Search

The negative interaction between multiple invasive species, when an invasive predator benefits from a previously introduced and abundant prey, poses unanticipated challenges for the joint management of invaders. To illustrate this question, we describe the surge and collapse of the invasive apple snail Pomacea maculata population before and after the arrival of the invasive blue crab, Callinectes sapidus, in the Ebro River (NE Spain). These two invaders have coincided for the first time beyond their respective native and prior invasive ranges, and thus lack any previous shared eco-evolutionary history facilitating coexistence. We leverage data from a 9-year apple snail removal programme (2014–2022) conducted by authorities to evaluate the effectiveness of the management programme and describe the apple snail temporal dynamics in the Ebro River. Since its arrival in 2013, the apple snail population increased exponentially along the river and adjacent rice-fields despite labour-intensive eradication efforts. Unexpectedly, riverine populations of the apple snail declined by 90% in 2018 relative to the prior year without apparent association with previous management efforts. Simultaneously, the blue crab was first recorded in the Ebro River in 2018, and its distribution rapidly overlapped the whole area invaded by apple snails. We suggest that over-predation by the blue crab is the main cause of the decline observed in the apple snail, and discuss the implications of this new invader-invader interaction for management. This study underscores the unforeseen consequences of subsequent waves of invasion, and the importance of supporting management with a deeper understanding of ecological interactions among invasive predator and prey species. [ABSTRACT FROM AUTHOR]

Aquatic invasive species decrease biodiversity and disrupt economic systems worldwide. Apple snails (Ampullaridae) from the genus Pomacea are globally invasive species that are highly damaging to aquaculture and aquatic ecosystems. Pomacea maculata was introduced to Louisiana in the early 2000s and rapidly spread throughout the southern half of the state, where invasive populations now threaten valuable aquaculture economies and a large area of aquatic ecosystems that sustain biodiversity important to commercial and recreational fisheries. Despite these risks, little work has been dedicated to understanding how apple snails disperse through invaded areas in Louisiana. To shed light on potential dispersal dynamics, we assessed population genetic structure of P. maculata in Louisiana at multiple spatial scales using microsatellites of snails collected from seven sampling locations. Overall, genetic diversity was relatively high across all sampling locations. Significant genetic structure was observed among sampling sites, indicating Barataria Preserve and the four sampling locations within Terrebonne Basin as distinct populations. Genetic distances were smallest among the four sampling locations within Terrebonne Basin. These findings suggest that dispersal within hydrologic units is higher than between units, meaning that apple snails may primarily move through systems through passive downstream dispersal. However, geographically distant populations also showed evidence of genetic mixing, pointing toward human-aided long-distance dispersal events. Regular dispersal of apple snails within and among hydrologic units highlights the risk of invasions in highly interconnected aquatic systems where dispersal rates may be especially high due to human modifications. [ABSTRACT FROM AUTHOR]

Pomacea maculata is a widely distributed agricultural and environmental pest in Asia. It is also causing ecological damage and threatening human health in the Southeastern United States. However, its limited mobility and fast consumption of aquatic vegetation may make it an excellent biomonitor to evaluate the pollution status of freshwater coastal ecosystems. This work investigated the capability of the operculum of this snail to accumulate toxic metals in a laboratory environment. We measured the elemental composition of the nucleus and edge regions on the varnish layer of the operculum by employing a MeV ion microprobe instrument. Iron, copper, and zinc were present in the operculum at trace levels. Copper was present at elevated levels in the operculum of snails exposed to copper for 2 weeks. Additionally, heterogeneity in the distribution of major and trace elements within the gastropod's operculum was revealed by 2D elemental images obtained using microparticle-induced X-ray emission spectrometry. On average, the nucleus of the operculum showed a higher accumulation of copper than did the edge. These results demonstrate that micro-PIXE can be used to look at the within-tissue distribution of toxic metals in hard tissues like a snail's operculum. We propose that the operculum metal concentrations can be used as a bioindicator capable of providing information on the ecosystem's health and potentially reveal temporal changes in this health. [ABSTRACT FROM AUTHOR]

The only wetland in Europe colonized successfully by the apple snail Pomacea maculata Perry, 1810, is the Ebro Delta (Spain). After 10 years, it has become widespread there, despite significant eradication attempts. In spite of its great negative ecological and economic impacts, its incorporation into food webs can result in an abundant potential resource for native and exotic predators. We identified the potential predators, including fishes, amphibians, crustaceans, birds, turtles and mammals in natural conditions using stable isotopic analyses (δ13C and δ15N). Six predator species, three native (two birds and one frog) and three invasive (one crustacean, one turtle and one mammal), were confirmed to consume apple snails. None of the 10 fish species analyzed consumed apple snails, although some have been previously observed consuming this snail under laboratory conditions. This study emphasizes the need to assess the consumption of apple snail, as well as other invasive organisms, by potential predators in natural conditions to confirm the establishment of new trophic relationships and to understand whether these potential predators actually act as biological control agents in nature. [ABSTRACT FROM AUTHOR]

