Outward potassium current in neurons of aestivated land snail Achatina fulica.

Aestivation and hibernation represent distinct forms of animal quiescence, characterized by physiological changes, including ion composition. Intracellular ion flows play a pivotal role in eliciting alterations in membrane potential and facilitating cellular communication, while outward K+ currents aid in the restitution and upkeep of the resting membrane potential. This study explores the relationship between inward and outward currents during aestivation in Achatina fulica snails. Specimens were collected near MSUBIT University in Shenzhen and divided into two groups. The first group was kept on a lattice diet, while the second one consisted of aestivating individuals, that were deprived of food and water until a cork-like structure sealed their shells. Recording of current from isolated neurons were conducted using the single-electrode voltage clamp mode with an AxoPatch 200B amplifier. Electrophysiological recordings on pedal ganglia neurons revealed significant differences in the inactivation processes of the Ia and Ikdr components. Alterations in the Ikdr component may inhibit pacemaker activity in pedal ganglion neurons, potentially contributing to locomotion cessation in aestivated animals. The KS current remains unaffected during aestivation. Changes in slow K+ current components could disrupt the resting membrane potential, possibly leading to cell depolarization and influx of Ca2+ and Na+ ions, impacting cell homeostasis. Thus, maintaining the constancy of outward K+ current is essential for cell stability.

Mitochondrial genome of the fluke pond snail, Austropeplea cf. brazieri (Gastropoda: Lymnaeidae).

BACKGROUND: Lymnaeid snails of the genus Austropeplea are an important vector of the liver fluke (Fasciola hepatica), contributing to livestock production losses in Australia and New Zealand. However, the species status within Austropeplea is ambiguous due to heavy reliance on morphological analysis and a relative lack of genetic data. This study aimed to characterise the mitochondrial genome of A. cf. brazieri, an intermediate host of liver fluke in eastern Victoria. METHODS: The mitochondrial genome was assembled and annotated from a combination of second- and third-generation sequencing data. For comparative purposes, we performed phylogenetic analyses of the concatenated nucleotide sequences of the mitochondrial protein-coding genes, cytochrome c oxidase subunit 1 and 16S genes. RESULTS: The assembled mt genome was 13,757 base pairs and comprised 37 genes, including 13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The mt genome length, gene order and nucleotide compositions were similar to related species of lymnaeids. Phylogenetic analyses of the mt nucleotide sequences placed A. cf. brazieri within the same clade as Orientogalba ollula with strong statistical supports. Phylogenies of the cox1 and 16S mt sequences were constructed due to the wide availability of these sequences representing the lymnaeid taxa. As expected in both these phylogenies, A. cf. brazieri clustered with other Austropeplea sequences, but the nodal supports were low. CONCLUSIONS: The representative mt genome of A. cf. brazieri should provide a useful resource for future molecular, epidemiology and parasitological studies of this socio-economically important lymnaeid species.

Assessment of the influence of levees along Yangtze River on Oncomelania hupensis, the intermediate host of Schistosoma japonicum.

BACKGROUND: Oncomelania hupensis is the exclusive intermediate host of Schistosoma japonicum in China. Snail control is an essential component of schistosomiasis elimination programme. With 70 years of continuous efforts, the range of O. hupensis had reduced significantly, but slowed down in last decades. A large number of levees against flooding were constructed along Yangtze River and its affiliated lakes in the middle and lower reaches, which influenced the hydrology and ecology in the alluvial plains. The purpose of this study was to assess the impact of levees on the distribution of O. hupensis in the middle and lower reaches of the Yangtze River. METHODS: The snail habitats were digitalised by hand-held GPS system. The years for discovery and elimination of snail habitats were extracted from historical records. The accumulated snail-infested range for each habitat was calculated on the basis of annual reports. The current distribution of O. hupensis was determined by systematic and environmental sampling. The geographical distribution of levees was obtained from satellite imagery. To assess the impact of levees, the data pertaining to O. hupensis were divided into two parts: inside and outside the Yangtze River. Joinpoint regression was utilised to divide the study time span and further characterise the regression in each period. The 5-year-period moving averages of eliminated area infested by snails were calculated for the habitats inside and outside Yangtze River. The moving routes of corresponding geographical median centres were simulated in ArcGIS. Hotspot analysis was used to determine the areas with statistical significance clustering of O. hupensis density. RESULTS: Three periods were identified according to Joinpoint regression both inside and outside Yangtze River. The area infested by O. hupensis increased in the first two periods. It decreased rapidly outside Yangtze River year over year after 1970, while that inside the Yangtze River did not change significantly. Furthermore, the latter was significantly higher than the former. It was observed that the present density of O. hupensis inside Yangtze River was lower than outside the Yangtze River. The median centre for eliminated ranges inside Yangtze River wavered between the east (lower reach) and the west (middle reach). In contrast, the median centre for eliminated ranges continuously moved from the east to the west. CONCLUSIONS: Our findings indicated that the levees had a considerable negative impact on the distribution of O. hupensis outside Yangtze River. Some hotspots observed in the irrigation areas need a sluice system at the inlet of branch for snail control. The major distribution of O. hupensis located in Hubei might be caused by severe waterlogging. The intensive surveillance should be implemented there. The biggest two freshwater lakes, the major endemic regions historically, were identified as cold spots. The long-term impact of Three Gorges Dam on the distribution of O. hupensis in the lakes should be monitored and evaluated.

