Invasive Freshwater Snail Research Articles

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.

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.

One Health monitoring reveals invasive freshwater snail species, new records, and undescribed parasite diversity in Zimbabwe

BackgroundSnail-borne trematodes afflict humans, livestock, and wildlife. Recognizing their zoonotic potential and possible hybridization, a One Health approach is essential for effective control. Given the dearth of knowledge on African trematodes, this study aimed to map snail and trematode diversity, focusing on (i) characterizing gastropod snail species and their trematode parasites, (ii) determining infection rates of snail species as intermediate hosts for medically, veterinary, and ecologically significant trematodes, and (iii) comparing their diversity across endemic regions.MethodsA cross-sectional study conducted in 2021 in Chiredzi and Wedza districts in Zimbabwe, known for high human schistosomiasis prevalence, involved malacological surveys at 56 sites. Trematode infections in snails were detected through shedding experiments and multiplex rapid diagnostic polymerase chain reactions (RD-PCRs). Morphological and molecular analyses were employed to identify snail and trematode species.ResultsAmong 3209 collected snail specimens, 11 species were identified, including schistosome and fasciolid competent snail species. We report for the first time the invasive exotic snail Tarebia granifera in Zimbabwe, which was highly abundant, mainly in Chiredzi, occurring at 29 out of 35 sites. Shedding experiments on 1303 snails revealed a 2.24% infection rate, with 15 trematode species identified through molecular genotyping. Five species were exclusive to Chiredzi: Bolbophorus sp., Schistosoma mansoni, Schistosoma mattheei, Calicophoron sp., and Uvulifer sp. Eight were exclusive to Wedza, including Trichobilharzia sp., Stephanoprora amurensis, Spirorchid sp., and Echinostoma sp. as well as an unidentified species of the Plagiorchioidea superfamily. One species, Tylodelphys mashonensis, was common to both regions. The RD-PCR screening of 976 non-shedding snails indicated a 35.7% trematode infection rate, including the presence of schistosomes (1.1%) Fasciola nyanzae (0.6%). In Chiredzi, Radix natalensis had the highest trematode infection prevalence (33.3%), while in Wedza, R. natalensis (55.4%) and Bulinus tropicus (53.2%) had the highest infection prevalence.ConclusionsOur xenomonitoring approach unveiled 15 trematode species, including nine new records in Zimbabwe. Schistosoma mansoni persists in the study region despite six mass deworming rounds. The high snail and parasite diversity, including the presence of exotic snail species that can impact endemic species and biomedically important trematodes, underscores the need for increased monitoring.Graphical

Invasive freshwater snails are less sensitive to population density than native conspecifics.

Understanding how and why some species or lineages become invasive is critically important for effectively predicting and mitigating biological invasions. Here, we address an important unanswered question in invasion biology: do key life-history traits of invasive versus native lineages within a species differ in response to key environmental stressors? We focus on the environmental factor of population density, which is a fundamental characteristic of all populations, and investigate how changes in density affect native versus invasive Potamopyrgus antipodarum (New Zealand mudsnail). P. antipodarum has invaded 39 countries and detrimentally affects invaded environments. Previous studies of native and invasive populations and from laboratory experiments have demonstrated that growth and reproduction of P. antipodarum is sensitive to population density, though whether and how this sensitivity varies across native versus invasive lineages remains uncharacterized. We quantified individual growth rate and reproduction in P. antipodarum from multiple distinct native and invasive lineages across three different population density treatments. The growth of native but not invasive lineages decreased as density increased. There was no differential effect of density treatment on embryo production of invasive versus native snails, but a significantly higher proportion of snails were reproductive in high density compared to intermediate density for invasive lineages. In native lineages, there were no significant differences in the relative frequency of reproductive snails across density treatments. While the extent to which these results from our laboratory study can be extrapolated to the more complex natural world remain unclear, our findings are consistent with a scenario where differential sensitivity to population density could help explain why some lineages become successful invaders. Our findings also align with previous studies that show that invasive P. antipodarum lineages exhibit a relatively wide range of tolerance to environmental stressors.

