Exotic Snail Research Articles

Invasion stage of the exotic snail Melanoides tuberculata related to environmental and biological factors in a subtropical river drainage

The mollusks represent the main invasive taxon of the freshwater ecosystem in North America. Environmental degradation may increase the susceptibility of the ecosystem to invasion and favor the abundance and density increment in some benthic mollusks. Melanoides tuberculata is a snail native from Africa and Asia that was introduced in Mexico in the sixties through aquarium activities. Its reproduction by parthenogenesis, fast growth, longevity, omnivore habits, and wide tolerance to pollution and environmental stressors, confers to this snail great capability like invasive species. However, the information concerning the relationships between the invasion stage of this exotic snail and environmental and biological variables is still unknown. This study aimed to document the establishment of several new registered populations of M. tuberculata in subtropical river drainage in central Mexico, since at least 10 years ago, and its relationship with indicator variables of environmental degradation. We visited 15 localities during the dry season in 2016 and 2022. At each study site, the macroinvertebrate assemblages were collected, and physical variables of habitat and physicochemical water characteristics were measured. In addition, the biological condition was assessed using aquatic macroinvertebrate assemblages. Each individual of M. tuberculata was counted and measured. The abundance and density of the snail with physical, chemical, and biological variables were correlated, and further multivariate analyses were performed to confirm these relationships. We demonstrated a positive relationship between the presence, abundance, and density of M. tuberculata with environmental variables that are indicators of degradation of physical attributes such as water flow alterations and loss of habitat heterogeneity in 2016 and 2022. We supported the hypothesis that anthropic habitat degradation can favor the invasion of M. tuberculata.

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

Multixenobiotic defence mechanism in native and exotic freshwater snails as a biomarker for land uses-changes

Human activities such as agriculture and urbanization generate a large number of substances like personal care products, pharmaceutical compounds, and pesticides, which often reach aquatic environments and represent a threat to biodiversity. Many organisms have developed different evolutionary strategies to remove pervasive substances from their bodies, allowing them to persist even in polluted environments, and one of these is the multixenobiotic resistance (MXR) mechanism associated with the expression of membrane proteins like P-glycoprotein (P-gp). Numerous chemical compounds with diverse functions and structures can modulate this mechanism, which can be employed as a pollution biomarker. We examined the MXR activity in two species of snails that inhabit Patagonian freshwaters. Functional assay measurements of MXR were conducted on the native Chilina dombeiana and the exotic Physella acuta in stream reaches affected by anthropogenic impacts. Results indicated that at agricultural sites, C. dombeiana snails had a more active MXR system than organisms sampled at reference and moderately disturbed urban sites, whereas P. acuta snails from agricultural and highly disturbed urban sites showed better detoxifying activity than organisms from reference sites. Only in exotic snails, part of this activity was due to the action of P-gp. The most important environmental variables explaining MXR activity were ammonium, nitrate and nitrite, phosphates, and electrical conductivity. These results show the promise of measuring MXR activity in native and exotic snails, as a biomarker in the environmental monitoring of Patagonian freshwaters.

The native snail shell–nesting beeOsmia conjuncta(Hymenoptera: Megachilidae) exploits a local abundance of exoticCepaeasnails (Stylommatophora: Helicidae), choosing empty shells by size, colour, and microhabitat

AbstractFor solitary bees, nesting substrate availability may limit population growth. Here, we investigate the nesting of a locally abundant beeOsmia conjunctaCresson (Hymenoptera: Megachilidae) in empty shells of exotic snails,Cepaeaspp. Held (Stylommatophora: Helicidae), in Hamilton, Ontario, Canada. A literature review determined thatO. conjunctawas sparsely distributed throughout its range, with a low relative abundance except for the Niagara Region of Ontario, Canada, three sites in Maryland, United States of America, and the focal study area in Hamilton, Ontario. The Hamilton field survey of five grassland bee communities foundO. conjunctato be the most abundant bee species. The average relative abundance was 18.7%, peaking at 87% on one spring day. A survey of 1088 empty snail shells was done at the site with the highestO. conjunctaabundance. It revealed an average of 10.87 empty shells per square metre with cocoons in 9.8% of the shells, averaging 1.6 cocoons per nest. The relation between shell traits and cocoon presence indicated thatO. conjunctapreferred nesting in shells with intermediate size and colour and avoided shells near shrubs. The presence ofCepaeasnails increasedO. conjunctapopulations with potential consequences to the local bee assemblage.

