Invasive Freshwater Snail Research Articles

Sharing the load: a survey of parasitism in the invasive freshwater pulmonate, Physa acuta (Hygrophila: Physidae) and sympatric native snail populations

The highly invasive freshwater snail, Physa acuta, was examined for parasites over temporal and spatial scales. All populations studied had a high prevalence of the parasitic morph of the oligochaete worm, Chaetogaster limnaei. This worm was also found to infect two native snails, Glyptophysa gibbosa and Austropeplea tomentosa, at lower prevalences. Seasonality and collection sites did not significantly influence the worm’s infection dynamics, but strong positive correlations were found between the sizes of P. acuta individuals and both the likelihood of infection and infection intensity. The ectocommensal morph of C. limnaei was found in all three pulmonate species. Physa acuta was infected with two digenean trematode species which were also found in two native snails, Posticobia brazieri and G. gibbosa. One digenean, found within the renal gland of P. acuta, did not significantly influence the presence or infection intensity of the renal gland-dwelling C. limnaei parasitic morph. All parasites infecting P. acuta were also found to be infecting sympatric native freshwater snails. The effects that such host sharing by parasites may have upon the establishment of P. acuta as a successful invader merit further study.

Temperature influences species interactions between a native and a globally invasive freshwater snail

AbstractWe experimentally assessed the interaction between a globally invasive snail (Potamopyrgus antipodarum) and an Australian native snail (Austropyrgus angasi) under temperatures based on current (1990–2000, mean = 17.94–19.02°C) and future (2100, mean = 19.42–21.65°C) predicted conditions. Temperature treatments were scenarios identified from down-scaled global circulation models. Growth rates (mm/d) for juveniles and adults were measured at low (1000 individuals [ind]/m2) and high (20,000 ind/m2) densities in intraspecific and interspecific interaction trials under the 2 temperature regimes. Juveniles of both species grew at similar rates regardless of temperature and density. On the other hand, adults had dissimilar growth rates among treatments. Under current temperatures, P. antipodarum adults grew significantly faster than A. angasi adults when both species were kept at high densities in the interspecific treatment (interspecific-high) and faster than when they were kept at high densities but w...

Mediterranean essential oils as effective weapons against the West Nile vector Culex pipiens and the Echinostoma intermediate host Physella acuta: what happens around? An acute toxicity survey on non-target mayflies.

Mosquitoes (Diptera: Culicidae) represent a threat for millions of people worldwide, since they act as vectors for important pathogens, including malaria, yellow fever, dengue and West Nile. Second to malaria as the world's most widespread parasitic disease, infection by trematodes is a devastating public health problem. In this study, we proposed two essential oils from plants cultivated in Mediterranean regions as effective chemicals against mosquitoes and freshwater snails vectors of Echinostoma trematodes. Chemical composition of essential oils from Achillea millefolium (Asteraceae) and Haplophyllum tuberculatum (Rutaceae) was investigated. Acute toxicity was evaluated against larvae of the West Nile vector Culex pipiens (Diptera: Culicidae) and the invasive freshwater snail Physella acuta (Mollusca: Physidae), an important intermediate host of many parasites, including Echinostoma revolutum (Echinostomidae). Acute toxicity of essential oils was assessed also on a non-target aquatic organism, the mayfly Cloeon dipterum (Ephemeroptera: Baetidae). Achillea millefolium and H. tuberculatum essentials oils were mainly composed by oxygenated monoterpenes (59.3 and 71.0 % of the whole oil, respectively). Chrysanthenone and borneol were the two major constituents of Achillea millefolium essential oil (24.1 and 14.2 %, respectively). Major compounds of H. tuberculatum essential oil were cis-p-menth-2-en-1-ol and trans-p-menth-2-en-1-ol (22.9 and 16.1 %, respectively). In acute toxicity assays, C. pipiens LC50 was 154.190 and 175.268 ppm for Achillea millefolium and H. tuberculatum, respectively. P. acuta LC50 was 112.911 and 73.695 ppm for Achillea millefolium and H. tuberculatum, respectively, while the same values were 198.116 and 280.265 ppm for C. dipterum. Relative median potency analysis showed that both tested essential oils were more toxic to P. acuta over C. dipterum. This research adds knowledge on plant-borne chemicals toxic against invertebrates of medical importance, allowing us to propose the tested oils as effective candidates to develop newer and safer vector control tools.

