More deterministic assembly constrains the diversity of gut microbiota in freshwater snails.

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

Effects of short-term exposure to Pomacea canaliculata secretions on Limnodrilus hoffmeisteri and Propsilocerus akamusi: A study based on behavior, intestinal microbiota, and antioxidant system.

Pomacea canaliculata is one of the most notorious invasive aquatic snail, capable of influencing various aquatic organisms through their secretions. Limnodrilus hoffmeisteri and Propsilocerus akamusi are the most prevalent and powerful bioturbators in aquatic ecosystems. However, the mechanism of P. canaliculata's secretions affecting bioturbators remains unknown. This study aimed to investigate the effects of P. canaliculata's secretion on L. hoffmeisteri and P. akamusi. L. hoffmeisteri and P. akamusi were treated for 24 h with P. canaliculata and the native species Bellamya aeruginosa secretions at different densities (1 or 20). The migration numbers and aggregation rate of L. hoffmeisteri indicated that P. canaliculata secretion caused L. hoffmeisteri to become alert and migrate away from the nucleus community, resulting in poor population identification, especially at high concentrations. Moreover, the antioxidant enzymatic activity, lipid peroxidation, intestinal microbial diversity, and composition of the two bioturbators were analyzed. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration were elevated following P. canaliculata secretion treatment, indicating oxidative damage. Furthermore, the composition and diversity of intestinal microbiota of L. hoffmeisteri and P. akamusi were changed. The abundance of functional microbiota decreased, and pathogenic bacteria such as Aeromonas became dominant in the intestines of both bioturbators. The current research evaluates the effects of P. canaliculata secretion on the behavior, oxidative stress, and intestinal microbial composition and diversity of two bioturbators, providing new insights into the assessment of post-invaded ecosystems.

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.

Effects of glyphosate-based herbicide on gut microbes and hepatopancreatic metabolism in Pomacea canaliculata.

Roundup®, a prominent glyphosate-based herbicide (GBH), holds a significant position in the global market. However, studies of its effects on aquatic invertebrates, including molluscs are limited. Pomacea canaliculata, a large freshwater snail naturally thrives in agricultural environments where GBH is extensively employed. Our investigation involved assessing the impact of two concentrations of GBH (at concentrations of 19.98 mg/L and 59.94 mg/L, corresponding to 6 mg/L and 18 mg/L glyphosate) during a 96 h exposure experiment on the intestinal bacterial composition and metabolites of P. canaliculata. Analysis of the 16 S rRNA gene demonstrated a notable reduction in the alpha diversity of intestinal bacteria due to GBH exposure. Higher GBH concentration caused a significant shift in the relative abundance of dominant bacteria, such as Bacteroides and Paludibacter. We employed widely-targeted metabolomics analysis to analyze alterations in the hepatopancreatic metabolic profile as a consequence of GBH exposure. The shifts in metabolites primarily affected lipid, amino acid, and glucose metabolism, resulting in compromised immune and adaptive capacities in P. canaliculata. These results suggested that exposure to varying GBH concentrations perpetuates adverse effects on intestinal and hepatopancreatic health of P. canaliculata. This study provides an understanding of the negative effects of GBH on P. canaliculata and may sheds light on its potential implications for other molluscs.

Population genetic structure of Pomacea canaliculata in China based on the COI and ITS1 genes.

Comprehending the phylogeography of invasive organisms enhances our insight into their distribution dynamics, which is instrumental for the development of effective prevention and management strategies. In China, Pomacea canaliculata and Pomacea maculata are the two most widespread and damaging species of the non-native Pomacea spp.. Given this species' rapid spread throughout country, it is urgent to investigate the genetic diversity and structure of its different geographic populations, a task undertaken in the current study using the COI and ITS1 mitochondrial and ribosomal DNA genes, respectively. The result of this study, based on a nationwide systematic survey, a collection of Pomacea spp., and the identification of cryptic species, showed that there is a degree of genetic diversity and differentiation in P. canaliculata, and that all of its variations are mainly due to differences between individuals within different geographical populations. Indeed, this species contains multiple haplotypes, but none of them form a systematic geographical population structure. Furthermore, the COI gene exhibits higher genetic diversity than the ITS1 gene. Our study further clarifies the invasive pathways and dispersal patterns of P. canaliculata in China to provide a theoretical basis.