Predation and prey preference of the exotic snail Anentome helena on two freshwater snails: implications for species invasion

Aim: The aim of the present study was to estimate the probable impact of predation of the exotic snail Anentome helena on two co-occurring freshwater snails, Racesina luteola and Physella acuta, in the laboratory set-up. Methodology: In the initial experiment, the predatory efficiency of A. helena was observed using R. luteola and P. acuta as prey, separately, under varying prey and predator densities. In the following experiment, the prey snails were provided in both conspecific and heterospecific conditions with different predator densities to deduce the prey preference of A. helena, if any. Results: The experiments show that A. helena can consume a considerable number of R. luteola and P. acuta. The predation rate of A. helena varied significantly (p< 0.0001) with different sizes of prey, prey and predator densities. Although the predation rate differed among conspecific and heterospecific prey conditions, A. helena did not demonstrate any significant prey preference towards any of the prey. Interpretation: The study revealed that the chance dispersal of predator A. helena from household aquaria to natural habitats may directly impact the population of the freshwater snail R. luteola and P. acuta.

The exotic snail Rumina decollata (Linnaeus, 1758) (Gastropoda, Achatinidae, Rumininae) in Argentina: new records, range extension, and areas of origin of Argentine populations

The decollate land snail Rumina decollata (Linnaeus, 1758), native to the Mediterranean region, has been introduced across several countries worldwide. We report here three new records for R. decollata in Argentina, two from Córdoba Province and the first one from Misiones Province, which also constitutes the northernmost record for the country, extending its northeastern distribution range. Species-specific identification was achieved based on anatomical, conchological, and molecular information. DNA data showed that different haplotypes are present in Argentina, which originated from distinct source areas along the native range.

Fator de condição relativo e modelo preditivo para a presença do caracol invasor Achatina (Lissachatina) fulica em Sergipe, Nordeste do Brasil

Abstract: Achatina fulica is among the world’s 100 most impactive invasive species, and is now found in almost all Brazilian states, including Sergipe. This exotic snail is known to have negative impacts, not only on the environment, due primarily to the rapid growth of its populations, but also on public health, given that it is an intermediate host of nematodes that cause zoonotic diseases. However, relatively little is known of the development of this snail, including its relative condition factor. We investigated the occurrence of A. fulica in 24 municipalities distributed in the eight subregions of the state of Sergipe in the dry and rainy season. Furthermore, we present here a predictive model for the occurrence of A. fulica based on the variation in climate and soil chemistry. This snail was more frequent on soils with a pH of 6.5-7.5. A negative correlation was found between the growth of A. fulica and the soil pH, then, the more acidic the soil, the more allometric the growth of A. fulica. The relative condition factor indicated differences in the development pattern of A. fulica among the eight subregions. The influence of rain in increasing the frequency of A. fulica showed a significant correlation. As well, higher temperatures influenced the resting behavior of A. fulica. The mathematical model used to identify the potential presence of A. fulica presented a high degree of agreement. This is the first ecological study of A. fulica to verify the association between the body mass-length relationship and the relative condition factor, and the results indicate that the development of this exotic land snail in Sergipe is influenced by climatic factors and principally, the soil pH. The predictive mathematical model provides valuable insights into the biotic and abiotic factors associated with the presence of A. fulica, and the influence of climatic variables and the chemical parameters of the soil on the occurrence of this species. These findings provide important guidelines for the development of measures for the control of A. fulica populations, which will contribute to both public and environment health.

Choosing exotic over the familiar taste: habitat-specific preferences of a malacophagous leech for freshwater snails as prey gastropod establishment?