Focal Philophthalmus gralli infection possibly persists in Melanoides tuberculata over two years following the definitive hosts' removal

Philophthalmosis is a zoonotic disease associated largely with the spread of the invasive freshwater snail Melanoides tuberculata, serving as an intermediate host. Here we examined Philophthalmus gralli focal fenced infection site reported recently as being associated with Tinamus major and M. tuberculata in Alajuela, Costa Rica. Removal of the definitive hosts allowed us to address also the long-term survival strategy of the parasite. Initially, the snail intermediate hosts displayed high prevalence of P. gralli infection across all its age cohorts. Two years following the removal of definitive hosts, the infection rate decreased by one order of magnitude, while the snails aging less than one year displayed zero infection prevalence. Additionally, phylogenetic analysis of mitochondrial (ND1) and nuclear (ITS1, ITS2) DNA loci revealed negligible intrasite DNA variability of the specimens obtained at the study site in Costa Rica (but not of those obtained earlier in Peru or New Zealand), supporting strongly the hypothesis on focal origin of the infection. The observed dynamics of infection suggests the explanation for the high variability in P. gralli prevalence in intermediate hosts experienced worldwide. We noticed that the reports claiming >20% prevalence of M. tuberculata infection by P. gralli originated exclusively from foci with known eye infection of the definitive hosts, while the P. gralli infection penetrance <2% is typically associated with sites, where the infection of definitive hosts was not observed, suggesting that the infected definitive hosts were present onsite only in the past, or were present only at a site upstream or downstream of the respective sampling site. Thus, this is the first evidence on the possible persistence of eye-trematode infection site for over two years following the last confirmed outbreak in its adult hosts.

Physella acuta: atypical mitochondrial gene order among panpulmonates (Gastropoda).

Mitochondrial (mt) sequences are frequently used for phylogenetic reconstruction and for identification of species of molluscs. This study expands the phylogenetic range of Hygrophila (Panpulmonata) for which such sequence data are available by characterizing the full mt genome of the invasive freshwater snail Physella acuta (Physidae). The mt genome sequences of two P. acuta isolates from Stubblefield Lake, New Mexico, USA, differed in length (14,490 vs 14,314 bp) and showed 11.49% sequence divergence, whereas ITS1 and ITS2 sequences from the nuclear genome differed by 1.75%. The mt gene order of P. acuta (cox1, P, nad6, nad5, nad1, D, F, cox2, Y, W, nad4L, C, Q, atp6, R, E, rrnS, M, T, cox3, I, nad2, K, V, rrnL, L1, A, cytb, G, H, L2, atp8, N, nad2, S1, S2, nad4) differs considerably from the relatively conserved gene order within Panpulmonata. Phylogenetic trees show that the 13 protein-encoding mt gene sequences (equivalent codons) of P. acuta group according to gastropod phylogeny, yet branch lengths and dN/dS ratios for P. acuta indicate elevated amino acid substitutions relative to other gastropods. This study indicates that mt sequences of P. acuta are phylogenetically informative despite a considerable intraspecific divergence and the atypical gene order in its mt genome.

Canal type affects invasiveness of the apple snail Pomacea canaliculata through its effects on animal species richness and waterweed invasion

Loss of complex natural microhabitats due to human activity is a major cause of decreased biodiversity but its effects on biological invasion are not well understood. The effects of physical environmental factors, especially the type of agricultural canals, on the invasive freshwater snail Pomacea canaliculata were studied at 33 sites in the Chikugogawa River basin, Kyushu, Japan. Differences among sites in the local fauna and vegetation were also monitored. Structural equation modeling with a model selection procedure revealed that canals with a concrete lining had more snails. The effect was indirect in that the concrete lining reduced animal species richness and increased the invasive waterweed Egeria densa, which may serve as a refuge, protecting the snails from predation. A tethering experiment conducted simultaneously indicated high predation pressure on the snails: over 20 % of the tethered snails were lost within a day. Thus, human impacts may increase biological invasion by reducing biotic resistance and increasing the risk of invasional meltdown.

