Since the mid 1990s populations of non-native apple snails (Ampullariidae) have been discovered with increasing frequency in the continental United States. Given the dramatic effects that introduced ...apple snails have had on both natural habitats and agricultural areas in Southeast Asia, their introduction to the mainland U.S. is cause for concern. We combine phylogenetic analyses of mtDNA sequences with examination of introduced populations and museum collections to clarify the identities, introduced distributions, geographical origins, and introduction histories of apple snails.
Based on sampling to date, we conclude there are five species of non-native apple snails in the continental U.S. Most significantly, we recognize three species within what has been called the channeled apple snail: Pomacea canaliculata (California and Arizona), Pomacea insularum, (Florida, Texas, and Georgia) and Pomacea haustrum (Florida). The first established populations of P. haustrum were discovered in the late 1970s in Palm Beach County Florida, and have not spread appreciably in 30 years. In contrast, populations of P. insularum were established in Texas by 1989, in Florida by the mid to late 1990s, and in Georgia by 2005, and this species continues to spread rapidly. Most introduced P. insularum haplotypes are a close match to haplotypes from the Río Uruguay near Buenos Aires, indicating cold tolerance, with the potential to spread from Florida, Georgia, and Texas through Louisiana, Alabama, Mississippi, and South Carolina. Pomacea canaliculata populations were first discovered in California in 1997. Haplotypes of introduced P. canaliculata match native-range haplotypes from near Buenos Aires, Argentina, also indicating cold tolerance and the potential to establish farther north.
The term "channeled apple snail" is descriptive of a morphology found in many apple snail species. It does not identify a single species or a monophyletic group. Clarifying species identifications permits a more accurate assessment of introduction histories and distributions, and provides a very different picture of the tempo and pattern of invasions than was inferred when the three species with channeled sutures were considered one. Matching introduced and native-range haplotypes suggests the potential for range expansion, with implications for native aquatic ecosystems and species, agriculture, and human health.
Foodborne zoonotic trematode (FZT) infections are common neglected tropical diseases in Southeast Asia. Their complicated life cycles involve freshwater snails as intermediate hosts. A ...cross-sectional study was conducted in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, to investigate the diversity of cercariae of potential FZT and to construct the phylogenetic relationship of trematode cercariae based on the Internal Transcribed Spacer 2 (ITS2) region. Among 17 snail species collected from various habitats, 13 were infected by 10 cercarial groups among which parapleurolophocercous, pleurolophocercous, and echinostome cercariae were of zoonotic importance. The monophyletic tree separated cercarial sequences into different groups following the description of the cercariae families in which Haplorchidae, Opisthorchiidae, Echinochasmidae, and Echinostomatidae are important families of FZT. The overall prevalence was different among snail species and habitats and showed a seasonal trend. Parapleurolophocercous and echinostome cercariae emerged as the most common cercariae in snails in Yen Bai, while monostome, echinostome, and megalura cercariae were most common in Thanh Hoa. Using a molecular approach, we identified
Parafossarulus striatulus
as the first intermediate snail host of
Clonorchis sinensis
in Thac Ba Lake.
Melanoides tuberculata
and
Bithynia fuchsiana
were we identified preferred intermediate snail hosts of a diverse range of trematode species including intestinal flukes (i.e.,
Haplorchis pumilio
and
Echinochasmus japonicus
) in Yen Bai and Thanh Hoa, respectively.
Snail-borne parasitic diseases, such as angiostrongyliasis, clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis, paragonimiasis and schistosomiasis, pose risks to human health and cause ...major socioeconomic problems in many tropical and sub-tropical countries. In this review we summarize the core roles of snails in the life cycles of the parasites they host, their clinical manifestations and disease distributions, as well as snail control methods.
Snails have four roles in the life cycles of the parasites they host: as an intermediate host infected by the first-stage larvae, as the only intermediate host infected by miracidia, as the first intermediate host that ingests the parasite eggs are ingested, and as the first intermediate host penetrated by miracidia with or without the second intermediate host being an aquatic animal. Snail-borne parasitic diseases target many organs, such as the lungs, liver, biliary tract, intestines, brain and kidneys, leading to overactive immune responses, cancers, organ failure, infertility and even death. Developing countries in Africa, Asia and Latin America have the highest incidences of these diseases, while some endemic parasites have developed into worldwide epidemics through the global spread of snails. Physical, chemical and biological methods have been introduced to control the host snail populations to prevent disease.
In this review, we summarize the roles of snails in the life cycles of the parasites they host, the worldwide distribution of parasite-transmitting snails, the epidemiology and pathogenesis of snail-transmitted parasitic diseases, and the existing snail control measures, which will contribute to further understanding the snail-parasite relationship and new strategies for controlling snail-borne parasitic diseases.
Many animals display specific internal or external features with left-right asymmetry. In vertebrates, the molecular pathway that leads to this asymmetry uses the signalling molecule Nodal, a member ...of the transforming growth factor- superfamily, which is expressed in the left lateral plate mesoderm, and loss of nodal function produces a randomization of the left-right asymmetry of visceral organs. Orthologues of nodal have also been described in other deuterostomes, including ascidians and sea urchins, but no nodal orthologue has been reported in the other two main clades of Bilateria: Ecdysozoa (including flies and nematodes) and Lophotrochozoa (including snails and annelids). Here we report the first evidence for a nodal orthologue in a non-deuterostome group. We isolated nodal and Pitx (one of the targets of Nodal signalling) in two species of snails and found that the side of the embryo that expresses nodal and Pitx is related to body chirality: both genes are expressed on the right side of the embryo in the dextral (right-handed) species Lottia gigantea and on the left side in the sinistral (left-handed) species Biomphalaria glabrata. We pharmacologically inhibited the Nodal pathway and found that nodal acts upstream of Pitx, and that some treated animals developed with a loss of shell chirality. These results indicate that the involvement of the Nodal pathway in left-right asymmetry might have been an ancestral feature of the Bilateria.
