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Freshwater Snail (freshwater + snail)
Selected AbstractsEVIDENCE FOR NEGATIVE FREQUENCY-DEPENDENT SELECTION DURING EXPERIMENTAL COEVOLUTION OF A FRESHWATER SNAIL AND A STERILIZING TREMATODEEVOLUTION, Issue 9 2009Britt Koskella Host,parasite coevolution is often suggested as a mechanism for maintaining genetic diversity, but finding direct evidence has proven difficult. In the present study, we examine the process of coevolution using a freshwater New Zealand snail (Potamopyrgus antipodarum) and its common parasite (the sterilizing trematode, Microphallus sp.) Specifically, we test for changes in genotypic composition of clonal host populations in experimental populations evolving either with or without parasites for six generations. As predicted under the Red Queen model of coevolution, the initially most common host genotype decreased in frequency in the presence, but not the absence, of parasitism. Furthermore, the initially most common host genotype became more susceptible to infection by the coevolving parasite populations over the course of the experiment. These results are consistent with parasite-meditated selection leading to a rare advantage, and they indicate rapid coevolution at the genotypic level between a host and its parasite. [source] THE EFFECTS OF MATING SYSTEM AND GENETIC VARIABILITY ON SUSCEPTIBILITY TO TREMATODE PARASITES IN A FRESHWATER SNAIL, LYMNAEA STAGNALISEVOLUTION, Issue 12 2004Mikael Puurtinen Abstract The amount and distribution of genetic variability in host populations can have significant effects on the outcome of host-parasite interactions. We studied the effect of mating system and genetic variability on susceptibility of Lymnaea stagnalis snails to trematode parasites. Mating system of snails from eight populations differing in the amount of genetic variability was manipulated, and self- and cross-fertilized offspring were exposed to naturally occurring trematode parasites in a controlled lake experiment. Susceptibility of snails varied between populations, but mating-system treatment did not have a significant effect. Heterozygosity of snails was negatively correlated with the probability of trematode infection, however, suggesting that parasitic diseases may pose a serious threat to populations lacking genetic variability. [source] FAMILY-LEVEL COVARIATION BETWEEN PARASITE RESISTANCE AND MATING SYSTEM IN A HERMAPHRODITIC FRESHWATER SNAILEVOLUTION, Issue 7 2002Jürgen Wiehn Abstract Genetic compatibility, nonspecific defenses, and environmental effects determine parasite resistance. Host mating system (selfing vs. outcrossing) should be important for parasite resistance because it determines the segregation of alleles at the resistance loci and because inbreeding depression may hamper immune defenses. Individuals of a mixed mating hermaphroditic freshwater snail, Lymnaea ovata, are commonly infected by a digenetic trematode parasite, Echinoparyphium recurvatum. We examined covariation between quantitative resistance to novel parasites and mating system by exposing snail families from four populations that differed by their inbreeding coefficients. We found that resistance was unrelated to inbreeding coefficient of the population, suggesting that the more inbred populations did not carry higher susceptibility load than the less inbred populations. Most of the variation in resistance was expressed among the families within the populations. In the population with the lowest inbreeding coefficient, resistance increased with outcrossing rate of the family, as predicted if selfing had led to inbreeding depression. In the other three populations with higher inbreeding coefficients, resistance was unrelated to outcrossing rate. The results suggest that in populations with higher inbreeding some of the genetic load has been purged, uncoupling the predicted relationship between outcrossing rate and resistance. Snail families also displayed crossing reaction norms for resistance when tested in two environments that presented low and high immune challenge, suggesting that genotype-by-environment interactions are important for parasite resistance. [source] Bioaccumulation of the hepatotoxic microcystins in various organs of a freshwater snail from a subtropical Chinese Lake, Taihu Lake, with dense toxic Microcystis bloomsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2007Dawen Zhang Abstract In this paper, we describe the seasonal dynamics of three common microcystins (MCs; MC-RR, MC-YR, and MC-LR) in the whole body, hepatopancreas, intestine, gonad, foot, remaining tissue, and offspring of a freshwater snail, Bellamya aeruginosa, from Gonghu Bay of Lake Taihu, China, where dense toxic