Two invasive freshwater snails new to Jordan (Mollusca: Gastropoda)

Two alien freshwater snails are reported from water bodies in the Jordan Valley, Jordan: Pseudoplotia scabra (O. F. Müller, 1774) (Family Thiaridae) was found at two locations, while Pyrgophorus cf. coronatus (L. Pfeiffer, 1840) (Family Cochliopidae) was collected from four sites. P. scabra is considered one of the most successful invasive molluscan species in many parts of the world including the Middle East, and its arrival in Jordan constitutes a threat to the local freshwater molluscan fauna.

Profound Effects of Population Density on Fitness-Related Traits in an Invasive Freshwater Snail

Population density can profoundly influence fitness-related traits and population dynamics, and density dependence plays a key role in many prominent ecological and evolutionary hypotheses. Here, we evaluated how individual-level changes in population density affect growth rate and embryo production early in reproductive maturity in two different asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail that is an important model system for ecotoxicology and the evolution of sexual reproduction as well as a potentially destructive worldwide invader. We showed that population density had a major influence on individual growth rate and early-maturity embryo production, effects that were often apparent even when comparing treatments that differed in population density by only one individual. While individual growth rate generally decreased as population density increased, we detected a hump-shaped relationship between embryo production and density, with females from intermediate-density treatments producing the most embryos and females from low- and high-density treatments producing the fewest embryos. The two lineages responded similarly to the treatments, indicating that these effects of population density might apply more broadly across P. antipodarum. These results indicate that there are profound and complex relationships between population density, growth rate, and early-maturity embryo production in at least two lineages of this important model system, with potential implications for the study of invasive populations, research on the maintenance of sex, and approaches used in ecotoxicology.

Cadmium biosorption potential of shell dust of the fresh water invasive snail Physa acuta

The ability of shell dust (PSD) of an invasive freshwater snail (Physa acuta) to remove cadmium from contaminated water was evaluated. The results indicate that PSD, a waste biomaterial, bear potential of cadmium removal from contaminated water with biosorption capacity of 16.66mgg−1 at pH 6. The adsorption data at equilibrium fitted significantly more to Langmuir (R2=0.996) than Freundlich equations (R2=0.969). The kinetics of the adsorption process followed the pseudo-second order model (R2=0.996) better than the Lagergren model (R2=0.833). The FT-IR analyses support that the main mechanism of biosorption was cadmium chelating with different functional groups such as OH, CO, CC, and CC. The result obtained from the experiments show that the PSD can be used as an efficient, low cost, environmentally friendly biosorbent for cadmium from aqueous solution.

Patterns of density dependence in growth, reproduction and survival in the invasive freshwater snail Pomacea canaliculata in Japanese rice fields

Summary Patterns of density dependence in growth, reproduction and survival are important for predicting the population dynamics of a species. The patterns may change with environmental factors, such as the harshness of winter, but very little is known about such patterns and their mechanisms in unmanipulated natural populations of invasive animal species. We studied the extent of density dependence in the growth, reproduction and survival of an invasive freshwater snail, Pomacea canaliculata, in rice fields in Nara (cold district) and Kumamoto (warm district), Japan, over 2‐ and 1‐year periods, respectively. In both areas, growth was negatively density dependent within the same generation, and the density of snails in the parental generation negatively affected the growth of offspring. The number of eggs per unit area was independent of adult density, suggesting eggs per adult female were few at high densities. Survival over the cold winter of 2005–2006 was independent of density in Nara. However, survival over the warm winter of 2006–2007 in both Nara and Kumamoto was negatively density dependent. Irrespective of the various negative density‐dependent patterns, population density tended to show positive correlations with the density of the previous generation. This appears to reflect the substantial capacity of this snail to resist extremely low densities due to the various negative density‐dependent patterns rather than indicating susceptibility to extinction at low densities.

