Prosobranch Snail Research Articles

Genome Evolution and Introgression in the New Zealand mud Snails Potamopyrgus estuarinus and Potamopyrgus kaitunuparaoa.

We have sequenced, assembled, and analyzed the nuclear and mitochondrial genomes and transcriptomes of Potamopyrgus estuarinus and Potamopyrgus kaitunuparaoa, two prosobranch snail species native to New Zealand that together span the continuum from estuary to freshwater. These two species are the closest known relatives of the freshwater species Potamopyrgus antipodarum-a model for studying the evolution of sex, host-parasite coevolution, and biological invasiveness-and thus provide key evolutionary context for understanding its unusual biology. The P. estuarinus and P. kaitunuparaoa genomes are very similar in size and overall gene content. Comparative analyses of genome content indicate that these two species harbor a near-identical set of genes involved in meiosis and sperm functions, including seven genes with meiosis-specific functions. These results are consistent with obligate sexual reproduction in these two species and provide a framework for future analyses of P. antipodarum-a species comprising both obligately sexual and obligately asexual lineages, each separately derived from a sexual ancestor. Genome-wide multigene phylogenetic analyses indicate that P. kaitunuparaoa is likely the closest relative to P. antipodarum. We nevertheless show that there has been considerable introgression between P. estuarinus and P. kaitunuparaoa. That introgression does not extend to the mitochondrial genome, which appears to serve as a barrier to hybridization between P. estuarinus and P. kaitunuparaoa. Nuclear-encoded genes whose products function in joint mitochondrial-nuclear enzyme complexes exhibit similar patterns of nonintrogression, indicating that incompatibilities between the mitochondrial and the nuclear genome may have prevented more extensive gene flow between these two species.

ADHEARING RESPONSE AMONG GASTROPOD SNAILS IN DESERT REGION OF RAJASTHAN (NORTH INDIA)

Adhearing preference among these gastropod snails namely Bellamya bengalensis, Gabbia orcula and Digoniostoma pulchella were studied in fresh water ponds namely Gajner pond and Kodemdesar pond near Bikaner, Rajasthan (Indian Desert) as well as under laboratory conditions.The study was carried out for an annual cycle encompassing all the three seasons summer, monsoon and winter (May,2009 to April 2010). Prosobranch snails collected by sieving method (vide 3.2.2) was studied under stereoscopic binocular microscope and bull lens. The forms were identified and counted. Identifications were made following Subba Rao (1989). In the field, observations were made with respect to the substrate preffered by individual species in water. B. bengalensis basically inhabitat 90% on pond mud, G.orcula were found to float (60%) close to surface and D. pulchella showed 67% free floating. In laboratory 20 healthy specimen of each recorded species were released in aquarium containg pond water and mud. Vegetation Hydrilla and wood pieces (dried twigs) were also placed in aquarium. Bellamya bengalensis did not harbour on artificial subsratates. G. orcula and D. pulchella found mostly free floating in aquarium and some found attached to the glass wall of aquarium.

Are Freshwater Snails, Melanoides sp. and Invasive Tarebia granifera (Gastropoda: Thiaridae) Suitable Intermediate Hosts for Calicophoron microbothrium (Trematoda: Paramphistomoidea)? An Experimental Study.

Prosobranch snails and adult Paramphistomoidea flukes were collected from water bodies and cattle abattoir located in Mpumalanga province of South Africa, respectively. The snails were identified based on morphological characters as well as the ITS-2 and 16S markers as Melanoides sp. and Tarebia granifera, respectively, and the Paramphistomoidea flukes were identified as Calicophoron microbothrium using the ITS-1/5.8S/ITS-2 marker. After confirming identification, the snails were bred to first filial generation (F1) under laboratory conditions. Ninety snails were randomly selected from the laboratory-bred F1 snails and 25 Melanoides sp. and 20 T. granifera were exposed to C. microbothrium miracidia, and the same numbers were maintained as non-exposed controls. Results showed that C. microbothrium successfully established in Melanoides sp. and produced cercariae, and the prepatent period recorded was 21 days. Three snails shed cercariae at day 21 postexposure (PE), and rediae and free cercariae were detected in the soft tissues of one snail on dissection at day 44 PE. The same fluke did not establish in T. granifera. Melanoides sp. started producing offspring at day 7 PE, and T. granifera at day 14 PE. In conclusion, our results showed that Melanoides sp. used in this study is a suitable intermediate host for C. microbothrium under experimental conditions, and given the wide distribution of this snail species, it is important to determine its role in the natural transmission of other Calicophoron species that have been reported in South Africa.