Gonadal transcriptome analysis of genes related to sex differentiation and sex development in the Pomacea canaliculata.

As an invasive alien animal, Pomacea canaliculata poses a great danger to the ecology and human beings. Recently, there has been a gradual shift towards bio-friendly control. Based on the development of RNA interference and CRISPR technology as molecular regulatory techniques for pest control, it was determined if the knockout of genes related to sex differentiation in P. canaliculata could induce sterility, thereby helping in population control. However, the knowledge of sex differentiation- and development-related genes in P. canaliculata is currently lacking. Here, transcriptomic approaches were used to study the genes expressed in the two genders of P. canaliculata at various developmental stages. Gonad transcriptomes of immature or mature males and females were compared, revealing 12,063 genes with sex-specific expression, of which 6066 were male- and 5997 were female-specific. Among the latter, 581 and 235 genes were up-regulated in immature and mature females, respectively. The sex-specific expressed genes identified included GnRHR2 and TSSK3 in males and ZAR1 and WNT4 in females. Of the genes, six were involved in reproduction: CCNBLIP1, MND1, DMC1, DLC1, MRE11, and E(sev)2B. Compared to immature snail gonads, the expression of HSP90 and CDK1 was markedly reduced in gonadal. It was hypothesized that the two were associated with the development of females. These findings provided new insights into crucial genetic information on sex differentiation and development in P. canaliculata. Additionally, some candidate genes were explored, which can contribute to future studies on controlling P. canaliculata using molecular regulatory techniques.

Ultrastructural study of neuronal cells and localization of ghrelin-like peptide and its receptor in the ganglia of the golden apple snail (Pomacea canaliculata).

Pomacea canaliculata is an invasive snail species causing major problems in agriculture. The snail biology was then investigated. The main objective of the present study was to investigate the nervous system of the snail. The nervous system comprises pairs of cerebral, buccal, pedal, pleural, parietal ganglia and an unpaired visceral ganglion. Most neurons were concentrated at the periphery of the ganglia. The neurons were classified into four types: NR1, NR2, NR3, and NR4. The percentages of the NR3 and NR4 in the pleural and pedal ganglia were significantly higher than those of other ganglia. Ultrastructural study revealed that nuclei of all neuronal types exhibited mostly euchromatins. Many organelles including ribosomes and endoplasmic reticulum were found in their cytoplasm. However, various mitochondria were found in the NR2 and NR3. The immunohistochemistry revealed immunoreactivity of ghrelin-like peptide in the neurons of the cerebral, pleural and pedal ganglia. However, immunoreactivity of GHS-R1a-like peptide existed only in the neurons of the pleural and pedal ganglia. The present study is the first to demonstrate the existence of ghrelin-like peptide and its receptor in P. canaliculata nervous system.

Molluscicidal effect mechanism study on metaldehyde to Pomacea canaliculate at low temperature.