In multiply invaded ecosystems, introduced species should interact with each other as well as with native species. Invader-invader interactions may affect the success of further invaders by altering ...attributes of recipient communities and propagule pressure. The invasional meltdown hypothesis (IMH) posits that positive interactions among invaders initiate positive population-level feedback that intensifies impacts and promotes secondary invasions. IMH remains controversial: few studies show feedback between invaders that amplifies their effects, and none yet demonstrate facilitation of entry and spread of secondary invaders. Our results show that supercolonies of an alien ant, promoted by mutualism with introduced honeydew-secreting scale insects, permitted invasion by an exotic land snail on Christmas Island, Indian Ocean. Modeling of land snail spread over 750 sites across 135 km
2
over seven years showed that the probability of land snail invasion was facilitated 253-fold in ant supercolonies but impeded in intact forest where predaceous native land crabs remained abundant. Land snail occurrence at neighboring sites, a measure of propagule pressure, also promoted land snail spread. Site comparisons and experiments revealed that ant supercolonies, by killing land crabs but not land snails, disrupted biotic resistance and provided enemy-free space. Predation pressure on land snails was lower (28.6%), survival 115 times longer, and abundance 20-fold greater in supercolonies than in intact forest. Whole-ecosystem suppression of supercolonies reversed the probability of land snail invasion by allowing recolonization of land crabs; land snails were much less likely (0.79%) to invade sites where supercolonies were suppressed than where they remained intact. Our results provide strong empirical evidence for IMH by demonstrating that mutualism between invaders reconfigures key interactions in the recipient community. This facilitates entry of secondary invaders and elevates propagule pressure, propagating their spread at the whole-ecosystem level. We show that identification and management of key facilitative interactions in invaded ecosystems can be used to reverse impacts and restore resistance to further invasions.
Sexual populations should be vulnerable to invasion and replacement by ecologically similar asexual females because asexual lineages have higher per capita growth rates. However, as asexual genotypes ...become common, they may also become disproportionately infected by parasites. The Red Queen hypothesis postulates that high infection rates in the common asexual clones could periodically favor the genetically diverse sexual individuals and promote the short‐term coexistence of sexual and asexual populations. Testing this idea requires comparison of competing sexual and asexual lineages that are attacked by natural parasites. To date no such data have been available. Here, we report on long‐term dynamics and parasite coevolution in a “mixed” (sexual and asexual) population of snails (Potamopyrgus antipodarum). We found that, within 7–10 years, the most common clones were almost completely replaced by initially rare clones in two different habitats, while sexuals persisted throughout the study period. The common clones, which were initially more resistant to infection, also became more susceptible to infection by sympatric (but not allopatric) parasites over the course of the study. These results are consistent with the Red Queen hypothesis and show that the coevolutionary dynamics predicted by the theory may also favor sexual reproduction in natural populations.
The Scaly-foot Snail, Chrysomallon squamiferum, presents a combination of biomineralised features, reminiscent of enigmatic early fossil taxa with complex shells and sclerites such as sachtids, but ...in a recently-diverged living species which even has iron-infused hard parts. Thus the Scaly-foot Snail is an ideal model to study the genomic mechanisms underlying the evolutionary diversification of biomineralised armour. Here, we present a high-quality whole-genome assembly and tissue-specific transcriptomic data, and show that scale and shell formation in the Scaly-foot Snail employ independent subsets of 25 highly-expressed transcription factors. Comparisons with other lophotrochozoan genomes imply that this biomineralisation toolkit is ancient, though expression patterns differ across major lineages. We suggest that the ability of lophotrochozoan lineages to generate a wide range of hard parts, exemplified by the remarkable morphological disparity in Mollusca, draws on a capacity for dynamic modification of the expression and positioning of toolkit elements across the genome.
is a hazardous snail that can damage ornamental plants and cause significant harm to plant sections in Egyptian areas. Herein, the molluscicidal activity of CuPb-Ferrite/TiO
and TiO
nanoparticles ...(NPs) against
was evaluated using the poisonous bait method. LC50 values were determined using the leaf dipping and contact methods, with values of 631.23 and 1703.49 ppm for CuPb-Ferrite/TiO
and 193.67 and 574.97 ppm for TiO
. Exposure to both NPs resulted in a significant increase in the biochemical parameters of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP), as well as a decrease in total protein (TP) percentage of
. Histological examinations revealed that many digestive cells had ruptured, and their contents had been lost, while the foot's epithelial layer became ruptured. The average reduction was 66.36% for CuPb-Ferrite/TiO
NPs compared to the recommended molluscicide, Neomyl, with a 70.23% reduction in the field application. Electrophoretic separation of total protein using sodium dodecyl sulfate-polyacrylamide gel electrophoresis after treatment with LC50 concentrations of TiO
and CuPb-Ferrite/TiO
demonstrated the potency of these synthetic compounds as molluscicidal agents. Therefore, we recommend the use of CuPb-Ferrite/TiO
NPs as a novel land snail molluscicide because it is safe to use, and the baits are arranged to not affect irrigation water, with a high molluscicidal effect.
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