Invasive Snail Research Articles

Response of native and invasive grazers to global warming: marine heatwaves vs. gradual trends

Ecological responses to global warming are likely driven by a combination of gradual warming trends and extreme climate events, which are increasing in frequency and intensity. Specifically, heatwaves may amplify the impact of ongoing warming, and thus affect species’ physiological responses, behaviour and eventually survival. Here, we tested the hypothesis that a tropical invasive grazer snail, Cerithium scabridum, will be more resilient to the effects of future gradual warming and marine heatwaves (MHWs) than its native congener C. lividulum, co-occurring in rocky intertidal pools along the Levantine coast. Survival and faecal production (as a proxy for feeding rate) of the 2 species were measured under 4 experimental temperature conditions: ambient summer mean (31°C), predicted warming scenario (ambient +3°C), and short-term MHWs (+5°C) added to either ambient or warming treatments, followed by a recovery period. No effect of warming alone was detected on either species, whereas MHW reduced faecal production only in the native C. lividulum. During the recovery period, C. lividulum survival dropped, but the few surviving individuals recovered from the heat stress as indicated by the increase in faecal production. Neither snail species survived under the combination of warming and MHW. These results suggest that both species, living in a thermally fluctuating and often extreme environment, can tolerate a +3°C gradual warming, but only the invasive snail can withstand a +5°C heatwave. However, neither species can endure a severe heatwave on top of predicted gradual warming, potentially leading to population collapse among both species in the region.

Population dynamics of planktonic and symbiotic Vibrio spp. associated with the freshwater invasive snail Physa acuta (Gastropoda: Physidae) in Wouri estuary (Douala, Cameroon)

In Cameroon, the coastal city of Douala is seriously confronted with major epidemics of waterborne diseases, especially cholera, caused by pathogenic bacteria. However, the related environmental factors are poorly understood. This study aimed to investigates the population dynamics of planktonic and symbiotic Vibrio spp. associated with the freshwater invasive snail Physa acuta in Wouri estuary, focusing on the impact of selected abiotic factors. Abiotic parameters were analyzed using standardardized methods. Microbiological analyses involved isolating, identifying and counting planktonic and symbiotic Vibrio spp. cells associated with Physa acuta. The Wouri Estuary streams exhibit hypoxia, with dissolved oxygen levels as low as 1 % at certain stations and characterized by high organic matter loads. Total symbiotic Vibrio spp. abundance peaked during the rainy season and increased from freshwater saltwater gradient. The survival of both planktonic and symbiotic Vibrio spp. cells associated with Physa acuta is influenced by several abiotic factors including precipitation, salinity, suspended solids and dissolved organic matter. The species of Vibrio spp. potentially pathogen to human were isolated in both planktonic and symbiotic forms. Vibrio parahaemolyticus was provisionally identified in this study as indigenous to Physa acuta, while V. alginolyticus, V. vulnificus, V. cholerae, V. fluvialis and V. mimicus, which may be responsible for public health problems, are present accidentally in both study environments. All the evidence suggests that the bacteria present in the digestive tract of Physa acuta accumulate indiscriminately from the natural environment and constitute transient populations. Based on this study, decisions on the management of public health problems can be envisaged to avoid the emergence and re-emergence of certain zoonotic diseases.

A Scoping Review of Angiostrongyliasis and Other Diseases Associated with Terrestrial Mollusks, Including Lissachatina fulica: An Overview of Case Reports and Series.

Terrestrial mollusks, including the invasive giant African snail (Lissachatina fulica), pose significant public health risks due to their role as carriers of various pathogens, such as Angiostrongylus cantonensis and Angiostrongylus costaricensis. This scoping review aims to provide a comprehensive evaluation of diseases associated with Lissachatina fulica and other terrestrial mollusks, with a particular focus on the prevention, diagnosis, and treatment of these conditions. Following the Joanna Briggs Institute guidelines and the PRISMA-ScR framework, we conducted a systematic search and filtered results, identifying 27 relevant case reports and series for analysis. Our findings reveal that ingesting raw or undercooked snails is the most hazardous exposure route, with a 75% mortality rate in affected adults, particularly in regions where snail consumption is culturally significant, such as France. A. cantonensis is the primary cause of eosinophilic meningitis, while A. costaricensis leads to abdominal angiostrongyliasis. The review also highlights the widespread impact of L. fulica in countries like France, the United States, Brazil, and Colombia, emphasizing the global nature of the threat. Children show consistent vulnerability across all exposure types, underscoring the need for targeted preventive strategies. This review underscores the urgent need for public health interventions, particularly educational campaigns to inform communities about the dangers of L. fulica. Additionally, it highlights the importance of enhancing diagnostic methods and expanding surveillance to better manage the risks associated with these invasive snails. The findings provide valuable insights for the scientific community and recommend a multidisciplinary approach to effectively mitigate the public health risks posed by L. fulica across diverse regions.