The spread of freshwater invasive species through aquarium trade poses a threat to the ecosystem, economy and human health. The availability of the exotic freshwater gastropod mollusc, Planorbarius corneus (Linnaeus, 1758) (Gastropoda: Planorbidae), in pet shops in Kolkata, West Bengal, India, raises concern for its potential establishment as an invasive species. Assuming the role of the native predators as a potential biotic barrier for invasion, observations on the predation pattern of the malacophagous leech, Glossiphonia weberi (Blanchard, 1897) (Clitellata: Glossiphoniidae) against P. corneus was made in single as well as in combination with the native snail Indoplanorbis exustus (Deshayes, 1834) (Gastropoda: Planorbidae). Using varying size classes and densities of P. corneus, the predation potential of G. weberi was estimated after a 24 hour period. In another set of experiments, the predation of G. weberi against the snail P. corneus was observed in the presence of I. exustus under four different habitat conditions. The purpose was to justify - (1) the effect of conspecific and heterospecific conditions of the prey availability and (2) the effect of habitat complexity on the predatory efficacy of G. weberi. The results indicated that G. weberi consumed varied numbers of P. corneus, depending on the size and the densities of the prey and predator. Although the prey heterogeneity and complex habitats caused significant reduction of predation on both of the prey species, G. weberi significantly preferred P. corneus over I. exustus in open (P < 0.0001), macrophyte (P = 0.002) and pebbles and macrophyte containing habitats (P < 0.0001). Apparently, G. weberi preferred the exotic snail P. corneus in presence of alternative prey snail I. exustus, under different habitat conditions. Therefore, G. weberi may act as a significant biotic resistance against the colonization and establishment of P. corneus in the Indian context. However, further studies including the multiple prey and predators are required to ascertain the food web level impact of the exotic snail P. corneus in invaded freshwater ecosystems.

Temperature Impacts on the Cardiac Activity of the Snail Pomacea canaliculata from Shatt Al-Arab Region, Basrah, Iraq

The effects of temperature on an exotic aquatic snail Pomacea canaliculata (Lamarck, 1819) collected from the Shatt Al-Arab intertidal zone were investigated. A series of laboratory experiments were conducted during the summer period of 2017. Individuals of new born snails hatched in the laboratory from adult snails were collected from Shatt Al-Arab intertidal zone, and subjected to five fixed temperatures: 15, 25, 35, 40 and 45 Cº, after short term thermal acclimation. The heartbeats (HB) were counted at each temperature level. The results showed significant direct increase of HB from 15 Cº (19.8 HB/min) up to 25 Cº (76 HB/min) (P<0.05) as well as from 25 Cº to 35 Cº (93 HB/min). At 40 Cº the snail HB shows only slight insignificant increase (79 HB/ min). At 45 ºC the HB became irregular and showed negative thermo cardiac activity (HB dropped to 50.4/min). The minimum HB rate of 11/min was recorded at 15 Cº and the maximum value of 119 HB/min was recorded at 40 Cº. The study concluded that P. canaliculata can be highly stressed when exposed to extreme temperature experienced during the prolonged summer months and will no longer tolerate living in the intertidal zone of Shatt Al-Arab.

Life history traits of the exotic freshwater snail Melanoides tuberculata Müller, 1774 (Gastropoda, Thiaridae), and its sensitivity to common stressors in freshwaters

