Family Planorbidae Research Articles

Different metazoan parasites, different transcriptomic responses, with new insights on parasitic castration by digenetic trematodes in the schistosome vector snail Biomphalaria glabrata

BackgroundGastropods of the genus Biomphalaria (Family Planorbidae) are exploited as vectors by Schistosoma mansoni, the most common causative agent of human intestinal schistosomiasis. Using improved genomic resources, overviews of how Biomphalaria responds to S. mansoni and other metazoan parasites can provide unique insights into the reproductive, immune, and other systems of invertebrate hosts, and their responses to parasite challenges.ResultsUsing Illumina-based RNA-Seq, we compared the responses of iM line B. glabrata at 2, 8, and 40 days post-infection (dpi) to single infections with S. mansoni, Echinostoma paraensei (both digenetic trematodes) or Daubaylia potomaca (a nematode parasite of planorbid snails). Responses were compared to unexposed time-matched control snails. We observed: (1) each parasite provoked a distinctive response with a predominance of down-regulated snail genes at all time points following exposure to either trematode, and of up-regulated genes at 8 and especially 40dpi following nematode exposure; (2) At 2 and 8dpi with either trematode, several snail genes associated with gametogenesis (particularly spermatogenesis) were down-regulated. Regarding the phenomenon of trematode-mediated parasitic castration in molluscs, we define for the first time a complement of host genes that are targeted, as early as 2dpi when trematode larvae are still small; (3) Differential gene expression of snails with trematode infection at 40dpi, when snails were shedding cercariae, was unexpectedly modest and revealed down-regulation of genes involved in the production of egg mass proteins and peptide processing; and (4) surprisingly, D. potomaca provoked up-regulation at 40dpi of many of the reproduction-related snail genes noted to be down-regulated at 2 and 8dpi following trematode infection. Happening at a time when B. glabrata began to succumb to D. potomaca, we hypothesize this response represents an unexpected form of fecundity compensation. We also document expression patterns for other Biomphalaria gene families, including fibrinogen domain-containing proteins (FReDs), C-type lectins, G-protein coupled receptors, biomphalysins, and protease and protease inhibitors.ConclusionsOur study is relevant in identifying several genes involved in reproduction that are targeted by parasites in the vector snail B. glabrata and that might be amenable to manipulation to minimize their ability to serve as vectors of schistosomes.

Comparative Mitogenome Analyses of Fifteen Ramshorn Snails and Insights into the Phylogeny of Planorbidae (Gastropoda: Hygrophila).

Ramshorn snails from the family Planorbidae are important freshwater snails due to their low trophic level, and some of them act as intermediate hosts for zoonotic trematodes. There are about 250 species from 40 genera of Planorbidae, but only 14 species from 5 genera (Anisus, Biomphalaria, Bulinus, Gyraulus, and Planorbella) have sequenced complete mitochondrial genomes (mitogenomes). In this study, we sequenced and assembled a high-quality mitogenome of a ramshorn snail, Polypylis sp. TS-2018, which represented the first mitogenome of the genus. The mitogenome of Polypylis sp. TS-2018 is 13,749 bp in length, which is shorter than that of most gastropods. It contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA). We compared mitogenome characteristics, selection pressure, and gene rearrangement among all of the available mitogenomes of ramshorn snails. We found that the nonsynonymous and synonymous substitution rates (Ka/Ks) of most PCGs indicated purifying and negative selection, except for atp8 of Anisus, Biomphalaria, and Gyraulus, which indicated positive selection. We observed that transpositions and reverse transpositions occurred on 10 tRNAs and rrnS, which resulted in six gene arrangement types. We reconstructed the phylogenetic trees using the sequences of PCGs and rRNAs and strongly supported the monophyly of each genus, as well as three tribes in Planorbidae. Both the gene rearrangement and phylogenetic results suggested that Polypylis had a close relationship with Anisus and Gyraulus, while Bulinus was the sister group to all of the other genera. Our results provide useful data for further investigation of species identification, population genetics, and phylogenetics among ramshorn snails.

High prevalence of natural infection by the ruminant blood fluke Schistosoma spindale in the intermediate snail host Indoplanorbis exustus in Uttaradit, Northern Thailand.

