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Snails
Kinds of Snails Terms modified by Snails 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] Androgen regulation of prostasin gene expression is mediated by sterol-regulatory element-binding proteins and SLUGTHE PROSTATE, Issue 9 2006Mengqian Chen Abstract BACKGROUND Prostasin is downregulated in hormone-refractory prostate cancers (HRPC). The mechanisms by which androgens regulate prostasin expression are unclear. METHODS LNCaP cells were treated with dihydrotestosterone (DHT), and mRNA expression of prostasin, SREBPs, SNAIL, and SLUG was examined by real-time PCR following reverse transcription. A human prostasin promoter was evaluated in HEK-293 cells co-transfected with transcription factor cDNAs. Regulation of endogenous prostasin expression by transfected SREBP-2 or SLUG was evaluated. Expression of SNAIL and SLUG mRNA in DU-145 cells treated with epidermal growth factor (EGF) was examined. RESULTS Prostasin mRNA expression in LNCaP cells was not responsive to DHT treatment. DHT marginally upregulated mRNA expression of SREBP-1c, SREBP-2, and SNAIL, but not SREBP-1a, while dramatically increased SLUG mRNA expression, in a dose-dependent manner. Co-transfection of prostasin promoter and SREBP cDNA in HEK-293 cells resulted in stimulation of promoter activity at ,twofold by SREBP-1c, and up to sixfold by SREBP-2; while co-transfection with SNAIL or SLUG cDNA resulted in repression of promoter activity to 43% or 59%, respectively. Co-transfection of the SLUG cDNA negated SREBP-2's stimulation of prostasin promoter in a dose-dependent manner. Transfection of an SREBP-2 cDNA in HEK-293 and DU-145 resulted in upregulation of prostasin while transfection of a SLUG cDNA in LNCaP repressed prostasin expression. EGF upregulated SNAIL and SLUG mRNA in DU-145. CONCLUSIONS DHT regulates prostasin expression in prostate cells via SREBP stimulation and SLUG repression of prostasin promoter. SLUG is upregulated by DHT and EGF, providing a molecular mechanism by which epithelial cell-specific genes are silenced during prostate cancer development and progression. Prostate 66: 911,920, 2006. © 2006 Wiley-Liss, Inc. [source] Analysis of regulatory elements of E-cadherin with reporter gene constructs in transgenic mouse embryosDEVELOPMENTAL DYNAMICS, Issue 2 2003Marc P. Stemmler Abstract Proper regulation of E-cadherin,mediated cell adhesion is important during early embryonic development and in organogenesis. In mice, E-cadherin is expressed from the fertilized egg onward and becomes down-regulated during gastrulation in mesoderm and its derivatives, but its expression is maintained in all epithelia. E-cadherin promoter analyses led to the identification of binding sites for two transcriptional repressors, Snail and SIP1, which are able to mediate down-regulation in vitro, but little is known about the regulatory elements that govern E-cadherin transcriptional activity in vivo. Here, we compared the developmentally regulated expression of a series of lacZ -reporter transgenes fused to different sequences of the murine E-cadherin gene between ,6 kb, including the promoter, and +16 kb, covering one third of intron 2. Four different segments with distinct regulatory properties were identified. The promoter fragment from +0.1 to ,1.5 kb remains inactive in most cases but occasionally induces ectopic expression in mesodermal tissues, although it contains binding sites for the repressors Snail and SIP1. This promoter fragment also lacks positive elements needed for the activation of transcription in ectoderm and endoderm. Sequences from ,1.5 to ,6 kb harbor regulatory elements for brain-specific expression and, in addition, insulator or silencer elements, because they are consistently inactive in the mesoderm. Only if sequences from +0.1 to +11 kb are combined with the promoter fragments is E-cadherin,specific transgene expression observed in endoderm and certain epithelia. Sequences between +11 and +16 kb contain cis -active elements that generally enhance transcription. Our analyses show that E-cadherin expression is governed by a complex interplay of multiple regulatory regions dispersed throughout large parts of the locus. Developmental Dynamics 227:238,245, 2003. © 2003 Wiley-Liss, Inc. [source] Upregulation of myosin Va by Snail is involved in cancer cell migration and metastasisINTERNATIONAL JOURNAL OF CANCER, Issue 1 2010Linxiang Lan Abstract Cell migration, which involves acto-myosin dynamics, cell adhesion, membrane trafficking and signal transduction, is a prerequisite for cancer cell metastasis. Here, we report that an actin-dependent molecular motor, unconventional myosin Va, is involved in this process and implicated in cancer metastasis. The mRNA expression