Freshwater Snail Research Articles

Assessing the dual toxicity of HfO2 nanoparticles and quinalphos on Pila virens

Pila virens (P. virens) is an edible freshwater snail, widely distributed in Asia and Africa. P. virens is used as one of the most promising model organisms for monitoring environmental contamination in aquatic ecosystems. The physiological responses to the contaminants such as pesticides and nanomaterials are inadequate, especially in relation to the effects of co-exposure. In this work, we have investigated on the noxious effects of co-exposure between an organophosphorus pesticide, quinalphos and hafnium oxide nanoparticles (HfO2NPs) on the antioxidant responses of P. virens. Phase pure forms of HfO2NPs (monoclinic, P21/c) were obtained by sol-gel method. The crystallinity, structure and surface morphology were analysed with various spectroscopic methods like powder X-ray, Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), High Resolution Scanning Electron Microscope (HR-SEM) and Transmission Electron Microscope (TEM). P. virens after exposure for 96 h to the different concentrations of quinalphos (0.25–2.25 mg/mL) and HfO2NPs (10–50 mg/mL), the median lethal concentration (LC50) was determined to be 1.159 mg/mL and 11.47 mg/mL, respectively and show a significant fatal effect against the snail. The P. virens were exposed to sub-lethal concentrations of LC25 (0.57 mg/mL quinalphos and 5.73 mg/mL HfO2NPs) individually and in combination as a binary toxicity (quinalphos + HfO2NPs), (0.57 mg/mL + 5.73 mg/mL) for 24 and 48 h. Further, the antioxidant responses were assessed which included catalase (CAT), glutathione sulfo-transferase (GST), and malonaldehyde (MDA) activity in the group exposed to quinalphos and HfO2NPs exhibited to show an enhancement in their activity in comparison to controls after 24 and 48 h and revealed that 48 h exposure has significant impact. These results provide a valuable insight towards increased awareness of the physiological defences of P. virens after co-exposure to quinalphos and HfO2NPs in aquatic ecosystem.

Impact of chemical snail control on intermediate host snail populations for urogenital schistosomiasis elimination in Pemba, Tanzania: findings of a 3-year intervention study.

The World Health Organization (WHO) has set the goal of eliminating schistosomiasis as a public health problem globally by 2030 and to interrupt transmission in selected areas. Chemical snail control is one important measure to reduce transmission and achieve local elimination. We aimed to assess the impact of several rounds of chemical snail control on the presence and number of the Schistosoma haematobium intermediate snail host (Bulinus spp.) in water bodies (WBs) on Pemba Island, Tanzania, a setting targeted for elimination of urogenital schistosomiasis. During the three annual intervention periods of the SchistoBreak study implemented in the north of Pemba from 2020 to 2024, malacological surveys were conducted up to four times per period in WBs of hotspot implementation units (IUs). Present freshwater snail species, vegetation, and WB characteristics were recorded. If Bulinus were found, the snails were inspected for Schistosoma infection and snail control with niclosamide was conducted. Across the three intervention periods, a total of 112 WBs were identified in 8 hotspots IUs. The spatial distribution of WBs with Bulinus per IU was heterogeneous, ranging from 0.0% (0/15) of WBs infested in one IU in 2022 to 80.0% (8/10) of WBs infested in one IU in 2021. Bulinus presence was significantly associated with lower pH values in WBs (odds ratio: 0.2, 95% confidence interval 0.1-0.4). A total of 0.2% (6/2360) of collected Bulinus were shedding Schistosoma cercariae. Following snail control, the number of Bulinus decreased or remained absent in 56.7% (38/67) of visits at WBs when compared with the previous visit in 2021, 54.9% (28/51) in 2022, and 33.3% (32/96) in 2023. In a total of 43.1% (22/55) of initially infested WBs, no Bulinus were found in the survey round conducted a few weeks after the first application of niclosamide. However, 25.4% (14/55) of WBs showed a pattern of recurring Bulinus presence. The distribution of WBs containing Bulinus was very heterogeneous. The percentage of Bulinus with patent Schistosoma infection in our study area was extremely low. Repeated niclosamide application reduced the number of Bulinus in WBs, but snails often recurred after one or multiple treatments. While chemical mollusciciding can reduce snail numbers, to fully break the S. haematobium transmission cycle, timely diagnosis and treatment of infected humans, access to clean water, sanitation, and health communication remain of prime importance. ISRCTN, ISRCTN91431493. Registered 11 February. 2020, https://www.isrctn.com/ISRCTN91431493.

