Apple Snail Species Research Articles

Phylogenetic variations in a novel family of hyperstable apple snail egg proteins: insights into structural stability and functional trends.

The relationship between protein stability and functional evolution is little explored in proteins purified from natural sources. Here, we investigated a novel family of egg proteins (Perivitellin-1, PV1) from Pomacea snails. Their remarkable stability and clade-related functions in most derived clades (Canaliculata and Bridgesii) make them excellent candidates for exploring this issue. To that aim, we studied PV1 (PpaPV1) from the most basal lineage, Flagellata. PpaPV1 displays unparalleled structural and kinetic stability, surpassing PV1s from derived clades, ranking among the most hyperstable proteins documented in nature. Its spectral features contribute to a pale egg coloration, exhibiting a milder glycan binding lectin activity with a narrower specificity than PV1s from the closely related Bridgesii clade. These findings provide evidence for substantial structural and functional changes throughout the genus' PV1 evolution. We observed that structural and kinetic stability decreased in a clade-related fashion and was associated with large variations in defensive traits. For instance, pale PpaPV1 lectin turns potent in the Bridgesii clade, adversely affecting gut morphology, while giving rise to brightly colored PV1s providing eggs with a conspicuous, probably warning signal in the Canaliculata clade. This work provides a comprehensive comparative analysis of PV1s from various apple snail species within a phylogenetic framework, offering insights into the interplay among their structural features, stability profiles and functional roles. More broadly, our work provides one of the first examples from natural evolution showing the crucial link among protein structure, stability and evolution of new functions.

Comparative Mitogenome Analysis of Two Native Apple Snail Species (Ampullariidae, Pomacea) from Peruvian Amazon.

Apple snails of the genus Pomacea Perry, 1810 (Mollusca: Caenogastropoda: Ampullariidae) are native to the Neotropics and exhibit high species diversity, holding cultural and ecological significance as an important protein source in Peru. However, most genetic studies in Pomacea have focused mostly on invasive species, especially in Southeast Asia, where they are considered important pests. In this study, we assembled and annotated the mitochondrial genomes of two Pomacea species native to the Peruvian Amazon: Pomacea reevei Ampuero & Ramírez, 2023 and Pomacea aulanieri (Deville & Hupé, 1850). The mitogenomes of P. reevei and P. aulanieri comprise 15,660 and 16,096 bp, respectively, and contain the typical 37 genes of the animal mitochondria with a large control region of 292 bp in P. reevei and 524 bp in P. aulanieri-which fall within the range of what is currently known in Pomacea. Comparisons with previously published mitogenomes in Pomacea revealed differences in the overlapping of adjacent genes, the size of certain protein-coding genes (PCGs) and the secondary structure of some tRNAs that are consistent with the phylogenetic relationships between these species. These findings provide valuable insights into the systematics and genomics of the genus Pomacea.

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

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

Description of two new species of apple snail (Ampullariidae: Pomacea) from Peruvian Amazonia

Two new species of apple snails are described, Pomacea penai sp. nov. and Pomacea reevei sp. nov. that are used as food resources in Peruvian Amazonia. We used anatomical and conchological features to diagnose these two species. Pomacea penai sp. nov. is characterized by a highly variable shell morphology, spire that is prominent to immersed, apical penis sheath gland covering 1/3 penis sheath and elongated basal gland, prostate broad proximally, reduced stomach septum, green eggs, and commonly inhabits temporary flooded areas, creeks, and oxbow lakes. Pomacea reevei sp. nov. possesses a large shell, ranging from 81-137 mm, grey broad penis sheath, small apical penis sheath gland and the basal gland covering 1/3 penis sheath, tall stomach septum, white eggs, and found in deep lentic water bodies.