Invasive freshwater snails provide resource for native marine hermit crabs

Invasive species can have significant direct and indirect impacts on native biota. Here, we conducted a survey of two invasive freshwater snail species (Melanoides tuberculata and Tarebia granifera) in Tobago and assessed the effects on shell use by native marine hermit crab populations (Clibanarius tricolor and C. vittatus). Abundant in freshwater, numbers of empty shells at the mouth of a river in Charlotteville (Northeast Tobago) increased from 75 to 800 m-2 after heavy rains in the wet-season of June 2012. Subsequent sampling of a nearby rocky shore revealed that the freshwater shells were occupied by 70.2% of hermit crabs. Mimicking a flood event, the experimental planting of marked alien freshwater shells showed that 20.3% of hermit crabs exchanged their marine shell for a freshwater shell. Similarly, a laboratory shell-choice experiment showed that C. tricolor hermit crabs changed shells repeatedly, and that 22.2% occupied a freshwater shell rather than a marine shell. Overall, due to the numeric abundance of freshwater shells and the compulsive shell changing behaviour of Clibanarius spp., the ongoing invasion of freshwater gastropods in the Caribbean may change the shell use patterns and population dynamics of the native hermit crabs.

Eye trematode infection in small passerines in Peru caused by Philophthalmus lucipetus, an agent with a zoonotic potential spread by an invasive freshwater snail

Until now, four species of eye trematodes have been found in South America. Of them, Philophthalmus lucipetus (synonymized with Philophthalmus gralli) displays a broad host spectrum, with at least 30 bird species (prevalently large water birds), five mammal species and humans serving as definitive hosts, and with snails Fagotia (Microcolpia) acicularis, Amphimelania holandri, Melanopsis praemorsa and Melanoides tuberculata serving as intermediate hosts. When examining a total of 50 birds of ten species in the wetland of Pantanos de Villa, Lima, Peru in July 2011, eye trematodes were identified visually in the edematous conjunctival sac of 11 (48%) out of 23 resident many-colored rush tyrants Tachuris rubrigastra. Based on morphometric characteristics, the trematodes were identified as P. lucipetus. ITS2 and CO1 gene of the examined specimens combined showed a 99% similarity to an Iranian isolate of Philophthalmus sp. from the intermediate host Melanoides tuberculata, an invasive freshwater snail, suggesting that these two isolates represent the same species with a wide geographical range. Moreover, the prevalence of infection with the philophthalmid cercariae was 31% in 744 Melanoides tuberculata examined in Pantanos de Villa in 2010. It is evident that P. lucipetus occurs throughout the world as well as locally, including Eurasia and South America. Here we report this trematode for the first time in Peru, and we were the first to sequence any of the South American eye trematodes. Low host specificity of P. lucipetus and the invasive character of Melanoides tuberculata as a competent intermediate host suggest that eye trematodosis caused by P. lucipetus may emerge frequently in various parts of the world, especially in the tropics. Increase of the zoonotic potential of the P. lucipetus associated with this invasive snail spreading across the world is predictable and should be of interest for further research.

Complex consequences of increased density for reproductive output in an invasive freshwater snail

Population density can have profound, often negative effects on fitness-related traits and population dynamics, and density dependence is of central importance to many prominent ecological and evolutionary hypotheses. Here, we used experimental manipulations of food, population density, and water conditioning to characterize the mechanisms underlying reproductive density-dependence in Potamopyrgus antipodarum. This New Zealand freshwater snail is a prominent model system for invasion biology, ecotoxicology, and the maintenance of sexual reproduction. We demonstrated that a primary source of negative density-dependence is food limitation, but surprisingly, we found that P. antipodarum reproductive output was much higher in high density versus low-density conditions when food was adequate. We then used manipulations of water environment to demonstrate that these positive effects of high density are likely caused by a waterborne substance produced by P. antipodarum. Altogether, these results indicate that there are strong and complex connections between food availability, density, and reproductive output in this important model system that could influence the dynamics of invasive populations, the costs and benefits of sex, and the approaches used for ecotoxicology studies.