Microcystis blooms occur in the warm seasons. Microcystins were determined by liquid chromatography electrospray ionization mass spectrum. Microcystin (MC-RR + MC-YR + MC-LR) content of the offspring and gonad showed high positive correlation, indicating that microcystins could transfer from adult females to their young with physiological connection. This study is the first to report the presence of microcystins in the offspring of the adult snail. The majority of the toxins were present in the intestine (53.6%) and hepatopancreas (29.9%), whereas other tissues contained only 16.5%. If intestines are excluded, up to 64.3% of the toxin burden was allocated in the hepatopancreas. The microcystin content in the intestine, hepatopancreas, and gonad were correlated with the biomass of Microcystis and intracellular and extracellular toxins. Of the analyzed foot samples, 18.2% were above the tolerable daily microcystin intake recommended by the World Health Organization (WHO) for human consumption. This result indicates that public health warnings regarding human ingestion of snails from Taihu Lake are warranted. In addition, further studies are needed to evaluate the occurrence by Microcystis in relation to spatial and temporal changes in water quality. [source] ADVICE OF THE ROSE: EXPERIMENTAL COEVOLUTION OF A TREMATODE PARASITE AND ITS SNAIL HOSTEVOLUTION, Issue 1 2007Britt Koskella Understanding host-parasite coevolution requires multigenerational studies in which changes in both parasite infectivity and host susceptibility are monitored. We conducted a coevolution experiment that examined six generations of interaction between a freshwater snail (Potamopyrgus antipodarum) and one of its common parasites (the sterilizing trematode, Microphallus sp.). In one treatment (recycled), the parasite was reintroduced into the same population of host snails. In the second treatment (lagged), the host snails received parasites from the recycled treatment, but the addition of these parasites did not begin until the second generation. Hence any parasite-mediated genetic changes of the host in the lagged treatment were expected to be one generation behind those in the recycled treatment. The lagged treatment thus allowed us to test for time lags in parasite adaptation, as predicted by the Red Queen model of host,parasite coevolution. Finally, in the third treatment (control), parasites were not added. The results showed that parasites from the recycled treatment were significantly more infective to snails from the lagged treatment than from the recycled treatment. In addition, the hosts from the recycled treatment diverged from the control hosts with regard to their susceptibility to parasites collected from the field. Taken together, the results are consistent with time lagged, frequency-dependent selection and rapid coevolution between hosts and parasites. [source] FAMILY-LEVEL COVARIATION BETWEEN PARASITE RESISTANCE AND MATING SYSTEM IN A HERMAPHRODITIC FRESHWATER SNAILEVOLUTION, Issue 7 2002Jürgen Wiehn Abstract Genetic compatibility, nonspecific defenses, and environmental effects determine parasite resistance. Host mating system (selfing vs. outcrossing) should be important for parasite resistance because it determines the segregation of alleles at the resistance loci and because inbreeding depression may hamper immune defenses. Individuals of a mixed mating hermaphroditic freshwater snail, Lymnaea ovata, are commonly infected by a digenetic trematode parasite, Echinoparyphium recurvatum. We examined covariation between quantitative resistance to novel parasites and mating system by exposing snail families from four populations that differed by their inbreeding coefficients. We found that resistance was unrelated to inbreeding coefficient of the population, suggesting that the more inbred populations did not carry higher susceptibility load than the less inbred populations. Most of the variation in resistance was expressed among the families within the populations. In the population with the lowest inbreeding coefficient, resistance increased with outcrossing rate of the family, as predicted if selfing had led to inbreeding depression. In the other three populations with higher inbreeding coefficients, resistance was unrelated to outcrossing rate. The results suggest that in populations with higher inbreeding some of the genetic load has been purged, uncoupling the predicted relationship between outcrossing rate and resistance. Snail families also displayed crossing reaction norms for resistance when tested in two environments that presented low and high immune challenge, suggesting that genotype-by-environment interactions are important for parasite resistance. [source] Comparing