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

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

A geospatial analysis of local intermediate snail host distributions provides insight into schistosomiasis risk within under-sampled areas of southern Lake Malawi.

BACKGROUND: Along the southern shoreline of Lake Malawi, the incidence of schistosomiasis is increasing with snails of the genera Bulinus and Biomphalaria transmitting urogenital and intestinal schistosomiasis, respectively. Since the underlying distribution of snails is partially known, often being focal, developing pragmatic spatial models that interpolate snail information across under-sampled regions is required to understand and assess current and future risk of schistosomiasis. METHODS: A secondary geospatial analysis of recently collected malacological and environmental survey data was undertaken. Using a Bayesian Poisson latent Gaussian process model, abundance data were fitted for Bulinus and Biomphalaria. Interpolating the abundance of snails along the shoreline (given their relative distance along the shoreline) was achieved by smoothing, using extracted environmental rainfall, land surface temperature (LST), evapotranspiration, normalised difference vegetation index (NDVI) and soil type covariate data for all predicted locations. Our adopted model used a combination of two-dimensional (2D) and one dimensional (1D) mapping. RESULTS: A significant association between normalised difference vegetation index (NDVI) and abundance of Bulinus spp. was detected (log risk ratio - 0.83, 95% CrI - 1.57, - 0.09). A qualitatively similar association was found between NDVI and Biomphalaria sp. but was not statistically significant (log risk ratio - 1.42, 95% CrI - 3.09, 0.10). Analyses of all other environmental data were considered non-significant. CONCLUSIONS: The spatial range in which interpolation of snail distributions is possible appears < 10km owing to fine-scale biotic and abiotic heterogeneities. The forthcoming challenge is to refine geospatial sampling frameworks with future opportunities to map schistosomiasis within actual or predicted snail distributions. In so doing, this would better reveal local environmental transmission possibilities.

Climate and urbanization drive changes in the habitat suitability of Schistosoma mansoni competent snails in Brazil.

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

How to Overcome a Snail? Identification of Putative Neurotoxins of Snail-Feeding Firefly Larvae (Coleoptera: Lampyridae, Lampyris noctiluca).

The larvae of some lampyrid beetles are highly specialized predators of snails. They have been observed to climb on the shells of their prey and use this exposed position to bite and inject secretions potentially originating from the midgut. Besides serving the purpose of extra-oral digestion (EOD), injected compounds also seem to have a paralyzing effect. Up to now, the toxins causing this paralyzing activity have not been identified. In the current study, we provide a first compositional analysis of the midgut secretion from lampyrid larvae, with a focus on identifying putative neurotoxins causing the observed paralyzing effect. For this purpose, we utilized a combined proteo-transcriptomic approach to characterize the compounds present in the midgut secretion of larval stages of Lampyris noctiluca. In terms of the absolute numbers of identified compounds, the midgut secretion is dominated by hydrolyzing enzymes comprising peptidases, carboxylesterases, and glycosidases. However, when considering expression levels, a few rather short cysteine-rich peptides exceed all other compounds. Some of these compounds show moderate similarity to putative neurotoxins identified in the venom of other arthropods and could be responsible for paralyzing effects. In addition to these potential toxins, we provide a list of peptides typical of the midgut secretion of L. noctiluca, supplemented by the corresponding precursor sequences.

Odd-Paired is Involved in Morphological Divergence of Snail-Feeding Beetles.

