosa and Filopaludina bengalensis, and four unionid mussels Lamellidens jenkinsianus, L. phenchooganjensis, L. marginalis, and L. corrianus collected from Darikanthal Beel, Trishal, Mymensingh. Twenty apparently healthy live snails and mussels from each population collected at the same date were selected for haemolymph analysis. A non-lethal sampling technique was adopted for collecting haemolymph from the snails and mussels. The haemolymph parameters Na+, K+, Cl−, glucose concentrations and pH levels were determined for each specimen. Significant differences (P < 0.05) were found in almost all the haemolymph parameters among the sampled snail and mussel populations. This study provided reference ranges for some vital haemolymph parameters of the two freshwater snail species and four unionid mussel species. These ranges are measurable non-lethally and could be applied to biological monitoring of environmental stressors using the molluscs as indicator species.

Study on the prevalence of trematode cercariae infection in freshwater snails in Manipur, India.

Freshwater snails act as first intermediate carriers for numerous trematodes, which can induce sickness in both humans and animals. In Manipur, various species of freshwater snails have been discovered to harbor trematode infections. In this study, we aimed to assess the prevalence of different varieties of freshwater snail species serving as the primary, intermediate hosts for various trematodes in endemic areas of paragonimiasis, a disease caused by Paragonimus trematodes found in two separate regions, Luwangsangbam matai in the Imphal East district and Moreh in the Tengnoupal district of Manipur province. These areas are known to be endemic for human paragonimiasis. We examined 4074 snails, including Bortia costula, Filopaludina bengalensis, Paludomous pustulosa,Indoplanorbis exustus using the shedding and crushing method. Our findings revealed that 43(1.05%) snails were positive for different trematode cercariae. Specifically, Bortia costula was infected with Fasciola spp, and unidentified cercariae, while Filopaludina bengalensis and Paludomous pustulosa harboured Gymnacephalous and Echinostomous cercariae. Interestingly, Indoplanorbis exustus did not show any infection with trematode cercariae. A strong association was found between these types of snail species and cercarial infection. Furthermore, statistical analysis did not demonstrate a significant correlation between the geographical location and cercarial infection among snail species. Our study provides the current status of the prevalence of trematode cercarial infection in these snails, offering insights into disease transmission dynamics and the role of snails in paragonimiasis epidemiology.

Introduction of a snake trematode of the genus Ochetosoma in eastern Japan

In Japan, trematodes of the family Ochetosomatidae are not naturally distributed. However, the introduced ochetosomatid Ochetosoma kansense (Crow, 1913) has been reported from the oral cavity of native snakes in western Japan since 2010s. In this study, trematodes were isolated from the oral cavities of the native Japanese snakes, Elaphe quadrivirgata (Boie, 1826), E. climacophora (Boie, 1826), and Rhabdophis tigrinus (Boie, 1826), in the central Kanto region of eastern Japan. Morphological and molecular analyses of the isolated trematodes revealed that all trematodes were identifiable to a newly introduced ochetosomatid species to Japan, O. elongatum (Pratt, 1903), which originated from North America; Lechriorchis tygarti Talbot, 1933 was synonymized with O. elongatum based on identical molecular data and morphological similarity. To identify first intermediate hosts of O. elongatum, seven freshwater snail species were examined in eastern Japan. Molecular analysis was used to identify O. elongatum sporocysts in the freshwater snail Physella acuta (Draparnaud, 1805), which also originated from North America. The other six species did not host O. elongatum, suggesting that Ph. acuta is the only first intermediate host of O. elongatum in Japan. Although O. elongatum has been detected in Japan, its invasion route and period of introduction are unclear. Frequent imports of freshwater snails and wild snakes from North America, after the 1990s and 2005, respectively, presumably introduced O. elongatum in Japan.

Molluscophagy in North East India: Assessment of Nutritive Value of Four Edible Freshwater Molluscs

ABSTRACT 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).

One Health monitoring reveals invasive freshwater snail species, new records, and undescribed parasite diversity in Zimbabwe

BackgroundSnail-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.MethodsA 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.ResultsAmong 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.ConclusionsOur 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.Graphical

Re-assessing thermal response of schistosomiasis transmission risk: evidence for a higher thermal optimum than previously predicted.