fecundity in parthenogenetic versus sexual populations of the freshwater snail Campeloma limum: is there a two-fold cost of sex?INVERTEBRATE BIOLOGY, Issue 1 2009Lisa T. Crummett Abstract. The predominance of sexuality in eukaryotes remains an evolutionary paradox, given the "two-fold cost of sex" also known as the "cost of males." [Correction added after online publication 29 January 2009: in the preceding sentence, extraneous words were deleted.] As it requires two sexual parents to reproduce and only one parthenogenetic parent, parthenogens should have twice the reproductive rate compared with their sexual counterparts and their genes should spread twice as fast, if all else is equal. Yet, parthenogenesis is relatively rare and considered an evolutionary dead-end, while sexuality is the dominant form of reproduction in multicellular eukaryotes. Many studies have explored short-term benefits of sex that could outweigh its two-fold cost, but few have compared fecundity between closely related sexuals and parthenogens to first verify that "all else is equal" reproductively. We compared six fecundity measures between sexual and parthenogenetic populations of the freshwater snail, Campeloma limum, during a brooding cycle (1 year) across two drainages. Drainages were analyzed separately because of a significant drainage effect. In the Savannah drainage, fecundity was not significantly different between sexuals and parthenogens, even though parthenogens had significantly more empty egg capsules per brood. In the Ogeechee drainage, parthenogens had significantly more egg capsules with multiple embryos and more hatched embryos than sexuals. Taken over 1 year, embryo size was not significantly different between parthenogens and sexuals in either drainage. Given these results and the close proximity of sexual and parthenogenetic populations, it is perplexing why parthenogenetic populations have not completely replaced sexual populations in C. limum. [source] Clinical Features and Outcome of Heterobilharzia americana Infection in DogsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 1 2010C. Fabrick Background: Heterobilharzia americana (HA), the causative agent of canine schistosomiasis, is a flatworm with a freshwater snail as an intermediate host. Only case reports or small case series evaluating naturally infected dogs have been published. Objective: Describe clinical signs in dogs naturally infected with HA. Animals: Twenty-two dogs naturally infected with HA from 1985 to 2009. Methods: Retrospective study. All medical records were searched for HA and schistosomiasis. Only dogs with a diagnosis based on identification of ova on histopathology or fecal saline sedimentation were included. Results: The median age was 3.1 years (1,12). The median duration of clinical signs before diagnosis was 0.63 months (0.03,12). The most common clinical signs were lethargy (91%), weight loss (77%), hyporexia (68%), vomiting (59%), and diarrhea (55%). Eleven of the 22 dogs were hypercalcemic. Hypercalcemia did not resolve without definitive treatment with praziquantel. HA infection was an incidental diagnosis in 7/22 dogs. Diagnosis was obtained via necropsy (4), histopathology (9), and fecal examination (9). Definitive treatment included praziquantel and fenbendazole. Eighteen dogs were diagnosed antemortem and 17 were treated. Twelve dogs were alive for 6 months to 3 years after diagnosis. Conclusions and Clinical Importance: HA infection occurs in younger, larger breed, indoor dogs. Hypercalcemia does not resolve without praziquantel treatment. Prognosis is good and neither hypercalcemic-induced renal failure nor ascites appears to worsen prognosis. Dogs in affected areas or that have traveled to affected areas that present for weight loss, gastrointestinal or liver disease, and hypercalcemia, should be tested. [source] Small effective population sizes in a widespread selfing species, Lymnaea truncatula (Gastropoda: Pulmonata)MOLECULAR ECOLOGY, Issue 9 2004C. MEUNIER Abstract We present here a spatial and temporal population genetic survey of a common freshwater snail, also a predominantly selfing species, Lymnaea truncatula. The rate of genetic diversity loss was quantified by estimating the effective size (Ne) of the snail populations, using two different methods. A temporal survey allowed estimation of a variance effective size of the populations, and a spatial survey allowed the estimation of an inbreeding effective size, from two-locus identity disequilibria estimates. Both methods were consistent and provided low Ne values. Drift due to (i) high amounts of selfing and (ii) fluctuations in population sizes because of temporary habitats, and also selection coupled to genome-wide