BACKGROUND: Metaldehyde is a molluscicide commonly used to control Pomacea canaliculate. Its efficacy is significantly impacted by water temperature, although the underlying mechanisms have not been fully explored. RESULTS: In this study, we systematically investigated the temperature effect and molecular mechanisms of metaldehyde on P. canaliculata. The molluscicidal effect at various temperatures indicated that metaldehyde's molluscicidal activity significantly decreases with a drop in temperature. The LC50 value was only 458.8176 mg/L at 10 °C, while it surged to a high of 0.8249 mg/L at 25 °C. The impact of low temperature (10 °C) on metaldehyde's molluscicidal activity was analyzed via transcriptomics. The results revealed that the effect of low temperature primarily influences immunity, lipid synthesis, and oxidative stress. The expression of stress and immune-related genes, such as MANF, HSP70, Cldf7, HSP60, and PclaieFc, significantly increased. Furthermore, we studied the function of five target genes using RNA interference (RNAi) and discovered that Cldf7 and HSP70 could notably affect metaldehyde's molluscicidal effect. The mortality of P. canaliculata increased by 36.17% (72 h) after Cldf7 interference and by 48.90% (72 h) after HSP70 interference. CONCLUSION: Our findings demonstrate that low temperature can induce the extensive expression of the Cldf7 and HSP70 genes, resulting in a substantial reduction in metaldehyde's molluscicidal activity. © 2024 Society of Chemical Industry.

Transcriptomic and metabolomic analysis of the mechanisms underlying stress responses of the freshwater snail, Pomacea canaliculata, exposed to different levels of arsenic.

Arsenic (As) pollution poses an important problem, but limited information is available about the physiological effects of As on freshwater invertebrates. Here, we investigated the physiological effects of chronic As exposure on Pomacea canaliculata, a freshwater invertebrate. High level of As (Ⅲ, 5 mg/L) inhibited the growth of P. canaliculata, whereas low level of As (Ⅲ, 2 mg/L) promoted growth. Pathological changes in shell and cellular ultrastructure due to As accumulation likely explain the growth inhibition at high As level. Low level of As simulated the expression of genes related to DNA replication and chitosan biosynthesis, potentially accounting for the growth promotion observed. High level of As enrichment pathways primarily involved cytochrome P450, glutathione, and arachidonic acid-mediated metabolism of xenobiotics. ATP-binding cassette (ABC) transporters, specifically the ABCB and ABCC subfamilies, were involved in As transport. Differential metabolites were mainly associated with the metabolism and biosynthesis of amino acids. These findings elucidate the dose-dependent effects of As stress on P. canaliculata growth, with low levels promoting and high levels inhibiting. Additionally, our findings also provide insights into As metabolism and transport in P. canaliculata.

Population genetics and genetic variation of Pomacea canaliculata (Gastropoda: Ampullariidae) in China revealed by sequence analyses of three mitochondrial genes.

The Golden apple snail, Pomacea canaliculata, is one of the world's 100 worst invasive alien species that is best known for its damage to wetland agriculture. It also acts as an intermediate host of some zoonotic parasites such as Angiostrongylus cantonensis, posing threats to human public health and safety. Despite is being an important agricultural pest, the genetic information and population expansion history of this snail remains poorly understood in China. In this study, we analyzed the genetic variation and population genetics of P. canaliculata populations in seven regions of China based on molecular markers of three mitochondrial (mt) genes. A total of 15 haplotypes were recognized based on single mt cox1, nad1, and nad4, and eight haplotypes were identified using the concatenated genes. High haplotype diversity, moderate nucleotide diversity, low gene flow, and high rates of gene differentiation among the seven P. canaliculata populations were detected. Shanghai and Yunnan populations showed higher genetic flow and very low genetic differentiation. The results of Tajima's D, Fu's F s, and mismatch distribution showed that P. canaliculata did not experience population expansion in China. Genetic distance based on haplotypes suggested that nad1 gene was more conserved than cox1 gene within P. canaliculata. The phylogenetic analyses showed there may be two geographical lineages in the Chinese mainland. The present study may provide a new genetic marker to analyze P. canaliculata, and results support more evidence for studying the genetic distribution of P. canaliculata in China and contribute to a deeper understanding of its population genetics and evolutionary biology.

Biological properties of mucus from land snails (Lissachatina fulica) and freshwater snails (Pomacea canaliculata) and histochemical study of mucous cells in their foot.