Current and potential distribution of the invasive apple snail, Pomacea canaliculata in Eastern Africa: evidence from delimiting surveys and modelling studies

The invasive apple snail Pomacea canaliculata has become a significant concern in invaded habitats beyond its native range. It was reported in Kenya in 2020 invading one of the largest rice-producing schemes, the Mwea irrigation scheme. Delimiting surveys were conducted across five key rice-producing schemes (Mwea, Bura, Hola, Ahero and West Kano) in Kenya to establish the extent of the invasion and develop effective quarantine and management strategies within the Mwea scheme and other risk areas. Additionally, the ensemble model approach was used to model the potential distribution of P. canaliculata in Eastern Africa (as defined by the United Nations Geoscheme). Over 80% of the Mwea scheme was infested with P. canaliculata, an expansion from the initial infestation point (Ndekia). The mean number of adults/m2 and egg clutches/m2 were 8.4 ± 0.9 (SEM) and 7.7 ± 1.4 (SEM), respectively, with varying densities across sections. No adults or eggs of P. canaliculata were found in the four schemes outside the Mwea scheme. The model predicted high suitability for P. canaliculata in the southwest of Kenya,and in coastal areas, with all surveyed areas marked as highly suitable.. Regionally, high-risk areas include Malawi, Madagascar, and Uganda. Mozambique, Tanzania, and Ethiopia showed localised areas of high suitability. Conversely, Sudan, South Sudan, Eritrea, Djibouti and Somalia were largely unsuitable for P. canaliculata. Given the potential for further spread, strict quarantine measures are essential to prevent the spread of P. canaliculata in Kenya and its introduction to uninvaded regions of Eastern Africa. Alongside this, implementing IPM e strategies is crucial for effective pest management and the protection of agricultural ecosystems.

Structural and functional differences of gut microbiota in Pomacea canaliculata from different geographical locations and habitats.

Gut microbiota is related to host fitness, and influenced by geographical locations and habitats. Pomacea canaliculata is a malignant invasive alien snail that threatens agricultural production and ecosystem functions worldwide. Clarifying the general rules of the gut microbial community structure and function of the snails in different geographical locations and habitats is of great significance for understanding their invasion at different spatial scales. This study used high-throughput sequencing technology to compare and analyze the differences in community structure and function of gut microbiota in P. canaliculata from five geographical locations (Liuzhou, Yulin, Nanning, Wuzhou, and Hezhou) and three different habitats (pond, paddy field, and ditch) in Guangxi Province. The results showed that intestinal microbial alpha diversity of P. canaliculata was higher in Liuzhou, Yulin, lower in Nanning, Wuzhou, Hezhou, and higher in ponds compared with paddy fields and ditches. The dominant phyla of gut microbiota in snails were Firmicutes, Cyanobacteria, Proteobacteria, Fusobacteriota, Bacteroidota, and the dominant genus was Lactococcus. The community structure of gut microbiota in snails varied significantly across different geographical locations and habitats, and the phyla Firmicutes, Cyanobacteria had significantly higher relative abundance in snails collected from Nanning and Yulin, respectively. Moreover, the relative abundance of gut functional microbiota associated with human disease in P. canaliculata was significantly affected by geographical locations and habitats, and with the highest abundance in ponds. However, the relative abundance of functional microbiota related to metabolism, genetic information processing, organizational system, environmental information processing, and cellular processes were only significantly affected by geographical locations. Collectively, geographical locations and habitats had significantly different effects on the community structure and function of gut microbiota in P. canaliculata, and the greater differences were caused by geographical locations rather than by habitats.