Freshwater snails belonging to the family Planorbidae serve as the first intermediate hosts of many species of important parasitic flukes of animals and humans. Information regarding the occurrence of planorbid snail larval trematode infection is limited in Northern Thailand. Thus, this study aimed to estimate the prevalence of larval trematode infection of the freshwater snail Indoplanorbis exustus in Uttaradit, Thailand, and to identify trematode species based on their morphological and molecular characteristics. Planorbid snail specimens were collected from a water reservoir in Uttaradit, Thailand, from June to August 2023. Snails were assessed for larval trematode infection through cercarial shedding and crushing methods. The released cercariae were preliminarily identified on the basis of their morphological characteristics. In addition, species identification of the detected cercariae was conducted using 28S ribosomal RNA and cytochrome c oxidase subunit 1 gene sequence analyses. The overall prevalence of cercarial infection was 61.5% (107/174) in planorbid snails in Uttaradit province. Two species of cercarial trematodes, Schistosoma spindale (106/174, 60.9%) and Artyfechinostomum malayanum (1/174, 0.6%), were identified using morphological and molecular analyses, of which S. spindale was the most abundant species. Our studied snails did not have mixed infection with more than two cercarial species. Our findings reveal a remarkably high prevalence of S. spindale cercariae infecting planorbid snails in Uttaradit, indicating that humans and animals across the study area are at risk of infection. Our data may contribute to the development of effective strategies to control this zoonotic infectious disease.

Population genetic structure of Indoplanorbis exustus (Gastropoda: Planorbidae) in Thailand and its infection with trematode cercariae.

Indoplanorbis exustus is a freshwater gastropod belonging to the family Planorbidae. This snail is widely distributed across the tropics and plays an important role as the intermediate host for trematodes. However, relatively little is understood regarding the genetic relationship between I. exustus and trematodes. The goals of this study were to investigate the current transmission status of trematode cercariae in I. exustus in Thailand and to examine the genetic diversity, genetic structure, and demographic history of I. exustus. We collected 575 I. exustus from 21 provinces across six regions of Thailand and investigated cercarial infections by using the shedding method. I. exustus from two provinces were infected with cercarial trematodes, and two types of cercarial stages were molecularly identified as furcocercous cercaria and xiphidiocercariae. Phylogenetic tree analysis based on 28S rDNA and ITS2 sequences demonstrated that furcocercous cercaria and xiphidiocercariae were closely clustered with a clade of Euclinostomum sp. and Xiphidiocercariae sp., respectively. Phylogenetic and network analyses of I. exustus haplotypes based on the COI, 16S rDNA, and ITS1 genes demonstrated four main clades. Only snails in clade A were distributed in all regions of Thailand and harbored trematode cercariae. The level of genetic diversity of I. exustus was relatively high, but most populations were not genetically different, thus suggesting the appearance of gene flow within the I. exustus populations. Overall, the haplotype network was star-shaped, thus suggesting the recent demographic expansion of populations. This result was also supported by the unimodal mode of the mismatch distribution graph and the large negative values of the neutrality tests. Therefore, the I. exustus snail was likely another freshwater snail of the invasive species in Thailand. This information will aid in monitoring the spread of the parasitic trematodes carried by I. exustus from different populations.

МОНИТОРИНГ ВОЗБУДИТЕЛЕЙ ОСНОВНЫХ ПАРАЗИТОЗОВ ВОДНЫХ ПТИЦ НА ИЗОЛИРОВАННОЙ ПРИРОДНОЙ ТЕРРИТОРИИ НАЦИОНАЛЬНОГО ПАРКА «ЛОСИНЫЙ ОСТРОВ»