Chapter 3. Release of Geothermal Energy: Hot Springs and Tufa-Travertines

Heat and groundwater flow through a rift basin are an integral part of its geodynamics, but predicting what is happening below the surface is often difficult due to a lack of direct information. Field observations on the occurrence, subaerial distribution, temperature and geochemistry of freshwater springs may help to form an idea of groundwater flow through the basin and what it is, or has been, flowing through. Hot springs in the Albertine Rift are common and their occurrence is directly linked to deep-seated main rift bounding faults, or major intra-basinal fault intersections. The majority of Lake Edward and Lake Albert active, or paleo-springs, are also associated with precipitation of localised tufa-travertine limestones. The cooler tufas may contain calcitised plant roots, leaf imprints and freshwater gastropods. Active scavenging of uranium can be demonstrated in the algae and cyanobacteria that inhabit active spring mouths and corresponding tufa-travertines are depleted in radioactive K, U and Th elements. The source for concentrated HCO3- in groundwater at depth, needed to precipitate limestones at the surface, remains problematic. However, REE+Y geochemistry of the tufa-travertines suggest end-member sources of either carbonatites or marine limestones, indicating the possibility of a pre-Neogene rift sequence beneath the Albertine Rift.

Freshwater snails (Bellamya aeruginosa) bioturbation to enhance nitrogen removal and associated mechanism in constructed wetlands

In this study, total nitrogen (TN) removal efficiency of Pontederia cordata and Myriophyllum elatinoides in surface flow constructed wetlands (SFCWs) with Bellamya aeruginosa were 6.43% and 3.54% higher, respectively, than those in non-B. aeruginosa SFCWs. Further, bioturbation could promote N uptake by plants and release from sediment. In summer and autumn, potential nitrification rate was significantly higher in SFCWs with snails than that in SFCWs without snails. In each season, potential denitrification rate was significantly higher in SFCWs with snails than that in SFCWs without snails. Additionally, ammonia oxidizing archaea, narG, nirS, nirK and nosZ gene abundances were significantly higher in SFCWs with snails than those in SFCWs without snails. Structural equation model analysis revealed a strong positive correlation between nitrifiers and denitrifiers in SFCWs with snails, suggesting that bioturbation enhanced N removal by increasing synergistic effect of nitrifying and denitrifying bacteria.

A new genus and species of spring snails (Caenogastropoda, Tateidae) from the ultramafic South of New Caledonia

During an expedition in 2016, a rich fauna of freshwater gastropods of the family Tateidae Thiele, 1925 was discovered on the ultramafic terrains of the Southeast of New Caledonia (NC). Hitherto, only three of the 62 known NC family members were reported from this type of bedrock. With less than 1.5 mm in length, many of the new species are particularly small. In order to establish a methodological setup for the description and phylogenetic analyses of these new species, we here describe Viriiella touaouroua gen. et sp. nov. and assess its relationships based on three gene fragments. Viriiella is morphologically well defined and resembles Fluviopupa Pilsbry, 1911 not present in NC. In the phylogenetic analyses, though, Viriiella appeared as a member of the Hemistomia-clade, the NC tateids occurring on non-ultramafic terrain. However, Viriiella had the longest branch and, sister group to different genera in maximum likelihood and Bayesian analyses, its position was unstable, probably an artifact due to long-branch attraction. Considering that Viriiella does not share the defining character states of Hemistomia s. lat., it may well be possible that inclusion of more related genera will show that the new taxa share a most recent common ancestor with the Hemistomia-clade, but as sister group.

Labeling of miracidium using fluorescent agents to visualize infection of schistosome in intermediate host snails

Schistosomiasis is a parasitic disease affecting more than 250 million people worldwide. Schistosomes infect humans by cercariae penetrating the skin in a freshwater environment. Findings obtained more than 100 years prior showed that miracidium develops into cercaria in freshwater snails, though detailed development dynamics have not been elucidated. Although results of histological analyses of development of schistosomes in snails were presented in our previous studies, findings obtained with dynamic imaging have yet to be reported. In the present study, imaging of schistosome infection and dynamics in snails occuring within a short period was performed using fluorescent labeling agents. Labeling of S. mansoni cercariae with carboxyfluorescein succinimidyl ester (CFSE) caused no toxicity, and allowed for monitoring of schistosome dynamics in snails for up to 10 days and release of infective cercariae without fluorescence in 40 days following infection.