Differential effects of increased salinity on growth and survival of a native and a nonnative apple snail species

Differential effects of increased salinity on growth and survival of a native and a nonnative apple snail species

Molecular analyses revealed three morphologically similar species of non‐native apple snails and their patterns of distribution in freshwater wetlands of Hong Kong

AbstractAimEffective control of invasive species and conservation of native biodiversity requires accurate species identification. Several species of apple snails (Ampullariidae: Pomacea) from South America have become widespread pests in Asia since their introduction in the early 1980s, but their taxonomic uncertainty has hindered our understanding of the invasive processes. We aim to determine the identity and distribution of Pomacea species in Hong Kong, which has been known as a stepping stone of species invasion.LocationHong Kong.MethodsWe collected 162 apple snails from five freshwater wetlands of Hong Kong, sequenced the mitochondrial COI, genotyped the nuclear EF1α and built a COI dataset of 1378 sequences of apple snails from mainland China, Malaysia, Argentina and Brazil. We identified the species, determine the introgression pattern and analysed their population structures.ResultsWe found the co‐occurrence of P. canaliculata, P. maculata and P. occulta in Hong Kong for the first time. Pomacea canaliculata represented the dominant species (85% of collected specimens). The three Pomacea species from Hong Kong had low genetic diversity. High genetic similarity existed between P. canaliculata populations of Hong Kong and Malaysia, P. occulta populations of Hong Kong and mainland China and P. maculata populations of mainland China and Malaysia. Our samples contained a high proportion of hybrids.Main conclusionsApple snails may have been introduced into Hong Kong multiple times: both P. canaliculata and P. occulta likely came from Argentina; P. maculata came from both Argentina and Brazil. Genetic drift largely explains the differentiation of Pomacea spp. among regions. Introgressive hybridization may have contributed to population fitness by increasing genetic variation to neutralize the founder effect. The knowledge on species identity, distribution and genetic diversity of apple snails from this study will contribute to better understanding their invasive mechanisms and prevention of their continued spread in Asia.

Widespread mislabeling of nonnative apple snails (Ampullariidae: Pomacea) as native field snails (Viviparidae: Cipangopaludina) on the Chinese food markets

Freshwater snails have been used extensively as a human food source in different countries for centuries. Due to increasing cases of fraudulent substitution or mislabeling affecting the safety and quality of food products, food authenticity has aroused crucial concern. This study aimed to identify processed freshwater snail products that were sold under the commercial term Tian luo in Chinese, which means local field snails and refers to Cipangopaludina spp. A total of 100 samples of snail skewers, snail snacks, and snail sauces from the online food market were tested. Species were diagnosed based on a combined analysis of the morphological characteristics and mitochondrial COI fragments. Our results demonstrated 100% improper labeling of Tian luo processed food in food market of China. All snails in the skewers and snacks were nonnative apple snails from the genus Pomacea. The snails in the snail sauces were from Bellamya, which is a genus closely related to Cipangopaludina. The most commonly used apple snail species was P. maculata, followed by P. canaliculata. One specimen was identified as P. occulta, which is a newly described species that has thus far only been reported in China. A comparison of the distribution patterns of the Pomacea spp. from the food market and the natural habits in China indicated that the majority of the snail material was probably imported especially from other Asian countries, whereas a small proportion was likely farmed or collected in China. Apple snails pose food safety concerns because they host various zoonotic parasites. Moreover, we detected the presence of toxic female albumen glands on the apple snail skewers. Our results emphasize the importance of effective supervision and standardization of food treatment measures in freshwater snail foods.

A multiple comparative study of putative endosymbionts in three coexisting apple snail species.