Abstract: Aim In the present study has analyzed several aspects of the life history traits of Melanoides tuberculata, an exotic species, under laboratory conditions, and its response to some stressors has also been applied. Methods Sensitivity to two toxic substances was tested. The mollusks were collected and cultured in the laboratory under controlled conditions of temperature of 25 ± 1 °C and ad libitum food regime. Growth rates and biomass were experimentally obtained and the individual growth curve obtained. Results The experiment lasted 287 days and the maximum shell lengths registered was 11.67 mm. The growth curve indicated a rate of 3.98 year-1 and a maximum theoretical length of 10.61 mm. The mean post-embrionary development time until first reproduction was 275 days and the size of the primipara was 10.13 mm. An accelerated growth of juveniles was observed with fast increase in the shell length until sexual maturity, but growth rate decreased afterwards as more energy was devoted to reproduction. Under the combination of 25 °C and fed on alternate days, M. tuberculata had a slow growth and a long-life expectancy under laboratory conditions. The tolerance of this mollusk to temperature as a stressor ranged between 16 °C and 37 °C, being the optimum temperature situated between 29 °C and 34 °C. The LC(I)50-24h for reference substances were: 0.70 g L-1 for KCl and 9.05 g L-1 for NaCl. Conclusion Based on these results, we can conclude that M. tuberculata is a species tolerant to temperature and salinity, what partially explains to accordance to its wide and rapid dispersion throughout tropical waters.

Warming alone increased exotic snail reproduction and together with eutrophication influenced snail growth in native wetlands but did not impact plants

Warming and eutrophication can have varying effects on exotic species performance and their interactions. These effects can vary with trophic level, but are rarely investigated simultaneously on exotic species from multiple trophic levels. To address this, we manipulated temperature, nutrients, and plant origin (native vs. exotic) in snail invaded wetland communities. Warming increased exotic apple snail (Pomacea maculata) reproduction (4-fold increase in egg mass) and also number of egg clutches produced while warming slowed exotic snail growth, suggesting a trade-off between reproduction and growth in exotic snails influenced by warming and nutrients. However, exotic snail size varied with warming and nutrients. Additionally, warming reduced native plant mass with no effect on exotic plants while nutrients had greater positive effects on exotic plants biomass. In combination warming and nutrient enrichment will likely increase exotic snail growth, while nutrient enrichment alone will contribute to exotic plant dominance. In conclusion, the individual and interactive effects of warming and eutrophication vary with the trophic level of exotic species with trade-offs in exotic herbivores depending on environmental conditions, making it difficult to predict effects of multiple anthropogenic factors on co-occurring exotic plants and their effects on native communities.

The distribution of terrestrial pest gastropods and their damage to agricultural crops in Kandy and Nuwara Eliya districts in Sri Lanka

An island wide survey from 1999 to 2002 in Sri Lanka highlighted the presence of 18 species of exotic snails and slugs, of which most were identified as pests of agriculture crops. However, since this survey, no studies on pest gastropods have been carried out in the country. Hence, the present study was carried out in Kandy and Nuwara Eliya districts in approximately 15 hectares of agricultural land to determine the current status of these gastropods. During the study, a total of 14 terrestrial gastropod species were recorded from agricultural lands of which eight species were recognized as exotic pest gastropods. They were Deroceras reticulatum, Laevicaulis altae, Mariaella dussumieri, Milax gagates, Lissachatina fulica, Bradybaena similaris, Allopeas gracile and Subulina octona. The damage from pest gastropods was observed in many crops and especially in the seedling or nursery stage plants. The highest damage to crops in Nuwara Eliya and Kandy districts were caused by D. reticulatum and Lissachatina fulica respectively. The study indicated that the distribution range of many of these pest gastropods, especially Laevicaulis altae and Lissachatina fulica has increased during the past fifteen years. Elevation is a key environmental factor that affects their distribution in these districts.

Primer registro del caracol viajero invasor Melanoides tuberculata (Gastropoda: Thiaridae) en San Luis Potosí, México

Background: The species red-rimmed melania Melanoides tuberculata Muller, 1774 is native to Asia and Africa. Due to the aquarium trade, its worldwide distribution has widely increased. In Mexico, its presence in the wild has been documented since 1973 in different Mexican states. Goals: Document the first record of the presence of the species in the state of San Luis Potosi. Methods: During 2015 - 2018, different perennial water bodies were sampled in San Luis Potosi, and the presence or absence of the species was recorded. Photographic images of the exotic snail were taken for taxonomic identification and specimens collected in the study were deposited at the Coleccion Nacional de Moluscos – Instituto de Biologia (UNAM). Results: On June 16, 2017, some individuals were found in an area near the town of San Francisco de Asis, municipality of Rioverde. Conclusions: This study contributes to the knowledge of the dispersal of the exotic red-rimmed melania in Mexico and is the first record of its presence in the state of San Luis Potosi. We consider that the current incidence of the exotic snail in the state is low. Because of its high dispersion potential, however, it could be a risk for native aquatic fauna, considering its role as an intermediate host of parasitic diseases of wild bird and fish species.

