Urban parks serve millions of visitors annually, yet antimicrobial resistance (AMR) surveillance programs rarely consider invasive species as environmental reservoirs. Here, we investigated antibiotic resistance genes (ARGs) and potential zoonotic pathogens in invasive giant African snails (Lissachatina fulica) across 23 urban parks in Xiamen, China, with comparative analysis of dog feces and earthworm casts collected from the same parks. Metagenomic profiling revealed that snails harbored extensive ARG diversity (1222 subtypes) comparable to dogs (1,393) and substantially exceeding earthworms (492), with 936 ARG subtypes shared between invasive snails and dogs. Invasive snails also carried substantial relative abundances of potential zoonotic pathogens (mean 15.7% relative abundance), including clinically relevant taxa such as Escherichia, Pseudomonas, and Enterococcus. Phenotypic testing of representative isolates confirmed the presence of antibiotic-resistant bacteria in snail and dog fecal samples. The convergence of broad ARG diversity, substantial potential zoonotic pathogen burdens, and coprophagous behavior suggests that invasive snails may represent previously unmonitored environmental hosts associated with AMR in urban parks. Field observations of snails consuming dog feces, together with the greater resistome similarity between snails and dogs than between snails and earthworms, are consistent with exposure to animal feces as a potential source of ARGs. This study underscores the need to integrate invasive species into One Health AMR surveillance and urban environmental management strategies.
Freshwater snails play essential roles in the transmission of trematode parasites that affect humans, livestock and wildlife. Australia's freshwater ecosystems are increasingly influenced by non-native and potentially invasive snail species that may pose biosecurity challenges and alter parasite transmission dynamics. This study characterised the complete mitochondrial genomes for four non-native snail taxa established in Australia (Pseudosuccinea columella, Orientogalba viridis, Physa acuta and Planorbella sp.) and for Galba truncatula, a high-priority exotic species considered a potential invader. Using long-read sequencing and comparative analyses, 15 complete mitogenomes were assembled, annotated and compared across three families (Lymnaeidae, Physidae and Planorbidae). Genome sizes ranged from 13.7 to 14.3 kb and exhibited conserved gene organisation and marked A + T bias. Australian populations of P. columella, O. viridis and Ph. acuta showed very limited mitochondrial nucleotide variability, consistent with founder effects, demographic bottlenecks and self-fertilisation, in contrast to the marked divergence observed among lineages within Galba from European laboratory strains. Phylogenetic inference based on concatenated and single-gene (cytochrome c oxidase subunit 1, cox1) datasets confirmed well-resolved family-level relationships and revealed cryptic diversity within Galba. The mitogenomes defined here provide molecular references for future taxonomic studies, diagnostic assay development and environmental (e)DNA monitoring of freshwater snails. These genomic resources establish a basis for biosecurity preparedness and vector surveillance in Australia and contribute to a broader One Health approach by supporting early detection, accurate identification and risk assessment of trematode-transmitting snails in freshwater ecosystems.
Freshwater snails are emerging sources of bioactive molecules with potential biomedical and therapeutic relevance. This study evaluated crude protein extracts from two Egyptian freshwater snails, Lanistes carinatus and Bellamya unicolor, for antioxidant enzymes, antimicrobial and antibiofilm activities, cytotoxicity against human cancer cell lines, and peptide composition. Both species exhibited low activities of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST), with slightly higher levels in L. carinatus. Despite this, the crude protein extracts inhibited the growth of Escherichia coli and Staphylococcus aureus; L. carinatus showed stronger antifungal activity against Candida albicans, while neither extract affected Aspergillus niger. Selective cytotoxicity was observed: L. carinatus was most active against MCF-7 and HeLa cells, whereas B. unicolor was highly potent against HCT-116 and moderately active against PC3 cells, with minimal effects on normal WI-38 cells. LC-MS/MS identified 26 short peptides, likely contributing to the antimicrobial and anticancer activities.These findings provide preliminary evidence of the therapeutic potential of L. carinatus and B. unicolor crude protein extracts, highlighting freshwater snails as candidate sources of bioactive molecules that merit further investigation.