We here compare morphological and molecular characters of some putative endosymbiotic elements of the digestive gland of three ampullariid species (Pomacea canaliculata, Pomacea scalaris and Asolene platae) which coexist in Lake Regatas (Palermo, Buenos Aires). The putative endosymbionts were reported in these species and were identified as C and K corpuscles. The three species show tubuloacinar glands, each adenomere was constituted mainly by two distinct cell types (columnar and pyramidal). C and K corpuscles together occupied from one-fourth to one-fifth of the tissue area in the three host species, where C corpuscles were round and greenish-brown, were delimited by a distinct wall, stained positively with Alcian Blue and were associated with columnar cells. K corpuscles were oval, dark-brown multilamellar bodies and were associated with pyramidal cells. Under TEM, C corpuscles occurred within vacuoles of columnar cells and contained many electron-dense clumps and irregular membrane stacks and vesicles spread in an electron-lucent matrix. Sometimes a membrane appeared detached from the inner surface of the wall, suggesting the existence of a plasma membrane. In turn, K corpuscles were contained within vacuoles of pyramidal cells and were made of concentric lamellae, which were in turn made of an electron-dense fibrogranular material. No membranes were seen in them. Interspecifically, C corpuscles vary significantly in width and inner contents. K corpuscles were also variable in length and width. However, both C and K corpuscles in the three studied species hybridised with generalised cyanobacterial/chloroplast probes for 16S rRNA. Also, both corpuscle types (isolated from gland homogenates) were sensitive to lysozyme digestion, which indicates that bacterial peptidoglycans are an integral part of their covers. The reported data confirm and extend previous studies on P. canaliculata in which the endosymbiotic nature of C and K corpuscles were first proposed. We further propose that the endosymbiotic corpuscles are related to the Cyanobacteria/chloroplasts clade. Based on the known distribution of these corpuscles in the major clades of Ampullariidae, we hypothesise they may be universally distributed in this family, and that may constitute an interesting model for studying the co-evolution of endosymbionts and their gastropod hosts.

Contrasting Patterns of Pomacea maculata Establishment and Dispersal in an Everglades Wetland Unit and a Central Florida Lake

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.

Antagonistic effects of a native apple snail on other snails and macroinvertebrates in Southern Pampas waterbodies: A mesocosm approach

Macroinvertebrates represent an important component of communities and trophic webs of freshwater ecosystems. Pomacea canaliculata (family Ampullariidae), an invasive apple snail native to the Pampas ecoregion, acts as a voracious grazer and plays a structuring role on submerged macrophytes that serve as food, habitat or foraging ground for many macroinvertebrates. Laboratory studies show that P. canaliculata can also act as a competitor or predator of other macroinvertebrates. Using a mesocosm approach, we sought to investigate if this species of apple snail affects other freshwater snails (Chilina parchappii, Heleobia parchappii, Biomphalaria peregrina and Melanoides tuberculata) as well as other macroinvertebrates and if consumption of submerged macrophytes and detritus mediates these effects. After twelve weeks we estimated in mesocosms with and without apple snails the abundance of snails and macroinvertebrates through samples taken separately from sediment and from macrophytes. We also estimated the coverage and biomass of macrophytes and the detritus biomass. Significantly lower abundance occurred in mesocosms with apple snails for all snail species and representative macroinvertebrates (i.e., Hirudinea, Ephemeroptera, Chironomidae and Odonata). Mesocosms with apple snails also resulted in lower total abundance of macroinvertebrates. We speculate that the negative effects of P. canaliculata on most other snails and macroinvertebrates living on macrophytes relates to their grazing on detritus and macrophytes. In contrast, the density of snails and macroinvertebrates in the samples from sediments were not affected by P. canaliculata. One snail species and Ephemeroptera were negatively affected by mechanisms not related to the reduction in macrophyte biomass and detritus. A decrease in the microhabitats provided by macrophytes probably mediated the negative effects on Odonata nymphs. The reduction in the abundances of snails and macroinvertebrates caused by P. canaliculata may have cascading effects on higher trophic levels in waterbodies from Southern Pampas but also in invaded regions.

Invisible apple snail invasions: importance of continued vigilance and rigorous taxonomic assessments.