An important point in the conservation of biological diversity and avifauna resources on the territory of national and zoological parks, reserves, as well as commercial breeding poultry enterprises is the study of the bioecology of parasitosis pathogens. In this study, for the first time in a long time, the results of bioecological monitoring of the main parasitoses of aquatic birds living in the isolated natural territory of NP "Losiny оstrov" are presented. The main focus of the work was the study of the spread of the invasive origin in intermediate, additional and final hosts, as well as the conservation potential of aquatic bird species and other components of the biogeocenosis. The article presents the results of helminthological studies of feces of birds of the gull families (lake gull Larus Ridibundus) and duck (mallard Anas Platyrhynchos); helminthological studies of the gastrointestinal tract of fish of the cyprinid family (bream Abramis Brama) and firebrand (perch Perca Fluviatilis); mollusks of the family Lymnaeidae and the family Planorbidae. 85 and 86 individuals of fish and shellfish, respectively, and 116 samples of bird droppings were studied. The number of identified samples from seagulls was 23, from ducks – 47, the remaining 46 samples were defined as «blind samples». The main composition of intestinal parasites of aquatic birds and aquatic organisms has been revealed. Data were obtained on the infection of aquatic birds with associative helminth-protozoal mixinvasion: genera – Eimeria and Trichomonas and helminths of genera: Capillaria, Amidostomum, Heterakis. At the same time, the presence of mixed invasion was noted in 64.28% of the total number of samples. Data were obtained on the infection of fish and shellfish, the helminth fauna of which is represented by the families Echinoctomatidae and Diplostomum sp. The extent of monoinvasion of mollusks of the species Lymnaea stagnalis by cercariae and metacercariae of trematodes of the family Echinoctomatidae was 62.16%.

Genetic variation of the freshwater snail Indoplanorbis exustus (Gastropoda: Planorbidae) in Thailand, inferred from 18S and 28S rDNA sequences.

Indoplanorbis exustus, a freshwater pulmonate snail, is widely distributed in tropical and subtropical zones and plays a significant role as an intermediate host for trematode parasites. Various genetic markers have been used for species identification and phylogenetic studies of this snail. However, there are limited studies about their molecular genetics based on nuclear ribosomal DNA (rDNA) genes. A genetic analysis of I. exustus in Thailand was conducted based on the nuclear 18S rDNA (339 bp) and 28S rDNA (1036 bp) genes. Indoplanorbis snails were collected from 29 localities in 21 provinces covering six regions of Thailand. Nucleotide sequences from 44 snails together with sequences from the GenBank database were examined for phylogenetic relationships and genetic diversity. All sequences of the selected nucleotide regions exhibited a high level of similarity (99%) to the sequences of I. exustus in the GenBank database. The maximum likelihood tree based on the 18S and 28S rDNA fragment sequences of I. exustus in Thailand revealed only one group with clear separation from another genus in the family Planorbidae. The I. exustus 28S rDNA sequences showed intraspecific genetic divergence ranging from 0 to 0.78% and were classified into 8 different haplotypes. Conversely, the 18S rDNA data showed lower variation than the 28S rDNA data and revealed a single haplotype and intraspecific distances of zero among all sampled individuals. The haplotype network of 28S rDNA sequences of I. exustus in Thailand revealed six unique haplotypes and two haplotypes shared by at least two regions. Overall, both markers were successful in the identification of I. exustus. However, these markers, particularly the 18S rDNA, may not be suitable for genetic analysis within the species, particularly for population genetic studies, due to their limited variation as seen in this study. In summary, this study not only enhances understanding of genetic variation in I. exustus but is also useful for the selection of molecular markers in future genetic research.

Notas sobre el conocimiento limnológico de los gasterópodos paranenses y sus relaciones tróficas. II Planorbidae, con aspectos distribucionales y sanitarios

.The present remarks on the family Planorbidae constitute a further work o f a series of contributions tending to fumish an integrated overview of the Paraná river’s malacologic fauna, the knowledge of which is most limited, particularly conceming thetaxonomic, biological and limnological aspects. To this effect, the aim of this work is, as well, to give an idea of its energy transfer to fishes and of its importance. This is best observed in the planorbids of the genus Biomphalaria, not particularly because of the importance of such energy contribution, but due to the preying capacity, consumption pressure, and consequent population control performed by certain fishes on these gastropods, some of which species are vectors of schistosomiasis. The fact becomes especially relevant when a sustained advance of this parasitosis towards Argentinianwaters is being noticed; for this reason, thorough investigations of this problem are suggested so as to prevent (or at least reduce) this serious threat which has to be realistically assumed.