Responses of survival, antioxidant system and intestinal microbiota of native snail Bellamya purificata to the invasive snail Pomacea canaliculata

Pomacea canaliculata is one of the most successful invader in worldwide, adversely affecting native ecosystem through direct predation or indirect competition, while the mechanism of indirect effects on native species remain poorly understood. To clarify the effects of P. canaliculata on the native near-niche species, Bellamya purificata, a widespread freshwater gastropod in China, was selected as the research subject. The changes of mortality, histology, antioxidant system as well as the intestinal flora diversity of B. purificata were explored in present study. The results showed that the median lethal dose of P. canaliculata culture solution for B. purificata was 23.76 ind/L and a concentration-dependent damage of both the gonad and hepatopancreas were observed, the gonadal villi were dissolved and the hepatopancreas cells were broken at 20 ind/L. Furthermore, different concentrations of P. canaliculata culture solution leading to the antioxidant damage on the enzyme or non-enzyme systems of B. purificata at various degrees. Additionally, a decrease in the diversity of the intestinal flora was observed, accompanied by an increase in the abundance of pathogenic bacteria such as Pseudomonas and Aeromonas after the exposure of the culture solution of P. canaliculata. Last, after being recovered in freshwater for 24 h, the antioxidant damage of B. purificata and the disturbance of intestinal flora diversity were still not recovered especially in the high concentration group. The indirect competitive mechanism of P. canaliculata culture solution on B. purificata were explored from the aspects of tissue, biochemical level and intestinal flora, which enriched the research of P. canaliculata invasion on native snails in China, and provided new insights for the study of the invasion strategy of P. canaliculata.

Trade and socioeconomic importance of an invasive giant snail in the endemic-rich island of São Tomé, Central Africa.

Managing invasive species is crucial to mitigate their negative impacts on ecosystems, yet conflicts may arise when their social benefits are disregarded. Human pressure on the endemic-rich forests of São Tomé has been high since the island was discovered by the Portuguese in the 15th century, and numerous species have been introduced. These include the invasive West African giant land snail (Archachatina marginata), which was introduced in the mid-20th century, is now widespread on the island, and is a potential threat to native flora and fauna. We assessed the frequency of consumption of this species and its socioeconomic importance to people across the island with household questionnaires, focus group discussions, and semistructured interviews. We explored the prevalence and potential drivers of use (e.g., wealth, household composition, and diversity of occupations) and characterized the commodity chain to identify demographic groups linked to the snail trade. We interviewed 672 people (1 person per household), conducted 6 focus groups, and interviewed 80 key actors belonging to 5 subcategories. The snail was the most widely consumed bushmeat and an important source of income, particularly for women and unemployed youth. Insecure and scarce livelihood alternatives, mostly in rural areas, were reported as drivers for trade involvement. Snail harvesting was more frequent in poorer households with low occupational diversity. Selling tended to occur in households that were well-established in the community and had a higher proportion of children. Both were stimulated by the proximity of communities to the native forest. Buying snails was common in all demographic groups, but it was linked to wealth and occupational diversity. Interventions to manage the impact of this introduced species on the valuable ecosystems of the island should involve multiple sectors of society to ensure societal support. This requires robust consideration of the welfare of vulnerable demographic groups that benefit from the species.

Molluscicidal activity and biochemical impacts of borrelidins against an aquatic invasive snail Pomacea canaliculata for crop protection

The invasive golden apple snail Pomacea canaliculata is one of the devastating threats to aquatic ecosystems and wetland agriculture worldwide. Macrolides from microbes display various advantages over other compounds in controlling snails. However, emergence of antibiotic-resistant phenotypes against certain macrolides in the field appeals for exploring more effectively molluscicidal macrolides. Here, two borrelidins, borrelidin BN1 and BN2, from the extract of a Streptomyces strain fermentation were evaluated for molluscicidal potential against P. canaliculata using both immersion and contact bioassay methods. Borrelidin BN1 (borrelidin A) presented a significant molluscicidal activity comparable to the chemical pesticide metaldehyde, and had a much lower median lethal concentration value (LC50, 522.984 μg·ml−1) than avermectin B1 at 72 h of contact-killing treatment. Snail growth was inhibited by borrelidin BN1 more than by metaldehyde at sublethal concentrations, consistent with responses of key biochemical parameters. Exposure to borrelidin BN1 decreased the activity of acetylcholinesterase (AChE), glutathione S-transferase (GST), aspartate aminotransferase (AST), alanine aminotransferase (ALT) as well as the levels of energy reserves and sex steroids in snail tissues, while increased the activity of superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH) and the level of lipid peroxidation (LPO). Further application assay confirmed that borrelidin BN1 protected crop plant Zizania latifolia from P. canaliculata damage via suppressing snail population density. These findings suggest great potential of borrelidin BN1 as a molluscicide. Additionally, its higher activity than the stereoisomeric borrelidin BN2 (borrelidin F) implied better molluscicidal borrelidins could be acquired through structural optimization.