Background: Mucus derived from many land snails has been extensively utilised in medicine and cosmetics, but some biological activities of the mucus need to be well documented. Nevertheless, most mucus is obtained from land snails, while mucus from freshwater snails has yet to be attended. Methods: This study aims to determine and compare mucus's antioxidant and anti-inflammatory activities from the land snail Lissachatina fulica and the freshwater snail Pomacea canaliculata. ABTS, DPPH, reducing power and total antioxidant activity assays were used to evaluate the antioxidant capacity. Inhibition of nitric oxide production in lipopolysaccharide-activated RAW 264.7 cells was performed to determine the anti-inflammatory activity. Additionally, the histochemical analysis of mucous cells in each snail foot was conducted to compare the distribution of mucous cells and types of mucins using periodic acid-Schiff and Alcian blue staining. Results: Mucus from L. fulica and P. canaliculata exhibited antioxidant and anti-inflammatory activities in different parameters. L. fulica mucus has higher total antioxidant (44.71 ± 2.11 mg AAE/g) and nitric oxide inhibitory activities (IC50 = 9.67 ± 0.31 µg/ml), whereas P. canaliculata mucus has better-reducing power activity (43.63 ± 2.47 mg AAE/g) and protein denaturation inhibition (IC50 = 0.60 ± 0.03 mg/ml). Histochemically, both species' dorsal and ventral foot regions contained neutral and acid mucins in different quantities. In the dorsal region, the neutral mucins level in L. fulica (16.64 ± 3.46%) was significantly higher than that in P. canaliculata (11.19 ± 1.50%), while the acid mucins level showed no significant difference between species. Levels of both mucins in the ventral foot region of L. fulica (15.08 ± 3.97% and 10.76 ± 3.00%, respectively) were significantly higher than those of P. canaliculata (2.25 ± 0.48% and 2.71 ± 0.56%, respectively). This study revealed scientific evidence of the biological capacity of mucus from L. fulica and P. canaliculata as well as provided helpful information on the region of the foot which produces effective mucus.

[Prevalence of Angiostrongylus cantonensis infection in snails in Fujian Province from 2017 to 2021].

OBJECTIVE: To investigate the prevalence of Angiostrongylus cantonensis infection in market-sold and field-captured snails in Fujian Province, so as to provide the scientific basis for the formulation of the angiostrongyliasis control measures. METHODS: In each month from May to October during the period from 2017 through 2021, Pomacea snails were collected from two field fixed surveillance sites and Bellamya aeruginosa collected from one agricultural product market in Fuzhou City, while Pomacea and B. aeruginosa snails were collected from two agricultural product markets and four restaurants in Xiamen City. At least 50 Pomacea snails and 500 g B. aeruginosa were sampled each time. A. cantonensis infection was detected in Pomacea snails using lung microscopy, and in B. aeruginosa using a tissue homogenate method. RESULTS: A total of 9 531 Pomacea snails were detected for A. cantonensis infection in two cities of Fuzhou and Xiamen, and the overall prevalence of A. cantonensis infection was 4.40%, with the highest prevalence in 2017 (6.82%, 116/1 701) and the lowest prevalence in 2019 (3.46%, 83/2 400). The prevalence of A. cantonensis infection was significantly higher in Pomacea snails sampled from Fuzhou City (11.23%, 326/2 903) than from Xiamen City (1.40%, 93/6 628) (χ2 = 461.48, P < 0.01). A. cantonensis larvae were detected in larval Pomacea snails in two cities of Fuzhou and Xiamen each month. The prevalence of A. cantonensis infection in Pomacea snails appeared an overall tendency towards a rise with month in Fuzhou City, with the highest prevalence in October (15.24%), and there was a significant difference among month (χ2 = 14.56, P < 0.05), while the prevalence of A. cantonensis infection in Pomacea snails was low in Pomacea snails sampled from Xiamen City each month, with the highest prevalence in June (2.64%), and there was a significant difference among month (χ2 = 23.17, P < 0.05). A total of 18 966 B. aeruginosa snails were detected for A. cantonensis infection in two cities of Fuzhou and Xiamen, and the overall prevalence of A. cantonensis infection was 0.01%. CONCLUSIONS: A. cantonensis infection was identified in Pomacea and B. aeruginosa snails in Fujian Province from 2017 to 2021, and there is a potential risk of human A. cantonensis infection.