Structural analogues of bisphenol A (BPA) are rapidly increasing in production and environmental concentrations, although a complete ecotoxicological assessment is still lacking. This study addresses chronic effects on reproduction of the selected bisphenols BPA, BPF, BPS, and BPAF in two aquatic invertebrates, the freshwater snail Potamopyrgus antipodarum and the freshwater amphipod Hyalella azteca. The reproductive output of snails was significantly enhanced at almost all tested nominal bisphenol concentrations ranging from 1 to 100 µg/L. The NOECs for BPA, BPS, and BPAF are below the lowest measured concentration. There was no significant reproductive effect on the amphipods in the tested concentration range (3.2 to 2000 µg/L), apart from a decrease in reproduction due to increasing mortality at the highest concentrations of BPA, BPF, and BPAF. All four bisphenols had a similar impact on the reproduction of the snails at environmentally relevant concentrations. Increases in the energy allocated to reproduction could negatively impact the survival of the population, ultimately also affecting the ecosystem. BPA analogues display a similar ecotoxicological hazard on the reproduction of the snails as BPA itself, therefore making their increasing production and release into the environment problematic.
The present study investigated the impact of aestivation of free-range snails on the intestinal microbiota and its potential to protect the host from infection by pathogenic bacteria. Bacterial strains were isolated just before and at the end of aestivation from the gut of free-range Cornu aspersum aspersum snails from the island of Crete (Greece). Α total of 31 BA (Before Aestivation) and 25 EA (End Aestivation) isolates, were tested for their in vitro probiotic properties. Principal component analysis (PCA) and a machine learning model showed that BA isolates exhibited a different pattern of in vitro properties from that of EA isolates, and that all the EA isolates, except one, were presumptive probiotics, while among BA only isolates BA2Ae and BA5An were presumptive probiotics. 16S rRNA sequencing analysis at species-level revealed that most BA isolates belonged to potentially snail pathogens, while EA isolates belonged to the genera of Citrobacter, Lactiplantibacillus and Enterococcus, that belong to normal intestinal microbiota and presumptive probiotics. Injection of selected isolates in snails resulted in increased immune activity such as chemotaxis and phagocytosis. Food administration of the strains, E. malodoratus BA5An and L. plantarum EA2An, exhibiting the highest immunomodulatory activity, showed further probiotic properties since symbiosis achieved by enhancing some immune humoral responses, as well as restoration of intestinal homeostasis by inhibiting the dysbiosis induced by the snail pathogenic strain Listeria monocytogenes SN3. Each presumptive probiotic strain exhibited a different pattern of immunomodulatory activity against the pathogen.
Air pollution is a major environmental and public health issue, largely driven by human activities. The present study evaluates the combined use of two bioindicators from different taxonomic groups, the moss Rhytidiadelphus squarrosus and the terrestrial snail Cornu aspersum, to assess early biological effects induced by atmospheric exposure to toxic elements. Both species, chosen for their sensitivity, simple physiology, and suitability for field transplantation, were exposed for 30 days at two sites in southern Italy with contrasting environmental conditions. Toxic element accumulation in moss biomass and snail tissues was measured using ICP-OES, while snail shell composition was analyzed using FTIR spectroscopy. Biological responses were assessed through oxidative stress biomarkers (ROS levels and catalase activity), HSP70 expression determined by Western blotting, and structural damage, including ultrastructural changes in mosses and histopathological alterations in snails. Results showed site-dependent patterns of toxic elements accumulation in both organisms, consistent with increased oxidative stress and induction of HSP70 expression. Enlargement of the albumen gland and histological alterations in digestive tubules and reproductive systems were found in snails. Mosses showed severe ultrastructural alterations. FTIR analysis revealed changes in snail shell composition consistent with metal exposure. Principal component analysis highlighted clear patterns linking contamination, oxidative stress, and structural damage, supporting the complementarity of the two bioindicators and their ability to capture distinct exposure pathways and biological effects.
Cryptic speciation is widely documented in marine gastropods, particularly in groups lacking distinct morphological characters. Carrier snails of the family Xenophoridae have long been celebrated by naturalists for their behavior of collecting and affixing foreign objects to their shells. We present the first molecular species delimitation of carrier snails (family: Xenophoridae), using cox1 sequences from 562 specimens encompassing 81% of valid species and all genera in this family. Integrating alpha-taxonomic data, we formalize five new species in descriptions-Xenophora simulans sp. nov., Xenophora brevis sp. nov., Onustus procellosus sp. nov., Collector altissimus gen. nov. et sp. nov., Collector alienus gen. nov. et sp. nov.-and recommend further investigations into other promising clades with potentially undiscovered species, pending corroboration from nuclear loci. This case study highlights the potential of species discovery using single-locus delimitation methods. We established a baseline framework for morphological species delimitation in Xenophoridae, showing that specimens distinguished only by subtle morphological characters often interpreted as intraspecific variation can exhibit species-level genetic divergence.