Diagnosis, presence of endoparasites, and local knowledge on the infestation of the exotic giant African snail (gastropoda: pulmonata: achatinidae), in the urban zone of Rio Branco, Acre, Brazil

Abstract The giant African land snail, Lissachatina fulica is considered to be one of the world's worst invader species. This snail can provoke major economic and public health problems in urban areas, in particular as a potential vector of nematodes that infect both humans and animals. In this context, the present study investigated the extent of the infestation of this exotic snail in the urban neighborhoods of the city of Rio Branco, verified the presence of endoparasites in these snails, and evaluated the knowledge of local residents with regard to the presence of this invader species. For this, daytime surveys were conducted between August 2015 and June 2016. For the analysis of endoparasites, 44 live specimens were sent to the National Reference Laboratory for Schistosomiasis-Malacology (LRNEM) of the Oswaldo Cruz Institute (FIOCRUZ). The knowledge of local residents in the infested neighborhoods was investigated using questionnaires with direct, closed questions. The exotic invader species (L. fulica) was detected in 24 of the 36 neighborhoods visited. A total of 858 L. fulica specimens were collected, of which, 329 were alive and 527 were dead. The total length of the shell ranged from 0.7 to 14.2 cm, with a mean±standard deviation of 4.8±2.21 cm. The density of snails in the areas surveyed varied from 0.34 individuals/m2 to 3.54 individuals/m2, while the mean density within the whole study area was estimated to be 0.54 individuals/m2. Mature eggs were found in only 9 (2.7%) of the 329 specimens dissected. The endoparasitological analysis revealed the presence of rhabditiform larvae in 84% of the specimens examined, as well as the nematodes Aelurostrongylus abstrusus (22.7% of the specimens) and Strongyluris sp. (2.2%). A total of 39 local residents were interviewed, and while all were conscious of the presence of the mollusk, none knew its origin or the most adequate way of dealing with it. The results of the study indicate an ample infestation of the city of Rio Branco by L. fulica, and confirmed a complete lack of intervention on the part of the local authorities for the implementation of measures foe the control and management of this pest within the urban zone of Rio Branco.

Experimental Test of Preferences for an Invasive Prey by an Endangered Predator: Implications for Conservation.

Identifying impacts of exotic species on native populations is central to ecology and conservation. Although the effects of exotic predators on native prey have received much attention, the role of exotic prey on native predators is poorly understood. Determining if native predators actively prefer invasive prey over native prey has implications for interpreting invasion impacts, identifying the presence of evolutionary traps, and predator persistence. One of the world’s most invasive species, Pomacea maculata, has recently established in portions of the endangered Everglade snail kite’s (Rostrhamus sociabilis plumbeus) geographic range. Although these exotic snails could provide additional prey resources, they are typically much larger than the native snail, which can lead to lower foraging success and the potential for diminished energetic benefits in comparison to native snails. Nonetheless, snail kites frequently forage on exotic snails. We used choice experiments to evaluate snail kite foraging preference in relation to exotic species and snail size. We found that snail kites do not show a preference for native or exotic snails. Rather, snail kites generally showed a preference for medium-sized snails, the sizes reflective of large native snails. These results suggest that while snail kites frequently forage on exotic snails in the wild, this behavior is likely driven simply by the abundance of exotic snails rather than snail kites preferring exotics. This lack of preference offers insights to hypotheses regarding effects of exotic species, guidance regarding habitat and invasive species management, and illustrates how native-exotic relationships can be misleading in the absence of experimental tests of such interactions.