The Eco-Immunological Relevance of the Anti-Oxidant Response in Invasive Molluscs.

Reactive oxygen species (ROS) are volatile and short-lived molecules playing important roles in several physiological functions, including immunity and physiological adaptation to unsuitable environmental conditions. In an eco-immunological view, the energetic costs associated with an advantageous metabolic apparatus able to cope with wide changes in environmental parameters, e.g., temperature range, water salinity or drought, could be further balanced by the advantages that this apparatus may also represent in other situations, e.g., during the immune response. This review provides an overview of molluscs included in the IUCN list of the worst invasive species, highlighting how their relevant capacity to manage ROS production during physiologically challenging situations can also be advantageously employed during the immune response. Current evidence suggests that a relevant capacity to buffer ROS action and their damaging consequences is advantageous in the face of both environmental and immunological challenges, and this may represent a trait for potential invasiveness. This should be considered in order to obtain or update information when investigating the potential of the invasiveness of emerging alien species, and also in view of ongoing climate changes.

Sex-Biased Survival, Behavior Response, and Recovery Performance of Pomacea canaliculata Snails to Drought Stress and Rewatering Condition.

As the frequency of droughts increases with climate change, the tolerance of aquatic organisms to abiotic stressors will become critical determinants of survival. Pomacea canaliculata has become a widely distributed agricultural and environmental pest in southern China. To evaluate their tolerance and adaptation under the drought condition, the survival, feeding, behavior, and antioxidant system changes in female and male P. canaliculata were investigated during drought stress and rewatering process through an indoor simulation experiment. The results showed that female snails laid eggs before burrowing into the soil to ensure offspring reproduction. Female P. canaliculata had higher survival rates than males under drought stress, and their recovery ability of activity after rewatering was also superior to those of males. The antioxidant system of P. canaliculata showed obvious activation with gender differences after rewatering. Overall, the survival rate of female P. canaliculata was higher after drought stress, and the resilience ability of female snails after rewatering was stronger, including in their behavior, feeding, and antioxidant system recovery. The P. canaliculata tolerance to drought and the ability to recover quickly after drought may contribute to their long-term survival and facilitate continuous invasion.

Sublethal effects of niclosamide on the aquatic snail Pomacea canaliculata.

Pomacea canaliculata is a malignant invasive aquatic snail found worldwide, and niclosamide (NS) is one of the primary agents used for its control. NS applied to water will exist in non-lethal concentrations for some time due to degradation or water exchange, thus resulting in sublethal effects on environmental organisms. To identify sublethal effects of NS on Pomacea canaliculata, we studied the aspects of histopathology, oxygen-nitrogen ratio (RO∶N), enzyme activity determination, and gene expression. After LC30 NS treatment (0.310 g/L), many muscle fibers of the feet degenerated and some acinar vesicles of the hepatopancreas collapsed and dissolved. The oxygen-nitrogen ratio (RO∶N) decreased significantly from 15.0494 to 11.5183, indicating that NS had changed the metabolic mode of Pomacea canaliculata and shifted it primarily to protein catabolism. Transcriptome analysis identified the sublethal effects of LC30 NS on the snails at the transcriptional level. 386, 322, and 583 differentially expressed genes (DEGs) were identified in the hepatopancreas, gills, and feet, respectively. GO (Gene Ontology) functional analysis and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway annotations showed that DEGs in the hepatopancreas were mainly enriched for sugar metabolism, protein biosynthesis, immune response, and amino acid metabolism functional categories; DEGs in the gills were mainly enriched for ion transport and amino acid metabolism; DEGs in the feet were mainly enriched for transmembrane transport and inositol biosynthesis. In the future, we will perform functional validation of key genes to further explain the molecular mechanism of sublethal effects.