Apple snail is one of the 100 invasive alien species of the world and saponin proved to be the most effective and promising bioactive compound to manage this pest. This study was conducted to develop a saponin based wettable powder formulation from Phaleria macrocarpa (Scheff.) Borel and to evaluate its efficacy against Pomacea maculata Perry undrer laboratory and glasshouse conditions. Results revealed that all prepared saponin based wettable formulations shown molluscicide effects towards P. maculata. However, F4 formulation consisted of Terwet® 157, Terspers® 2700 and Kaolin at proportion of 15:15:70 revealed significantly higher feeding deterrent activities among prepared formulations and it was not significantly different from positive controls niclosamide and tea seed cake. In terms of lethel effects, the shortest LT50 (154 minutes) was recorded in niclosamide followed by 702 minutes in F4 formulation and 728 minutes in tea seed cake. F4 formulation along with positive control tea seed cake was further assessed in glasshouse condition. F4 formulation illustrated shortest LT50 value (750 minutes) with lowest feeding consumption percentage (0.6%) compared to LT50 (784 minutes) and feeding consumption percentage (1.3%) in positive control tea seed cake. Feeding consumption percentage (40.6%) was recorded for negative control water. Results sugest that F4 saponin based wettable powder overall performed better and can be efficiently used to control the apple snails as an eco friendly botanical molluscicide. [ABSTRACT FROM AUTHOR]

After a long hiatus, interest in the morphology of the respiratory organs in apple snails (Ampullariidae, Caenogastropoda) and its functional and evolutionary bearings is making a comeback. The variability in the morphology of the gill and lung and its link to different lifestyles and patterns of air dependency within the Ampullariidae make research on the morphology of the respiratory organs particularly suitable for approaching the evolution of terrestriality in animals. Additionally, morphology is a valuable source of hypotheses regarding the several functions the ampullariid respiratory organs have besides respiration. However, this is an underexplored field that only recently has incorporated ultrastructural and three-dimension visualization tools and in which more research is much needed, particularly, comparisons between species representing the diversity within the Ampullariidae. In this paper, I examine Mueck, Deaton & Lee’s (2020a) assessment of the morphology of the gill and lung of Pomacea maculata and compare it with earlier and contemporary studies on other ampullariid species. I show that Mueck, Deaton & Lee’s paper combines significant morphological misinterpretations, conceptual and terminological mistakes, and crucial literature omissions. I also reinterpret their results and point to the similarities and differences between them and available data on other ampullariids. [ABSTRACT FROM AUTHOR]

Apple snail is one of the major pest of rice crop and saponin proved to be the most promising bioactive compound to control it. This study was carried out to quantify saponin from God's Crown, Phaleria macrocarpa and to evaluate its efficacy against the biological activities of black apple snail, Pomacea maculata. Fruits, leaves and stem-barks of P. macrocarpa were quantified for saponin using HPLC. The toxicity of leaf and fruit crude extracts was evaluated through mortality and feeding deterrent bioassays using complete randomized design and data were analyzed by ANOVA for LSD test. The highest saponin contents 24.67 ppm was detected in fruits followed by 22.67 ppm in leaves and 5.94 ppm in stembark. Bioassays showed the highest mortality percentage (44%) after 24 hours exposure at the concentration of 1000 ppm of a leaf extract followed by 36% and 28% @ 750 and 1000 ppm of leaf and fruit extracts, respectively. After the exposure of 48 hours, mortality percentage increased to 100% @ 1000 and 750 ppm of both crude extracts while the mortality percentage recorded at the concentration of 500 ppm of leaves and fruits were 56% and 52% respectively. Mortality percentage at the concentration of 500 ppm was increased to 80% and 68% in leaf and fruit extracts after exposure of 72 hours, respectively. In terms of feeding deterrent, 1000, 750 and 500 ppm concentration of both crude extracts were not significantly different from the positive control niclosamide (p>0.05). The results obtained from the study revealed that saponin extracted from fruits and leaves of P. macrocarpa has a potential to control black apple snails. [ABSTRACT FROM AUTHOR]

After a long hiatus, interest in the morphology of the respiratory organs in apple snails (Ampullariidae, Caenogastropoda) and its functional and evolutionary bearings is making a comeback. The variability in the morphology of the gill and lung and its link to different lifestyles and patterns of air dependency within the Ampullariidae make research on the morphology of the respiratory organs particularly suitable for approaching the evolution of terrestriality in animals. Additionally, morphology is a valuable source of hypotheses regarding the several functions the ampullariid respiratory organs have besides respiration. However, this is an underexplored field that only recently has incorporated ultrastructural and three-dimension visualization tools and in which more research is much needed, particularly, comparisons between species representing the diversity within the Ampullariidae. In this paper, I examine Mueck, Deaton & Lee’s (2020a) assessment of the morphology of the gill and lung of Pomacea maculata and compare it with earlier and contemporary studies on other ampullariid species. I show that Mueck, Deaton & Lee’s paper combines significant morphological misinterpretations, conceptual and terminological mistakes, and crucial literature omissions. I also reinterpret their results and point to the similarities and differences between them and available data on other ampullariids.