Absolute Abundance of Dominant Freshwater Mollusks of an Irrigation Canal

Mollusks are a diverse group of invertebrates that perform fundamental ecological functions within freshwater ecosystems. This study evaluated the absolute abundance of dominant freshwater benthic mollusks in an irrigation canal, utilizing a partial count method across seven established sampling stations. Results revealed that the endemic freshwater snail (Jagora spp.) was the most abundant species, followed by golden apple snail (Pomacea spp.) and freshwater clam (Corbicula spp.), which are both invasive species. Effective monitoring and management strategies are essential to mitigate the adverse effects of the invasive species in their particular environment.

Functional characterization of optic photoreception in Lymnaea stagnalis.

Optic photoreception is a critical function for animal survival. Across the evolutionary spectrum, diverse animal models have been used to investigate visual system function and potential mechanisms under physiological or pathophysiological states. However less is known on photoreceptive behaviors and retinal processing in invertebrates, especially molluscs. This study focuses on the freshwater pond snail, Lymnaea stagnalis (L. stagnalis), to explore its visual function and underlying mechanisms. Using anatomical and histological approaches we characterized the L. stagnalis eye structure and demonstrated structural connections and retinal rhodopsin-positive sensory cells potentially critical for phototransduction. To assess the snail phototactic responses, we developed a new neurobehavioral protocol and employed DeepLabCut to track and quantify animal locomotion. We demonstrated that L. stagnalis exhibits a positive locomotory response to intense focal light and has diverse photo-locomotory responses. Further, we conducted phylogenetic and protein structure analyses and demonstrated that L. stagnalis has a unique repertoire of both vertebrate and invertebrate phototransduction genes. Further characterization of a rhodopsin-like gene identified unique characteristics compared to other mollusks and vertebrates, suggesting different mechanisms of phototransduction. Taken together, our work establishes L. stagnalis as a model organism for studying optic photoreception, offering new insights into the evolution and diversity of visual function across animal species.

Idiopyrgus Pilsbry, 1911 (Gastropoda, Tomichiidae): a relict genus radiating into subterranean environments

The freshwater gastropod fauna in Brazil presently consists of circa 180 known species, though this is deemed an underestimate. The little-studied cavern faunas have been considered a potential source of undescribed species, particularly regarding the Truncatelloidea. Here, based on new collection efforts in caves in Bahia state, Brazil, we describe two new troglobitic species of Idiopyrgus (Tomichiidae): Idiopyrgus eowynaesp. nov. and Idiopyrgus meriadocisp. nov. We improve upon the previous molecular phylogeny of this genus and take the opportunity to reclassify Spiripockia umbraticola Simone & Salvador, 2021, as Idiopyrgus umbraticola (Simone & Salvador, 2021), comb. nov. The genus Idiopyrgus now contains ten species, reinforcing the presence of Tomichiidae in Brazil as a relict lineage that largely radiated into cave environments. Furthermore, considering that so far only snapshots of their biology are known, we have collated all the information currently available from the literature and field observations on the cavernicolous species of Idiopyrgus. Notably, due to human action in the area where the two new species have been found, they can already be considered vulnerable.

Cold Tolerance and Physiological Response of Natural Overwintering Pomacea canaliculata in South China.

Pomacea canaliculata (Lamarck 1822), a freshwater gastropod indigenous to lower Del Plata Basin of Argentina, has become the most destructive and invasive rice pests in south China since its introduction in the 1980s. In Guangdong, the main production areas for double rice, most of P. canaliculata overwinter in paddy field ditches after late-rice harvesting in mid-November and diapause to temporarily to avoid the damaging effects of extreme low temperatures. This pest aroused from diapause and migrated to the paddy field after early-rice reviving in next late March. Overwintering and cold tolerance of natural P. canaliculata have a non-negligible impact on population dynamics and distribution in the following year. We tested the supercooling capability, levels of cryoprotectant synthesis, activity of antioxidant defense system (antioxidant enzymes and reduced glutathione), and degree of oxidative damage (concentration of malondialdehyde as an index of lipid peroxidation) monthly, using natural P. canaliculata samples with a size-gender structure (i.e., juveniles, female, and male adults) from experimental ponds during the period of mid-November to the following April. P. canaliculata survived the winter with a monthly death rate of 7%-16.5% in coldest January. The supercooling point (SCP) of overwintering P. canaliculata decreased initially before increasing subsequently with monthly changes in water temperature. P. canaliculata accumulated a high glycogen content before December, which depleted towards the end of January, while lipid content reached peak in January and depleted since February. Activity of antioxidant defense system of P. canaliculata exhibited significant monthly differences and showed relatively higher size heterogeneity than monthly variations. The results contribute to the knowledge of adaptability in overwintering P. canaliculata and help to understand the mechanism of the invasive success of this species.