Characterization of the shell proteins in two freshwater snails Pomacea canaliculata and Cipangopaludina chinensis.

Uncovering the molecular mechanism of shell formation not only reveals the evolution of molluscs but also lay a foundation for shell-inspired biomaterial synthesis. Shell proteins are the key macromolecules of the organic matrices that guide the calcium carbonate deposition during shell mineralization and have thus been intensively studied. However, previous studies on shell biomineralization have mainly focused on marine species. In this study, we compared the microstructure and shell proteins in the apple snail Pomacea canaliculata which is an alien species that has invaded Asia, and a freshwater snail Cipangopaludina chinensis which is native to China. The results showed that although the shell microstructures were similar in these two snails, the shell matrix in C. chinensis contained more polysaccharides. Moreover, the compositions of shell proteins were quite different. While the shared 12 shell proteins (including PcSP6/CcSP9, Calmodulin-A, and proline-rich protein) were supposed to play key roles in shell formation, the differential proteins were mainly immune components. The presence of chitin in both shell matrices and the chitin-binding domains containing PcSP6/CcSP9 underpinned the relevance of chitin as a major fraction in gastropods. Interestingly, carbonic anhydrase was absent in both snail shells, suggesting that freshwater gastropods might have unique pathways to regulate the calcification process. Our study suggested that shell mineralization might be very different in freshwater and marine molluscs, and therefore, the field should pay more attention to the freshwater species to achieve a more comprehensive insight into biomineralization.

Discovery of a Potential Molluscicide Based on Protein PcRoo in Gill Cilia of Pomacea canaliculata.

In modern pesticide discovery, target-based drug design is an attractive and cost-effective approach. Previous studies found that protein rootletin (PcRoo) is a target protein of arecoline, when interacted with Pomacea canaliculata. In this study, we modeled the target protein through threading, and the binding energy between arecoline and protein PcRoo was calculated as -5.02 kcal/mol by molecular docking. Furthermore, two target compounds, baclofen and acedoben, with molluscicidal activity in theory were obtained by virtual screening in database DrugBank. The in vivo bioassay showed that baclofen could induce typical poisoning symptoms on P. canaliculata, which were characterized by weakness of foot muscles and loss of gill cilia, and the LC50 value was 16.2437 mg/L (72 h). Additionally, after 15 mg/L baclofen treatment, the oxygen consumption rate, ammonia excretion rate, and oxygen nitrogen ratio of P. canaliculata declined. Furthermore, the treatment of baclofen also decreased the gene expression level of PcRoo. These trends were the same as the changes after 5 mg/L arecoline treatment. The pharmacophore characteristics were further analyzed, and the results showed that the chemical structures of baclofen and arecoline were correlated in molluscicidal activity. These findings indicate that baclofen has the potential to be used as a molluscicide in agricultural production, and other new molluscicides may be obtained by virtual screening based on protein PcRoo.

Dose-dependent inhibitory effects of glyphosate on invasive Pomacea canaliculata reproductive and developmental growth under oxidative deposition.

Glyphosate (GLY) is the most widely used herbicide worldwide, and its effects on animals and plants have attracted increasing attention. In this study, we explored the following: (1) the effects of multigenerational chronic exposure to GLY and H2O2, alone or in combination, on the egg hatching rate and individual morphology of Pomacea canaliculata; and (2) the effects of short-term chronic exposure to GLY and H2O2, alone or in combination, on the reproductive system of P. canaliculata. The results showed that H2O2 and GLY exposure had distinct inhibitory effects on the hatching rate and individual growth indices with a substantial dose effect, and the F1 generation had the lowest resistance. In addition, with the prolongation of exposure time, the ovarian tissue was damaged, and the fecundity decreased; however, the snails could still lay eggs. In conclusion, these results suggest that P. canaliculata can tolerate low concentrations of pollution and in addition to drug dosage, the control should focus on two time points, the juvenile and early stage of spawning.