Smaragdinella marine snails are the only members of the family Haminoeidae and the order Cephalaspidea that inhabit hard substrates in the upper tidal zone, making them of special evolutionary interest. To investigate whether possible novel trophic adaptations coupled with unique morphological traits may underlie this ecological shift, we analysed the gut contents and microbiota of Smaragdinella viridis using DNA metabarcoding (COI and 16S rRNA) and scanning electron microscopy (SEM). COI metabarcoding revealed a diverse assemblage of dietary components dominated by diatoms, rotifers, small arthropods, and fungi. SEM observations partially corroborated these findings, indicating an omnivorous feeding strategy rather than strict herbivory. The gut bacterial community was dominated by Firmicutes (Mycoplasma), Proteobacteria (Vibrio, Photobacterium), and Fusobacteriota (Psychrilyobacter, Propionigenium), taxa associated with the degradation of complex carbohydrates and proteins. Morphological traits in Smaragdinella, including an increased number of gizzard plate ridges, a flattened ovoid shell, and an enlarged foot, most likely facilitate the processing of diverse food items and survival in wave-exposed environments. In addition, the functionality of the gut microbiome may contribute to dietary flexibility enhancing survival in dynamic, resource-variable tidal habitats. The adaptation of these snails to tidal hard bottom habitats could have been prompted by the acquisition of novel morphological features and by a diet shift, but the data do not permit to establish a causal relationship and alternative hypotheses may have to be considered.
AbstractPlasticity in individual thermal physiology is dependent on a species' evolutionary history as well as local environments that influence acclimatization capacity. To test how physiology and acclimatization capacity vary with species and local thermal conditions, we investigated the thermal performance of two rocky shore snails in the genus Nerita. Thermal environments experienced by the snails and their physiological performances (using heart rate) were quantified for two tropical locations (Hong Kong and Singapore; two sites per species in each location) where one or both species were present. Nerita undata, which has a tropical evolutionary origin, was present in both locations, while Nerita yoldii, which has a more subtropical-temperate lineage, was present in Hong Kong but not Singapore. Thermal tolerance of N. undata increased with the maximum environmental temperature in Hong Kong but not Singapore, where sites were hotter and snails had higher but less variable thermal tolerances (~50 °C). Nerita yoldii inhabited hotter sites in Hong Kong than N. undata but, similar to N. undata in Singapore, showed limited plasticity to environmental temperatures. Such extended tolerances but limited plasticity reflect a trade-off that constrains acclimatization capacity, where extreme thermal stress may elicit high energy expenditure but restrict energy gain through feeding when the rock becomes hot and dry. The ability to exhibit physiological plasticity is therefore limited on thermally harsh rocky shores, supporting the hypothesis that tropical ectotherms live close to their thermal limits and are limited in their ability to acclimatize further to survive episodes of extreme thermal stress.
Terrestrial organisms employ diverse camouflage strategies, yet the fluctuating humidity and light conditions of arboreal habitats demand dynamic adaptations. This study investigated a novel mechanism of dynamic camouflage in the arboreal snails Hypselostyla camelopardalis (Camaenidae) and Reinia variegata (Clausiliidae). These phylogenetically distant species exhibit a reversible hygrochromic change: their mottled shell patterns disappear upon wetting, turning uniform dark brown, and rapidly reappear as they dry. Using a multimodal approach-including confocal laser microscopy, scanning electron microscopy, and spectrophotometry, this study shows that the colour change is associated with structural modifications within the bilayered organic periostracum. In the white regions, hydration fills microscale voids and smooths surface irregularities, effectively matching the refractive index of the periostracum and increasing light transmittance. While camouflage in terrestrial gastropods was previously considered static, our findings reveal an environmentally responsive system that dynamically adjusts to ambient moisture. This mechanism parallels strategies observed in certain insects, and is consistent with functional convergent evolution. Furthermore, the water-responsive thin-film structure of the snail shell provides a biological blueprint for the development of bioinspired smart materials, such as humidity-sensitive coatings and adaptive optical technologies.