The geographical range of schistosomiasis is affected by the ecology of schistosome parasites and their obligate host snails, including their response to temperature. Previous models predicted schistosomiasis' thermal optimum at 21.7 °C, which is not compatible with the temperature in sub-Saharan Africa (SSA) regions where schistosomiasis is hyperendemic. We performed an extensive literature search for empirical data on the effect of temperature on physiological and epidemiological parameters regulating the free-living stages of S. mansoni and S. haematobium and their obligate host snails, i.e., Biomphalaria spp. and Bulinus spp., respectively. We derived nonlinear thermal responses fitted on these data to parameterize a mechanistic, process-based model of schistosomiasis. We then re-cast the basic reproduction number and the prevalence of schistosome infection as functions of temperature. We found that the thermal optima for transmission of S. mansoni and S. haematobium range between 23.1-27.3 °C and 23.6-27.9 °C (95 % CI) respectively. We also found that the thermal optimum shifts toward higher temperatures as the human water contact rate increases with temperature. Our findings align with an extensive dataset of schistosomiasis prevalence in SSA. The refined nonlinear thermal-response model developed here suggests a more suitable current climate and a greater risk of increased transmission with future warming for more than half of the schistosomiasis suitable regions with mean annual temperature below the thermal optimum.

Amphistome Infection and Species Diversity of Freshwater Snails Collected from Selected Wildlife Drinking Water Sources in Matebeleland Region of 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.

Ecological observations of freshwater snails in the vicinity of an artificial lake

This investigation delves into the ecological dimensions of freshwater snails in the vicinity of an artificially created lake. The aim of this research was to comprehend the distribution, prevalence, and variety of freshwater snail species within the ecosystem surrounding the manmade lake. The study spanned from August to November 2023, conducted at three distinct sample stations (I, II, and III), with bi-weekly sample collections. Standard keys were employed for the identification of snails, and the Shanon-Weiner and Simpson's similarity indices were used to explore the diversity of snail species. Throughout the study, a total of 311 individuals representing three distinct species encountered in this study were documented. Acathina fulica exhibited the highest abundance (129 individuals), while Pomacea bridgesii displayed the lowest abundance (66 individuals). The month of August registered the highest population (122 individuals), contrasting with the lowest count in November (37 individuals). Abundance varied across stations, with Station II recording the lowest (77 individuals) and Station III the highest (116 individuals). Regarding diversity, Pomacea bridgesii emerged as the most diverse species (0.3670 &amp; 0.3662), while Littorina littorea exhibited the least diversity (0.0000) across the stations. This investigation contributes valuable insights into the dynamics of freshwater snail populations in the periphery of artificial lakes, shedding light on their distribution patterns and ecological interactions.

Experimental study on the artificial infection of common freshwater snails with Angiostrongylus cantonensis in Dali Bai Autonomous Prefecture, Yunnan Province

To evaluate the potential risk of transmission of angiostrongyliasis by common freshwater snails in Dali Bai Autonomous Prefecture, Yunnan Province, so as to provide insights into local surveillance of angiostrongyliasis. Common freshwater snails were collected from Dali Bai Autonomous Prefecture, Yunnan Province from March to April, 2020, and identified and bred in laboratory. SD rats were infected with third-stage larvae of Angiostrongylus cantonensis that were isolated from commercially available Pomacea canaliculata snails in Dali Bai Autonomous Prefecture, and freshwater snails were infected with the first-stage larvae of A. cantonensis that were isolated from the feces of SD rats 39 days post-infection at room temperature. The developmental process and morphological characteristics of worms in hosts were observed, and the percentages of A. cantonensis infections in different species of freshwater snails were calculated. Then, SD rats were infected with the third-stage larvae of A. cantonensis that were isolated from A. cantonensis-infected freshwater snails, and the larval development and reproduction was observed. More than 3 000 freshwater snail samples were collected from farmlands, ditches and wetlands around Erhai Lake in Dali Bai Autonomous Prefecture, and Cipangopaludina chinensis, P. canaliculata, Parafossarulus striatulus, Oncomelania hupensis robertsoni, Galba pervia, Physa acuta, Radix swinhoei, Assiminea spp., Tricula spp. and Bellamya spp. were morphologically identified. A total of 105 commercially available P. canaliculata snails were tested for A. cantonensis infections, and 2 P. canaliculata snails were found to be infected with A. cantonensis, in which the third-stage larvae of A. cantonensis were isolated. Ten species of freshwater snails were artificially infected with the third-stage larvae of A. cantonensis, and all 10 species of freshwater snails were found to be infected with A. cantonensis, with the highest positive rate of A. cantonensis infections in Bellamya spp. (62.3%, 137/204), and the lowest in C. chinensis (35.5%, 11/31). After SD rats were infected with the third-stage larvae of A. cantonensis isolated from different species of freshwater snails, mature adult worms of A. cantonensis were yielded. Multiple species of freshwater snails may serve as intermediate hosts of A. cantonensis under laboratory conditions in Dali Bai Autonomous Prefecture of Yunnan Province. Further investigations on natural infection of A. cantonensis in wild snails in Dali Bai Autonomous Prefecture seem justified.