Prevalence of Angiostrongylus cantonensis infection in snails in Fujian Province from 2017 to 2021 / 中国血吸虫病防治杂志

Objective To investigate the prevalence of Angiostrongylus cantonensis infection in market-sold and field-captured snails in Fujian Province, so as to provide the scientific basis for the formulation of the angiostrongyliasis control measures. Methods In each month from May to October during the period from 2017 through 2021, Pomacea snails were collected from two field fixed surveillance sites and Bellamya aeruginosa collected from one agricultural product market in Fuzhou City, while Pomacea and B. aeruginosa snails were collected from two agricultural product markets and four restaurants in Xiamen City. At least 50 Pomacea snails and 500 g B. aeruginosa were sampled each time. A. cantonensis infection was detected in Pomacea snails using lung microscopy, and in B. aeruginosa using a tissue homogenate method. Results A total of 9 531 Pomacea snails were detected for A. cantonensis infection in two cities of Fuzhou and Xiamen, and the overall prevalence of A. cantonensis infection was 4.40%, with the highest prevalence in 2017 (6.82%, 116/1 701) and the lowest prevalence in 2019 (3.46%, 83/2 400). The prevalence of A. cantonensis infection was significantly higher in Pomacea snails sampled from Fuzhou City (11.23%, 326/2 903) than from Xiamen City (1.40%, 93/6 628) (χ2 = 461.48, P < 0.01). A. cantonensis larvae were detected in larval Pomacea snails in two cities of Fuzhou and Xiamen each month. The prevalence of A. cantonensis infection in Pomacea snails appeared an overall tendency towards a rise with month in Fuzhou City, with the highest prevalence in October (15.24%), and there was a significant difference among month (χ2 = 14.56, P < 0.05), while the prevalence of A. cantonensis infection in Pomacea snails was low in Pomacea snails sampled from Xiamen City each month, with the highest prevalence in June (2.64%), and there was a significant difference among month (χ2 = 23.17, P < 0.05). A total of 18 966 B. aeruginosa snails were detected for A. cantonensis infection in two cities of Fuzhou and Xiamen, and the overall prevalence of A. cantonensis infection was 0.01%. Conclusions A. cantonensis infection was identified in Pomacea and B. aeruginosa snails in Fujian Province from 2017 to 2021, and there is a potential risk of human A. cantonensis infection.

Study on the relationship of Hsp70 with the temperature sensitivity of pedunsaponin A poisoning Pomacea canaliculata.

Previous studies have found that temperature influences molluscicidal the activity of pedunsaponin A (PA), which may be related to the expression of Hsp70, a cold-tolerance gene in Pomacea canaliculata. We determined the temperature effect of PA and the relationship between Hsp70 and temperature sensitivity of P. canaliculata poisoned by PA. Toxicity tests resulted in LC50 values of 17.7239 mg⋅L-1 at 10 °C, which decreased to 2.5774 mg⋅L-1 at 30 °C, implying a positive correlation between toxicity of PA and temperature. After Hsp70 being interfered, the mortality rate of P. canaliculata treated with PA for 72 h was 70%, which was significantly higher than that of snails treated with PA for 72 h without interfering (56.7%). Meanwhile, immune enzyme activities such as SOD, ACP and AKP were significantly increased in the interfered group and expression level of PcAdv in the gill was also significantly increased. These results suggest that deletion of Hsp70 promotes the activation of some immune enzymes of P. canaliculata and elevates the content of target proteins to cope with the dual stresses of low temperatures and molluscicides. These findings indicate that the Hsp70 plays an important role in influencing the temperature sensitivity of P. canaliculata when treated with PA.