Gastropod Molluscs rely exclusively on the innate immune system to protect from pathogens, defending their embryos through maternally transferred effectors. In this regard, Pomacea snail eggs, in addition to immune defenses, have evolved the perivitellin-2 or PV2 combining two immune proteins into a neurotoxin: a lectin and a pore-forming protein from the Membrane Attack Complex/Perforin (MACPF) family. This binary structure resembles AB-toxins, a group of toxins otherwise restricted to bacteria and plants. Many of these are enterotoxins, leading us to explore this activity in PV2. Enterotoxins found in bacteria and plants act mainly as pore-forming toxins and toxic lectins, respectively. In animals, although both pore-forming proteins and lectins are ubiquitous, no enterotoxins have been reported. Considering that Pomacea snail eggs ingestion induce morpho-physiological changes in the intestinal mucosa of rodents and is cytotoxic to intestinal cells in culture, we seek for the factor causing these effects and identified PmPV2 from Pomacea maculata eggs. We characterized the enterotoxic activity of PmPV2 through in vitro and in vivo assays. We determined that it withstands the gastrointestinal environment and resisted a wide pH range and enzymatic proteolysis. After binding to Caco-2 cells it promoted changes in surface morphology and an increase in membrane roughness. It was also cytotoxic to both epithelial and immune cells from the digestive system of mammals. It induced enterocyte death by a lytic mechanism and disrupted enterocyte monolayers in a dose-dependent manner. Further, after oral administration to mice PmPV2 attached to enterocytes and induced large dose-dependent morphological changes on their small intestine mucosa, reducing the absorptive surface. Additionally, PmPV2 was detected in the Peyer's patches where it activated lymphoid follicles and triggered apoptosis. We also provide evidence that the toxin can traverse the intestinal barrier and induce oral adaptive immunity with evidence of circulating antibody response. As a whole, these results indicate that PmPV2 is a true enterotoxin, a role that has never been reported to lectins or perforin in animals. This extends by convergent evolution the presence of plant- and bacteria-like enterotoxins to animals, thus expanding the diversity of functions of MACPF proteins in nature.

Pomacea canaliculata and P. maculata are freshwater apple snails considered two of the most invasive alien species worldwide. They are expanding their ranges in Asia, Europe and North America, damaging crops, wetland ecosystems and endangering human health. Despite having different invasive potential, they have systematically been misidentified because of their morphological plasticity with highly variable shells, which hampers efforts to manage their spread and impact. Thus, additional work is needed to clarify species boundaries in this group of Pomacea. Here we report a new taxonomic character based on the spectroscopic characteristics of their pigmented perivitellins (egg proteins) and a fast and simple method for measuring it. The egg perivitelline fluid is analyzed via conventional agarose gel electrophoresis and the naturally-colored egg carotenoproteins are extracted, without the need for staining, and analyzed spectrophotometrically. Then, the ratio between two wavelengths (PQ) of the absorbance spectra is calculated. Results can be obtained in less than 24 h. The method was validated in the field by analysing seven populations from Asia (non-native) and South America (native) that had been genetically identified and in which PQ differed consistently between the two species. Eggs are oviposited in conspicuous reddish masses above the waterline, allowing rapid detection and easy collection of samples in the field. This novel tool would be valuable in integrative taxonomic studies to distinguish these two lineages of Pomacea and contribute to our understanding of Pomacea diversity. [ABSTRACT FROM AUTHOR]

Gastropod Molluscs rely exclusively on the innate immune system to protect from pathogens, defending their embryos through maternally transferred effectors. In this regard, Pomacea snail eggs, in addition to immune defenses, have evolved the perivitellin-2 or PV2 combining two immune proteins into a neurotoxin: a lectin and a pore-forming protein from the Membrane Attack Complex/Perforin (MACPF) family. This binary structure resembles AB-toxins, a group of toxins otherwise restricted to bacteria and plants. Many of these are enterotoxins, leading us to explore this activity in PV2. Enterotoxins found in bacteria and plants act mainly as pore-forming toxins and toxic lectins, respectively. In animals, although both pore-forming proteins and lectins are ubiquitous, no enterotoxins have been reported. Considering that Pomacea snail eggs ingestion induce morpho-physiological changes in the intestinal mucosa of rodents and is cytotoxic to intestinal cells in culture, we seek for the factor causing these effects and identified PmPV2 from Pomacea maculata eggs. We characterized the enterotoxic activity of PmPV2 through in vitro and in vivo assays. We determined that it withstands the gastrointestinal environment and resisted a wide pH range and enzymatic proteolysis. After binding to Caco-2 cells it promoted changes in surface morphology and an increase in membrane roughness. It was also cytotoxic to both epithelial and immune cells from the digestive system of mammals. It induced enterocyte death by a lytic mechanism and disrupted enterocyte monolayers in a dose-dependent manner. Further, after oral administration to mice PmPV2 attached to enterocytes and induced large dose-dependent morphological changes on their small intestine mucosa, reducing the absorptive surface. Additionally, PmPV2 was detected in the Peyer's patches where it activated lymphoid follicles and triggered apoptosis. We also provide evidence that the toxin can traverse the intestinal barrier and induce oral adaptive immunity with evidence of circulating antibody response. As a whole, these results indicate that PmPV2 is a true enterotoxin, a role that has never been reported to lectins or perforin in animals. This extends by convergent evolution the presence of plant- and bacteria-like enterotoxins to animals, thus expanding the diversity of functions of MACPF proteins in nature. [ABSTRACT FROM AUTHOR]