Spatial and temporal variation in the diversity of malacofauna from Aripal stream of Kashmir Himalaya, India

This paper presents the spatial and temporal variation in the diversity of malacofauna in relation to the water chemistry of the Aripal stream of Kashmir Himalaya. A total of 12 species were reported which belong to four families, Lymnaeidae, Physidae, Planorbidae, and Bithyniidae from class Gastropoda, and two families, Cyrenidae and Pisidiidae from class Bivalvia. The family Planorbidae contributed 34% to the total annual molluscan population followed by Lymnaeidae (28%) and Bithyniidae (18%). During the collection, Gyraulus sp., Planorbis sp., and Bithynia tentaculata were prevalent at all sites, with predominance of Bithynia tentaculata. Species richness and abundance were observed maximum at site A3 (down-stream) and minimum at site A1 (up-stream) while in the case of temporal variation, species richness and abundance were maximum in summer and minimum in winter. Shannon-Wiener index, Simpson index, Margalef index, and Pielou evenness index were used to calculate the diversity, dominance, richness, and evenness of molluscan species, respectively. Physico-chemical parameters revealed a non-significant spatial variation (P >0.05) except pH, total hardness, and alkalinity while a significant temporal variation (P <0.05) was observed in the physico-chemical parameters except dissolved oxygen. A significant positive correlation was seen between the molluscan species and total hardness. In the present study, the stone mining, channel morphology of stream, habitat heterogeneity, and physico-chemical parameters were also found to promote the spatial and temporal diversity of malacofauna.

Morphological and molecular identification of trematode cercariae related with humans and animal health in freshwater snails from a lake and a dam in Myanmar.

Freshwater snails play an essential role in the transmission of trematode parasitic flatworms that can infect wild and domestic animals, as well as humans. This study aimed to investigate the rate of cercarial infections in freshwater snails collected from two study areas, Inlay Lake and Yezin Dam, in Myanmar. A total of 4,740 snail samples were collected from Inlay Lake (n = 3,837) and Yezin Dam (n = 903), and infection rate by cercarial emergence was examined. Cercarial DNA samples were analysed by PCR. Based on morphological characteristics, eleven snail species and eight cercarial types were identified. Snails of Melanoides tuberculata in the family Thiaridae were found as the most abundant, followed by Indoplanorbis exustus of the family Planorbidae, in both study areas. The infection rate by cercarial emergence in snails in Inlay Lake and Yezin Dam was 5.8% (224/3,837) and 48.6% (439/903), respectively. Echinostome cercariae showed the highest infection rate in both study areas. Phylogenetic analysis of cercarial internal transcribed spacer 2 (ITS2) sequences revealed that at least seven cercaria types belonged to five digenean trematode families, two of which were zoonotic trematodes in the families of Opisthorchiidae/Heterophyidae and Schistosomatidae. Furthermore, cercarial 28S ribosomal RNA gene analysis showed that the furcocercous cercariae in Yezin Dam were identified as Schistosoma spindale, a causative agent of ruminant schistosomiasis. This is the first report on zoonotic trematode cercariae in snails in Myanmar. The findings indicate that various snail species act as intermediate host for trematode species that infect aquatic animals, mammals and humans in the country.

An annotated checklist of Planorbinae (Heterobranchia, Hygrophila, Planorbidae) from northwestern Argentina

The family Planorbidae comprises freshwater gastropods with planispiral, spiral and limpet-shaped shells. Subfamily Planorbinae sensu stricto, has a richness of almost 300 species, with some of the main genera being Biomphalaria Preston, 1910 and Drepanotrema Fischer & Crosse, 1880. Some Biomphalaria species are of concern to human health as they are intermediate hosts of blood flukes in Latin America. In Argentina, the family Planorbidae is represented by 15 species in four genera. In Northern Argentina (NOA region), records of the family are scarce, and most of them are a result of occasional collecting. We provide an updated checklist of Planorbinae in NOA resulting from fieldwork, material in malacological collections, and data in the literature. Nine species occur in the area: four species of Biomphalaria and five of Drepanotrema. Among Biomphalaria species, we recorded Biomphalaria straminea (Dunker, 1848), which is considered a natural host of the blood fluke Schistostoma mansoni Sambon, 1907, for first time in Salta province; the known geographic distribution of B. straminea is extended in the country.