Due to the similarities of overall shell morphology among apple snail species and considerable variability within species, substantial taxonomic confusion has plagued the accurate identification of Pomacea species. Many invasive apple snails have been mistakenly identified as P. canaliculata since their introduction to Asia around 1980. In 2008, three other introduced species in addition to P. canaliculata were recognized. In 2013, a fifth, previously unrecognized lineage was reported from China, indicating that despite the taxonomic clarity brought by previous work, continued surveys and taxonomic research are necessary to prevent additional introductions and continued spread, as well as to develop effective management strategies. Phylogenetic analysis of mitochondrial COI sequences confirmed the presence of a widespread unidentified Pomacea lineage in China. All sequences from samples of this newly documented lineage were recovered in a monophyletic clade delineated from closely related species; however, different DNA barcoding methods yielded inconsistent species boundaries. Additionally, nuclear EF1α sequences indicated incomplete lineage sorting or recent hybridization of the unidentified lineage with the other two established species. Barcoding is a valuable tool for species discovery, and a powerful approach for delineating introduced species. However, determining the identity of the newly discovered invasive lineage in China will require an integrated taxonomic approach incorporating individuals from the native range, and examination of natural history collections at museums around the world. To manage and prevent additional spread of already established species, and to stop the introduction of new taxa, continued monitoring and rigorous taxonomic assessments must be undertaken. © 2018 Society of Chemical Industry.

VARIASI MORFOMETRI DAN KARAKTER MORFOLOGI KEONG MAS (Pomacea canaliculata) PADA SAWAH DI DESA ABIANSEMAL BADUNG-BALI

The purpose of this study was to determine variations in morphology and morphological characteristics of golden apple snails (P. canaliculata) in rice fields in Abiansemal Village. Gold apple snails can be found living in fresh water, including lakes, rivers, small ditches and also in rice fields. Rice field habitats in Bali can still be found in Abiansemal village, Badung regency, but not much information has been disclosed about the snails in the rice field habitat, especially the golden apple snail species (P. canaliculata). Therefore, it is necessary to do research on the golden apple snails in Abiansemal Village. This research was carried out in rice fields located in Abiansemal Village, Abiansemal District, Badung Regency, Bali Province. The study was conducted from April to May 2017. Sampling of golden apple snail (P. canaliculata) was carried out in three plots of rice fields in three banjars in Abiansemal Village, namely in the Latu Sari, Banjar Aseman, and Juwet banjars. The rice field was chosen randomly and then in each selected field of rice the golden apple snail sample was taken using a 1x1m square. Samples on each plot of rice were taken three times. All samples of golden snail contained in the squared were taken and cleaned and then preserved with 70% alcohol. The golden apple snail sample obtained was calculated for its density and all morphological and morphometric characters were analyzed descriptively. In this study it was found that the morphology of golden apple snail patterned lines for morphometric characters, the shell height was higher in the banjar Juwet area, for the width of the shell mouth was greater in the banjar area Aseman and the height of the shell cover was higher in the banjar area of Latu Sari, while the morphology was plain patterned for morphometric characters, the height of the shell and the height of tendrils were higher in the banjar area of Latu Sari, and for the height and width of the cover the shell was higher and wider in the banjar area of Aseman, while for the other morphometric characters the results were found almost the same.
 Keywords: snail, rice field, morphology, morphometry

AmpuBase: a transcriptome database for eight species of apple snails (Gastropoda: Ampullariidae)