Body shape and size diversity and their evolutionary rates correlate with species richness at the macroevolutionary scale. However, the molecular genetic mechanisms underlying the morphological diversification across related species are poorly understood. In beetles, which account for one-fourth of the known species, adaptation to different trophic niches through morphological diversification appears to have contributed to species radiation. Here, we explored the key genes for the morphological divergence of the slender to stout body shape related to divergent feeding methods on large to small snails within the genus Carabus. We show that the zinc-finger transcription factor encoded by odd-paired (opa) controls morphological variation in the snail-feeding ground beetle Carabus blaptoides. Specifically, opa was identified as the gene underlying the slender to stout morphological difference between subspecies through genetic mapping and functional analysis via gene knockdown. Further analyses revealed that changes in opa cis-regulatory sequences likely contributed to the differences in body shape and size between C. blaptoides subspecies. Among opa cis-regulatory sequences, single nucleotide polymorphisms on the transcription factor binding sites may be associated with the morphological differences between C. blaptoides subspecies. opa was highly conserved in a wide range of taxa, especially in beetles. Therefore, opa may play an important role in adaptive morphological divergence in beetles.

Research on the Mechanism of Metaldehyde on Pomacea canaliculata.

Golden apple snail (Pomacea canaliculata), a major alien invasive organism in China, affects food production and poses a threat to human health. Metaldehyde is a highly effective, commonly used snail killer with low toxicity. Virulence determination, tissue section, iTRAQ and RNA interference were used to systematically study the toxicity of metaldehyde on P. canaliculata. The molluscicidal activity tests showed that metaldehyde exhibits strong toxicity against P. canaliculata. Physiological and biochemical data indicate that metaldehyde can cause damage to the gills, liver, pancreas, and kidneys of snails, also reduce the oxygen consumption rate and ammonia excretion rate of golden apple snails, and cause neurological diseases. The proteome of the gill region of the golden apple snail after exposure to metaldehyde was analyzed by using iTRAQ technology. A total of 360 differential proteins were identified, and four target proteins were screened, namely, alpha-protein kinase 1 (ALPK1), cubilin (CUBN), sodium- and chloride-dependent GABA transporter 2 (GAT2), and acetylcholinesterase (AChE). RNAi was used to target the four proteins. After the ALPK1 and CUBN protein genes were interfered with by metaldehyde treatment, it was found that the mortality rate of the golden apple snail significantly increased. However, interference of GAT2 and AChE protein genes by metaldehyde led to no significant change in the mortality rates of the snails. The histopathological observation of the gill showed that the rate of cilia shedding in the gill decreased after the interference of ALPK1 and CUBN protein genes.

Bioaccumulation of trace metals in edible terrestrial snails, Theba pisana and Otala spp., in a dumpsite area in Morocco and assessment of human health risks for consumers.

This study assessed the bioaccumulation patterns of five trace metals (Cd, Cr, Co, Cu, and Zn) in two edible snail species, Theba pisana and Otala spp., collected from a dumpsite in Safi City, Morocco. The results indicated that bioaccumulation might be species-specific, as metal concentration profiles varied between the two snail species. Additionally, higher metal levels in the dumpsite snails confirmed their potential as bioindicators of trace metal pollution in terrestrial environments. However, the distribution of trace elements within the edible parts of the snails showed marked unevenness, with the viscera accumulating more metals than the foot. The study also evaluated the potential human health risks associated with consuming these snails. Trace metal levels in the edible parts exceeded most international safety thresholds. The estimated daily intakes (EDIs) of trace metals through snail consumption were below the provisional tolerable daily intakes (PTDIs) for both children and adults, suggesting that daily consumption is generally safe. Nonetheless, the hazard index (HI) indicated that children might face health risks from long-term consumption of contaminated snails (HI > 1), while adults are less likely to experience such complications (HI < 1). The total target carcinogenic risk (TTCR) was below 1E-04 for both children and adults, indicating negligible to acceptable carcinogenic risks for all consumer groups.

Systematics and life cycles of four avian schistosomatids from Southern Cone of South America.