Egg predation and parasite prevalence in the invasive freshwater snail, Melanoides tuberculata (Müller, 1774) in a west Texas spring system

Melanoides tuberculata Muller, 1774 (Thiaridae), a freshwater prosobranch snail native to regions of Asia and Africa, was introduced into the U.S. in the 1960s and is now found in fifteen states. Melanoides tuberculata can affect native communities directly by displacing native snail species and indirectly by introducing foreign trematodes into novel environments. As the exact mechanisms of displacement of native snails by M. tuberculata are unknown, egg predation rates on native snails (Physella spp.) by two different size classes (>30 mm and 30 mm were found to consume Physella spp. and only 2.8% of M. tuberculata snails consumed egg masses. None of the M. tuberculata collected from Diamond Y Spring were found to be infected with C. formosanus.

Predator-driven biotic resistance and propagule pressure regulate the invasive apple snail Pomacea canaliculata in Japan

Species richness in local communities has been considered an important factor determining the success of invasion by exotic species (the biotic resistance hypothesis). However, the detailed mechanisms, especially the role of predator communities, are not well understood. We studied biotic resistance to an invasive freshwater snail, Pomacea canaliculata, at 31 sites in an urban river basin (the Yamatogawa) in western Japan. First, we studied the relationship between the richness of local animal species and the abundance of P. canaliculata, demonstrating a negative relationship, which suggests that the intensity of biotic resistance regulates local snail populations. This pattern was due to the richness of native predator communities rather than that of introduced species or non-predators (mainly competitors of the apple snail). Local snail abundance was also affected by immigration of snails from nearby rice fields (i.e. propagule pressure), where few predators occur. Second, we assessed short-term predation pressure on the snail by means of a tethering experiment. Predation pressure was positively correlated with the number of individual predators and negatively correlated with snail abundance. The introduced crayfish Procambarus clarkii was responsible for the variance in predation pressure. These results indicate that the predator community, composed of both native and introduced species, is responsible for resistance to a novel invader even in a polluted urban river.

Consumption, survival and growth in the invasive freshwater snail Pomacea canaliculata: does food freshness matter?

Understanding factors that determine the fitness of invasive species may help us predict their spread and impact. Previous studies of the survival, growth and reproduction of Pomacea canaliculata, a freshwater apple snail native to South America now widely spread in Asia, North America and Hawaii, have emphasized the use of fresh leaves as food. We compared the consumption and growth of P. canaliculata reared on fresh and decaying leaves of three species of macrophytes with contrasting content of phenolics (general plant defence chemicals) and nutrients. We conducted 1-day consumption assays using adult snails and a 1-month survival and growth experiment using snails of various sizes. Our results showed that the consumption, survival and growth of P. canaliculata were determined by plant nutrients and phenolics, rather than plant freshness. For Murdannia nudiflora, a species with low phenolic content, fresh leaves with high nitrogen content were more palatable and valuable for growth than decaying leaves with low nitrogen content. Survival was high and not different between the fresh and decaying leaf treatments. For Myriophyllum aquaticum, decaying leaves with moderate nitrogen and low phenolic contents were more palatable and valuable for snail survival and growth than fresh leaves with high nitrogen and high phenolic contents. For Polygonum barbatum, a species with low nitrogen and medium phenolic contents, both fresh and decaying leaves were unpalatable, resulted in low snail survivorship, and did not support snail growth. The results thus indicate that P. canaliculata can utilize both fresh and decaying leaves of adequate levels of nutrients and low levels of phenolics. This dietary flexibility may have contributed to its successful colonization of many types of freshwater wetlands in regions where high-quality fresh leaves are not available throughout the year.