Climate warming is increasingly reshaping the population dynamics of Oncomelania hupensis, the sole intermediate host of Schistosoma japonicum in China. Investigating the response of O. hupensis to climate warming is crucial for guiding targeted and precise interventions against these snails, thereby advancing the progress towards schistosomiasis elimination and sustaining the achievement of elimination in China. This study aims to quantify the multi-scale responses of O. hupensis to climate warming. We conducted a 45-day temperature-controlled laboratory experiment with adult O. hupensis from Hubei Gongan County, China, exposing snails to the Low Temp group (5 ˚C), the Control group (25 ˚C), and the High Temp group (30 ˚C) to assess body-size-dependent survival. We then analyzed O. hupensis surveillance data from 1990 to 2022 across 12 provinces in China (34,554 villages), linked to climate data downloaded from ERA5-Land. We developed sliding-window models to examine climate exposure across life stages to assess population-level responses to climate warming, and used general linear mixed-effects models to explore the environmental factors influencing climate responses (geographic variables: latitude, longitude, altitude, land use, historical climate variability). Model performance was evaluated to identify the best predictive models, which were subsequently used to project future O. hupensis density under the SSP1-2.6, SSP2-4.5, and SSP5-8.5 scenarios. We further sampled 240 wild O. hupensis and measured their body sizes to validate the previous results inversely. At the individual level, we observed that larger snails had a higher survival rate at both the Low Temp group (91.6%, 95% CI 85.8-97.7%) and High Temp group (45.7%, 95% CI 31.9-65.6%) compared with the control group (76.5%, 95% CI 58.7-99.5%). At the population level, O. hupensis density closely tracks climate warming, with 92.0% of populations showing positive temperature sensitivity. Exposure during the coldest (January: 2.7 × 10-2, 95% CI 3 × 10-3-5.1 × 10-2; February: 3.3 × 10-2, 95% CI 1.1 × 10-2-5.6 × 10-2) and breeding seasons (April: 2.4 × 10-2, 95% CI 6 × 10-3-4.3 × 10-2; September-October: 3.5 × 10-2, 95% CI 2 × 10-3-6.8 × 10-2) had a greater influence on O. hupensis density under climate warming. O. hupensis in waterbody-dominated areas showed the largest density growth rates (ß = 1.6 × 10-1, 95% CI 1.1 × 10-1-2.2 × 10-1), whereas crop populations were the most sensitive to land cover, a 1% increase in crop cover was associated with a 0.2 increase in population density. At the ecosystem level, only 19.0-24.6% of populations were expected to benefit from climate change by 2100, and these benefiting populations were concentrated in regions where sampled wild snails had a mean body size of 8.2 mm. Cropland will account for 72.0% of populations benefiting from climate warming, compared with 17.2% in forests and 8.3% in impervious-dominated areas. The O. hupensis populations grow under climate warming but are regulated by land-use types. To mitigate the impacts of climate warming and land-use on snails, surveillance and integrated interventions should be strengthened through multi-sector collaboration.
Schistosomiasis is an important snail-borne neglected tropical disease, and detecting infected snails is a priority for its control and elimination. However, conventional parasitological methods, such as crushed snails and cercarial shedding, have limited sensitivity. In this study, we developed a novel loop-mediated isothermal amplification (LAMP) assay (smND1-LAMP) targeting the mitochondrial NADH dehydrogenase subunit 1 (ND1) gene of Schistosoma mansoni. The assay was optimized at 65 °C for 1 h and demonstrated a detection limit of one copy of the pUC57/smND1 recombinant plasmid. Its diagnostic performance was evaluated using laboratory-infected Biomphalaria snails and field-collected samples from Zimbabwe and Burkina Faso, and compared with microscopy, conventional PCR and SYBR Green real-time PCR (SGPCR). In laboratory experiments, smND1-LAMP achieved 100% specificity and 75% sensitivity, outperforming microscopy and showing a similar performance to SGPCR. In field surveys, smND1-LAMP detected a higher positive rate (25.9%) than conventional PCR (22.2%) in Burkina Faso, while microscopy failed to identify any positive snails. Both molecular methods identified infections that were missed by parasitological techniques. These findings demonstrate that smND1-LAMP assay is a sensitive, specific, and field-applicable tool for detecting S. mansoni infection in snails. It provides an effective alternative for routine surveillance and early warning of changing schistosomiasis endemicity.