linkage disequilibria, could explain such reductions in Ne. The loss of genetic diversity appears to be counterbalanced only very partially by low apparent rates of gene flow. [source] Microsatellites in the freshwater snail Bulinus globosus (Gastropoda: Planorbidae) from ZanzibarMOLECULAR ECOLOGY RESOURCES, Issue 1 2003Aidan M. Emery Abstract Six microsatellite loci were isolated and characterized in Bulinus globosus, a freshwater snail with a wide distribution throughout sub-Saharan Africa. Bulinus globosus is an intermediate host of Schistosoma haematobium, the causative agent of human urinary schistosomiasis. Microsatellites were tested using 32 snails from four populations collected from Pemba and Unguja islands of Zanzibar. The microsatellite loci displayed relatively low levels of variation, with between two and five alleles per locus. FST estimates indicate that gene flow is low, as has previously been suggested for other species of Bulinus. [source] Temporal patterns of geographic parthenogenesis in a freshwater snailBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2007FRIDA BEN-AMI Geographic parthenogenesis describes the observation that parthenogenetic organisms tend to occupy environments different from those of their close, sexually reproducing relatives. These environments are often described as extreme or disturbed habitats. We examined whether patterns of geographical parthenogenesis persist over time, by conducting a 3-year life-history survey and comparing two very proximate habitats of the freshwater snail Melanoides tuberculata: Nahal Arugot, a desert stream naturally disturbed by flash floods, and Or Ilan, a stable freshwater pond. Both sites occur in a xeric environment and are subject to otherwise similar biotic (e.g. parasites, predators) and climatic conditions. In the stable habitat, male frequencies and snail densities were significantly higher than in the disturbed one, whereas infection levels, mean embryo counts, and water temperatures were similar at both sites. Additionally, male frequencies declined after density decreased, thereby providing evidence for geographical parthenogenesis via reproductive assurance. Infection prevalence was very low regardless of reproduction mode. Although further genetic work is required, the apparent metapopulation structure of M. tuberculata in the Judean desert may be suitable for evaluating other possible explanations of geographical parthenogenesis. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 711,718. [source] Molluscicides from some common medicinal plants of eastern Uttar Pradesh, IndiaJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2010Sunil Kumar Singh Abstract Many aquatic snails act as intermediate hosts for the larvae of trematodes, Fasciola hepatica and Fasciola gigantica, which cause the diseases fascioliasis and schistosomiasis. The WHO has tested several thousands of synthetic compounds for the control of the snail host. Although effective, these molluscicides have so far not proved themselves to be entirely satisfactory. With a growing awareness of environmental pollution, efforts are being made to discover molluscicidal products of plant origin. Being products of biosynthesis, these are potentially biodegradable in nature. Several groups of compounds present in various plants have been found to be toxic to target organisms at acceptable doses ranging from <1 to 100,ppm. Common medicinal plants, i.e. Thevetia peruviana, Alstonia scholaris (Family; Apocynaceae), Euphorbia pulcherima and Euphorbia hirta (Family; Euphorbiaceae), have potent molluscicidal activity against freshwater snails. The toxicological actions of Thevetia peruviana may be due to the presence of apigenin-5-methyl ether (flavonoid) and triterpenoid glycosides, while a number of alkaloids (pseudo-akuammigine in addition to betulin, ursolic acid and ,-sitosterol), steroids and triterpenoids are present in Alstonia scholaris and the diterpenoids, pulcherrol, ,-sitosterol, hentriacontane, ellagic acid and ,-amyrin are present in Euphorbia hirta and in Euphorbia pulcherima. Although, at present very little literature is available on the control of vector snails through plant origin pesticides, an attempt has been made in this review to assemble all the known information on molluscicidal properties of common medicinal plants of eastern Uttar Pradesh, India, which might be useful for the control of harmful snails. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fine-scale population structure and dispersal in Biomphalaria glabrata, the intermediate snail host of Schistosoma mansoni, in VenezuelaMOLECULAR ECOLOGY, Issue 5 2002J. Mavárez Abstract Biomphalaria glabrata is the main intermediate host of Schistosoma mansoni in America and one of the most intensely studied species of freshwater snails, yet very little is known about its population biology. Here, we used seven highly polymorphic microsatellite loci to analyse genetic diversity in the Valencia lake basin, which represents the core of the endemic area for schistosomiasis in Venezuela. Populations were sampled at short spatial scale (a few kilometres), both inside the lake and in ponds or rivers near the lake. Our results indicate that B. glabrata essentially cross-fertilizes, with little variation in selfing rates among populations. Our markers detected considerable genetic variation, with an average heterozygosity of 0.60. More diversity per population was found within than outside the lake, suggesting an influence of connectivity among populations on the levels of genetic diversity. A marked population structure was detected and lake populations were less structured than other populations. Most individuals were assigned to their population of origin using an assignment test. No strong demographic signal (e.g. bottleneck) was detected, though lake populations are likely to experience bottlenecks more frequently than the other populations analysed. Differences in gene flow therefore seem to play an important role in population differentiation and in the restoring of genetic diversity in demographically unstable populations. [source] Competition and intraguild egg predation among freshwater snails: re-examining the mechanism of interspecific interactionsOIKOS, Issue 11 2007Andrew M. Turner Experimental and field studies suggest that freshwater snail species have negative effects on each other's population growth rates. Because snails share similar diets, these interactions have been interpreted as the result of exploitative competition, but they could also result from intraguild predation. Here we present three experiments aimed at testing the hypothesis that interspecific interactions among three species of freshwater gastropod (Helisoma trivolvis, Physa acuta and Stagnicola elodes) are mediated by intraguild egg predation. Foraging trials, conducted in a laboratory, showed that some snails readily prey on eggs, but the extent of egg predation depended on both the identity of the snail predator and the identity of the egg mass. Of the three species considered, Stagnicola had the largest effect on egg mortality and Physa had no effect on egg mortality. Foraging trials also showed that the eggs of Physa were the most vulnerable to predators and that the eggs of Stagnicola were largely invulnerable. A study conducted in large outdoor mesocosms assessed the occurrence of egg mortality in an environment of more extensive spatial scale and complexity. The results largely mirrored those of the laboratory study, with Stagnicola being the most voracious predator and the eggs of Physa being most vulnerable to predation. The reproductive success of Physa and Stagnicola raised in sympatry and allopatry was assessed in a mesocosm study conducted over three months. Recruitment of both species was depressed in sympatry, but patterns of growth in the survivors suggest contrasting mechanisms of suppression: Physa suppressed Stagnicola via exploitative competition, but Stagnicola suppressed Physa via egg predation. These experiments support the hypothesis that freshwater snail assemblages are structured by strong interspecific interactions and that a rich interplay of egg predation and interspecific competition underlie interactions among the members of this guild. [source] Social facilitation affects longevity and lifetime reproductive success in a self-fertilizing land snailOIKOS, Issue 3 2000Bruno Baur Factors that reduce the reproductive output of self-fertilizing hermaphrodites are receiving increasing attention. The combined effects of reduced fecundity of selfing parents and inbreeding depression of the progeny have been referred to as self-fertilization depression. In isolated freshwater snails the reproductive output of selfing individuals also decreases due to the lack of social facilitation (absence of a conspecific). We examined the effect of social facilitation on lifetime reproductive success (number of young produced and longevity) over two generations in the simultaneously hermaphroditic land snail Balea perversa. In a parallel study we showed that B. perversa kept singly and in pairs reproduced exclusively by self-fertilization. In the parent generation, snails kept singly produced less offspring than snails kept in pairs. The difference in lifetime number of young was mainly due to differences in adult life span. Snails of the two groups did not differ in reproductive rate (number of young produced per 