BackgroundGastropoda, with approximately 80,000 living species, is the largest class of Mollusca. Among gastropods, apple snails (family Ampullariidae) are globally distributed in tropical and subtropical freshwater ecosystems and many species are ecologically and economically important. Ampullariids exhibit various morphological and physiological adaptations to their respective habitats, which make them ideal candidates for studying adaptation, population divergence, speciation, and larger-scale patterns of diversity, including the biogeography of native and invasive populations. The limited availability of genomic data, however, hinders in-depth ecological and evolutionary studies of these non-model organisms.ResultsUsing Illumina Hiseq platforms, we sequenced 1220 million reads for seven species of apple snails. Together with the previously published RNA-Seq data of two apple snails, we conducted de novo transcriptome assembly of eight species that belong to five genera of Ampullariidae, two of which represent Old World lineages and the other three New World lineages. There were 20,730 to 35,828 unigenes with predicted open reading frames for the eight species, with N50 (shortest sequence length at 50% of the unigenes) ranging from 1320 to 1803 bp. 69.7% to 80.2% of these unigenes were functionally annotated by searching against NCBI’s non-redundant, Gene Ontology database and the Kyoto Encyclopaedia of Genes and Genomes. With these data we developed AmpuBase, a relational database that features online BLAST functionality for DNA/protein sequences, keyword searching for unigenes/functional terms, and download functions for sequences and whole transcriptomes.ConclusionsIn summary, we have generated comprehensive transcriptome data for multiple ampullariid genera and species, and created a publicly accessible database with a user-friendly interface to facilitate future basic and applied studies on ampullariids, and comparative molecular studies with other invertebrates.

System productivity alters predator sorting of a size-structured mixed prey community.

Predator-prey interactions are often size-structured and focused on smaller vulnerable size classes. Predators are also predicted to sort prey communities according to relative vulnerabilities. Increased system productivity and juvenile growth may benefit some species more than others, making relative vulnerability non-static and growth-mediated. We hypothesized that increased system productivity would weaken juvenile-stage predation generally, and potentially shift the community sorting effects of a predator. Using replicated wetland mesocosms we quantified the effects of a generalist size-specific crayfish predator (Procambarus fallax) on juveniles of two species of apple snails (Pomacea spp.) under two levels of system productivity (low vs. high). After 6weeks of exposure, we quantified predator and productivity effects on snail survival, biomass, and composition of the assemblage. Crayfish depressed the final density and biomass of snails, and sorted the assemblage, selectively favoring survival of the native P. paludosa over the intrinsically more vulnerable invasive P. maculata. Both snails grew faster at higher productivity, but growth differentially increased survival of the invasive snail in the presence of crayfish and weakened the sorting effect. The native P. paludosa hatches at a larger less vulnerable size than the invasive P. maculata, but higher productivity reduced the relative advantage of P. paludosa. Our results are inconsistent with predictions about the sorting effects of predators across productivity gradients because the more resistant prey dominated at low productivity. Our findings highlight that the relative vulnerabilities of prey to a common predator are not always fixed, but can be growth-mediated.

The complete mitochondrial genome of Pomacea diffusa (Gastropoda: Ampullariidae)

In this study, we analyzed the complete mitochondrial genome of the spike-topped apple snail, Pomacea diffusa Blume, 1957 (Gastropoda: Ampullariidae). The mitochondrial genome of P. diffusa was 16,373 bp, consisting 13 protein-coding genes, 2 rRNAs, and 22 tRNAs and a non-coding region with a 12 bp repeat unit. There were 29 mitochondrial genes of P. diffusa are distributed on the H-strand, and the other eight tRNA genes encoded on the L-strand. The average AT content of 13 protein-coding genes was 68.7%. A phylogenetic analysis showed that there was a close relationship between P. diffusa and invasive apple snail species, Pomacea canaliculata and Pomacea aff. maculata.

Survival, recovery, and reproduction of apple snails (Pomacea spp.) following exposure to drought conditions

AbstractClimate change has dramatically altered freshwater ecosystems and will continue to affect them further. As water-level fluctuations increase in frequency and intensity, the tolerance of aquatic organisms to abiotic stressors will become critical determinants of survival. Apple snail species in the genus Pomacea (Ampullariidae) live in freshwater throughout the tropics and subtropics, but deposit egg clutches on terrestrial substrates. Two species, Pomacea canaliculata and Pomacea maculata, are amongst the world’s most invasive species and are expanding their invasive ranges. To evaluate their survival during extreme dry-down conditions in their native range, we collected 156 apple snails (Pomacea spp.) from 4 permanent water bodies in Uruguay and buried them in dry sand to simulate drought. We placed the snails outside, sheltered from sun and rain (ambient temperature: 15.2–28.1°C, ambient humidity: 44.9–100.6% below sand surface, 34.2–98.7% in outside air), and checked survival daily. Genetic ide...