Global change is the origin of increased occurrence of disturbance events in natural communities, with biological invasions constituting a major threat to ecosystem integrity and functioning. The apple snail (Pomacea maculata) is a freshwater gastropod mollusk from South America. Considered one of the 100 most harmful invasive species in the world, due to its voracity, resistance, and high reproductive rate, it has become a global problem for wetland crops. In Catalonia, it has affected the rice fields of the Ebre Delta since 2010 with significant negative impact on the local economy. As a gastropod mollusc it possesses statocysts consisting of a pair of sacs, one located on each side of the foot, that contain multiple calcium carbonate statoconia. This study shows the first ultrastructural images of pathological changes in the sensory epithelium of the statocyst of apple snail adults with an increase in the severity of the lesions over time after exposure to low frequency sounds. Sound-induced damage to the statocyst could likely result in an inhibition of its vital functions resulting in a potential reduction in the survival ability of the apple snail and lead to an effective mitigation method for reducing damage to rice fields.

Aquatic habitats have been highly modified by human actions that reduce their native diversity and create conditions suitable for tolerant alien species. Pomacea maculata was detected in 2009 in both the alluvial plain and the final stretch of the Ebro River. Since then, a permanent population has stabilized in the littoral area of the river where the water level fluctuates according to the river discharge. Melanopsis tricarinata is an endemic snail species highly affected by the reduction in its natural habitat. Currently, the two species do not share the same reaches in the river, but the possibility exists, as the distribution of the P. maculata is constantly increasing. This study aims to analyse the diets and to assess the responses of both snails to global change. The diet of both species was analysed in the field and their responses to water warming and dryness compared under laboratory conditions. This study includes the calculation of future river water temperatures based on air temperature projections. In addition, based on water discharge management scenarios, the study estimated the increase in dry river bed area. The diet of both snail species was similar and based on Cladophora. P. maculata better resisted high temperatures and dry conditions than M. tricarinata. The projections of water temperatures showed an increase in daily temperatures, especially in summer. The hydraulic model suggested that a relevant increase in dry river bed areas will occur. Overall, these results provide insight into the global change factors that could favour P. maculata spread in the river and the reduction in suitable habitat for M. tricarinata and will be useful for future decisions of water discharge management. [ABSTRACT FROM AUTHOR]

Invasive species of Pomacea snails are of growing concern when it comes to the conservation of global biodiversity. Pomacea canaliculata has been listed among the world's 100 worst invasive species. In this work, phylogeographic patterns and the demographic history of P. canaliculata and P. maculata from different countries were analyzed using mtDNA cytochrome c oxidase subunit-I (COI) sequences. The results showed that P. canaliculata and P. maculata had high genetic diversity, significant genetic differentiation, limited gene flow and stable population dynamics among different countries. Genetic diversity of P. canaliculata was higher than P. maculata. Our study will also provide important information for the effective prevention and control of the spread of Pomacea snails. [ABSTRACT FROM AUTHOR]

The Limpkin (Aramus guarauna) is a medium-sized wading bird found in peninsular Florida and Central and South America, whose distribution is strongly tied to the presence of apple snails (genus Pomacea). Historically, Limpkins have been infrequently observed in the lower Apalachicola-Chattahoochee-Flint (ACF) watershed, including Lake Seminole, the most downstream reservoir in the system. In the past decade in Lake Seminole, a rapid increase in the nonnative P. maculata has been documented. In 2016, a Limpkin was observed in the lake, and we made efforts to document all subsequent Limpkin observations there. In the following year, we observed Limpkins (including several mating pairs) each month from February to July 2017. Limpkins were only observed in the Flint River section of the reservoir, the same area where the greatest abundance of P. maculata has been documented. We hypothesize the rapid increase of P. maculata is responsible for the recent regular Limpkin observations at the lake because observations of Limpkins prior to the recent expansion of P. maculata were rare and infrequent. Apple snails are likely to expand within the southeastern United States in the future, thereby creating additional suitable habitat for Limpkins and other specialist avian predators of apple snails. [ABSTRACT FROM AUTHOR]