Relative to the numerous studies focused on mammalian schistosomes, fewer include avian schistosomatids particularly in the southern hemisphere. This is changing and current research emerging from the Neotropics shows a remarkable diversity of endemic taxa. To contribute to this effort, nine ducks (Spatula cyanoptera, S.versicolor, Netta peposaca), 12 swans (Cygnus melancoryphus) and 1,400 Physa spp. snails from Chile and Argentina were collected for adults and larval schistosomatids, respectively. Isolated schistosomatids were preserved for morphological and molecular analyses (28S and COI genes). Four different schistosomatid taxa were retrieved from birds: Trichobilharzia sp. in N. peposaca and S. cyanoptera that formed a clade; S.cyanoptera and S. versicolor hosted Trichobilharzia querquedulae; Cygnus melancoryphus hosted the nasal schistosomatid, Nasusbilharzia melancorhypha; and one visceral, Schistosomatidae gen. sp., which formed a clade with furcocercariae from Argentina and Chile from previous work. Of the physid snails, only one from Argentina had schistosomatid furcocercariae that based on molecular analyses grouped with T. querquedulae. This study represents the first description of adult schistosomatids from Chile as well as the elucidation of the life cycles of N.melancorhypha and T. querquedulae in Chile and Neotropics, respectively. Without well-preserved adults, the putative new genus Schistosomatidae gen. sp. could not be described, but its life cycle involves Chilina spp. and C. melancoryphus. Scanning electron microscopy of T. querquedulae revealed additional, undescribed morphological traits, highlighting its diagnostic importance. Authors stress the need for additional surveys of avian schistosomatids from the Neotropics to better understand their evolutionary history.

Screening the Efficacy and Safety of Molluscicides from Three Leaf Extracts of Chimonanthus against the Invasive Apple Snail, Pomacea canaliculata.

Pomacea canaliculata, the invasive snail, is a host of the parasitic nematode Angiostrongylus cantonensis, which has adverse effects on the agriculture system and human health. This work evaluated the molluscicidal activity of petroleum ether extracts (PEEs) from three species of Chimonanthus against the snail P. canaliculate. Pcp (PEE of C. praecox) showed the most effective molluscicide activity. Sixty-one compounds were identified by GC-MS and the main components were terpenoids and fatty acids. The half-lethal concentration (LC50) of Pcp at 24 h (0.27 mg/mL) and 48 h (0.19 mg/mL) was used to evaluate the biochemical alterations in snail tissue. These sublethal concentrations caused the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity to increase, while acetylcholinesterase (AChE) activity decreased. Also, under LC50 treatment, several histological changes were observed in the hepatopancreas and foot of the snail compared with the control group. Moreover, the toxic test in rice demonstrated that Pcp has low toxicity. These results suggest that Pcp could be developed as an effective molluscicide for P. canaliculata control.

Genetic diversity and population structure of Physella acuta (Gastropoda: Physidae) in Thailand using mitochondrial gene markers: COI and 16S rDNA.

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

[Trends in Oncomelania hupensis distribution in Wuhan City from 2003 to 2022 based on the Joinpoint regression model].