Potamopyrgus antipodarum (Gastropoda: Tateidae) in central Chile: new records, reproductive output assessment, and coexistence with native species

ABSTRACT Three new populations of the invasive New Zealand mud snail, Potamopyrgus antipodarum, have been discovered in central Chile, increasing the documented records in the country to 23. Only females were observed in the present study. Significant differences in shell length and fecundity were found among populations. The size of the snails was less than 6 mm, while fecundity varied from 0 to 45 offspring per snail. A significant correlation was found between adult shell length and brood size in one of the three populations discovered. In these localities, Potamopyrgus antipodarum coexists with native and possibly other invasive gastropods.

Nematodes of concern to public and animal health associated with the invasive snail Achatina fulica, in Sergipe, Northeastern Brazil

The giant African land snail Achatina fulica is known to be the intermediate host of a number of nematode species that are prejudicial to human and veterinary health, being also an agricultural and urban pest. The present study investigated the presence of nematodes in A. fulica and other terrestrial mollusks in 24 municipalities of Sergipe State, northeastern of Brazil, in the dry and rainy seasons. In 2019 and 2020, the specimens were collected in standard 20 m × 10 m plots (10 min/01 collector), while in 2021, they were collected by convenience sampling. The nematode species were identified based on sequencing of the mitochondrial Cytochrome C Oxidase Subunit I (COI) gene and the ribosomal nuclear Internal Transcribed Spacer (ITS 2). Specimens of A. fulica infected with Angiostrongylus cantonensis, a nematode that causes eosinophilic meningitis (EM) in humans and animals, were collected in four municipalities. Two nematodes of veterinary importance were also identified, Aelurostrongylus abstrusus and Cruzia tentaculata in seven municipalities. This is the first record of Cruzia tentaculata in Sergipe. Free-living nematodes were also found in 18 municipalities. One of these species – Caenorhabditis briggsae – was identified in the municipality of Itabaiana. Specimens of other mollusks species were also collected. Only one of these mollusks, C. fasciata from Japaratuba, was found infected with free-living nematodes. A. fulica showed greater positivity for nematodes in the dry season, especially in the regions of Lower São Francisco River, Greater Aracaju and South Central Sergipe. The probability of infection increased when mollusks were larger and more recurrent in plots. Given that A. cantonensis is the etiological agent of EM and was found associated to A. fulica in four municipalities, it will be important to implement programs of continuous monitoring of the mollusk's fauna, combined with educational programs that provide information necessary to control A. fulica.

Strategies of invasive snail Pomacea canaliculata during hibernation in rice fields of south China: effects of body size, sex, and soil depth.

The invasive freshwater snail Pomacea canaliculata is an agricultural pest with a certain level of tolerance to abiotic stress. After the harvest of late rice, the snails usually burrow themselves into the soil surface layers to overwinter and pose a renewed threatto rice production in the following year. Revealing the response of snails to environmental stresses is crucial for developing countermeasures to control their damage and spread. In this study, we conducted a 120-day in situ experiment during the winter to investigate the survival and physiological changes of hibernating snails in 0-5 and 5-10 cmsoil depths, aiming to explore their overwintering strategies. Our results showed that 73.61%, 87.50%, and 90.28% of male, female, and juvenile snails survived after hibernation for 120 days in 0-10 cm soil depth, respectively. The differences in survival rates based on sex and size of snailspotentially reflect the countermeasures of snails to rapidly reproduce after hibernation. Simultaneously, the hibernating snails exhibited the ability to maintain a certain level of body weight. During this period, the snails increased their antioxidant enzyme activities to cope with oxidative stress, and enhanced their lipid storage. The hibernation survival of snails was not significantly affected by different soil depths, indicating that they have the potential to hibernate into deeper soils. Furthermore, snails were capable of increasing their contents of bound water and glycerol to cope with sudden cold spells during hibernation. Our findings emphasize the adaptive changes of P. canaliculata snails overwintering in paddy soils. In future studies, the vulnerabilitiesof P. canaliculata during hibernation (e.g. shell characteristics, nutrient reserves, and dehydration tolerance, etc.,) should be investigated to develop effective control methods for this period. © 2024 Society of Chemical Industry.