Characterisation of Nematoda and Digenea in selected Australian freshwater snails

Freshwater snails are integral to local ecosystems as a primary food source for various vertebrate species, thereby contributing significantly to ecological food webs. However, their role as intermediate hosts also makes them pivotal in the transmission of parasites. In Australia, research on freshwater snails has predominantly focused on their role as intermediate hosts for livestock parasites, while there has been limited exploration of the impact of these parasites on snail health and population dynamics. The aim of this study was to determine parasitic infection in freshwater snails. This study was conducted in the south-eastern region of Australia, in 2022. A total of 163 freshwater snails from four different species were collected and examined in the Murrumbidgee catchment area in the southeastern part of Australia during the Southern Hemisphere summer and autumn months (February to May). The species included Isidorella hainesii, Glyptophysa novaehollandica, Bullastra lessoni (endemic species), and Physella acuta (an introduced species). Through the analysis of sequence data from the various regions of the nuclear ribosomal DNA, we determined that the Digenea species in this study belonged to three distinct species, including Choanocotyle hobbsi, Petasiger sp. and an unidentified species belonging to Plagiorchioidea. Additionally, analysis of the sequences from Nematoda found in this study, revealed they could be categorized into two separate taxa, including Krefftascaris sp. and an unidentified nematode closely associated with plant and soil nematodes. This research holds significant implications for the future understanding and conservation of Australian freshwater ecosystems. Most parasites found in the present study complete their life cycle in snails and turtles. As many of freshwater snail and turtle species in Australia are endemic and face population threats, exploring the potential adverse impacts of parasitic infections on snail and turtle health, is crucial for advancing our understanding of these ecosystems and also paving the way for future research and conservation efforts. While none of the native snail species in the present study have been listed as endangered or threatened, this may simply be attributed to the absence of regular population surveys.

Green synthesis of silver nanoparticles using Croton urucurana and their toxicity in freshwater snail species Biomphalaria glabrata

Green silver nanoparticles (G-Ag NPs) have contributed to the development of ecological technologies with low environmental impact and safer for human health, as well as demonstrating potential for the control of vectors and intermediate hosts. However, knowledge about its toxicity in the early stages of gastropod development remains scarce. Therefore, the current study aimed to investigate the toxicity of G-Ag NPs synthesized from Croton urucurana leaf extracts in snail species Biomphalaria glabrata, which is an intermediate host for Schistosoma mansoni parasite. G-Ag NPs were synthesized using two types of plant extracts (aqueous and hydroethanolic) and characterized using multiple techniques. Bioassays focused on investigating G-Ag NPs and plant extracts were carried out with embryos and newly hatched snails, for 144 h and 96 h, respectively; toxicity was analyzed based on mortality, hatching, development inhibition, and morphological changes. Results have shown that both G-Ag NPs were more toxic to embryos and newly hatched snails than the investigated plant extracts. G-Ag NPs deriving from aqueous extract have higher molluscicidal activity than those deriving from hydroethanolic extract. Both G-Ag NPs induced mortality, hatching delay, development inhibition, and morphological changes (i.e., hydropic embryos), indicating their molluscicidal activities. Moreover, embryos were more sensitive to G-Ag NPs than newly hatched snails. Thus, the toxicity of G-Ag NPs to freshwater snails depends on the type of extracts and the snail's developmental stages. These findings can contribute to the development of green nanobiotechnologies applicable to control snails of medical importance.

THE COCCIDIA SPECIES PFEIFFERINELLA ELLIPSOIDES EXHIBITS SPATIAL AND SPECIES-SPECIFIC VARIATION IN PREVALENCE AMONG FRESHWATER SNAILS.