Toxicokinetics and responses of multiple biomarkers of sediment-associated fluoroquinolones in an ecologically important freshwater snail Bellamya aeruginosa

Fluoroquinolones (FQs) have the propensity to accumulate in sediments once introduction into aquatic environments, thereby posing potential threats to benthic organisms, yet the ecotoxicity of sediment-associated FQs remains unclear. In this study, the toxicokinetics and responses of multiple biomarkers in Bellamya aeruginosa, exposed to the three commonly used FQs (norfloxacin, NOR; ciprofloxacin, CIP; levofloxacin, LEVO) at environmentally relevant concentrations were investigated under sediment exposure scenario. The results revealed that FQs were effectively ingested by B. aeruginosa from sediments, CIP showing the highest bioaccumulation (180.59 μg/kg), followed by NOR (74.49 μg/kg) and LEVO (36.02 μg/kg). CIP exhibiting a highest uptake rate constant (Ks) (4.64 g/(g.d)) and the lowest elimination rate constant (Ke) (0.05 g/(g.d)). The descending order of biological half-life is as follows: CIP (13.62 d), LEVO (8.14 d), and NOR (6.83 d). NOR induced the activity of superoxide dismutase, catalase, and glutathione-S-transferase while CIP and LEVO depressed their activities and increased malondialdehyde content, indicating a more pronounced oxidative damage to B. aeruginosa caused by CIP and LEVO than NOR. Furthermore, all three FQs were found to induce DNA damage and elevate acetylcholinesterase activity, suggesting distinct genotoxic and neurotoxic effects. Interestingly, despite its low bioaccumulation potential, LEVO exhibited high toxicity towards B. aeruginosa. These findings enhance our understanding of the ecotoxicity of FQs in sediments, providing further evidence of their potential ecological risks.

Infection status and species diversity of trematode cercariae in freshwater snails from canal networks in the Bangkok Metropolitan Region, Thailand.

This study aimed to investigate the infection status and species diversity of trematode cercariae in freshwater snails from canal networks in the Bangkok Metropolitan Region (BMR), Thailand. The snails were collected from 35 sites during 2 cycles of the wet (July-October) and dry (November-June) seasons in 2018-2019. A total of 29,420 snails representing 24 species/subspecies were examined for cercarial infection using shedding and crushing techniques. We found that 1,275 snails from 12 species/subspecies were infected, resulting in an overall prevalence of 4.3%. Infections were significantly higher (p<0.001) during the wet season (5.9%; 970/16,473) than during the dry season (2.4%; 305/12,947). Morphological identification revealed 37 distinct types within 15 morphotypes, with the armatae morphotype showing the highest infection rate (1.8%) and the greatest cercarial diversity (8 distinct types). This study highlights the health risk posed by the Bithynia siamensis siamensis, which was the second most prevalent (8.5%) and hosted the greatest cercarial diversity (11 morphotypes, 15 distinct types). This subspecies also displayed a wide distribution range (31 localities) with a generally high occurrence frequency in the BMR. This study firstly documents a gymnophallid digenean as a freshwater digenean, presenting evidence of a dichotoma cercarial morphotype from 4 species/subspecies (Filopaludina martensi martensi, F. sumatrensis polygramma, B. siamensis siamensis, and Wattebledia siamensis) with a low infection range (0.1-0.4%). A staggering diversity of cercariae was observed in the BMR canal networks with seasonal fluctuations. The B. siamensis siamensis displayed notable epidemiological importance in the BMR flowing-water networks. This study provides quantitative and qualitative morphological descriptions and measurement guidelines for the dichotoma cercaria in Thailand.