The complete mitochondrial genome of the file ramshorn snail Planorbella pilsbryi (Mollusca: Gastropoda: Hygrophila: Planorbidae)

The file ramshorn snail Planorbella pilsbryi Baker, 1926 (Gastropoda: Hygrophila: Planorbidae) is a widespread herbivorous North American freshwater snail found in diverse habitats, including standing and moving water bodies. Genome skimming by Illumina sequencing allowed the assembly of a complete nuclear rRNA repeat sequence and a complete circular mitogenome of 13,720 bp from P. pilsbryi consisting of 75.3% AT nucleotides, 22 tRNAs, 13 protein-coding genes, 2 rRNAs and a control region in the typical order found in panpulmonate snails. Planorbella pilsbryi COXI features a rare TTG start codon while COXII, CYTB, ND2, ND3, and ND5 exhibit incomplete stop codons completed by the addition of 3′ A residues to the mRNA. Phylogenetic reconstruction of mitochondrial protein-coding gene and rRNA sequences places P. pilsbryi as sister taxon to Planorbella duryi (Planorbidae) within family Planorbidae, which is consistent with previous phylogenetic hypotheses.

Genetic characterisation of cercarial stages of Choanocotyle Jue Sue and Platt, 1998 (Digenea: Choanocotylidae) in a native Australian freshwater snail, Isidorella hainesii (Tryon).

Isidorella hainesii (Tryon, 1866) is a native freshwater snail, belonging to the family Planorbidae, commonly found on aquatic vegetation in south eastern parts of Australia. In the present study, we report natural infection with a species of Choanocotyle Jue Sue and Platt, 1998 (Digenea: Choanocotylidae) parasite in inland Australia for the first time, followed by characterisation of the parasite using both morphological and molecular approaches. Snails (n = 150) were collected from recently drained, natural ponds at a local fish farm located in the Riverina region, New South Wales, Australia. Parasites were subjected to preliminary morphological examination followed by DNA extraction to obtain their ITS-2, 18S and 28S sequences. Based on their sequence data and phylogenetic analyses they were identified as Choanocotyle hobbsi Platt and Tkach, 2003, which has only previously been described from Chelodina oblonga Gray, 1841 (snake-necked turtle) in Western Australia. Previous researchers suggested that in Australia, C. oblonga and its parasite fauna are separated from their eastern counterparts due to formation of impenetrable waterless desert in the country during the late Cretaceous. Our study extends the distribution of Choanocotyle hobbsi from Western Australia to the Murray Darling Basin in New South Wales, however, the definitive host remains unknown in New South Wales.

Challenges and Opportunities Presented by Current Techniques for Detecting Schistosome Infections in Intermediate Host Snails: A Scoping Review.

Schistosomiasis, a neglected tropical disease (NTD), causes morbidity and mortality in over 250 million people globally. And 700 million people are at risk of contracting it. It is caused by a parasite of the genus Schistosoma. Freshwater snails of the family Planorbidae are of public health significance as they are intermediate hosts of these highly infective flukes. Accurate diagnostic techniques to detect schistosome infections in intermediate host snails (IHS) and environmental surveillance are needed to institute measures for the interruption of transmission and eventual elimination. We carried out a systematic review of the literature to assess advantages and limitations of different diagnostic techniques for detecting schistosome infections in snails. Literature from Scopus, Web of Science, and PubMed databases from 2008 to 2020 were searched using combinations of predefined search terms with Boolean operators. The studies revealed that conventional diagnostics are widely used, although they are labor-intensive, have low specificity and sensitivity levels, and cannot detect prepatent infections. Whereas more advanced techniques such as immunological, nucleic-acid amplification, and eDNA diagnostics have high sensitivity and specificity levels, they are costly, hence, not suitable for field applications and large-scale surveys. Our review highlights the importance of designing and developing innovative diagnostics that are high in specificity and sensitivity as well as affordable and technically feasible for use in field laboratories and for large-scale surveys.