Since 2009 the apple snail Pomacea maculata has become a new invader of Oryza sativa (rice) fields and wetlands in Europe, only invading the Ebro Delta (north‐eastern Spain) thus far. It is considered a highly invasive and damaging species, resulting in large economic losses worldwide.Despite the severe impact of the invasive apple snail on both cultivated and natural wetlands, it has become an abundant potential resource for native avian predators.In this study, stable isotope analysis was used to assess the consumption of the apple snail by the glossy ibis Plegadis falcinellus in the Ebro Delta.The results indicate the importance of the apple snail in the diet of this native bird. In particular, isotopic results indicated that apple snails and freshwater coleopterans were the main prey in the diet of glossy ibis chicks, accounting for 26–40% of their diet. Thus, this native bird species could potentially help in the biological control of this invasive snail, but is not expected to eradicate it.Although the spread of this pest in rice fields and wetlands is not desirable, we predict that the apple snail will follow a path similar to other invasive species, such as the red swamp crayfish Procambarus clarkii, in establishing itself as part of the wetland food web. [ABSTRACT FROM AUTHOR]

Pomacea spp. are freshwater gastropods that significantly reduce rice productivity around the world, particularly in Asian countries. Pomacea maculata was first reported in Europe in 2009 in the rice fields of the Ebro Delta, Tarragona (Catalonia), Spain. At present, tea seed ( Camellia oleifera ) saponins are the only authorized treatment by the Spanish agriculture authorities, but due to its comparatively high toxicity to non-target species such as fish, more environmental-friendly products are urgently needed. This study evaluated the performance of a novel molluscicide based on modified saponins derived from quinoa ( Chenopodium quinoa ) husks against Pomacea maculata under laboratory and field conditions in the Ebro Delta. Under laboratory conditions, the molluscicide killed 100% of the P. maculata above 7 ppm of saponins after 72 h. Field trials performed in three rice fields showed that after 96 h the molluscicide killed 88, 89 and 93% of P. maculata at doses of 6.5, 7.2 and 7.7 ppm saponin, respectively. Toxicological assays showed that the product is highly safe for aquatic environments, with an effect concentration of (EC 50 ) >36 mg saponins/L for crustaceans ( Daphnia) and algae ( Selenastrum capricornutum ) and a lethal concentration (LC 50 ) against common carp >36 mg saponins/L. Studies on rats, rabbits and guinea pigs showed that the molluscicide is generally non-hazardous for acute oral toxicity, slightly hazardous for acute dermal toxicity, a moderate irritant for acute eye irritation/corrosion, a non-irritant for acute dermal irritation/corrosion and a non-skin sensitizer. These results suggest that this novel molluscicide may be a viable product to safely control P. maculata in rice fields. [ABSTRACT FROM AUTHOR]

Low, L. and Anderson, C.J., 2017. The threat of a nonnative, invasive apple snail to oligohaline marshes along the northern Gulf of Mexico. Aquatic invasive species continue to be a persistent ecological problem. Management of these species requires understanding of their impact and the conditions favorable for their occurrence. Pomacea maculata is an invasive, nonnative freshwater apple snail threatening wetlands through substantial herbivory. Recent detection of P. maculata in coastal Alabama has raised concerns regarding the susceptibility of estuarine marshes in Mobile Bay and the northern Gulf of Mexico. To evaluate this threat, mesocosms were created to examine snail response to the combined effects of salinity and plant species common to estuaries throughout the region. Over a 5-week period, snails in brackish-water mesocosms (∼10 parts per thousand [ppt], with Juncus roemerianus or Cladium jamaicense) became dormant and neither fed nor reproduced. Snails in freshwater mesocosms (<1 ppt, with Alternanthera philoxeroides or Sagittaria lancifolia) were active and exhibited herbivory, whereas snails in mixed salinity (∼5 ppt, with Typha angustifolia and Scirpus validus) exhibited some activity but minimal herbivory. In follow-up studies examining salinity and plant species individually, snails fed on palatable leaves in only freshwater and mixed salinity conditions. Further, snails in freshwater did not consume measureable amounts of S. validus, T. angustifolia, J. roemerianus, and C. jamaicense, suggesting that plant palatability of common estuarine plants may also restrict herbivory. From these results, managers are cautioned that estuarine marshes with low to mixed salinities and colonized by palatable plants may be susceptible to invasion by P. maculata. [ABSTRACT FROM AUTHOR]

The spread of non-native species raises concerns about native species displacement, while other negative effects on native species (e.g., habitat degradation) should also be considered. The highly invasive non-native apple snail Pomacea maculata has raised such concerns as it has become established in a wide range of aquatic systems worldwide. While monitoring native Florida P. paludosa populations in Lake Tohopekaliga (LTOHO) from 2001 to 2009 and in Water Conservation Area 3A (WCA3A, Everglades) from 2006 to 2015, we opportunistically documented the establishment and distribution of P. maculata. We estimated snail densities and recorded egg cluster presence in three study sites (12 total plots, LTOHO) and 137 sites (WCA3). On LTOHO, native snails were absent or at very low densities prior to finding P. maculata. Few snails of either species were found in high-stem-density vegetation of the littoral zone. Pomacea maculata immigration into the littoral zone occurred following managed vegetation removal, and Hydrilla verticillata proliferation in LTOHO likely contributed to the spread of P. maculata. We found both native and non-native apple snail species in many WCA3A sites following P. maculata invasion. We initially found the non-native snail in two sites in southern WCA3A; they were mostly restricted to within three kilometers of initial sites over the next four years. Overall plant community compositions in LTOHO and WCA3A appeared less impacted than expected based on previous reports of P. maculata invasions.