Linkage of cold hardiness with desiccation tolerance in the invasive freshwater apple snail, Pomacea canaliculata (Caenogastropoda: Ampullariidae)

Linkage between cold hardiness and desiccation tolerance was examined in an invasive freshwater apple snail, Pomacea canaliculata, collected from locations in three different climatic zones. Snails collected from temperate Kyushu, Japan, showed enhanced cold hardiness after cold acclimation, and cold-tolerant snails survived longer after exposure to desiccation than cold-intolerant snails without cold acclimation. Progenies of tropical snails collected from Luzon and Mindanao, the Philippines, which had never experienced cold weather revealed the same response as Japanese snails to cold stress: enhancement of cold hardiness after cold acclimation. Cold-tolerant snails from tropical populations also attained better survivorship under desiccation conditions. Thus, linkage of tolerance between cold weather and desiccation appears to be a general feature of P. canaliculata. Cold hardiness of snails before and after cold acclimation, respectively, did not differ among the three populations from temperate and tropical regions. A trend was found for snails from Mindanao, in the tropical rainforest climatic zone (having a milder dry season), to be less desiccation-tolerant than snails from Kyushu and Luzon, having a colder or more severe dry season.

Palatability of macrophytes to the invasive freshwater snail Pomacea canaliculata: differential effects of multiple plant traits

Summary1. By selective grazing, invasive grazers can alter macrophyte‐herbivore relationships in shallow freshwater bodies. Evaluating the palatability of macrophytes and understanding the determinants of plant palatability can help predict grazing impact. In no‐choice feeding assays, we tested the palatability of 21 species of freshwater macrophytes to the invasive freshwater apple snail Pomacea canaliculata.2. Daily feeding rate varied greatly with plant species, ranging from 1.1 to 22% of snail body mass. We assessed six plant properties and examined their correlation with feeding rate. Total nitrogen content was positively related, and C:N ratio and dry matter content (DMC) negatively related, to snail feeding rate. There was no significant correlation between snail feeding rate and plant phenolic content, but the feeding rate on Myriophyllum aquaticum (the plant with the highest phenolic content) was very low.3. We repeated the feeding assays for 15 species that were not palatable as fresh leaves with reconstituted plant tissues formed by mixing ground up dried leaves with agar. The feeding rate still differed greatly among macrophyte species. Phragmites australis and Vallisneria natans (two species with the highest DMC) were eaten much more as reconstituted plant than as fresh leaves, indicating that structure (i.e. DMC) may be important in their defence against snail herbivory. For two plants (M. aquaticum and Alternanthera philoxeroides) that had moderate amounts of nitrogen/phosphorus but were consumed very little as fresh and reconstituted tissues, we incorporated their extracts into a palatable agar‐based food. The extracts from both species greatly reduced snail feeding rate, indicating the presence of chemical defences in these two species.4. These results indicated that feeding was affected by several plant traits. The snail favoured plants with a high nitrogen content and avoided plants with a high DMC. Only a few plants possessed chemical feeding deterrents that were effective against this snail. Given the invasive spread of P. canaliculata in Asia, ecologists and managers should consider plant palatability when selecting plants for use in wetland restoration and when predicting the impact of further invasion by this species.

Expansion of an invasive freshwater snail Physa acuta (Gastropoda: Physidae) in China

The pulmonate freshwater snail Physa acuta Draparnaud, 1805 has been previously reported as an invasive species in China and many other parts of the world. Populations in Beijing and Shandong, Shanxi, Yunnan and Hubei Provinces are reported for the first time based on collections made between August and October 2007. The potential for further spread of this species in China is discussed.

Dependence on aerial respiration and its influence on microdistribution in the invasive freshwater snail Pomacea canaliculata (Caenogastropoda, Ampullariidae)

The invasive Neotropical snail Pomacea canaliculata is usually regarded as amphibious, although the relative significance of aerial and aquatic respiration is unknown. To investigate the degree of dependence on aerial respiration and its influences on microdistribution, experiments were performed in the laboratory and under seminatural and natural conditions. Restriction of aerial respiration negatively affected survivorship, activity and feeding, its effects worsening with temperature and water fouling; females were more seriously affected than males although the effect depended on reproductive effort. Snails were unevenly distributed relative to the access to air, both in a stream and in an outdoor tank, being concentrated less than 2–4 m from the nearest emergent substratum. Accessibility to air would be an important trait of waterbodies prone to invasions of P. canaliculata, especially in tropical areas. The effectiveness of some control measures could be increased by focusing on areas where snails are concentrated due to their dependence on air.