Salt tolerance and survival of the freshwater bioinvasive gastropod Melanoides tuberculata (Thiariidae): when different methodologies tell us different stories

ABSTRACT The study of the ecophysiology of invasive species is one of the main steps in understanding the dynamics of territorial expansion of these species and establishing prevention, control, and combat measures and protocols. For freshwater molluscs, one of the main limiting factors is salinity. Laboratory tests closer to reality are needed to make more efficient models. Melanoides tuberculata is an invasive freshwater snail monitored worldwide, and it also has implications for human health. Recent studies supported that its rapid expansion has been enabled through its adaptation to both estuarine conditions and saline waters. The present study aims to determine the real tolerance range of M. tuberculata through a stepwise acclimation test as a more realistic model of a transitional gradient from a lentic to an estuarine environment and so determine the real potential for salinity adaptation. It also aims to check differences in the tolerance responses between age groups and life history, using two distinct populations subject to distinct ambient conditions. The stepwise acclimation test was effective in proving that M. tuberculata may be highly adaptable to salinity variation, contrasting with all previous tests. Thus, the results support the hypothesis of dispersion via estuaries by salinity-tolerant M. tuberculata juveniles.

Spatial distribution of two invasive freshwater snails and environmental correlates of the mollusc community abundance, a case study in Chile

Invasive species can produce negative effects on native species. We studied the densities of Physa acuta and Potamopyrgus antipodarum, two invasive freshwater snails in Chile, and analyzed the relationship between environmental parameters and the relative abundances of the mollusc community in several ecosystems. Densities of both species were studied in three habitat types (stones, smooth sediment, and vegetation) in the Consuelo Stream, Coquimbo Region. Densities of Potamopyrgus antipodarum were significantly higher on stones, while Physa acuta showed no significant differences between habitats. A canonical correspondence analysis (CCA) demonstrated that both Physa acuta and Potamopyrgus antipodarum were related to oxidation-reduction potential but not to salinity. The results also showed that native mollusc fauna is sparsely represented in the study area, possibly due to the presence of these invaders, although drought, water pollution, and other unstudied anthropogenic factors may also be involved.

Comparison of development and overwintering rates and feeding efficiency on rice seedlings among two invasive freshwater apple snails and their hybrid

Since the 1980s, the freshwater apple snails, Pomacea canaliculata, Pomacea maculata, and their hybrid, have been introduced into a wide range of freshwater ecosystems in tropical to temperate regions. Although P. canaliculata has become established in temperate East Asia, P. maculata and the hybrid are rarely found in this region. To evaluate the risk of P. maculata and the hybrid particularly as rice pests in temperate regions, we compared growth rate, winter survival rate, and feeding efficiency on rice seedlings of these snails with P. canaliculata. When P. maculata and P. canaliculata hatchlings were reared under laboratory or field conditions, the adult P. maculata had larger shells than adult P. canaliculata. Neither P. maculata nor F1 hybrids could survive winter in a simulated drained paddy field, and only a few individuals of P. maculata and F1 hybrids overwintered successfully in freshwater. Pomacea maculata juveniles fed on rice seedlings at the highest rate at temperatures above 27°C. These results suggest that P. maculata becomes a serious rice pest in temperate region as P. canaliculata once it is introduced from warmer regions under global warming. Further biological examination of P. maculata is needed to evaluate the risk of this snail in detail.

Assessment of the socio-economic impacts associated with the arrival of apple snail (Pomacea canaliculata) in Mwea irrigation scheme, Kenya.

In Kenya, rice (Oryza sativa L.) is mainly produced under irrigation by small-scale farmers. Mwea irrigation scheme (MIS) in Kirinyaga County accounts for 80-88% of rice production. Here, rice is the main source of livelihood and a source of revenue generation for the county. However, a recently established invasive freshwater snail, Pomacea canaliculata (Lamarck) (family: Ampullariidae), a species of apple snail, presents a serious threat to rice production. Household surveys, focus group discussions and key informant interviews highlight apple snail as a serious problem in MIS. Households that observed at least a moderate level of infestation (>20% of cultivated area) experienced significant reductions in rice yield (~14%) and net rice income (~60%). Farmers reported increased use of chemical pesticides for management of apple snail. In addition, the cost of hired labor for physical removal of egg masses and snails is resulting in substantial negative effects on net income. Farmer age, area of land owned, responsibility for decision-making, receipt of extension advice, training, and membership of a farmer organization, were all statistically significant variables to explain farmers awareness of the need for area-wide apple snail management. Strategies to limit the spread of apple snail are urgently needed. A Multi-Institutional Technical Team (MITT) has been established to spearhead management efforts and consolidate advice to farmers on how to manage apple snail. However, without action to mitigate spread, the consequences could be disastrous for rice production and food security in Kenya, and for other rice growing regions across Africa. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Steam Pretreated Rice Biomass Condensate Containing Soluble Solid Inhibitors on Disruption of Pomacea Canaliculata Egg