Temperature dependence of feeding activity in the invasive freshwater snail Pomacea canaliculata: implications for its response to climate warming

AbstractPomacea canaliculata, a freshwater snail native to South America, has become widely naturalised in many countries, causing serious damage to agricultural and native ecosystems. Although climate warming is likely to expand the distribution of this species, limited information exists regarding its impact on feeding activities. In this study, we examined the effects of temperature on the feeding activity of this species and estimated the impact of climate warming on its feeding potential. The feeding activity was determined by measuring the amount of standard food (Japanese mustard spinach, komatsuna) ingested at different temperatures. It tended to increase from 15 to 25 °C but became almost stable from 25 to 35 °C. The respiration rate determined by the O2 consumption rate, showed a similar response to temperature. Based on these findings, we constructed a simple model to estimate the relative feeding activity using climatic data recorded at meteorological stations throughout the Japanese Archipelago. The model estimated that, with warming of + 2 °C, annual feeding potential (relative value) increased by 21.1% at the present northern distribution limit of this species. The effect of warming on percentage increase in feeding potential was estimated to be smaller at the southern distribution limit (9.9%), although the absolute feeding potential was larger than that at the northern sites. The model also suggested that if this species expanded its northern distribution range as a result of climate warming, it would have a high feeding potential comparable to that of the southern regions.

Impact of invasive apple snails on shallow water ecosystems under different nutrient conditions: results from a mesocosm study

Impact of invasive apple snails on shallow water ecosystems under different nutrient conditions: results from a mesocosm study

Prevalence of Snails and Farmers' Practice Towards the Management of Giant African Snail, Achatina fulica Bowdich, 1822 in Kapilvastu, Nepal

The Giant African Snail (GAS), Achatina fulica Bowdich, 1822, is the world's largest, most damaging, and highly invasive land snail, capable of consuming about 10% of its body weight daily and affecting at least 500 types of plants. Despite the high incidence of this pest, management options are limited and ineffective. In this context, this study was carried out to assess overall snail distribution, damage and management practices adopted by farmers against GAS. A household survey of randomly selected 60 households was carried out using semi-structured questionnaires at Banganga Municipality-01, Kapilvastu, Nepal. The results revealed the prevalence of three different snails: the GAS, Achatina fulica Bowdich, 1822, the Common snail, Indoplanorbis exustus (Deshayes, 1834), and the Paddy Snail or Ghonghi or Ghongi, Pila globose (Swainson, 1822) in moist areas, drains, and grassy lands, among them, GAS causing the most significant damage during the rainy season. The most vulnerable stage of crops to GAS was the vegetative stage of development (53.3%) in vegetables and fruits, with the most preferred crop family being the Cucurbitaceae (45%). The majority of respondents (48%) believed that the lack of effective control measures was the main reason for the growing infestation and extent of damage. The 'Hand-picking and killing' method was considered the most effective and suitable method in the farming community over other control measures. It has been reported that the snail problem has increased over the years, and very little effort has been made by the concerned authorities to manage this pest. In conclusion, snails, especially GAS, pose major challenges to agricultural production in Nepal. Therefore, appropriate and cost-effective management strategies are required for their sustainable management.

Habitat suitability and niche interaction between the invasive snail Achatina fulica and its biocontrol flatworm Platydemus manokwari in Southeast Asia

Bioinvasions are increasingly altering community structures around the world, especially with the changing climate. In invaded areas, biocontrol agents are introduced to regulate the invasive species. However, without thorough evaluation, these agents can proliferate and threaten other organisms. We assessed the niche dynamics between invasive Achatina fulica (Giant African Snail) and its biocontrol agent, the Platydemus manokwari (New Guinea Flatworm), in Southeast Asia. Species occurrence and environmental data were used to model the habitat suitability of both species in the present and future climate scenarios using ecological niche modeling with the MaxEnt algorithm. These models predicted 25.9% and 42.0% of the current conditions to be suitable and 73.8% and 57.8% to be unsuitable for A. fulica and P. manokwari, respectively. There was a predicted steady increase in suitable areas and a gradual decrease in A. fulica’s unsuitable areas as the carbon emissions are predicted to increase. Moderate to high niche overlap of 61.2% to 83.4% was expected between the species under different climate scenarios. Predicting the suitable areas for invasive species and their niche interaction with other species in future scenarios will aid in identifying vulnerable areas for conservation.