THE SPREAD OF SHEEP FLUKES ON THE ECOLOGICALY DIFFERENT TYPES OF PASTURES IN THE DAGESTAN LOWLAND

The trematodeses (fascioliasis, dicrocoeliosis, paramphistomatosis) are widespread helminthes of sheep. Animals are infected with pathogens of these helminthes on pastures and near water sources. It is established that these trematodoses are common among sheep with different intensity on ecologically different types of pastures of the Dagestan lowland. So, fascioliasis is recorded among sheep on wet lowland with many waterholes, as well as on steppe ecosystems with irrigation and near permanently functioning artesian wells with wetlands with developed freshwater malacofauna. Paramphistomatosis occur in habitats with permanent water sources with the fauna of freshwater mollusks of the family Planorbidae. Dictyocaulosis among sheep is observed in the dry steppe territories with an abundance of land mollusks and ants. Sheep were infected with fascioles in the Dagestan lowlands with an invasion extensity (IE) of 10.0–26.6%, with an invasion intensity (II) of 5–216 copies, with paramphistomum and calicoforum 3.0–15.8% and 4–140 copies, with dicrocelium 18,0–76,6% and 120–2670 copies, respectively. Mixed infestations of trematodoses, strongylatoses, and larval teniidoses are recorded in the interfluve area of Sulak, Terek, Talovka, and Kuma, as well as near the Arakum, Lower Terek, and Shirokolsky reservoirs.

A comparative study of enzymatic and immunological parameters in Planorbarius corneus and Biomphalaria glabrata exposed to the organophosphate chlorpyrifos

This study aimed to investigate the acute effects of chlorpyrifos on biomarkers related to neurotoxicity and immunotoxicity in two allopatric freshwater gastropod species belonging to the family Planorbidae. For this purpose, Planorbarius corneus and Biomphalaria glabrata were exposed to chlorpyrifos (active ingredient or commercial formulation) for 48 h at environmentally realistic concentrations (1 and 7.5 μg L−1). Basal acetylcholinesterase activity in soft tissues and hemolymph was almost one order of magnitude higher in P. corneus than in B. glabrata. However, upon chlorpyrifos exposure, statistically significant inhibition of enzymatic activity was registered in both species. Acetylcholinesterase was more sensitive to inhibition in soft tissues than in hemolymph. The highest inhibition was observed in the B. glabrata soft tissues exposed to the commercial formulation (88 % at 1 μg L-1 and 93 % at 7.5 μg L−1). Hemocyte number and lysosomal membrane stability did not show significant changes with respect to controls in any of the exposed groups. Superoxide anion generation was diminished (21–46 %) in P. corneus hemocytes exposed to the active ingredient and in B. glabrata hemocytes exposed to the active ingredient or the formulation. In contrast, hemocyte phagocytic activity increased in all exposed groups. Phagocytosis was most stimulated (89 %) in hemocytes sampled from B. glabrata treated with 7.5 μg L−1 chlorpyrifos. Altogether the results suggest that the freshwater gastropods P. corneus and B. glabrata are suitable model animals for environmental monitoring studies in the Northern Hemisphere and Latin America, respectively. Furthermore, these results add information on the relevance of testing pesticide formulations and on the usefulness of acetylcholinesterase inhibition and immunological parameters as biomarkers of the acute effects of chlorpyrifos in these species.

Marsh Rams-Horn, Marsh Ramshorn Helisoma (Planorbella) trivolvis (Say) (Gastropoda: Planorbidae)

The marsh rams-horn, Helisoma (Planorbella) trivolvis (Say), is a species of air-breathing freshwater aquatic snail that is native to Florida. It belongs to the family Planorbidae, commonly known as the ramshorn snail, which comes from the shape of its shell.https://edis.ifas.ufl.edu/in1234
 Also published on Featured Creatures: http://entnemdept.ufl.edu/creatures/MISC/GASTRO/marsh_ramshorn.html

The mitochondrial genome of the planorbid snail Planorbella duryi

The complete mitochondrial genome of a freshwater planorbid snail, Planorbella duryi (Mollusca, Gastropoda) was recovered from de novo assembly of genomic sequences generated with the Illumina NextSeq500 platform. The P. duryi mitogenome (14,217 base pairs) is AT rich (72.69%) and comprises 13 protein-coding genes, two ribosomal subunit genes, and 22 transfer RNAs. The gene order is identical to that of Biomphalaria glabrata and other snail species in the family Planorbidae. This is the first full characterization of a mitochondrial genome of the genus Planorbella.

Description of a new species Gyraulus (Pulmonata: Planorbidae) from the land thermal spring Khakusy of Lake Baikal.