Diversity of benthic macroinvertebrates in anthropogenically disturbed Aturukuku River, Eastern Uganda

Biodiversity conservation has focused on large vertebrates and plants with pronounced economic value, compared with smaller organisms such as benthic macroinvertebrates that play a particular role in freshwater ecosystems. The increasing loss and degradation of freshwater habitats, coupled with low taxonomic and ecological knowledge and limited conservation efforts in the tropical regions, threaten macroinvertebrate biodiversity. This study investigated spatial and seasonal variability in benthic macroinvertebrate diversity and the underlying environmental variables within the Aturukuku River in Tororo, Uganda. Benthic macroinvertebrates were evaluated by comparing their composition at a reference site in the upstream rural area with two urban midstream sites and one rural downstream site during dry and wet seasons in 2018. Benthic macroinvertebrate diversity in the Aturukuku River was lower than that reported from least disturbed small rivers within the same region; with moderate to high pollution tolerant taxa, dominating. Chironomidae, Oligochaeta and Simulium sp. predominated at the urban sites receiving sewage and abattoir effluent. The Shannon–Wiener diversity index, species richness and species evenness in the river were generally low. Prosobranch (Thiaridae) snails and bivalves (Sphaeridae) were among the taxa with low tolerance to changes in the river. Canonical Correspondence Analysis revealed that total nitrogen, dissolved oxygen, temperature and streambed substrate were predominant in structuring benthic macroinvertebrate assemblages. There was no potential species-rich area for macroinvertebrate conservation, given the poor environmental conditions and diversity in the entire river. However, specific mitigation measures against the declining quality of the river are recommended, to boost conservation of macroinvertebrates and the entire riverine ecosystem.

The Life Cycle of Heterophyes yacyretana n. sp. (Digenea, Heterophyidae), Parasitic in the Endemic Snail Aylacostoma chloroticum (Caenogastropoda, Thiaridae) in Argentina.

Here we describe a new heterophyid species, Heterophyes yacyretana n. sp., and resolve its life cycle experimentally. We found the prosobranch snail Aylacostoma chloroticum in Candelaria, Province of Misiones, Argentina (a sector of the High Paraná River affected by the Yacyretá Dam), naturally infected with opisthorchioid cercariae. These cercariae lacked pigmented eyespots as well as body pigment and possessed 7 pairs of penetration glands arranged in 2 lateral bands, together with 18 pairs of flame cells and a V-shaped excretory vesicle. We exposed specimens of 21 fish species to emerging cercariae and obtained metacercariae from the muscles of the caudal peduncle of 3 species of siluriform fish, and adults from chicks infected with experimentally obtained metacercariae from the albino variety of the bronce corydoras, Corydoras aeneus. The new species differs from other species in the genus by the number of sclerites on the genital sac, the distribution of the vitelline follicles, and the combination of the size relationship of the suckers and the genital sac with respect to the posterior extent of intestinal ceca. Heterophyes yacyretana is the first species of the genus reported from the Americas.

Thirty years of change in a benthic macroinvertebrate community of southwestern Lake Ontario after invasion by four Ponto-Caspian species

AbstractBeginning in the mid-1980s, the Laurentian Great Lakes underwent successive invasions by Ponto-Caspian species. We quantified major changes in the diversity and relative abundance of pre-invasion benthic macroinvertebrates at the same study site in southwestern Lake Ontario from 1983–2014. The zebra mussel Dreissena polymorpha Pallas arrived at the study site before 1991, the quagga mussel Dreissena rostriformis bugensis Andrusov and the amphipod Echinogammarus ischnus Stebbing arrived before 1999, and the Round Goby Neogobius melanostomus Pallas arrived about 2004. The macroinvertebrate community in 2014 was very different from 3 earlier communities in 1983, 1991, and 1999. In 2014, pulmonate and prosobranch snails and sphaeriid bivalves were absent, D. r. bugensis replaced D. polymorpha, E. ischnus replaced Gammarus fasciatus Say as the dominant amphipod, and a previously diverse community of benthic fish was replaced by abundant N. melanostomus. From 1983 to 1999, the relative abundance of pros...