Dispersal and local environmental factors are major determinants of invasive species distribution. We examined how both dispersal-related geospatial characteristics and environmental factors influence an ongoing invasion of wetlands in a south-central Florida ranchland by non-native apple snails ( Pomacea maculata, Ampullariidae). We found P. maculata in 73 (43%) of a random set of 171 wetlands in 2014. We used model selection to evaluate multiple hypotheses of predictors of P. maculata occurrence in 95 wetlands with standing water, including spatially-explicit distances in ditches from wetlands to the presumed entry point, Euclidean (overland) distances, presence/absence of ditches in wetlands, and environmental variables (e.g. pH). We also performed a 5-month field experiment in 20 wetlands to evaluate if snail absence was associated with conditions that limit survival and growth (i.e. unfavorable habitats). Snail occurrence was primarily associated with presence of ditches in wetlands and more neutral wetland pH. These variables more plausibly explained snail occurrence than did Euclidean (overland) distance and minimum ditch travel (rectilinear) distance from propagule sources (a major waterway). Wetland pH best explained survival and growth under the experimental conditions. We found no evidence that prior occupancy by conspecifics affected survival and growth, suggesting that dispersal limitation may contribute to lack of occupancy of wetlands, despite suitable pH. Our study supports man-made conduits as facilitators of dispersal by non-native species, where environmental characteristics (here pH) then also affect colonization within habitats. An understanding of both dispersal mechanisms and local environmental factors is necessary to better predict invasive species distribution. [ABSTRACT FROM AUTHOR]

Golden Apple Snail (GAS) is the most destructive invasive rice pest in Southeast Asia. The cost of synthetic molluscicides, their toxicity to non-target organisms, and their persistence in the environment have propelled the research of plant-derived molluscicides. Most research efforts have focused on individual plant extracts for their molluscicidal potency against GAS and have not been proven to be entirely effective in rice field conditions. Selective combination of synergistically acting molluscicidal compounds from various plant extracts might be an effective alternative. In this direction, ethanolic extracts from six different plants (Neem, Tobacco, Nerium, Pongamia, Zinger, and Piper) were evaluated against Pomacea maculata Perry. Of the various combinations studied, a binary extract (1:1) of nerium and tobacco (LC90 177.71 mg/L, 48 h), and two tri-herbal extract formulations (1:1:1) of (nerium + tobacco + piper) and (nerium + tobacco + neem) were found to be most effective, with LC90 values of 180.35 mg/L and 191.52 mg/L, respectively, in laboratory conditions. The synergistic effect of combined herbal extracts resulted in significant reduction in LC90 values of the individual extracts. The findings of this study demonstrate that the selective combinations of potent molluscicidal herbal extracts are effective for management of P. maculata under laboratory conditions. [ABSTRACT FROM AUTHOR]

This study examines the potential for silicon soil amendments and nitrogen to reduce apple snail, Pomacea canaliculata Lamarck, damage to rice ( Oryza sativa L.) seedlings. A rate of 75 kg/ha of nitrogen applied as (NH 4 ) 2 SO 4 to rice (cv IR64 and cv YTH183) seedbeds increased seedling biomass, allowing the seedlings to gain critical stem thickness and avoid snail herbivory. These seedlings remained relatively large after exposure to snails in pot experiments, mainly because of faster growth rates, but also due to lower damage from snails to >21 day-old IR64 seedlings. Silicon applied as Na 2 O 3 Si·9H 2 0 alone (without nitrogen) reduced seedling growth compared to control seedlings. When nitrogen and silicon were applied together, the addition of silicon resulted in reduced seedling growth in YTH183 compared to seedlings treated with nitrogen alone. However, the same effect was not noted for IR64 seedlings, indicating clear variety-specific responses to seedbed inputs. Regardless of variety, silicon-treated seedlings that were transplanted to snail-infested pots at 21 days after seeding (DAS) had lower biomass than seedlings without silicon despite silicon-treated IR64 seedlings having less snail damage than untreated controls. From an experiment conducted in snail-infested ponds, we found no difference between snail damage to silicon (SiO 2 )-treated and control cv IR50 seedlings. Although we did not determine silicon levels in plant tissues, our results indicate that the effects of silicon soil amendments are largely insufficient to reduce the impact of apple snails to young rice seedlings (≤21 DAS). [ABSTRACT FROM AUTHOR]