of myosin Va is increased in a number of highly metastatic cancer cell lines and metastatic colorectal cancer tissues. Suppressing the expression of myosin Va by lentivirus-based RNA interference in highly metastatic cancer cells impeded their migration and metastasis capabilities both in vitro and in vivo. In addition, the levels of myosin Va in cancer cell lines are positively correlated with the expression of Snail, a transcriptional repressor that triggers epithelial,mesenchymal transition. Repression or overexpression of Snail in cancer cells caused reduced or elevated levels of myosin Va, respectively. Furthermore, Snail can bind to an E-box of the myosin Va promoter and induce its activity, which indicates that Snail might act as a transcriptional activator. These data demonstrate an essential role of myosin Va in cancer cell migration and metastasis, and suggest a novel target for Snail in its regulation of cancer progression. [source] Activation of epidermal growth factor receptor results in Snail protein but not mRNA overexpression in endometrial cancerJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 9b 2009Susanne Hipp Abstract Reduced E-cadherin expression is associated with tumour progression of many carcinomas, including endometrial cancers. The transcription factor Snail is known as one of the most prominent transcriptional E-cadherin repressors; its regulation in cancer tissues, however, still remains unclear. Here, we report that activation of epidermal growth factor receptor (EGFR) resulted in overexpression of Snail and also identified critical downstream signalling molecules. Stimulation of two endometrial carcinoma cell lines with epidermal growth factor (EGF) lead to an increase of Snail protein expression. In primary human endometrioid endometrial carcinomas Snail protein expression correlated with the activated, phosphorylated form of EGFR (Tyr1086) as revealed by profiling 24 different signalling proteins using protein lysate microarrays. In addition, we observed an inverse correlation between Snail and E-cadherin protein levels in these tumours. Most likely, p38 MAPK, PAK1, AKT, ERK1/2 and GSK-3, are involved in the up-regulation of Snail downstream of EGFR. Snail mRNA expression did not show a correlation with activated EGFR in these tumours. Taken together, profiling of signalling proteins in primary human tissues provided strong evidence that EGFR signalling is involved in Snail protein overexpression. [source] Snail controls differentiation of hepatocytes by repressing HNF4, expressionJOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2006Carla Cicchini Epithelial-to-mesenchymal transition (EMT) is a coordinated process, occurring both during morphogenesis and tumor progression, that allows epithelial cells to dissociate from initial contacts and migrate to secondary sites. The transcriptional repressors of the Snail family induce EMT in different epithelial cell lines and their expression is strictly correlated with EMT during the development and progression of carcinomas. We have previously shown that EMT in hepatocytes correlates with the downregulation of hepatic differentiation key factors HNFs (hepatocyte nuclear factors), and in particular of HNF4,. Here, we demonstrate that Snail overexpression is sufficient (i) to induce EMT in hepatocytes with conversion of morphology, downregulation of several epithelial adhesion molecules, reduction of proliferation and induction of matrix metalloproteinase 2 expression and, (ii) most relevantly, to repress the transcription of the HNF4, gene through a direct binding to its promoter. These finding demonstrate that Snail is at the crossroads of the regulation of EMT in hepatocytes by a dual control of epithelial morphogenesis and differentiation. J. Cell. Physiol. 209: 230,238, 2006. © 2006 Wiley-Liss, Inc. [source] Alcohol Stimulates Activation of Snail, Epidermal Growth Factor Receptor Signaling, and Biomarkers of Epithelial,Mesenchymal Transition in Colon and Breast Cancer CellsALCOHOLISM, Issue 1 2010Christopher B. Forsyth Background:, Alcohol consumption is associated with the risk of progressive cancers including colon and breast cancer. The mechanisms for the alcohol-induced aggressive behavior of these epithelial cancer cells have not been fully identified. Epithelial,mesenchymal transition (EMT) is a developmental program recently shown to play a role in cancer progression and metastases. We hypothesized that alcohol might promote cancer progression by inducing EMT in cancer cells and tested this hypothesis by assessing alcohol-stimulated changes in phenotypic markers of EMT as well as the EMT transcription factor Snail and its related cell signaling. Methods:, Colon and breast cancer cell lines and a normal intestinal