Bioaccumulation of heavy metals in freshwater snails in relation to lining of water courses in Egypt.

The present study was aimed to determine the heavy metal concentrations in whole body of fresh water snails in relation to lining of water courses in two governorates (Behaira (Nubaria) and Giza) Through four successive seasons from Septemper 2013, to October 2014. The obtained results indicated that the electrical conductivity (EC) and iron metal (Fe) showed the highest values and generally the physicochemical measurements indicated that no significant difference between the two tested habitats, however, the conductivity of water in lined water bodies was lower than those of unlined ones. The present study recorded 14 species of snails belonging to class Gastropoda; these species belonged to Pulmonate and Prosobranch snails. The density of all recorded Pulmonate snails in lined sites were lower than those in unlined ones. On the other hand, the abundance of Prosobranch snails was higher in numbers in the lined sites than those in the unlined. In Nubaria the most abundant snails were Melanoides tuberculata and Theodoxus niloticus and exhibited their maximum percentages in the lined (82.15%) and unlined (72.34%) sites during summer, respectively. While, in Giza Governorate Physa acuta snails had the highest percentages among collected snails approximately at all seasons, and exhibited its maximum percentages during spring in lined (90.22%) and unlined sites (85.38%). Correlations between physicochemical parameters and the collected snails, revealed that there were different negative or positive correlations depending on the sites of investigation. The bioconcentration factor of heavy metals in snail’s soft tissues at the investigated in lined and unlined sites compared to the content of the metals (Cd, Cu, Fe, Pb and Zinc) in the water showed high variation in BCF values depending on the type of metal and the snail. Generally P. acuta (7626.95μg.g-1 DW for Fe) and H. duryi (8787.10 μg.g-1 DW for Cu) were the highest snails of accumulated metal contents in the tested sites of the two surveyed governorates, respectively.

Phylogenetic relationships of some species of the family Echinostomatidae Odner, 1910 (Trematoda), inferred from nuclear rDNA sequences and karyological analysis.

The family Echinostomatidae Looss, 1899 exhibits a substantial taxonomic diversity, morphological criteria adopted by different authors have resulted in its subdivision into an impressive number of subfamilies. The status of the subfamily Echinochasminae Odhner, 1910 was changed in various classifications. Genetic characteristics and phylogenetic analysis of four Echinostomatidae species – Echinochasmus sp., Echinochasmus coaxatus Dietz, 1909, Stephanoprora pseudoechinata (Olsson, 1876) and Echinoparyphium mordwilkoi Skrjabin, 1915 were obtained to understand well enough the homogeneity of the Echinochasminae and phylogenetic relationships within the Echinostomatidae. Chromosome set and nuclear rDNA (ITS2 and 28S) sequences of parthenites of Echinochasmus sp. were studied. The karyotype of this species (2n=20, one pair of large bi-armed chromosomes and others are smaller-sized, mainly one-armed, chromosomes) differed from that previously described for two other representatives of the Echinochasminae, Echinochasmus beleocephalus (von Linstow, 1893), 2n=14, and Episthmium bursicola (Creplin, 1937), 2n=18. In phylogenetic trees based on ITS2 and 28S datasets, a well-supported subclade with Echinochasmus sp. and Stephanoprora pseudoechinata clustered with one well-supported clade together with Echinochasmus japonicus Tanabe, 1926 (data only for 28S) and Echinochasmus coaxatus. These results supported close phylogenetic relationships between Echinochasmus Dietz, 1909 and Stephanoprora Odhner, 1902. Phylogenetic analysis revealed a clear separation of related species of Echinostomatoidea restricted to prosobranch snails as first intermediate hosts, from other species of Echinostomatidae and Psilostomidae, developing in Lymnaeoidea snails as first intermediate hosts. According to the data based on rDNA phylogeny, it was supposed that evolution of parasitic flukes linked with first intermediate hosts. Digeneans parasitizing prosobranch snails showed higher dynamic of karyotype evolution provided by different chromosomal rearrangements including Robertsonian translocations and pericentric inversions than more stable karyotype of digenean worms parasitizing lymnaeoid pulmonate snails.