The socioeconomic consequences of schistosomiasis have forced the integration of control strategies. Currently, all control efforts have tended to involve the control of snail intermediate hosts. However, the integration of snail control into the general schistosomiasis control strategy has not yet been effective in Burkina Faso. While snail occurrence data have been collected intermittently since the last systematic assessment in 1980, there has been no recent synthesis of the distribution of intermediate host snails in Burkina Faso. The aim of this study was to integrate historical and recent datasets to assess temporal shifts in species distribution, identify key climatic drivers, and produce spatially explicit risk maps to support targeted control strategies in Burkina Faso. Snail occurrence data were compiled for three time periods: 1980, 2018, and 2021. Data from 1980 and 2018 were obtained through a comprehensive literature review, while field sampling was conducted in 2021 in two basins: the Mouhoun basin and the Nakanbé basin. The Maximum Entropy (Maxent) modeling approach was used to predict changes in species distributions over time by integrating occurrence records from each period with relevant environmental variables. Model performance was evaluated using the Area Under the Curve (AUC) of the Receiver Operating Characteristic (ROC) curve and the Boyce index. The contribution of each environmental variable was assessed using a jackknife test. Five schistosomiasis intermediate hosts were collected: Bulinus truncatus, Bulinus forskalii, Bulinus senegalensis, Bulinus globosus, and Biomphalaria pfeifferi. The number of snail intermediate host species for schistosomes did not significantly change between 1980 and 2021. Except for B. umbilicatus, the results show that the two basins host almost the same species of snail intermediate host of schistosomes. The rivers, reservoirs, and irrigated plains provide favorable conditions for the occurrence of all species of snail intermediate hosts. The area under the curve (AUC) of the selected variables ranged from 0.877 to 0.985. Except for B. globosus, the Boyce index ranged from 0.6 to 0.924. Spatial distribution modeling indicated that the western part of the Volta Basin is more suitable for the occurrence of schistosome intermediate host snails. Schistosomiasis intermediate host snails are common in the Nakanbé and Mouhoun basins, where suitable habitats are widespread. The Maxent model successfully identified areas with high environmental suitability for these intermediate host snails. This study integrated historical and recent occurrence data to assess temporal changes in intermediate host snail distribution, identify key climatic drivers of distribution shifts over the past 40 years, and highlight priority areas for targeted snail control in Burkina Faso.
Urban ecological reserves in Buenos Aires city (Argentina) were intended as spaces for outdoor recreation, preservation of natural environments and protection of native species. Reserva Ecológica Costanera Sur (RECS) and Reserva Ecológica Ciudad Universitaria Costanera Norte (RECUCN) are located on the right bank of the Río de la Plata estuary. In view of the repeated appearance of non-native land snails and slugs in Argentina during the last four decades, we wanted to know to what extent the terrestrial gastropod faunas of these two reserves were composed of native or non-native species. As RECS is larger than RECUCN, we also tested the hypothesis that abundance, species richness and diversity would be higher in the former than in the latter. Fifty-two and 25 sites were sampled for terrestrial snails and slugs in RECS and RECUCN, respectively. Land gastropod species richness was similar in RECS (14 species) and RECUCN (12 species). Non-native gastropods were much more diverse and overwhelmingly more abundant than native ones. The terrestrial gastropod fauna is dominated by non-native snails and slugs (98.4% non-native individuals vs. 1.6% native in RECS, 97.5% vs. 2.5% in RECUCN), most of them never previously reported from these reserves. More than 78% of the individuals found in RECUCN belonged to the non-native snail Vallonia pulchella, which was the species that most contributed to the dissimilarity between reserves. This study shows that so far, urban ecological reserves in Buenos Aires city are sites where mainly exotic rather than native terrestrial molluscs are being preserved. The dominance of nonnative species in these urban ecological reserves endorses the pervasive advance of synanthropic species in urban land snail assemblages already documented for other biogeographic regions.