epithelial cell line were tested as well as colonic mucosal biopsy samples from alcoholic subjects. Cells were treated with alcohol and assessed for EMT-related changes using immunofluorescent microscopy, western blotting, reporter assays, RT-PCR, and knockdown of Snail with siRNA. Results:, We show alcohol upregulated the signature EMT phenotypic marker vimentin as well as matrix metalloprotease (MMP)-2, MMP-7, and MMP-9 and cell migration in colon and breast cancer cells,all characteristics of EMT. Alcohol also stimulated nuclear localization of Snail phosphorylated at Ser246, transcription from a Snail reporter plasmid, and Snail mRNA expression by RT-PCR. Snail siRNA knockdown prevented alcohol-stimulated vimentin expression. In vivo, Snail expression was significantly elevated in colonic mucosal biopsies from alcoholics. Also, we found alcohol stimulated activation of epidermal growth factor receptor (EGFR) signaling and an EGFR inhibitor blocked alcohol-induced cell migration and Snail mRNA expression. Conclusions:, Collectively, our data support a novel mechanism for alcohol promoting cancer progression through stimulating the EMT program in cancer cells via an EGFR-Snail mediated pathway. This study reveals new pathways for alcohol-mediated promotion of cancer that could be targeted for therapy or prevention of alcohol-related cancers. [source] Effect of Dietary Protein Sources on Growth and Body Composition of Snail, Semisulcospira gottscheiJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2010Sang-Min Lee A feeding experiment was conducted to determine a dietary protein source for juvenile snail, Semisulcospira gottschei. Eight experimental diets (designated as 1,8) were formulated to contain 31% casein, 42% fish meal, 31% blood meal, 39% meat meal, 46% corn gluten meal, 57% soybean meal, 50% cottonseed meal with 23% casein, and 50% wheat flour with 6% casein, respectively, as dietary sole protein sources. Snails (37 ± 3.4 mg/snail) were randomly distributed into 25 L aquaria (20 L water each) in a recirculating aquarium system at a density of 100 juveniles per aquarium. Three replicate groups of snails were fed one of the experimental diets ad libitum once in every 2 d for 12 wk. At the end of the feeding experiment, survival of snails ranged from 77 to 89%, and was not significantly different among the treatments. Snails fed Diet 7 containing 25.3% crude protein deriving from cottonseed meal and casein grew faster than did snails fed other diets, except for snails fed Diet 6 containing soybean meal as a protein source. Growth of snails fed diets containing blood meal, corn gluten meal, and meat meal was the least of snails fed any diet. Crude protein, crude lipid, and ash contents of whole body varied remarkably with dietary protein source. The present findings suggest that dietary protein source could affect the body weight and proximate composition of snails. Cottonseed meal and soybean meal might be a more preferable dietary protein source for snail juvenile compared with other ingredients tested. [source] Transforming growth factor-, induces epithelial to mesenchymal transition by down-regulation of claudin-1 expression and the fence function in adult rat hepatocytesLIVER INTERNATIONAL, Issue 4 2008Takashi Kojima Abstract Background/Aims: Transforming growth factor-, (TGF-,) initiates and maintains epithelial,mesenchymal transition (EMT), which causes disassembly of tight junctions and loss of epithelial cell polarity. In mature hepatocytes during EMT induced by TGF-,, changes in the expression of tight junction proteins and the fence function indicated that epithelial cell polarity remains unclear. Methods: In the present study, using primary cultures of adult rat hepatocytes at day 10 after plating, in which epithelial cell polarity is well maintained by tight junctions, we examined the effects of 0.01,20 ng/ml TGF-, on the expression of the integral tight junction proteins, claudin-1, -2 and occludin, as well as the fence function. Results: In adult rat hepatocytes, TGF-, induced EMT, which was indicated as upregulation of Smad-interacting protein-1 (SIP1) and Snail and down-regulation of E-cadherin. Down-regulation of claudin-1 and upregulation of occludin were observed beginning from a low dose of TGF-,, whereas upregulation of claudin-2 was observed at a high dose of TGF-,. Furthermore, treatment with TGF-, caused disruption of the fence function, which was closely associated with the expression of claudin-1 via p38 mitogen-activated protein kinase (MAPK), phosphoinositide-3 kinase and protein kinase C but not MAPK signalling pathways. Conclusion: These results suggest that in mature hepatocytes in vitro, TGF-, induces EMT by down-regulation of claudin-1 and the fence function via distinct