The mitochondrial genome of Pomacea maculata (Gastropoda: Ampullariidae)

The golden apple snail, Pomacea maculata Perry, 1810 (Gastropoda: Ampullariidae) is one of the most serious invasive alien species from the native range of South America. The mitochondrial genome of P. maculata (15 516 bp) consists of 37 genes (13 protein-coding genes, two rRNAs, and 22 tRNAs) and a non-coding region with a 16 bp repeat unit. Most mitochondrial genes of P. maculata are distributed on the H-strand, except eight tRNA genes, which are encoded on the L-strand. A phylogenetic analysis showed that there was a close relationship between P. maculata and another invasive golden apple snail species, Pomacea canaliculata (Lamarck, 1822).

Correction: Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea)

Correction: Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea)

Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea)

Winning the war against invasive species requires early detection of invasions. Compared to terrestrial invaders, aquatic species often thrive undetected under water and do not garner notice until too late for early action. However, fortunately for managers, apple snails (Family Ampullariidae, Genus Pomacea) provide their own conspicuous sign of invasion in the form of vibrantly colored egg clutches. Managers can potentially use egg clutches laid in the riparian zone as a means of early detection and species identification. To facilitate such efforts, we quantified differences in characteristics (length, width, depth, mass, egg number) of field-laid clutches for the two most common invasive species of apple snail, P. canaliculata and P. maculata, in native and non-native populations. Pomacea canaliculata native and non-native populations differed noticeably only in width. Native P. maculata clutches possessed significantly greater width, mass and eggs numbers compared with native P. canaliculata. Non-native P. maculata clutches significantly exceeded all other populations in all measured characteristics. Consequently, these traits may successfully distinguish between species. Fecundity data also allowed us to develop models that accurately estimated the number of eggs per clutch for each species based on clutch dimensions. We tested one, two and three dimensional models of clutches, including rendering a clutch as either a complete ellipsoid or an ellipsoid intersected by a cylinder to represent the oviposition site. Model comparisons found the product of length and depth, with a different function for each population, best predicted egg number for both species. Comparisons of egg number to clutch volume and mass implied non-native P. canaliculata may be food limited, while non-native P. maculata appeared to produce such enormous clutches by having access to greater nutrients than the native population. With these new tools, researchers and managers can quickly identify, quantify and begin eradication of new non-native apple snail populations.

Genetic exchange between two freshwater apple snails, Pomacea canaliculata and Pomacea maculata invading East and Southeast Asia

Two species of apple snails, Pomacea canaliculata and Pomacea maculata (formerly Pomacea insularum), have invaded many countries of East and Southeast Asia from their native range in South America. This study investigated the genetic structure of the two species invading these areas. Phylogenetic analysis based on sequences of the nuclear gene elongation factor 1-alpha (EF1α) detected two well-supported clades (Clade C and Clade M). Both P. canaliculata and P. maculata were represented in each clade. Some snails had both Clade C and Clade M EF1α sequences. These results suggest genetic exchange between snails of the two clades. A mating experiment between P. canaliculata with Clade C EF1α sequences and P. maculata with Clade M EF1α sequences resulted in viable F1 progeny under laboratory conditions. The genetic exchange was also inferred in some populations collected from Argentina, suggesting an existence of hybrid in the native range. Simple identification of EF1α types using a restriction enzyme, ApaLI, detected significant geographical structure of the EF1α variants in the invaded area. The divergent geographical structure could have resulted from either the founder effect or the bridgehead effect, although further genetic analysis is needed to clarify this. Average individual egg weight, which is an indicator of egg size, was higher in P. canaliculata than P. maculata in both field and laboratory reared samples, suggesting that some (probably most) P. canaliculata and P. maculata invading East and Southeast Asia still maintain species-specific populations.