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.

Genetic diversity and connectivity of the invasive gastropod, Callinina georgiana (Caenogastropoda: Viviparidae) across a fragmented riverscape: A mitonuclear perspective

Abstract Aquatic invasive species are a significant threat to global freshwater biodiversity. This study focuses on the banded mystery snail, Callinina georgiana, an invasive species in the Adirondack region of northern New York—an important section of the New York Great Lakes Basin. This project aims to explore the genetic connectivity of C. georgiana within its invasive range using a combination of mitochondrial and nuclear markers. Sampling was conducted in the Raquette River and adjacent waterways, with a total of 229 snails collected from 16 distinct populations distributed across eight different waterbodies. Also included were two populations from the species' native range in the southern U.S.A. DNA was extracted, and a 710‐bp fragment of the mitochondrial DNA marker cytochrome c oxidase 1 and a 351‐bp fragment of nuclear marker histone‐3 were amplified. Population genetic analyses including haplotype patterning, AMOVA and genetic diversity estimates, neutrality tests and tests for isolation by distance were performed to assess connectivity patterns. Results showed moderate to high levels of genetic admixture within the snail's invasive range as indicated by the lack of geographic patterning of haplotypes and low to moderate levels of genetic differentiation across multiple sites. Demographic analyses combined with high numbers of private haplotypes indicate historic population expansion. Interestingly, a case of mitonuclear discordance was detected for native and invasive populations as evident by incongruent haplotype patterns for the cytochrome c oxidase 1 and histone‐3 markers. Callinina georgiana exhibits a high level of genetic connectivity in its invasive range. The presence of dams does not significantly affect apparent gene flow, indicating that anthropogenic activities, such as boat traffic might be key in dispersing the snails across this fragmented freshwater system. This study offers new insights into the dispersal and genetic structure of an invasive freshwater snail. It highlights the importance of considering anthropogenic factors when confronting complex patterns of genetic diversity. The findings are significant for biodiversity conservation and provide a basis for developing strategies to manage and contain the spread of aquatic invasive species such as C. georgiana, especially in regions with high human activity.

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.

Distribution, abundance, population structures, and potential impacts of the invasive snail, Tarebia granifera in aquatic ecosystems of north-eastern South Africa.

Aquatic ecosystems globally have been invaded by molluscs. Tarebia granifera is a highly successful invader, often becoming the dominant aquatic invertebrate species in an invaded ecosystem. Resultingly, it has been suggested that T. granifera may have severe negative impacts on these invaded ecosystems. Limited information is available regarding the population structures and densities of T. granifera, particularly in invaded countries such as South Africa, and information on this could assist in developing management and control strategies for this invasive species. The present study aimed to assess the current distribution, densities, and population structures of T. granifera in invaded habitats on the Limpopo and Phongolo River systems in South Africa. This was accomplished by collecting aquatic molluscs from sites across these systems. Water quality parameters were measured at each site and water samples were collected for chemical nutrient analyses. The density of snails was determined for each site and the population size and structure as well as birth rate was calculated for T. granifera. Tarebia granifera was found to be the dominant molluscan species in habitats where it was present and all size classes from newborn to mature adults were found throughout at some of the highest densities globally. Worryingly, native molluscan species, were often absent or in much lower densities than reported in literature at sites where T. granifera was present, suggesting a negative effect on the native molluscan density and diversity. Contrary to most previous studies, there were no significant correlations between T. granifera and the selected water quality parameters. Higher densities and newborn recruitment of T. granifera were observed in the spring than in autumn, likely in response to shifts in environmental conditions. This study provides crucial insights into the population structure, densities, and impacts of T. granifera in invaded habitats, particularly for relatively newly invaded regions such as southern Africa.

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.