The genus Tylodelphys comprises globally distributed digenean flukes with complex life cycles involving freshwater snails, fish or amphibians, and piscivorous birds. However, species delimitation remains challenging due to morphological convergence among larval stages and incomplete resolution of the life cycles. This study conducted a global meta-analysis of mitochondrial cytochrome c oxidase subunit I (cox1) sequences retrieved from GenBank and BOLD Systems to assess genetic diversity, phylogenetic relationships, and life-cycle linkage within the genus, and to explore the influence of continental isolation or host-driven diversification. Analyses of 496 sequences revealed substantial genetic diversity and recovered 29 well-supported lineages, indicating widespread cryptic speciation. Despite this diversity, only four species (Tylodelphys mashonense, Tylodelphys circibuteonis, Tylodelphys clavata, and Tylodelphys excavata) have life cycles supported by molecular data in databases that link larval and adult stages. Phylogeographic patterns showed strong continental structuring, with no evidence of haplotype sharing among regions, suggesting long-term isolation, host-associated diversification, or sampling bias. Conserved use of planorbid snails as first intermediate hosts and consistent metacercarial tissue tropism indicate evolutionary stability in key life-history traits. In contrast, variation in the second intermediate and definitive hosts suggests ecological flexibility and potential host-switching. Overall, these findings highlight a pronounced gap between cox1-barcoded species and biologically validated species and demonstrate the need to increase barcoding effort in Tylodelphys studies. This study recommends that future studies employ geographic collaborations and integrative approaches that combine multilocus data with targeted life-cycle studies to improve species delimitation and phylogeography and to clarify transmission dynamics in freshwater ecosystems.
This study assessed toxicological effects of anthropogenic pollution in Las Catonas stream (Reconquista River basin, Argentina) on the freshwater gastropod Biomphalaria straminea and water physicochemical parameters including Cd, Cu, Pb, Zn and the pesticides chlorpyrifos and glyphosate detection. Water samples were collected (April 2022 and 2023) downstream of industrial treatment facilities and peri urban farms and acute and subchronic bioassays were performed exposing B. straminea snails to the samples. A multibiomarker approach was employed, including biochemical and reproductive responses. Although most physicochemical variables were within guideline values, fluctuations in pH, dissolved oxygen, ammonium and nitrites levels were noted. Metals and pesticides were not above the detection limits (Cu and Zn: 50 μgL1; Cd and Pb: 0.1 μgL1; chlorpyrifos and glyphosate: 0.01 μgL1). Water samples from both sites elicited some variable biological responses, indicating site and year dependent alterations, so longer term and seasonal assessments are required to obtain conclusions more robust. The reduction in hatching success in snails exposed to water samples reinforces the importance of incorporating early life stages of B. straminea into ecotoxicological water assessments.
Cercarial dermatitis is an important occupational health problem among rice farmers in Assam and other parts of India. We surveyed 1657 paddy farmers from sixteen villages across four districts of Assam, Northeast India, to determine the prevalence of cercarial dermatitis. Of these, 555 (33.5%) reported dermatitis during the preceding three months, and a subset of affected farmers from Barpeta district showed a high proportion of moderate-to-severe disease, often complicated by secondary bacterial infection. Snail surveys were conducted in thirteen villages across eight districts. Examination of 13,309 freshwater snails representing six species identified Indoplanorbis exustus as the only intermediate host shedding Schistosome cercariae, with an infection prevalence of 6.3% among I. exustus. Experimental infections in mice yielded adult worms that were used for morphological, molecular, immunological, and proteomic studies. Molecular identification based on partial 28S rDNA sequencing confirmed the Assamese isolates as Schistosoma spindale, and phylogenetic analysis placed them firmly within the S. spindale clade together with reference sequences from Nepal and Sri Lanka. SDS-PAGE and immunoblotting identified four dominant immunoreactive antigens of approximately 25, 38, 60, and 100 kDa. Two-dimensional PAGE coupled with MALDI-TOF/TOF MS identified several conserved proteins, including paramyosin, tropomyosin, actin, and heat shock protein 70, based on best database matches. ELISA developed using adult worm antigen showed high diagnostic performance (96% sensitivity and 100% specificity) and outperformed the cercarial antigen-based ELISA. This integrated epidemiological, malacological, molecular, proteomic, and immunological investigation provides comprehensive insight into S. spindale the causative agent of cercarial dermatitis in Assam. The findings highlight the need to recognize cercarial dermatitis as a neglected occupational and zoonotic disease within a One Health framework.