First Record of Transversotrema Witenberg, 1944 (Digenea) from the Americas, with Comments on the Taxonomy of Transversotrema patialense (Soparkar, 1924) Crusz and Sathananthan, 1960, and an Updated List of Its Hosts and Geographic Distribution.

Specimens of Transversotrema patialense (sensu lato) ( Soparkar, 1924 ) Crusz and Sathananthan, 1960 (Digenea: Transversotrematidae) infected the skin (epidermal spaces beneath scales near pectoral fins) of 4 of 126 (prevalence 3%; mean intensity 1.8) zebrafish ( Danio rerio (Hamilton, 1822) [Cypriniformes: Cyprinidae]) purchased in 2009 and cultured by a California (USA) fish supplier. These fish were sold as "laboratory-reared" and "specific pathogen free," purportedly raised in a recirculating aquaculture system that included zebrafish only. We herein describe the morphological features of this transversotrematid using light and scanning electron microscopy, provide a comprehensive list of hosts (snails and fishes) and geographic locality records for specimens reported as T. patialense, which is perhaps a species complex, and provide a brief historical synopsis of the taxonomic and life history research that has been conducted on this fluke. No species of Transversotrema previously had been reported from the Americas; however, this discovery is not surprising given that: (1) a suitable intermediate host (red-rimmed melania, Melanoides tuberculata (Müller, 1774) [Cerithioidea: Thiaridae]) has been established in California and elsewhere in North America, (2) the zebrafish is a susceptible definitive host, and (3) T. patialense reportedly matures on a broad ecological and phylogenetic spectrum of freshwater fishes. To our knowledge, this is the northern-most geographic locality record for a species of this genus. We suspect this case study represents an example of a parasite that may now be established in North America by the fortuitous co-occurrence of a susceptible, exotic snail host (the red-rimmed melania) and a susceptible, widely distributed, exotic fish host (the zebrafish).

Experimental test of the Invasional Meltdown Hypothesis: an exotic herbivore facilitates an exotic plant, but the plant does not reciprocally facilitate the herbivore

Summary 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.

Size Distribution and Nutrient Excretion ofMelanoides tuberculatain a Southern Nevada Spring Ecosystem

To better understand the impact of Melanoides tuberculata on ecosystem processes via nutrient recycling, we quantified the body size distribution, density, and ammonia-nitrogen (NH4-N) and soluble reactive phosphorus (SRP) excretion of M. tuberculata in Rogers Spring, which is located in southern Nevada. We examined how nutrient recycling rates were related to body size and body nutrient content. We found that small individuals dominated the size structure, density, and NH4-N and SRP excretion rates and that nutrient recycling was determined by biomass rather than by high per capita excretion rates. The NH4-N excretion rates of M. tuberculata are between 2 and 27 times higher than the SRP excretion rates in Rogers Spring. These results indicate that M. tuberculata in Rogers Spring may be P limited and rather conservative in P recycling. In contrast to stoichiometric predictions, body nutrient content was a poor predictor of excretion rates. However, there was a close correlation between the measured and modeled NH4-N:SRP recycling ratio (NH4-N:SRPr), which suggests that diet N:P is more important in predicting NH4:SRPr than body elemental composition. Assuming that all excreted nutrients enter the water column, we determined that M. tuberculata contributes 17.3 mg N m-2d-1 and 3.3 mg P m-2d-1 to Rogers Spring. Although densities of M. tuberculata in the spring brook were lower than those reported in other studies, we assume that these exotic snails can have a significant impact on ecosystem processes, especially by N recycling in systems with very low ambient nutrient concentrations.

Rapid development of tool use as a strategy to predate invasive land snails

Abstract There are few examples of facultative tool use in animals under natural conditions. We provide the first description of tool use in great antshrikes (Taraba major), which were observed using stone anvils to break the shells of the land snail (Achatina fulica). This behavior is almost certainly of extremely recent origin given the lack of previous reports of tool use in T. major and the very recent (1980s) introduction of A. fulica into Brazil. Tool use in this particular population is probably a flexible behavioral trait that arose in response to the high density of exotic snails in this locality.

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