Pomacea canaliculata is an invasive freshwater snail species that has become a serious pest of rice in irrigation and paddy fields and is popularly known as the golden apple snail. They are species that are capable of surviving and spreading rapidly, causing significant changes in the ecosystem. The application of natural by-products of a physicochemical method of biomass steam pre-treated condensate is one option for disrupting Pomacea Canaliculata egg. This experiment was conducted to investigate the feasibility of steam pre-treated rice biomass condensate which contained soluble solid inhibitors as a biopesticide to eradicate Pomacea canaliculata. Rice straw, rice husk, and a combination of rice straw and rice husk (1:1) were pre-treated by the saturated steam pre-treatment in a batch reactor at high temperatures (190°C and 210°C) for 10 min. The steam condensate produced from this system was analysed for major degraded products or inhibitors such as furfural, hydroxymethylfurfural (HMF), and phenol. The steam condensate which contained soluble solid inhibitors was then analysed for solubility test on P. canaliculata eggs. The effect of soluble solid inhibitors on the eggs was structurally examined by using a scanning electron microscope (SEM). The results revealed that rice husk which was pre-treated at 210°C reflected the highest contents of furfural (0.300 g/L), HMF (1.670 g/L), and phenol (0.087 g/L). However, the combination of rice biomass sample (1:1) condensate at 210°C demonstrated the greatest solubility percentage (11.51%) when treated to the eggs P. canaliculata eggs. The image of the egg structure examined by SEM clearly displayed the fractures forming on the cuticle layer of the eggs. SEM results demonstrated that the condensate from saturated steam pre-treated rice biomass has the possibility to be used as a biopesticide to disrupt the eggs and eventually could prevent the snails’ invasion. 

Field surveys reveal physicochemical conditions promoting occurrence and high abundance of an invasive freshwater snail (Potamopyrgus antipodarum)

Environmental conditions promoting the occurrence and high abundance of non-native taxa are linked to critical stages of species invasions: establishment, whether a site can sustain a population of the non-native taxon, and impact, the extent to which the consequences of establishment negatively affect the invaded ecosystem. Using surveys across environmental gradients, we examined the physicochemical conditions associated with the occurrence and abundance of the invasive New Zealand mudsnail (Potamopyrgus antipodarum) and co-occurring native mollusks. Abundance of Potamopyrgus very strongly increased with stream width and conductivity (specifically with chloride, sulfate, potassium, and sodium ions). Also, Potamopyrgus were most likely to occur at sites with relatively low pH and water velocity and relatively high calcium ion concentration and abundance also slightly increased in these conditions. The physicochemical conditions indicate the characteristics of sites that are suitable for establishment and secondary spread of Potamopyrgus. Native mollusks differed from Potamopyrgus in the physicochemical conditions associated with abundance suggesting that variation among habitats could permit native mollusks to persist at larger geographic scales even if they often co-occur with Potamopyrgus. Abundance of native Physa moderately decreased with abundance of Potamopyrgus. Because abundance of Physa and Potamopyrgus responded oppositely to stream width and conductivity, the negative relationship between the abundance of these two taxa may be caused by contrasting responses to physicochemical conditions, acting alone or in concert with biotic interactions.