Freshwater snails are commonly studied within the context of their role as intermediate hosts for digenetic trematodes. However, there are fundamental data deficiencies related to our understanding of directly transmitted parasites, such as coccidia, for freshwater snails. Because variation in coccidia pathogenicity and transmission among snail species likely has major impacts on snail community structure, we aimed to investigate the spatial distribution and prevalence of coccidia in several freshwater snail species throughout the Ozark and Ouachita Mountains ecoregions in Arkansas. We opportunistically collected 220 freshwater snails from 24 Ozark sites in summer 2022 and scanned fecal slides for the presence of coccidia. In summer 2023, we surveyed an additional 146 snails from 19 Ouachita sites. To test for apparent interactions among coccidia and trematodes, we scanned feces from a subset of snails (Physa and Planorbella in the Ozarks) that did not have concurrent trematode infections and from those that did. We observed oocysts that morphologically conformed to Pfeifferinella ellipsoides in 2 of the 9 snail taxa from 7 of the 43 sites. Planorbella trivolvis was infected at 2 of 6 sites in the Ozarks and 0 of 5 sites in the Ouachitas. Physa species were infected at 6 of 14 sites in the Ozarks and 0 of 12 sites in the Ouachitas. In the Ozarks, Pl. trivolvis had an overall prevalence of 0.13 (6 of 47), whereas individuals in the genus Physa had an overall prevalence of 0.08 (8 of 97). Our chi-square and Fisher exact tests revealed no significant evidence for trematode-coccidia competition or synergism within the two snail species. There were no other species infected, and we did not observe any coccidia in the snails from the Ouachitas. Our survey of 366 snails among 9 taxa and 43 sites represents the largest survey for freshwater snail coccidia to date and indicates that both Pl. trivolvis and Physa spp. may be primary hosts and/or reservoir hosts for Pf. ellipsoides in freshwater snail communities. The highly aggregated distribution of Pf. ellipsoides in northwestern Arkansas requires further investigation. Our results led to proposal of several hypotheses for additional research, including questions regarding the variation of coccidia host specificity and virulence.

A new species of freshwater snail of Fenouilia (Gastropoda, Pomatiopsidae) from northern Guangxi, China, based on morphological and DNA evidence.

A new species of pomatiopsid freshwater snail, Fenouiliaundata 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.

Detection of two species of non-indigenous freshwater snails in Arctic Siberia

ABSTRACT Some species of freshwater gastropods, known for their adaptability and resilience, have gained attention globally as invasive species. However, to date, only one invasive population of freshwater snails has been documented beyond the Arctic Circle. In this study, we report the discovery of two non-indigenous species, Planorbella duryi (Wetherby, 1879) and Physella acuta (Draparnaud, 1805), north of 69°N in the Norilsk Industrial District (Central Siberia). Their identification was based on morphological features and COI gene sequences. Both species are native to the temperate and subtropical zones of North America and may have entered the Arctic Asian reservoirs through aquarium introductions. The distribution of these populations is constrained to areas affected by thermal pollution, and their further spread into pristine reservoirs of Northern Siberia is unlikely.

Host species of freshwater snails within the same freshwater ecosystem shapes the intestinal microbiome

BackgroundFreshwater 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.MethodsIn 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.ResultsUnifrac PCoA (P&amp;lt;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 &amp;lt; 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.ConcludesLelliottia, Romboutsia, Clostridium_sensu_stricto_1, 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.

Environmental influence on abundance and infection patterns of snail intermediate hosts of liver and intestinal flukes in North and Central Vietnam.

Liver and intestinal flukes (LIF) are important groups of foodborne zoonotic trematodes (FZTs) in Southeast Asia, including Vietnam. Their complex life cycles require specific freshwater snail species as the obligatory first intermediate hosts. In 2019, we conducted a longitudinal study in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, respectively, to investigate the diversity of LIF and their infection prevalence in relation to snail host abundance and environmental factors. Using a combination of morphological and molecular identification techniques, we identified 10 LIF species infecting 11 snail host species. We observed significant seasonal variation in the mean abundance of several snail host species, with the majority of snails collected during the spring. We also detected seasonal changes in LIF species composition, with the highest species richness reported in the spring. Clonorchis sinensis and Fasciola gigantica, two medically important human liver flukes in Asia, were found only in the spring in Yen Bai. Our study revealed that not all snail host species have the same probability of becoming infected, and we recorded seasonal variations in the prevalence of LIF infection in different snail species in relation to water parameters.

Rediscovery and systematics of the enigmatic genus Helicostoa reveals a new species of sessile freshwater snail with remarkable sexual dimorphism.