The life cycle of Pseudosellacotyla lutzi (Digenea: Cryptogonimidae), in Aylacostoma chloroticum (Prosobranchia: Thiaridae), and Hoplias malabaricus (Characiformes: Erythrinidae), in Argentina.

Pseudosellacotyla lutzi ( Freitas, 1941), at present included in the Faustulidae, is redescribed, and its life cycle was resolved experimentally. The prosobranch snail Aylacostoma chloroticum Hylton Scott (Thiaridae), collected in the Yacyretá Dam, Province of Misiones, Argentina, was found naturally infected with cercariae that lacked pigmented eyespots, and possessed 7 pairs of penetration glands, 8 pairs of flame cells, and a V-shaped excretory vesicle. The cercariae developed in oval cysts, which were found on fin rays, vertebrae, and spines of poeciliid and tetragonopterid fish species. Adults were obtained experimentally from Hoplias malabaricus (Erythrinidae) infected with metacercariae from albino Gymnocorymbus ternetzi (Tetragonopteridae), which had been exposed to emerging cercariae. Adults were also found in naturally infected H. malabaricus collected in the Yacyretá Dam. The morphology of the cercariae, and the characteristics of the life cycle show that P. lutzi should be included in the Cryptogonimidae.

Molecular cloning of α-2-macroglobulin from hemocytes of common periwinkle Littorina littorea

We report the sequence of the proteinase inhibitor with a wide inhibition spectrum, α-2-macroglobulin (α2M), belonging to the thioester superfamily of proteins. This is the first α2M sequence from coenogastropod prosobranch snails. The full-length cDNA was cloned by RACE method, spans 7897 bp and contains an open reading frame of 5460 bp. The ORF encodes a protein of 1819 amino acids. The deduced mature protein contains 1795 amino acids with a molecular weight of 200 kDa and isoelectric point of 5.00. Littorina littorea α2M bears 4 conserved α2M domains and one internal thioester. Phylogenetic analysis showed that the sequence forms well supported cluster with Mollusca species and other representatives of Lophotrochozoa.

Identification of an estrogen receptor gene in the natural freshwater snail Bithynia tentaculata

Mollusks have received increasing interest in ecotoxicological studies but so far the available scientific analyses of how their genes are affected by anthropogenic pollutants are scarce. The focus of this study is to identify an estrogen receptor (er) gene in the common prosobranch snail Bithynia tentaculata and to test a hypothesis that 17α-Ethinylestradiol (EE2) will modulate er gene expression after short-term exposure. We set up exposure experiments with a total of 144 snails, which were collected from a natural population in southern Sweden. Snails were exposed to either 10ng/L or 100ng/L EE2 during 24h and/or 72h. From the isolated B. tentaculata RNA we successfully identified and characterized a novel er gene and phylogenetic analyses strongly indicate that the Bithynia er gene is an ortholog to the human ERα (ESR1, NR3A1). We found a significant interaction between EE2-dose and exposure duration on the er's gene expression (Two-way ANOVA; p=0.04). We also found a significant difference in the gene expression of the er when comparing the control and 100ng/L treatment groups after 72h in female snails (One-way ANOVA; p=0.047). The results from this study should be useful for future field-related studies of estrogen receptors in natural populations of mollusks.