The freshwater snails Pomacea Perry, 1810 lay conspicuous aerial egg clutches that are ignored by most predators. Egg biochemical defenses in the apple snail Pomacea canaliculata (Lamarck, 1822) are provided by multifunctional proteins. We analyzed the eggs of a sympatric species, Pomacea maculata Perry, 1810, studying the gross composition, toxicity, hemagglutinating activity, and its antinutritive and antidigestive properties. Eggs are mostly composed of polysaccharides (mainly galactogen) and proteins, followed by lipids and nonsoluble calcium. Two perivitellins account for ∼85% dry mass of the egg protein. The major lipids are phospholipids and sterols. A suite of potential defenses was determined, including strong lethal neurotoxicity on mice and moderate antidigestive and lectin activities. Remarkably, their polysaccharides were refractive to in vitro digestion by digestive glycosidases. This study characterized ∼99% of egg composition and identified multiple potential defenses, provided not only by proteins but also by polysaccharides. This is the first evidence to our knowledge that reserve sugars may be involved in defenses, giving further insight into the unusual reproductive strategy of these well-defended snail eggs. [ABSTRACT FROM AUTHOR]

Identifying impacts of non-native species on native populations is central to conservation and ecology. While effects of non-native predators on native prey populations have recently received much attention, impacts of introduced prey on native predator populations are less understood. Non-native prey can influence predator behavior and demography through direct and indirect pathways, yet quantitative assessments of the relative impacts of multiple, potentially counteracting, effects on native predator population growth remain scarce. Using ≈20 years of range-wide monitoring data, we tested for effects of a recently introduced, rapidly spreading non-native prey species ( Pomacea maculata) on the behavior and demography of the endangered Snail Kite ( Rostrhamus sociabilis). Previous studies found that food-handling difficulties caused by the large size of P. maculata (relative to the native P. paludosa) can lead to energetic deficiencies in juvenile kites, suggesting the potential for evolutionary traps to occur. However, high densities of P. maculata populations could facilitate kites by providing supplemental food resources. Contrary to prior hypotheses, we found that juvenile apparent survival increased ≈50% in wetlands invaded by non-native snails. Breeding rates and number of young fledged/successful nests were also positively associated with non-native snail presence, suggesting direct trophic benefits to kites. We found no direct effects of the invasive snail on adult survival or daily nest survival rates. Kite movements and breeding distribution closely tracked the spread of non-native snail populations. Since 2005, kites have been heavily concentrated in northern regions where non-native snails have established. This geographic shift has had hidden costs, as use of northern regions is associated with lower adult survival. Despite negative impacts to this key vital rate, matrix population modeling indicated that the multifarious effects of the non-native snail invasion on kites culminated in increased population growth rates, likely lowering short-term extinction risks. Results suggest that considering only particular components of behavior or demography may be inadequate to infer the population-dynamic importance of non-native prey on native predators, including their role in creating potential evolutionary traps. Our findings provide information pertinent to Everglades restoration, highlighting potential management trade-offs for non-native species that may aid imperiled species recovery yet disrupt other native communities. [ABSTRACT FROM AUTHOR]

Avian vacuolar myelinopathy (AVM) is a neurologic disease causing recurrent mortality of Bald Eagles ( Haliaeetus leucocephalus) and American Coots ( Fulica americana) at reservoirs and small impoundments in the southern US. Since 1994, AVM is considered the cause of death for over 170 Bald Eagles and thousands of American Coots and other species of wild birds. Previous studies link the disease to an uncharacterized toxin produced by a recently described cyanobacterium, Aetokthonos hydrillicola gen. et sp. nov. that grows epiphytically on submerged aquatic vegetation (SAV). The toxin accumulates, likely in the gastrointestinal tract of waterbirds that consume SAV, and birds of prey are exposed when feeding on the moribund waterbirds. Aetokthonos hydrillicola has been identified in all reservoirs where AVM deaths have occurred and was identified growing abundantly on an exotic SAV hydrilla ( Hydrilla verticillata) in Lake Tohopekaliga (Toho) in central Florida. Toho supports a breeding population of a federally endangered raptor, the Florida Snail Kite ( Rostrhamus sociabilis) and a dense infestation of an exotic herbivorous aquatic snail, the island applesnail ( Pomacea maculata), a primary source of food for resident Snail Kites. We investigated the potential for transmission in a new food chain and, in laboratory feeding trials, confirmed that the AVM toxin was present in the hydrilla/ A. hydrillicola matrix collected from Toho. Additionally, laboratory birds that were fed apple snails feeding on hydrilla/ A. hydrillicola material from a confirmed AVM site displayed clinical signs (3/5), and all five developed brain lesions unique to AVM. This documentation of AVM toxin in central Florida and the demonstration of AVM toxin transfer through invertebrates indicate a significant risk to the already diminished population of endangered Snail Kites. [ABSTRACT FROM AUTHOR]

Apple snails, P. canaliculata and P. maculata are the two most successful invaders of many macrophytes especially rice in many countries of the world particularly Southeast Asia. Many studies have been conducted on ecology and management of P. canaliculata but little is known about the life cycle of P. maculata especially on rice. Therefore, comparative life cycle studies of P. maculata and P. canaliculata were conducted on rice. Results suggested that P. canaliculata showed significantly higher growth than P. maculata and matured during the 27th week of development, whereas the latter matured during the 32nd week. At maturity, no difference was recorded between two species for shell length and width. However, individuals of both species started consuming rice during the 4th week of the development. Shell length and width of both species were highly correlated with each other during the entire growth. Egg diameter was significantly higher in P. canaliculata than P. maculata, however, no significant difference was observed in the number of eggs, hatching period and rate for the two species. The results obtained can be utilized for the rearing technique of Pomacea spp. on rice to maintain cultures of different stages to study their unique features contributing to their successful invasion, and suggest appropriate management strategies to reduce their damage and spread. [ABSTRACT FROM AUTHOR]