Helicostoa sinensis E. Lamy, 1926 is a unique freshwater gastropod species with a sessile habit. This enigmatic species was first found cemented on river limestones from China about 120 years ago and described together with the genus. It was never collected again and has been considered monotypic. Here, we report the rediscovery of Helicostoa from several rivers in China, and describe a second species of this genus based on a comprehensive study. In addition to the unique sessile habit of both species, the new Helicostoa species presents one of the most remarkable cases of sexual dimorphism within molluscs. Only the adult female is sessile and the original aperture of the female is sealed by shell matter or rock, while an opening on the body whorl takes the function of the original aperture. The male is vagile, with a normal aperture. Our results confirm the recently suggested placement of Helicostoa within the family Bithyniidae. The sessility of Helicostoa species is considered as an adaption to the limestone habitat in large rivers. The extreme sexual dimorphism and secondary aperture of females are considered as adaptations to overcome the obstacles for mating and feeding that come with a sessile life style.

Investigating the effects of three trace metals on the viability, embryonic development, and locomotor behavior of the Seminole ramshorn snail at environmentally relevant concentrations.

Trace metal contamination is a widespread issue due to its many natural and anthropogenic sources and known carcinogenic, teratogenic, and reproductive effects. As previous invertebrate trace metal research has primarily focused on model species (Daphnia magna, Chironomidae, etc.), our understanding of effects on non-model invertebrate species remains relatively poor. As such, this study assessed the exposure effects of cadmium, arsenic, and lead on viability, locomotor behavior, and embryonic development of the Seminole ramshorn snail (Planorbella duryi). Exposure treatments of CdCl2 , Na2 HAsO4 • 7H2 O, or Pb (NO3 )2 were prepared at concentrations of 0, 0.01, 0.1, 1, and 10mg/L and confirmed using inductively coupled plasma optical emission spectroscopy (ICP-OES). Individual adult P.duryi were exposed for 7 days with viability assessed every 24 h, and locomotor behavior was accessed on Days 1 and 7 using ToxTrac v2.97 automated behavior software. Individual embryos from newly laid (<6h old) embryonic clutches were exposed for 10days, during which embryonic development stage was documented every 24 h. Based on our results, an additional follow-up study for cadmium was conducted using a lower range of 0-0.1mg/L to allow for the observation of sublethal endpoints. Adult lead and cadmium exposure resulted in significant mortality in the highest treatments (1 and 10mg/L), dose-dependent behavioral effects, and delayed embryonic development. Arsenic exposures resulted in little to no impacts for all assessed endpoints. Our results provide new insight into the sublethal impacts of these contaminants and highlight potential for behavior and embryonic development as useful tools for risk assessment. PRACTITIONER POINTS: The exposure effects of lead, cadmium, and arsenic on the viability, embryonic development, and locomotor behavior of a common freshwater snail species was investigated using environmentally relevant concentrations. The severity of impact differed for each trace metal, with cadmium being the most toxic and arsenic the least toxic at concentrations ranging from 0 to 10 mg/L. Embryonic development appeared to be the most sensitive endpoint of those tested in this study, suggesting that exposure may have prolonged effects that extend to population and community levels. The Seminole ramshorn snail serves as a sensitive alternative model species that can be used to assess the impacts of contaminants on freshwater invertebrates in future studies.

Identification of freshwater snail species and survey of their trematode infections in Ordos, China

In order to investigate and study the species and distribution of freshwater snails in Ordos area of Inner Mongolia, as well as the trematode infection in different periods, and to provide a scientific basis for the effective prevention and control of livestock trematodiasis. In this paper, freshwater snails distributed in Ordos were widely collected for morphological identification, and PCR amplification of freshwater snails COI gene and ITS2 gene was carried out with the help of molecular biology. At the same time, microscopic examination was used to observe the trematode infection of freshwater snails in two different periods from May to July and July to September, and the molecular biology of the trematodes was identified. The results showed that the 1796 freshwater snails collected belonged to two orders, three families and four genera, i.e. Bellamya, Radix, Galba, and Gyraulus. Microscopic examination of snails showed that the infection rate of trematode larvae from July to September was significantly higher than that from May to July. The collected trematodes were identified as five species, namely Cotylurus marcogliesei, Fasciola hepatica, Fasciola gigantica, Paramphistomum cervi, and Parastrigea robusta. The combination of freshwater snail species in Ordos and the infection of trematode in snails showed that a large number of freshwater snails were infected with trematodes, especially from July to September, when there is more rain and suitable climate, which causes serious harm to local livestock.