Production and population dynamics of the prosobranch snail Sulcospira hainanensis (Pachychilidae), a major secondary consumer in Hong Kong streams

Pachychilid snails are common and widespread in tropical Asian streams, and given their abundance, these heavy-shelled prosobranchs may serve as a ‘trophic dead-end’ preventing energy transfer to higher trophic levels. Sulcospira hainanensis (Brot, 1872) is an abundant secondary consumer in Hong Kong streams, and tends to have higher standing biomass in less shaded sites. We predicted that S. hainanensis would be more productive in unshaded streams, where snails have a higher assimilation of more nutritious algal carbon. The production and population dynamics of S. hainanensis were studied along a gradient of shading in four Hong Kong streams. The increment-summation method was considered to most realistically represent snail production, which ranged from 1,612.8 to 6,123.9 mg ash-free dry mass m−2 year−1; these estimates were among the upper range of values reported for stream prosobranchs. Production, turnover, and growth were higher in unshaded streams, where the combined effects of higher light input and nutrient concentrations likely enhanced the supply of algal food. Despite high standing biomass (26% of total benthic fauna), S. hainanensis had a relatively low (~16%) contribution to total production in one site, suggesting that it is not a major trophic dead-end in the food webs of tropical Hong Kong streams.

Coming out of the Shell: Building the Molecular Infrastructure for Research on Parasite-Harbouring Snails

Coming out of the Shell: Building the Molecular Infrastructure for Research on Parasite-Harbouring Snails

SELECTIVE LAND SNAIL PREDATION BY THE SPINY MOUSE, ACOMYS CAHIRINUS, IN NAHAL OREN, MT. CARMEL, ISRAEL

ABSTRACT Microclimatic differences between the south-facing slope and the north-facing slope of the Lower Nahal Oren, Mt. Carmel, Israel result in a dramatic biological divergence. The south-facing slope harbors predominantly African representatives, including the spiny mouse, Acomys cahirinus. The north—facing slope harbors predominantly European taxa, including the prosobranch land snail Pomatias olivieri. Here we show that predation by Acomys on European Pomatias exceeds the proportion of Pomatias shells among the large land snail fauna at the microsite. The ratios of consumed to unconsumed Pomatias were approximately 4:1 and 7:1 in the north—and south-facing slopes, respectively. In all other land snail species, the consumed constituted at most 2/3 of the unconsumed. Remarkably, the selective predation of Acomys on Pomatias is significantly higher on the warmer and drier south-facing slope. We hypothesize that natural selection led to an adaptive behavioral predator—prey relationship at the microsite.

Cryptic phenotypic plasticity in populations of the freshwater prosobranch snail, Pleurocera canaliculata

We sampled four populations of the robustly shelled Pleurocera canaliculata from large rivers and five pleurocerid populations bearing more fusiform shells (nominally P. acuta and P. pyrenellum) from smaller streams in a study area extending from upstate New York to northern Alabama, USA. Gene frequencies at 9 allozyme-encoding loci revealed that each population of P. acuta or P. pyrenellum was more genetically similar to the P. canaliculata population inhabiting the larger river immediately downstream than to any nominal conspecific. Thus, the extensive intraspecific variation in shell robustness displayed by these nine populations has apparently been rendered cryptic by taxonomic confusion. We then employed geometric morphometrics to explore a gradient in shell morphology from the acuta form to the typical canaliculata form in 18 historic samples collected down the length of Indiana’s Wabash River. The shell forms appeared generally distinctive on the major axes yielded by relative warp analysis (increasing robustness and decreasing spire elongation), although some overlap was apparent. MANCOVA returned a significant relationship between multivariate shape variation and stream size, as measured by drainage area. Possible drivers for this phenomenon include an environmental cline in the risk of dislodgement due to hydrodynamic drag and shifts in the community of predators.

Paragonimiasis in KwaZulu-Natal province, South Africa

Nine cases of paragonimiasis have been reported from cats (4), dogs (2) and children (3) in South Africa, with an additional suspected case in an adult female patient. Details of these cases are reviewed. All nine cases, and perhaps the adult case as well, were from the province of KwaZulu-Natal but locality data are only available for six of them. These six cases represent four localities which all lie below 100m above sea level in the province's lowlands, suggesting that there may be a focus of transmission here. The molluscan first intermediate host must be one of the two prosobranch snail species present in the area, Melanoides tuberculata or Tomichia natalensis, and the decapod second intermediate host the common river crab Potamonautes sidneyi. All infected cats and dogs had pulmonary infections, while two human cases for which there is sufficient information had extrapulmonary infections. Transmission appears to be ongoing but the invasive snail Tarebia granifera may be competing with both M. tuberculata and T. natalensis. If so, this may bring transmission to an end.