Evaluating the combined use of feeding trials and a micrographic technique to study the natural diet of Pomacea canaliculata

Aquatic macrophytes supply an important link in freshwater systems through their multiple functions and ecosystem services. However, invasive generalist herbivores threatened their diversity and abundance. Pomacea canaliculata, one species of invasive freshwater apple snail, shows generalist macrophyte tendencies. Information about its natural diet would allow better anticipate its impacts but diet studies determining the macrophytes species eaten in natural aquatic environments are lacking. We evaluated the feasibility of identifying and quantifying macrophyte remains in P. canaliculata digestive contents. We performed single species and multiple species trials with five pre-weighed aquatic macrophytes to record the amount ingested of each of them and then dissected the snails to analyse their digestive contents microscopically. Microscopic traits provided ways to characterize macrophytes and distinguish them in combined species trials. Identifiable macrophyte remains highly varied in both single species (4.5–58.0%) and multiple species trials (5.7–35.1%); the total percentage of identifiable remains in the latter was 51–52%. The amount of identifiable remains in the multiple species trial was in general correlated with the amount ingested of each macrophyte although in one case it was strongly overestimated due to leaf fragmentation. The microscopic identification and quantification of macrophyte remains in the digestive contents appears feasible, even with several species that differ in abundance, if feeding trials accompany gut content analyses.

Effect of long-term temperature stress on the intestinal microbiome of an invasive snail.

The gut microbiome is vital to the physiological and biochemical functions of the host, and changes in the composition of these microbial communities may affect growth and adaptability to the environment. Pomacea canaliculata is an invasive freshwater snail which has become a serious agricultural pest. Temperature adaptation is considered an important reason for the widespread distribution of this species. To date, the contribution of the gut microbes to host fitness of P. canaliculata during long-term temperature stress is not well understood. In this study, the morphological changes and intestinal microbiome of P. canaliculata under long-term stress at low temperature (15°C) and high temperature (35°C) were investigated with laboratory experiments. Compared with control group (25°C), the alpha diversity increased and pathogenic bacteria enriched changed under high and low temperature stress. The effect of high temperature stress on the intestinal microbiome of P. canaliculata was more significant than that of low temperature stress. A sustained high temperature environment led to an increase in the abundance of pathogenic bacteria, such as Aeromonas and Enterobacter, and a decrease in the abundance of immune-related bacteria such as Bacteroidetes, Firmicutes, and Lactococcus. These intestine microbiome changes can increase the risk of diseases like intestinal inflammation, and lead to more deaths at high temperature environments. In addition, with the extension of stress time from 14 to 28 days, the beneficial bacteria such as Bacteroidetes, Firmicutes, and Lactococcus were significantly enriched, while potential pathogenic bacteria such as Pseudomonas, Acinetobacter, Shivalella, and Flavobacterium decreased, suggesting that intestinal microbiota may play an important role in host response to heat stress. These results are consistent with previously reported results that the survival rate of both male and female P. canaliculata no longer significantly reduced after 21 days of high temperature stress, suggesting that the surviving P. canaliculata had gradually adapted to high temperature environments under long-term high temperature stress.

Responses of survival, growth, and feeding of the invasive Golden Apple Snail (Pomacea canaliculata) to salinity stress

The Golden Apple Snail Pomacea canaliculata (Lamark, 1822) is one of the most aggressive invasive freshwater snails and has been found in tropical and subtropical regions around the world. Their presence threatens trophic structure in invaded ecosystems (e.g., wetlands) and harms human health both directly (e.g., as a vector of parasites) and indirectly (e.g., through altering the provision of ecosystem services from uninvaded ecosystems). The tolerance of Golden Apple Snails to saltwater is of concern because they may pose an invasion risk into estuary habitats. We studied the salinity tolerance of Golden Apple Snails by determining differences in their survival, growth, and feeding at 5 salinity levels (0, 2.5, 5.0, 7.5, and 10.0 practical salinity units [PSU]) over 30 d. Artificial seawater was prepared with aerated tap water and synthetic sea salt, consisting of NaCl (68.88%), KCl (1.79%), CaCl2 (2.55%), MgCl2 (8.67%), MgSO4 (5.36%), and NaHCO3 (12.75%). Snails were classified into 3 life stages based on shell length: juvenile (10–19.99 mm), mature (20–29.99 mm), and old snails (30–39.99 mm). Snails at all 3 life stages survived in salinities of 0 to 5.0 PSU but died within 9 d in salinities of 7.5 and 10.0 PSU. The survival percentage of snails decreased in the order: mature > old > juvenile. Snails across all life stages had reduced shell and mass growth with salinity exposure, but their feeding rate in salinity 2.5 and 5.0 PSU became similar to the control group after 23 d. Generally, Golden Apple Snails may live in waters of ≤5.0 PSU. Therefore, special attention should be paid to the activity of Golden Apple Snails in tropical and subtropical areas with salinities ≤5.0 PSU, which would be important for protecting against the snails’ destructive effects on productive resources.