The first record the Limnia unguicornis (Diptera, Sciomyzidae) parasites on a vulnerable pulmonate land snail, Vertigo moulinsiana (Gastropoda: Eupulmonata: Vertiginidae) and a literature review on Limnia species

The literature about mollusc-parasite interactions is focused on species affecting human health, such as trematodes on freshwater snails as intermediate hosts. Far less attention has been paid to parasite-snail interactions in terrestrial habitats. Here we present the first observation of a sciomyzid larva of Limnia unguicornis, parasitizing a vulnerable, tiny air-breading snail, Vertigo moulinsiana (strictly protected by Polish law). Sciomyzids are almost exclusively malacophagous but their biology and ecology are understudied. Thus, we have reviewed the available information on Limnia species and discussed the results of our research.

In-vitro studies of B2O3 – Li2O – P2O5 – CaO – ZrO2 nano glasses for biomedical applications

The current work focuses on developing 40B2O3-(20-X)Li2O-15P2O5-20CaO-XZrO2 (X= 0, 1 and 2 mol %) bioactive nano glasses by a novel microemulsion method and conducting in-vitro studies. CaO derived from fresh water snail shells has been used to produce cost effective glasses. DTA, FTIR, XRD, FESEM, degradation, pH, BET and cell viability tests have been carried out for these glasses. The glasses show good bioactivity and cell viability. ZrO2 reduces the formation of hydroxyapatite and decreases cell viability. The role of ZrO2 on the glass structure and in-vitro properties has been clearly discussed.

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.

Schistosomiasis Chemotherapy, Chemoprevention, and Vaccines: History, Progress, and Priorities.

Schistosomiasis is a major human disease of public health importance. Freshwater snails serving as intermediary hosts and human interaction with surface water tainted by feces or urine are both necessary components of the transmission cycle. Schistosoma haematobium, Schistosoma mansoni, and Schistosoma japonicum are the primary pathogen species. Over 250 million individuals are infected globally, according to the World Health Organization, causing significant morbidity and an estimated loss of 1.9 million disability-adjusted life years, a number that is probably underestimated. Immunological protection is slowly built up through complex immunological systems, although innate factors also play a role. Chronic schistosomiasis affects mainly individuals residing in poor rural area. Vaccination is considered as one of the most sustainable options for the control of any pathogen, but schistosomiasis vaccine for humans or animals is not available till now despite the discovery of numerous potentially promising schistosome vaccine antigens. To provide an overview of the schistosomiasis chemotherapy, chemoprevention, and vaccines history and progress. Review article. PubMed, ISI Web of Science, Science Direct, and the World Health Organization database. Favorably praziquantel (PZQ) is a medication with excellent chemopreventive treatment compliance. Due to the extensive usage of PZQ, there is a great deal of debate surrounding the emergence of drug resistance. PZQ is effective against all species of schistosomes, schistosomiasis prevalence has remained largely unaffected, due to reinfection in high transmission areas and growing juvenile worms that were not affected by the drug, even though the need for a schistosomiasis vaccine is even more pressing.

PREVALENCE OF SNAIL VECTORS OF SCHISTOSOMIASIS ALONG ANTAU RIVER, KEFFI, NASARAWA STATE

Schistosomiasis, or bilharzia, is a parasitic disease that affects over 230 million people worldwide, with 700 million at risk, primarily in tropical and subtropical regions, including Nigeria. The disease is transmitted through freshwater snails that host Schistosoma parasites. This study aims to understand the prevalence of snail vectors responsible for transmitting schistosomiasis along Antau River, Keffi, Nasarawas State. A snail sampling survey conducted at three locations - Saura Bridge, Antau Bridge, and Mannu Bridge - along Antau River yielded a total of 216 snails. The distribution showed Saura Bridge with the highest population (96 snails, 44.4%), followed by Antau Bridge (81 snails, 37.5%) and Mannu Bridge (39 snails, 18.1%). Five snail species were identified, with Melanoides spp dominating (173 snails, 80.1%), followed by Anisus spp (28 snails, 13.0%), Planorbarius spp (11 snails, 5.1%), Biomphalaria spp (3 snails, 1.4%), and Physa spp (1 snail, 0.5%). Biomphalaria spp, a known schistosomiasis vector, had a high cercarial shedding rate (66.7%) near Antau Bridge, signaling a potential risk for disease transmission. Physico-chemical analysis revealed favorable snail habitat conditions, with a mean water temperature of 28.0°C, pH of 7.0, and dissolved oxygen ranging from 6.58 mg/L to 6.75 mg/L. The study concludes that while the overall risk of schistosomiasis transmission may be low due to the small population of Biomphalaria spp, targeted vector control measures are necessary, particularly around Antau Bridge, to prevent further transmission of schistosomiasis. Key recommendations include regular monitoring of snail populations, public health education, and targeted mollusciciding to control the Biomphalaria spp population. The findings provide data for the development of control strategies aimed at reducing the burden of schistosomiasis in the region.