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

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

Sediment contact test with Potamopyrgus antipodarum in effect-directed analyses—challenges and opportunities

Effect-directed analysis is increasingly used for the identification of key toxicants in environmental samples and there is a growing need for in vivo biotests as diagnostic tools. Within this study, we performed an in vivo sediment contact test, applicable on both native field samples and their extracts or fractions, in order to be able to compare the results from both field and laboratory studies. A sediment contact test with the prosobranch snail, Potamopyrgus antipodarum, was carried out on extracts and fractions of field sediments from three European river basins. The results were compared with previous results of the native field samples. In contrast to the native sediments, the extracts of the samples led to an overall decrease in reproduction. Even the chosen reference sites had an adverse effect on the snails' reproduction. It appeared that a higher bioavailability in the organic extracts, together with a changing composition of compounds could have lead to this change in effects. The fractionation of the extracts partly led to a more differentiated picture, but the resolution was not high enough to see any distinct effects on the snails' reproduction. Our results highlight the importance of the use of in vivo biotests and point out the relevance of bioavailability in native sediments. For further fractionation studies, a more realistic extraction procedure, together with a higher resolution fractionation, would be appropriate in order to separate individual bioavailable compounds more efficient.

Opisthorchiidosis-A Review

The discovery history of opisthorchiid flukes dates back more than 200 years. The life cycle of these liver flukes includes prosobranch snails as the first and a big variety of freshwater fish as the second intermediate hosts. Opisthorchis felineus, O. viverrini and Clonorchis sinensis are species of major medical importance, while sporadic cases of human infection with other representatives of this family are also documented in the literature. There are estimations that 17 million people are infected and more than 350 million people are at risk, mainly in Asian countries. Although opisthorchiid flukes live in the bile ducts of the liver and in the gall bladder, they can affect surrounding liver tissue and even other organs. They are also known to induce the production of autoantibodies as well as allergic reactions. However, the main medical significance is their role in the formation of malignant tumors. Since the clinical symptoms are not specific, a diagnosis must be confirmed by parasitological examination or the detection of antibodies. Apart from coproscopical methods, there are more recent and highly specific assays available, like the detection of coproantigen or the detection of DNA. Praziquantel is the drug of choice for the treatment of opisthorchiidosis. In order to prevent infection, consumption of raw flesh of freshwater fish must be avoided.

Environmental-endocrine control of reproductive maturation in gastropods: implications for the mechanism of tributyltin-induced imposex in prosobranchs

Prosobranch snails have been afflicted globally by a condition whereby females develop male sex characteristics, most notably a penis. This condition, known as imposex, has been causally associated with the ubiquitous environmental contaminant tributyltin (TBT). Deduction of the mechanism by which TBT causes imposex has been hampered by the lack of understanding of the normal endocrine regulation of reproductive tract recrudescence in these organisms. We have reviewed the relevant literature on the environmental and endocrine factors that regulate reproductive tract recrudescence, sexual differentiation, and reproduction in gastropods. We provide a cohesive model for the environmental-endocrine regulation of reproduction in these organisms, and use this information to deduce a most likely mechanism by which TBT causes imposex. Photoperiod appears to be the predominant environmental cue that regulates reproductive tract recrudescence. Secondary cues include temperature and nutrition which control the timing of breeding and egg laying. Several hormone products of the central and peripheral nervous systems have been identified that contribute to recrudescence, reproductive behaviors, oocyte maturation and egg laying. Retinoic acid signaling via the retinoid X-receptor (RXR) has shown promise to be a major regulator of reproductive tract recrudescence. Furthermore, TBT has been shown to be a high affinity ligand for the RXR and the RXR ligand 9-cis retinoic acid causes imposex. We propose that TBT causes imposex through the inappropriate activation of this signaling pathway. However, uncertainties remain in our understanding of the environmental-endocrine regulation of reproduction in gastropods. Definitive elucidation of the mechanism of action of TBT awaits resolution of these uncertainties.