signalling pathways. [source] Ultraviolet radiation stimulates expression of Snail family transcription factors in keratinocytesMOLECULAR CARCINOGENESIS, Issue 4 2007Laurie G. Hudson Abstract The related zinc finger transcription factors Slug and Snail modulate epithelial mesenchymal transformation (EMT), the conversion of sessile epithelial cells into migratory fibroblast-like cells. EMT occurs during development, wound healing, and tumor progression. Growth factors, acting through mitogen-activated protein kinase (MAPK) cascades, regulate expression of Slug and Snail. Expression of Snail family transcription factors appears to be elevated in UVR-induced murine squamous cell carcinomas (SCC). We report here that ultraviolet radiation (UVR), which activates MAPK cascades, also stimulates Snail and Slug expression in epidermal keratinocytes. UVR exposure transiently elevated Slug and Snail mRNA expression in human keratinocytes in vitro and mouse epidermis in vivo. This induction was mediated, at least in part, through the ERK and p38 MAPK cascades, as pharmacological inhibition of these cascades partially or completely blocked Slug and Snail induction by UVR. On the other hand, UVR induction of Slug and Snail was enhanced by inhibition of JNK. Slug appears to play a functional role in the acute response of keratinocytes to UVR, as UVR induction of keratin 6 in the epidermis of Slug knockout mice was markedly delayed compared to wild-type mice. Slug and Snail are known to regulate molecules important in the cytoskeleton, intercellular adhesion, cell motility, and apoptosis, thus it seems probable that transiently or persistently elevated expression of these factors fosters the progression of UVR-induced SCC. © 2007 Wiley-Liss, Inc. [source] Snail, Slug, and Smad-interacting protein 1 as novel parameters of disease aggressiveness in metastatic ovarian and breast carcinoma,,CANCER, Issue 8 2005Sivan Elloul M.Sc. Abstract BACKGROUND It was demonstrated previously that the Snail family of transcription factors and Smad-interacting protein 1 (Sip1) regulate E-cadherin and matrix metalloproteinase 2 (MMP-2) expression, cellular morphology, and invasion in carcinoma. For the current study, the authors analyzed the relation between the expression of Snail, Slug, and Sip1; the expression of MMP-2 and E-cadherin; and clinical parameters in patients with metastatic ovarian and breast carcinoma. METHODS One hundred one fresh-frozen, malignant effusions from patients who were diagnosed with gynecologic carcinomas (78 ovarian carcinomas and 23 breast carcinomas) were studied for mRNA expression of Snail, Slug, Sip1, MMP-2, and E-cadherin using reverse transcriptase-polymerase chain reaction analysis. Snail mRNA and E-cadherin protein expression levels also were studied in ovarian carcinoma effusions using in situ hybridization and immunocytochemistry. The results were analyzed for possible correlation with clinicopathologic parameters in both tumor types. RESULTS E-cadherin mRNA expression was lower in breast carcinoma (P = 0.001), whereas Snail expression was higher (P = 0.003). The Snail/E-cadherin ratio (P < 0.001) and the Sip1/E-cadherin ratio (P = 0.002) were higher in breast carcinomas. Sip1 mRNA expression (P < 0.001) and Slug mRNA expression (P < 0.001) were correlated with the expression of MMP-2 in ovarian carcinomas. The Sip1/E-cadherin ratio was higher in primary ovarian carcinomas at the time of diagnosis compared with postchemotherapy ovarian carcinoma effusions (P = 0.003), higher in Stage IV tumors compared with Stage III tumors (P = 0.049), and higher in pleural effusions compared with peritoneal effusions (P = 0.044). In a univariate survival analysis of patients with ovarian carcinoma, a high Sip1/E-cadherin ratio predicted poor overall survival (P = 0.018). High E-cadherin mRNA expression predicted better disease-free survival (P = 0.023), with a similar trend for a low Slug/E-cadherin ratio (P = 0.07). High Snail mRNA expression predicted shorter effusion-free survival (P = 0.008), disease-free survival (P = 0.03), and overall survival (P = 0.008) in patients with breast carcinoma. CONCLUSIONS Transcription factors that regulate E-cadherin were expressed differentially in metastatic ovarian and breast carcinoma. Snail may predict a poor outcome in patients who have breast carcinoma metastatic to effusions. E-cadherin expression generally was conserved in effusions from patients with ovarian carcinoma, but the subset of patients with postulated Sip1-induced repression of this adhesion molecule had a significantly worse outcome. This finding was in agreement with the stronger suppression of E-cadherin by Snail and Sip1 in breast carcinoma effusions, a clinical condition associated with extremely poor survival. Cancer 