OBJECTIVE: To analyze the trends in Oncomelania hupensis distribution in Wuhan City, Hubei Province from 2003 to 2022, so as to provide insights into precision schistosomiasis control. METHODS: Data pertaining to O. hupensis snail survey in Wuhan City from 2003 to 2022 were collected. The trends in the proportion of areas with snail habitats, actual area with snail habitats, mean density of living snails and prevalence of Schistosoma japonicum infection in snails were evaluated in schistosomiasis-endemic areas of Wuhan City from 2003 to 2022 with the slope of trend curve (ß), annual percent change (APC) and average annual percent change (AAPC) using a Joinpoint regression model. RESULTS: During the period from 2003 through 2022, there were two turning points for the proportion of areas with snail habitats in Wuhan City in 2005 and 2015, with a rise during the period from 2003 to 2005 (ß1 = 5.93, t = 1.280, P > 0.05), a decline from 2005 to 2015 (ß2 = -0.88, t = -2.074, P > 0.05) and a rise from 2015 to 2022 (ß3 = 1.46, t = -2.356, P < 0.05). During the period from 2003 through 2022, there were two turning points for the proportion of areas with snail habitats in islet endemic areas of Wuhan City in 2006 and 2015, with no significant differences in the trends from 2003 to 2006 (ß1 = 4.64, t = 1.888, P > 0.05) or from 2006 to 2015 (ß2 = -1.45, t = -2.143, P > 0.05), and with a tendency towards a rise from 2015 to 2022 (ß3 = 2.04, t = -3.100, P < 0.05). During the period from 2003 through 2022, there were two turning points for the proportion of areas with snail habitats in inner embankment endemic areas of Wuhan City in 2012 and 2020, with a tendency towards a decline from 2003 to 2012 (ß1 = -0.39, t = -4.608, P < 0.05) and with no significant differences in the trends from 2012 to 2020 (ß2 = 0.03, t = 0.245, P > 0.05) and from 2020 to 2022 (ß3 = 1.38, t = 1.479, P > 0.05). During the period from 2003 to 2022, the actual area with snail habitats all appeared a tendency towards a decline in Wuhan City, and in islet and inner embankment endemic areas of Wuhan City from 2003 to 2022 (AAPC = -2.39%, -5.75% and -2.35%, all P values < 0.05). The mean density of living snails reduced from 0.087 snails/0.1 m2 in 2003 to 0.027 snails/0.1 m2 in 2022 in Wuhan City, with a significant difference in the tendency towards the decline (APC = AAPC = -11.47%, P < 0.05). The annual mean decline rate of the mean density of living snails was 17.36% in outside embankment endemic areas of Wuhan City from 2003 to 2022 (APC = AAPC = -17.36%, P < 0.05), and there was no significant difference in the trends in the mean density of living snails in islet endemic areas of Wuhan City from 2003 to 2022 (APC = AAPC = -0.97%, P > 0.05). In addition, the prevalence of S. japonicum infection in snails appeared a tendency towards a decline in Wuhan City from 2003 to 2022 (APC = AAPC = -12.45%, P < 0.05). CONCLUSIONS: The proportion of areas with snail habitats, actual area with snail habitats, mean density of living snails and prevalence of S. japonicum infection in snails all appeared a tendency towards a decline in Wuhan City from 2003 to 2022. Intensified snail control, modification of snail habitats, shrinking of areas with snails and implementation of grazing prohibition in snail-infested settings are required, in order to facilitate the progress towards schistosomiasis elimination in Wuhan City.

[Soil microorganisms and physicochemical properties in marshlands along the Yangtze River basin at different types of land use and their effects on distribution of Oncomelania hupensis snails].

OBJECTIVE: To investigating the microbial communities and physicochemical properties of soil and distribution of Oncomelania hupensis snails in marshlands along the Yangtze River basin at different types of land use, and to examine the effects of soil microorganisms and physicochemical properties on snail distribution, so as to provide insights into snail control and schistosomiasis prevention in marshland along the Yangtze River basin. METHODS: Marshlands with four types of land use were selected along the Yangtze River basin on April 2021, including poplar forest-crops integrated planting, reed areas, agricultural cultivation lands and ditches. The distribution of snails and physicochemical properties of soil were investigated in marshlands with different types of land use, and the V3 to V4 regions of the bacterial 16S ribosomal RNA (16S rRNA) gene, fungal internal transcribed spacer-1 (ITS1) gene and algal ribulose-bisphosphate carboxylase (rbcL) gene in soils were subjected to high-throughput sequencing. The occurrence of frames with living snails and density of living snails were compared in marshland with different types of land use. The associations of soil microorganisms and physicochemical properties with the density of living snails were examined using Pearson correlation analysis, and the contributions of soil microorganisms and physicochemical properties to the density of living snails were evaluated using variance partitioning analysis. RESULTS: In marshlands with four types of land use, the greatest occurrence of frames with living snails [(4.94 ± 2.14)%] and density of living snails [(0.070 ± 0.026) snails/0.1 m2] were seen in ditches, and the lowest were found in [(1.23 ± 1.23)%] agricultural cultivation lands [(0.016 ± 0.019) snails/0.1 m2]. A total of 2 phyla, 5 classes, 8 orders, 9 families and 11 genera of algae were detected in soils at four types of land use, with Chlorophyta as the dominant phylum and Pseudoneochloris as the dominant genus. A total of 44 phyla, 134 classes, 281 orders, 338 families and 516 genera of bacteria were detected in soils at four types of land use, with Proteobacteria and Acidobacteriota as the dominant phyla and uncultured Acidobacterium, MND1, Mitrospira, Haliangium and Sphingomonas as dominant genera. A total of 11 phyla, 41 classes, 108 orders, 223 families and 408 genera of fungi were detected in soils at four types of land use, with phyla Ascomycota, Basidiomycota and Mortierellomycota presenting high relative abundances and genera Cladorrhinum, Mortierella and Humicola presenting high relative abundances. Pearson correlation analysis revealed that the density of living snails correlated negatively with the relative abundance of Proteobacteria (r = -0.965, P < 0.05) and soil electronic conductivity (r = -0.962, P < 0.05) and positively with soil moisture (r = 0.951, P < 0.05). Variance partitioning analysis demonstrated that the physicochemical properties and microorganisms of soil contributed 69% and 10% to the density of living snails, respectively. CONCLUSIONS: The diversity of microbial communities varies in soils at different types of land use in marshland along the Yangtze River basin, and the physicochemical properties and microorganisms of soils may affect the distribution of O. hupensis snails.