A new species of the family Planorbidae is described from the land thermal spring Khakusy, on the north-eastern shore of Lake Baikal. The description of Gyraulus takhteevi sp. n. includes morphological characters and gene sequences (COI of mtDNA) for the species separation from sister taxon Gyraulus acronicus (A. Férussac, 1807) collected from the small Krestovka River in-flowing into the south-western part of the Lake. The new species differs from G. acronicus in small shell size of adults, having smaller number of prostate folds (maximal up to 26 in G. takhteevi n. sp. vs. 40 in G. acronicus), a short preputium (approximately twice shorter than the phallotheca), and an elongated bursa copulatrix. The population of Gyraulus takhteevi sp. n. consists of two co-existent morphs: one of them has a narrow shell spire and the second is characterized by wide spire similar to the shell of G. acronicus. One of the two revealed haplotypes of the new species includes both morphs, while the second consists of snails with wide spired shells.

Retraction Note to: The complete mitochondrial genomes of two freshwater snails provide new protein-coding gene rearrangement models and phylogenetic implications

Mitochondrial (mt) genome sequences are widely used for species identification and to study the phylogenetic relationships among Gastropoda. However, to date, limited data are available as taxon sampling is narrow. In this study we sequenced the complete mt genomes of the freshwater gastropods Radix swinhoei (Lymnaeidae) and Planorbarius corneus (Planorbidae). Based on these sequences, we investigated the gene rearrangement in these two species and the relationships with respect to the ancestral gene order and assessed their phylogenetic relationships. The complete mt genomes of R. swinhoei and P. corneus were sequenced using Illumina-based paired-end sequencing and annotated by comparing the sequence information with that of related gastropod species. Putative models of mitochondrial gene rearrangements were predicted for both R. swinhoei and P. corneus, using Reishia clavigera mtDNA structure as the ancestral gene order. The phylogenetic relationships were inferred using thirteen protein sequences based on Maximum likelihood and Bayesian inference analyses. The complete circular mt genome sequences of R. swinhoei and P. corneus were 14,241 bp and 13,687 bp in length, respectively. Comparison of the gene order demonstrated complex rearrangement events in Gastropoda, both for tRNA genes and protein-coding genes. The phylogenetic analyses showed that the family Lymnaeidae was more closely related to the family Planorbidae, consistent with previous classification. Nevertheless, due to the position recovered for R. swinhoei, the family Lymnaeidae was not monophyletic. This study provides the complete mt genomes of two freshwater snails, which will aid the development of useful molecular markers for epidemiological, ecological and phylogenetic studies. Additionally, the predicted models for mt gene rearrangement might provide novel insights into mt genome evolution in gastropods.

RETRACTED ARTICLE: The complete mitochondrial genomes of two freshwater snails provide new protein-coding gene rearrangement models and phylogenetic implications

BackgroundMitochondrial (mt) genome sequences are widely used for species identification and to study the phylogenetic relationships among Gastropoda. However, to date, limited data are available as taxon sampling is narrow. In this study we sequenced the complete mt genomes of the freshwater gastropods Radix swinhoei (Lymnaeidae) and Planorbarius corneus (Planorbidae). Based on these sequences, we investigated the gene rearrangement in these two species and the relationships with respect to the ancestral gene order and assessed their phylogenetic relationships.MethodsThe complete mt genomes of R. swinhoei and P. corneus were sequenced using Illumina-based paired-end sequencing and annotated by comparing the sequence information with that of related gastropod species. Putative models of mitochondrial gene rearrangements were predicted for both R. swinhoei and P. corneus, using Reishia clavigera mtDNA structure as the ancestral gene order. The phylogenetic relationships were inferred using thirteen protein sequences based on Maximum likelihood and Bayesian inference analyses.ResultsThe complete circular mt genome sequences of R. swinhoei and P. corneus were 14,241 bp and 13,687 bp in length, respectively. Comparison of the gene order demonstrated complex rearrangement events in Gastropoda, both for tRNA genes and protein-coding genes. The phylogenetic analyses showed that the family Lymnaeidae was more closely related to the family Planorbidae, consistent with previous classification. Nevertheless, due to the position recovered for R. swinhoei, the family Lymnaeidae was not monophyletic.ConclusionThis study provides the complete mt genomes of two freshwater snails, which will aid the development of useful molecular markers for epidemiological, ecological and phylogenetic studies. Additionally, the predicted models for mt gene rearrangement might provide novel insights into mt genome evolution in gastropods.