Prediction of the potential Brazilian distribution for invasive mollusc Melanoides tuberculata (Müller, 1774), including a new record from Northern Coastal Region

The freshwater snail Melanoides tuberculata (Müller, 1774) native from Africa and Asia, recently spreads out over the world. Records of invasive species are extremely important, because it helps in future invasions mitigation. Here, we report for the first time the occurrence of M. tuberculata in a protected area of Northern Brazilian Coast and use predictive distribution modeling to know the potential Brazilian distribution for this species. The gastropod M. tuberculata were collected in the municipalities of Tutóia and Santo Amaro - Maranhão State. According to the results of the predictive map distribution for Brazil, the regions with the highest susceptibility are the northeast, southeast and midwest. Preciptation of month and Isothermalithy were de variables that most contribute to the species’ potential distribution. This species presented high to medium suitability of occurrence in 32 national protected areas. Futher studies are recommended to monitor the growth and dispersion, in order to determine its real impact.

Oxidative stress, histopathological and genotoxicity of copper oxide nanoparticles in Biomphalaria alexandrina snail

AbstractHigher usage of copper oxide nanomaterials in industrial and biomedical fields may cause an increase of these nanoparticles in aquatic environments, which could have a detrimental ecological effect. Thus, the objective of this study was to evaluate the acute toxicity of copper oxide nanoparticles on the freshwater gastropod, Biomphalaria alexandrina. Transmission electron microscopy, x-ray diffraction analysis and UV–VIS spectrophotometer of CuO NPs revealed a typical TEM image and a single crystal structure with average crystallite size of approximately 40 nm also, a sharp absorption band was appeared. Following exposure to sub-lethal concentrations of CuO NPs (LC10, 15.6 mg/l and LC25, 27.2 mg/l), treated snails revealed a significant decrease (p < 0.05) in total antioxidant capacity, reduced glutathione contents as well as catalase, and sodium dismutase activities were significantly declined (p < 0.05) in comparison to the control group. Also, histopathological alterations were observed in the digestive gland, including ruptured and vacuolated digestive cells, and a marked increase in the number of secretory cells and the severity of the damage increased with rising concentrations. Furthermore, changes in RAPD profiles were detected in the treated snails. In conclusion, our research highlights the potential ecological impact of CuO NPs release in aquatic ecosystems and advocates for improved monitoring and regulation of CuO NPs industrial usage and disposal.

Abundant genetic variation is retained in many laboratory schistosome populations.

Schistosomes are obligately sexual blood flukes that can be maintained in the laboratory using freshwater snails as intermediate and rodents as definitive hosts. The genetic composition of laboratory schistosome populations is poorly understood: whether genetic variation has been purged due to serial inbreeding or retained is unclear. We sequenced 19 - 24 parasites from each of five laboratory Schistosoma mansoni populations and compared their genomes with published exome data from four S. mansoni field populations. We found abundant genomic variation (0.897 - 1.22 million variants) within laboratory populations: these retained on average 49% (π = 3.27e-04 - 8.94e-04) of the nucleotide diversity observed in the four field parasite populations (π = 1.08e-03 - 2.2e-03). However, the pattern of variation was very different in laboratory and field populations. Tajima's D was positive in all laboratory populations except SmBRE, indicative of recent population bottlenecks, but negative in all field populations. Current effective population size estimates of laboratory populations were lower (2 - 258) compared to field populations (3,174 - infinity). The distance between markers at which linkage disequilibrium (LD) decayed to 0.5 was longer in laboratory populations (59 bp - 180 kb) compared to field populations (9 bp - 9.5 kb). SmBRE was the least variable; this parasite also shows low fitness across the lifecycle, consistent with inbreeding depression. The abundant genetic variation present in most laboratory schistosome populations has several important implications: (i) measurement of parasite phenotypes, such as drug resistance, using laboratory parasite populations will determine average values and underestimate trait variation; (ii) genome-wide association studies (GWAS) can be conducted in laboratory schistosome populations by measuring phenotypes and genotypes of individual worms; (iii) genetic drift may lead to divergence in schistosome populations maintained in different laboratories. We conclude that the abundant genetic variation retained within many laboratory schistosome populations can provide valuable, untapped opportunities for schistosome research.