All organisms need protection against infection. Bacteria are often primarily seen as infectious agents, but they also need protection against bacterial viruses, so-called bacteriophages. To this end, bacteria have developed very complex defense systems, including apoptosis-like mechanisms, restriction enzymes, and even adaptive-type mechanisms involving immunological memory of immune responses through a system called CRISPR-Cas. An earlier dominating view was that adaptive immunity in eukaryotes only exists in jawed vertebrates, as their immune system includes the classical and highly variable immunoglobulins (Igs) and T-cell receptors (TCR). However, other types of variable molecules, which may be involved in immunity, have also been identified in insects, snails, lancelets, plants, sea urchins, and jawless fishes. Interestingly, fishes without jaws, such as the hagfish and lamprey, have a very complex adaptive immunity built on lymphocyte-like cells and variable lymphocyte receptors (VLRs). Notably, the variability of these VLRs has been estimated to be in the same range as Igs and T-cell receptors. This illustrates that very diverse strategies have been used to create an adaptive immune system in different organisms, indicating potent convergent evolution. Vertebrate immunity includes both adaptive and non-adaptive components, which work closely together to form a very powerful immune system for defense against infections. In contrast to adaptive immunity, the majority of the non-adaptive innate defense mechanisms, such as pattern recognition receptors, antimicrobial peptides (AMPs), iron-binding proteins, the complement system, and lysozymes, can be traced back to early eukaryotes. Immunity of invertebrates seems to rely almost entirely on innate defense mechanisms, while the presence of complex adaptive mechanisms in invertebrates, such as the VLRs of jawless fishes and Igs and TCR of jawed vertebrates, is questionable. This review summarizes old and recent findings of importance for our understanding of how immunity became an integrated part of all living organisms, from bacteria to humans, and the very different strategies that different organisms use in the protection against infection.
The Floc & Lock (F&L) technique is a promising approach for mitigating eutrophication. However, gaps remain regarding its effects on benthic fauna directly exposed to the applied materials. In this study, we evaluated the effects of polyaluminium chloride (PAC) and lanthanum-modified bentonite (LMB) on the activity of the enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and trypsin in the snail Melanoides tuberculata (Müller, 1774) and larvae of the insect Chironomus sancticaroli (Strixino & Strixino, 1981). We tested the hypothesis that exposure to PAC and/or LMB alters the activity of these enzymes in benthic macroinvertebrates in a species-dependent manner. Under in vivo experimental conditions, enzymatic responses were assessed after 72 h of exposure to the following treatments: control (no materials), + PAC, + LMB, and the combined treatment + LMB and PAC. In addition, in vitro assays for enzymatic inhibition were conducted. AChE was strongly inhibited in larvae, with reductions exceeding 90% in treatments containing PAC, whereas M. tuberculata showed a mean reduction of approximately 50%. BChE exhibited contrasting responses: marked reduction in larvae under + LMB and PAC and increased activity in snails exposed to PAC, suggesting a greater capacity for metabolic compensation in M. tuberculata. Trypsin showed a dual response, with in vivo enhancement under combined treatment and direct in vitro inhibition, indicating compensatory digestive adjustments. These results demonstrate that the application of the F&L technique can induce significant species-dependent alterations in the enzymatic biomarkers of benthic macroinvertebrates, underscoring the need to incorporate these biomarkers into ecological risk assessments for F&L applications in eutrophic reservoirs.
Marine-to-freshwater transitions are frequent in neritid snails. However, phylogenetic relationships among genera remain incompletely resolved, largely because many lineages lack mitogenome data and public records sometimes contain misidentified sequences. Here we assembled complete mitochondrial genomes for three Neritidae species from China-the seagrass specialist Smaragdia rangiana, the brackish-water Neripteron pileolus, and the brackish-to-freshwater Vittina cumingiana-using genome skimming. The mitogenomes range from 15.68 to 15.82 kb, each containing the typical 37 genes and a major non-coding region. All three mitogenomes are AT-rich (62.8%-66.0%) with negative AT-skews and positive GC-skews. Codon usage analysis revealed that UCU (Serine) exhibits the highest relative synonymous codon usage across all three species, while nucleotide diversity among Neritidae PCGs is highest at third codon positions. Phylogenetic analyses were conducted using multiple datasets (13PCGs123, 13PCGs12, 13PCGsAA, with/without rRNA genes) under maximum likelihood and Bayesian inference, with TreeSpace analysis revealing three distinct topological clusters. All trees recovered the two-subfamily framework (Neritinae vs. Neritininae). Within Neritininae, S. rangiana clustered with other Smaragdia sequences, N. pileolus grouped with Neripteron violaceum, and V. cumingiana formed a lineage sister to Vitta and Puperita. Several public sequences showed discordant placements consistent with historical synonymy or mislabeling, underscoring the need for voucher-supported identifications. These new mitogenomes improve taxon sampling for Neritidae and provide a foundation for revisiting habitat transitions with broader genomic data.