Golden Apple Snail (GAS) is the most destructive invasive rice pest in Southeast Asia. The cost of synthetic molluscicides, their toxicity to non-target organisms, and their persistence in the environment have propelled the research of plant-derived molluscicides. Most research efforts have focused on individual plant extracts for their molluscicidal potency against GAS and have not been proven to be entirely effective in rice field conditions. Selective combination of synergistically acting molluscicidal compounds from various plant extracts might be an effective alternative. In this direction, ethanolic extracts from six different plants (Neem, Tobacco, Nerium, Pongamia, Zinger, and Piper) were evaluated against Pomacea maculata Perry. Of the various combinations studied, a binary extract (1:1) of nerium and tobacco (LC90 177.71 mg/L, 48 h), and two tri-herbal extract formulations (1:1:1) of (nerium + tobacco + piper) and (nerium + tobacco + neem) were found to be most effective, with LC90 values of 180.35 mg/L and 191.52 mg/L, respectively, in laboratory conditions. The synergistic effect of combined herbal extracts resulted in significant reduction in LC90 values of the individual extracts. The findings of this study demonstrate that the selective combinations of potent molluscicidal herbal extracts are effective for management of P. maculata under laboratory conditions.

Abstract EFSA requested the PLH Panel to review the current state of the art of the biology and ecology of apple snails, reported in this opinion, and to perform an environmental risk assessment for validation of the Plant Health environment guidance document, which will be provided in a second opinion. The Panel presents in this opinion the current state of the art of the biology of apple snails, and develops and uses a population dynamics model to assess the potential establishment of apple snails in the EU. A thorough review of the literature on the biology of Pomacea canaliculata and P. maculata was performed to collect information and data on life history characteristics related to temperature, which was used in the population dynamics model. Although uncertainties on the systematics and taxonomy of the genus Pomacea remain, it is now acknowledged that Pomacea insularum is a synonym of P. maculata and can be undoubtedly differentiated from P. canaliculata. Natural spread occurs via rivers and canals, in which the snails crawl, drift, float and raft. Flooding increases spread. In addition, attachment to animals (e.g. birds, cattle, horses, deer and aquatic invertebrates) results in spread. Human assistance results in spread through cultivation transport of rice seedlings, aquaculture, aquaria, boats, and agricultural field machinery. The potential distribution of P. canaliculata in Europe was obtained by calculating with the population dynamics model, the average snail abundance per year in each node of a grid of 0.25 × 0.25 degrees covering Europe, which resulted in the following conclusions: (1) the area of potential establishment comprises wetlands of southern Europe (i.e. Spain, southern France, most of Italy and Greece) and the Balkans up to the latitude of the Danube river, (2) the potential area of establishment includes the rice production areas in Europe.

Ecosystems with multiple exotic species may be affected by facilitative invader interactions, which could lead to additional invasions (invasional meltdown hypothesis). Experiments show that one-way facilitation favours exotic species and observational studies suggest that reciprocal facilitation among exotic species may lead to an invasional meltdown. We conducted a mesocosm experiment to determine whether reciprocal facilitation occurs in wetland communities., We established communities with native wetland plants and aquatic snails. Communities were assigned to treatments: control (only natives), exotic snail ( Pomacea maculata) invasion, exotic plant ( Alternanthera philoxeroides) invasion, sequential invasion (snails then plants or plants then snails) or simultaneous invasion (snails and plants)., Pomacea maculata preferentially consumed native plants, so A. philoxeroides comprised a larger percentage of plant mass and native plant mass was lowest in sequential (snail then plant) invasion treatments., Even though P. maculata may indirectly facilitate A. philoxeroides, A. philoxeroides did not reciprocally facilitate P. maculata. Rather, ecosystems invaded by multiple exotic species may be affected by one-way facilitation or reflect exotic species' common responses to abiotic factors or common paths of introduction. [ABSTRACT FROM AUTHOR]

One of the most successful groups of invasive consumers worldwide is freshwater snails of the family Ampullariidae, including Pomacea maculata, yet little is known about snail survival and growth in the range of conditions found in estuarine ecosystems. Here, we provide an experimental assessment of P. maculata survivability in estuarine conditions, documenting: (1) egg susceptibility to tidal inundation (2) salinity tolerance of snails, and (3) salinity effects on hatchling growth. Results indicate that estuarine conditions will not limit apple snail colonization in oligohaline and mesohaline reaches of estuaries, with eggs remaining viable when exposed to periodic inundations typical of a tidal regime and modest, albeit reduced, growth and survival at moderate salinities (5 and 10 ppt). For this reason, rapid detection and eradication of P. maculata in estuarine areas is needed to avoid the invasion of snails in these vital, productive environments. [ABSTRACT FROM AUTHOR]