Hypoxia Decreases Thermal Sensitivity and Increases Thermal Breadth of Locomotion in the Invasive Freshwater Snail Potamopyrgus antipodarum.

AbstractUnderstanding the physiology of invasive species will contribute to better prediction and prevention measures to avoid the economic and environmental consequences of biological invasions. Predicting the future range of Potamopyrgus antipodarum, a globally invasive aquatic snail, relies on a comprehensive understanding of its physiological tolerances to individual and combined environmental stressors. We conducted a laboratory study to investigate the interacting effects of temperature and dissolved oxygen in shaping the abiotic niche of P. antipodarum. We generated thermal performance curves (7°C-35°C) for resting respiration rate and voluntary locomotor behaviors under normoxia and hypoxia to find the conditions that limited each performance. Extreme high (>30°C) and low (<12°C) temperatures limited respiration and activity, but respiration rate was most oxygen sensitive at low temperatures. Under hypoxic conditions, activity was less thermally sensitive. Increased activity under high temperatures (22°C-28°C) may be fueled by anaerobic metabolism. Relying on anaerobic energy is a time-limited survival strategy, so further warming and deoxygenation of freshwater systems may limit the spread of this very tolerant invasive species.

Pomacea canaliculata Ampullar Proteome: A Nematode-Based Bio-Pesticide Induces Changes in Metabolic and Stress-Related Pathways.

Simple SummaryPomacea canaliculata is a South American invasive freshwater snail, affecting biodiversity, crop production and public health, now retrieved in Asian, North American and European countries. The identification of molecules connected to P. canaliculata adaptability may prove helpful in developing strategies that could overcome the snail’s resilience and stop its spread in non-original countries. This research presents the changes occurring in the proteome of a small organ, i.e., the ampulla, after challenging the snails with a nematode-based bio-pesticide. Transmission electron microscopy (TEM) analysis demonstrated that this organ has a complex connective ultrastructure and contains rhogocytes. TEM also confirmed the ampulla as a deposit of nitrogen-based material. After exposure to the nematode-based bio-pesticide, significant changes were observed for enzymes mainly involved in antioxidant defence, energy metabolism and cytoskeletal dynamics. These changes recall the systemic oxidative stress response that the snails undergo during the arousal after aestivation/hibernation, a physiological response involving other organs that, similarly to the ampulla, store nitrogen-based compounds. As fundamental players of the response against bio-pesticides and environmental cues, the enzymes identified in this research and involved in stress-related pathways may represent a suitable target for the efficacious and sustainable control of P. canaliculata spread.Pomacea canaliculata is a freshwater gastropod known for being both a highly invasive species and one of the possible intermediate hosts of the mammalian parasite Angiostrongylus cantonensis. With the aim of providing new information concerning P. canaliculata biology and adaptability, the first proteome of the ampulla, i.e., a small organ associated with the circulatory system and known as a reservoir of nitrogen-containing compounds, was obtained. The ampullar proteome was derived from ampullae of control snails or after exposure to a nematode-based molluscicide, known for killing snails in a dose- and temperature-dependent fashion. Proteome analysis revealed that the composition of connective ampulla walls, cell metabolism and oxidative stress response were affected by the bio-pesticide. Ultrastructural investigations have highlighted the presence of rhogocytes within the ampullar walls, as it has been reported for other organs containing nitrogen storage tissue. Collected data suggested that the ampulla may belong to a network of organs involved in controlling and facing oxidative stress in different situations. The response against the nematode-based molluscicide recalled the response set up during early arousal after aestivation and hibernation, thus encouraging the hypothesis that metabolic pathways and antioxidant defences promoting amphibiousness could also prove useful in facing other challenges stimulating an oxidative stress response, e.g., immune challenges or biocide exposure. Targeting the oxidative stress resistance of P. canaliculata may prove helpful for increasing its susceptibility to bio-pesticides and may help the sustainable control of this pest’s diffusion.