[Trends in the distribution of Oncomelania hupensis in forestlands in Songjiang District, Shanghai Municipality from 2009 to 2023].

OBJECTIVE: To investigate the changes in distribution of Oncomelania hupensis snails in forestlands in Songjiang District, Shanghai Municipality from 2009 to 2023, so as to provide insights into formulation of O. hupensis snail surveillance programs. METHODS: The reports on O. hupensis snail surveillance in Songjiang District, Shanghai Municipality from 2009 to 2023 were collected, and the snail surveillance data in forestlands were extracted. The trends in the proportion of areas with snails in forestlands in total areas with snails, occurrence of frames with living snails and density of living snails were evaluated using a Joinpoint regression model in Songjiang District from 2009 to 2023, and the annual percent change (APC) and average annual percent change (AAPC). RESULTS: A total of 40 sites with snails were found in forestlands in 14 administrative villages of 4 townships, Songjiang District, Shanghai Municipality from 2009 to 2023. A total of 39 065 frames were surveyed for snails in settings covering an area of 609 600 m2, and there were 6 084 frames with snails, covering 151 250 m2 snail habitats. A total of 22 210 snails were captured, with the highest density of 260.00 snails/0.1 m2, and 6 262 snails were dissected, with no Schistosoma japonicum infection identified in snails. The proportion of areas with snails in forestlands in total areas with snails appeared a tendency towards a rise in forestlands in Songjiang District, Shanghai Municipality from 2009 to 2023 (APC = AAPC = 24.9%, P > 0.05); however, there were no turning points in the trend curve, with the highest proportion seen in 2009 (53.81%), the lowest in 2011 and 2023 (both 0) and a mean proportion of 24.81%. The occurrence of frames with living snails appeared a tendency towards a rise from 2009 to 2023 (APC = AAPC = 41.5%, P > 0.05); however, there were no turning points in the trend curve, with the highest occurrence in 2009 (53.81%), the lowest in 2011 and 2013 (both 0), and the mean occurrence of 15.57%. In addition, the density of living snails appeared a tendency towards a rise from 2009 to 2023 (APC = AAPC = 55.0%, P > 0.05); however, there were no turning points in the trend curve, with the highest density in 2023 (0.96 snails/0.1 m2), the lowest in 2011 and 2013 (both 0), and a mean density of 0.57 snails/0.1 m2. CONCLUSIONS: The difficulty in O. hupensis snail control and risk of imported snails appeared a tendency towards a rise in forestlands in Songjiang District, Shanghai Municipality over years from 2009 to 2023. Supervision and assessment prior to seedling transplantation and intensified surveillance post-transplantation are recommended to reduce the risk of O. hupensis snail importation and spread.

[Effect of ground cage use on Oncomelania hupensis spread].

OBJECTIVE: To examine the effect of ground cage use on Oncomelania hupensis spread, so as to provide insights into precision snail control. METHODS: Twenty ground cages that were frequently used to capture rice field eels were purchased, including 11 packaging tape-made cages, 7 plastic cages and 2 nylon rope-made cages. The eel-capturing activity was mimicked, and 20 ground cages were assigned in settings with relatively high (1.00 snail/0.1 m2 and higher) and low snail densities (< 1.00 snail/0.1 m2) in Xindai Township, Pinghu City, Zhejiang Province during the period from 15 : 00 to 8 : 00 of the following day on April 13, 26 and 28. The numbers of snails carried by different types of ground cages were compared in settings with different types of snail densities using the rank-sum test. RESULTS: A total of 11 cage-times were assigned in settings with a high snail density, and a total of 77 snails were captured, with a mean number of 7 snails in each cage-time and 2.15 snails in 0.1 m2 ground cage. The mean numbers of snails carried by packaging tape-made and plastic cages were 2.47 snails/0.1 m2 cage and 0.37 snails/0.1 m2 cage, respectively. A total of 24 cage-times were assigned in settings with a low snail density, and a total of 8 snails were captured, with a mean number of 0.33 snails in each cage-time and 0.09 snails in 0.1 m2 ground cage. The mean numbers of snails carried by packaging tape-made cages were 0.12 snails/0.1 m2 cage; however, no snails were carried by plastic or nylon rope-made cages. The number of snails carried by ground cages was higher in settings with a high snail density than in settings with a low snail density (Z = -4.019, P < 0.01), and the number of snails carried by packaging tape-made cages was higher in settings with a high snail density than in settings with a low snail density (Z = -4.086, P < 0.01). No significant differences were found in the numbers of snails carried by different types of ground cages. CONCLUSIONS: The use of ground cage in snail habitats is a contributor to snail spread.