100 d of reproductive life) and hatchling size. In the offspring generation, snails kept singly did not differ from individuals kept in pairs in the lifetime number of young and hatchling survival. As in the parent generation, snails kept singly reproduced during a shorter period than snails kept in pairs. However, the shorter reproductive life span of snails kept singly was compensated for by a slightly (but not significantly) higher reproductive rate which resulted in a similar number of offspring produced for both groups. In both generations, snails of the two groups did not differ in size at first reproduction, adult growth rate and size at death. These findings suggest that social facilitation may affect longevity in selfing B. perversa. [source] A global phylogeny of apple snails: Gondwanan origin, generic relationships, and the influence of outgroup choice (Caenogastropoda: Ampullariidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2009KENNETH A. HAYES Apple snails (Ampullariidae) are a diverse family of pantropical freshwater snails and an important evolutionary link to the common ancestor of the largest group of living gastropods, the Caenogastropoda. A clear understanding of relationships within the Ampullariidae, and identification of their sister taxon, is therefore important for interpreting gastropod evolution in general. Unfortunately, the overall pattern has been clouded by confused systematics within the family and equivocal results regarding the family's sister group relationships. To clarify the relationships among ampullariid genera and to evaluate the influence of including or excluding possible sister taxa, we used data from five genes, three nuclear and two mitochondrial, from representatives of all nine extant ampullariid genera, and species of Viviparidae, Cyclophoridae, and Campanilidae, to reconstruct the phylogeny of apple snails, and determine their affinities to these possible sister groups. The results obtained indicate that the Old and New World ampullariids are reciprocally monophyletic with probable Gondwanan origins. All four Old World genera, Afropomus, Saulea, Pila, and Lanistes, were recovered as monophyletic, but only Asolene, Felipponea, and Pomella were monophyletic among the five New World genera, with Marisa paraphyletic and Pomacea polyphyletic. Estimates of divergence times among New World taxa suggest that diversification began shortly after the separation of Africa and South America and has probably been influenced by hydrogeological events over the last 90 Myr. The sister group of the Ampullariidae remains unresolved, but analyses omitting certain outgroup taxa suggest the need for dense taxonomic sampling to increase phylogenetic accuracy within the ingroup. The results obtained also indicate that defining the sister group of the Ampullariidae and clarifying relationships among basal caenogastropods will require increased taxon sampling within these four families, and synthesis of both morphological and molecular data. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 61,76. [source] A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuriesBOREAS, Issue 1 2007JINGLU WU Wu, J. L., Schleser, G. H., Lücke, A. & Li, S. 2007 (January): A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuries. Boreas, Vol. 36, pp. 38,46. Oslo. ISSN 0300,9483. Lake Xingcuo is a small, closed, hardwater lake situated in the eastern Tibetan Plateau. Stable isotope data (,18O and ,13C) from the freshwater snail Gyraulus sibirica (Dunker) in a 34-cm-long, radioactive isotope-dated sediment core represent the past 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the snail yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the snail's life-span. Living and fossil shells from Lake Xingcuo were collected. ,18O values in the living shells from Lake Xingcuo are in equilibrium with ambient waters, while ,13C values may trace snail dietary carbon. On comparing ,18O and ,13C in the shell of Gyraulus sibirica with monitored data for the period 1954,1995, we found that the ,18O composition in the shell is an efficient proxy revealing air temperature during the warmer months from April to September. There is a positive correlation between the ,18O in the shells of Gyraulus sibirica and the running average temperature of the warmer months. Climatic variability in the eastern Tibetan Plateau for the past two centuries has been inferred from the ,18O record from the freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years' palaeoclimatic record for this region can be separated into three periods representing oscillations between warm and cool conditions consistent with the Guliya ice record in the Tibetan Plateau. [source] | |||||||||||||