Annotated and Updated Checklist of Land and Freshwater Molluscs from Asturias (Northern Spain) with Emphasis on Parasite Transmitters and Exotic Species

Land and freshwater molluscs are the most abundant non-arthropod invertebrates from inland habitats worldwide, playing important ecological roles and some being important pests in agriculture. However, despite their ecological, and even economic and sanitary importance, their local diversity in many European regions is not perfectly understood, with a particularly notableknowledge gap in the northern Iberian malacofauna. This work aims at providing a revised checklist of continental gastropods and bivalves from the Asturias (northern Spain), based on the examination of newly collected and deposited material and on the critical analysis of published and gray literature. A total of 165 molluscan species are recognized. Ten species constitute new records from Asturias and seven from northern Iberian Peninsula. Seventeen species are introduced or invasive, evidencing the current increase of the bioinvasion rate in continental molluscs. Furthermore, all these exotic species are parasite transmitters or trematode intermediate hosts, and thus represent a potential bio-sanitary risk for human and other animal health. The provided data strongly suggest that the increase of invasive freshwater snail species can lead to an increase in parasitic infections, and this is a crucial point that transcends the merely scientific to the political-social sphere.

Invasive snails, parasite spillback, and potential parasite spillover drive parasitic diseases of Hippopotamus amphibius in artificial lakes of Zimbabwe

BackgroundHumans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction. Anthropogenic pressures can also occur indirectly, such as artificial lake creation and the subsequent introduction of invasive species that alter the ecosystem. These events can lead to drastic changes in parasite diversity and transmission, but generally receive little scientific attention.ResultsIn order to document and identify trematode parasites of the common hippopotamus (Hippopotamus amphibius) in artificial water systems of Zimbabwe, we applied an integrative taxonomic approach, combining molecular diagnostics and morphometrics on archived and new samples. In doing so, we provide DNA reference sequences of the hippopotamus liver fluke Fasciola nyanzae, enabling us to construct the first complete Fasciola phylogeny. We describe parasite spillback of F. nyanzae by the invasive freshwater snail Pseudosuccinea columella, as a consequence of a cascade of biological invasions in Lake Kariba, one of the biggest artificial lakes in the world. Additionally, we report an unknown stomach fluke of the hippopotamus transmitted by the non-endemic snail Radix aff. plicatula, an Asian snail species that has not been found in Africa before, and the stomach fluke Carmyerius cruciformis transmitted by the native snail Bulinus truncatus. Finally, Biomphalaria pfeifferi and two Bulinus species were found as new snail hosts for the poorly documented hippopotamus blood fluke Schistosoma edwardiense.ConclusionsOur findings indicate that artificial lakes are breeding grounds for endemic and non-endemic snails that transmit trematode parasites of the common hippopotamus. This has important implications, as existing research links trematode parasite infections combined with other stressors to declining wild herbivore populations. Therefore, we argue that monitoring the anthropogenic impact on parasite transmission should become an integral part of wildlife conservation efforts.Graphical abstract

Lethal and sub-lethal activity of Brevibacillus laterosporus on the mosquito Aedes albopictus and side effects on non-target water-dwelling invertebrates

The biocidal potential of Brevibacillus laterosporus against mosquitoes of major medical importance has been widely documented, but its effects on non-target invertebrates are still poorly known. In this study, we determined the lethal and sub-lethal effects of B. laterosporus strain UNISS 18, an entomopathogenic bacterium known for its effectiveness against synanthropic Diptera, on the larvae of the Asian tiger mosquito Aedes albopictus, a vector of several pathogens to humans. Moreover, we compared the larvicidal activity with the lethal action on the invasive snail Physella acuta and on two non-target water-dwelling species: the mayfly Cloeon dipterum, and the harlequin fly Chironomus riparius. B. laterosporus exhibited significant lethal effects on all the tested species with a concentration-dependent activity. However, the susceptibility varied among species, with a higher susceptibility of Ae. albopictus (LC50 = 0.16 × 107 spores mL−1) than the other species (LC50 = 0.31, 0.33, and 0.30 × 107 spores mL−1 for C. dipterum, C. riparius, and P. acuta, respectively). While 1st instar mosquito larvae were very susceptible to the bacterial infection, no effects on preimaginal development stages and adult emergence were observed at sub-lethal spores’ concentrations. Even if the efficacy of B. laterosporus against Ae. albopictus and the invasive freshwater snail P. acuta is promising for their control, the susceptibility of non-target beneficial aquatic insects, highlights the need of accurate evaluations before applying B. laterosporus for pest management in water environments.