Assessment of the effects of 2,4-D-dichlorophenoxyacetic acid-based herbicide exposure in eggs and embryos of golden apple snails using OCT.

This study aimed to evaluate the effects of herbicide 2, 4-D-dichlorophenoxy acetic acid on golden apple snail eggs and embryos. Additionally, the study assessed the applicability of optical coherence tomography (OCT), a non-invasive depth cross-sectional microscopic imaging technique, as a novel method, to the best of our knowledge, for studying morphological changes in golden apple snail eggs and embryos, in comparison to the conventional approach of using white light microscopy. The study revealed that the herbicide 2,4-D-dichlorophenoxy acetic acid affected the hatchery rate and morphological changes of the eggs and embryos. The lethal concentration (LC50), representing the concentration of a substance that is expected to cause death in half of the population being studied, of the golden apple eggs and embryos increased with longer exposure time and higher concentrations. The estimated median effective concentration (EC50), which denotes the concentration producing the desired effect in 50% of the exposed golden apple embryos, exhibited a similar trend of change as the LC50. When compared to the microscopic study, it was observed that OCT could be employed to investigate morphological changes of golden apple snail eggs and embryos, enabling evaluation of alterations in both 2D and 3D structures.

Analyses of the bioluminescence mechanism in the land snail, Quantula weinkauffiana.

The mechanism of bioluminescence in the luminous land snails remains largely unknown. Here, we analyzed basic biochemical properties of the luminous land snail, Quantula weinkauffiana. The luminescence activity was extracted from the light organ located near the mouth using a neutral buffer containing detergent. The reaction of the crude buffer extract was triggered by the addition of only hydrogen peroxide (H2O2). These results are inconsistent with the single precedent report on the bioluminescence in the Quantula striata by Shimomura and Haneda in 1986, in which the luminescence of the buffer extract (without detergent) from the light organ was induced by the coaddition of three indispensable components H2O2, ferrous ion, and 2-mercaptoethanol. Based on the present findings, we suggested that an insoluble photoprotein is involved in the bioluminescence of the luminous land snails and the luminescence reaction is simply triggered by H2O2.

Mapping of intermediate host snails for schistosomiasis in the Democratic Republic of Congo: a systematic review.

Schistosomiasis is a snail-borne disease that has a considerable impact on human and animal health, particularly in sub-Saharan Africa. The intermediate hosts of the schistosome parasites are freshwater snails of the genera Biomphalaria Preston, 1910 and Bulinus Müller, 1781. In order to identify existing gaps in the spread of the disease in the Democratic Republic of Congo (DRC), this study compiled the available knowledge of the distribution, population dynamics and ecology of the intermediate hosts of schistosomiasis. A systematic literature search was conducted in PubMed, Embase and Scopus for all malacological studies on schistosoma intermediate hosts in DRC published between 1927 and October 2022. A total of 55 records were found, of which 31 met the inclusion criteria: these were published field and experimental studies conducted in the DRC and focused on snails as intermediate hosts of schistosomes. The analysis of these studies revealed that more up-to-date data on the distribution of snail intermediate hosts in the DRC are needed. Moreover, ecological factors have been less studied for Bulinus species than for Biomphalaria species. These factors play a crucial role in determining suitable snail habitats, and the lack of comprehensive information poses a challenge in snail control. This review makes it clear that there are no current malacological data in the DRC. There is a clear need for molecular and ecological research to update the exact species status and population dynamics of all potential intermediate host species. This will facilitate targeted snail control measures that complement drug treatment in the control of schistosomiasis in the country.