2005. © 2005 American Cancer Society. [source] Influence of the SCGE protocol on the amount of basal DNA damage detected in the Mediterranean mussel, Mytilus galloprovincialisENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 8 2006Nicola Machella Abstract Genotoxicity studies using the single cell gel electrophoresis (SCGE) assay indicate that basal levels of DNA strand breaks (SBs) in marine invertebrates are higher and more variable than those in marine vertebrates. This elevated level of DNA damage was attributed to a large number of alkali-labile sites, which are characteristic of the tightly-packaged DNA in invertebrate cells. To investigate if altering the SCGE protocol can artificially modulate high levels of SBs, SCGE experiments were performed on haemocytes from the Mediterranean mussel (Mytilus galloprovincialis) using proteinase K (PK) digestion in combination with assay buffers containing various concentrations of EDTA. In addition, the effects of Trolox® (soluble antioxidant) and aurintricarboxylic acid (ATA; inhibitor of Ca2+/Mg2+ -dependent nucleases) also were tested. The levels of SBs in M. galloprovicialis cells were compared with SBs in cells from a terrestrial mollusk (the snail Helix aspersa), and a teleost fish (the seabass Dicentrarchus labrax). The integrity of M. galloprovincialis DNA isolated with phenol extractions using EDTA, Trolox, and ATA was further assayed by gel electrophoresis. High SBs in mussel cells were reduced by combining EDTA with PK digestion, or using Trolox® or ATA during cell processing for the SCGE assay. Snails and seabass had lower levels of SBs in the SCGE assay, and the levels were not affected by the protocol modifications. Adding EDTA, Trolox®, or ATA to phenol extractions of M. galloprovincialis genomic DNA also reduced the extent of DNA fragmentation. These results suggest that the internal fluids of M. galloprovincialis may increase the basal levels of DNA SBs through oxidative and/or enzyme-mediated pathways. M. galloprovincialis is used extensively as a sentinel species for assessing the genotoxic hazard of marine pollutants. Our data suggest that the SCGE protocol should be carefully considered when assessing DNA damage in these species. Environ. Mol. Mutagen., 2006. © 2006 Wiley-Liss, Inc. [source] Histopathological alterations in the edible snail, Babylonia areolata (spotted babylon), in acute and subchronic cadmium poisoningENVIRONMENTAL TOXICOLOGY, Issue 2 2005P. Tanhan Abstract Histopathological alterations in 6- to 8-month-old juvenile spotted babylon, Babylonia areolata, from acute and subchronic cadmium exposure were studied by light microscopy. The 96-h LC50 value of cadmium for B. areolata was found to be 3.35 mg/L, and the maximum acceptable toxicant concentration (MATC) was 1.6 mg/L. Snails were exposed to 3.35 and 0.08 mg/L (5% of MATC) of cadmium for 96 h and 90 days, respectively. After exposure the gill, the organs of the digestive system (proboscis, esophagus, stomach, digestive gland, and rectum), and the foot were analyzed for cadmium accumulation. The results showed that most digestive organs had a high affinity for cadmium. The main target organ was the stomach, which could accumulate on average 1192.18 ,g/g dry weight of cadmium. Cadmium was shown to accumulate to a lesser extent in the digestive gland, gill, rectum, esophagus, proboscis, and foot. Histopathological alterations were observed in the gill and digestive organs (proboscis, esophagus, stomach, and rectum). The study showed that the stomach and gill were the primary target organs of both acute and subchronic exposure. Gill alterations included increased size of mucous vacuoles, reduced length of cilia, dilation and pyknosis of nuclei, thickening of basal lamina, and accumulation of hemocytes. The epithelial lining of the digestive tract showed similar alterations such as increased size of mucous vacuoles, reduced length of cilia, and dilation of nuclei. In addition, fragmentation of the muscle sheath was observed. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 142,149, 2005. [source] Direct and indirect effects of a potential aquatic contaminant on grazer,algae interactionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009Michelle A. Evans-White Abstract Contaminants have direct, harmful effects across multiple ecological scales, including the individual, the community, and the ecosystem levels. Less, however, is known about how indirect effects of contaminants on consumer physiology or behavior might alter community interactions or ecosystem processes. We examined whether a potential aquatic contaminant, an ionic liquid, can indirectly alter benthic algal biomass and primary production through direct effects on herbivorous snails. Ionic liquids are nonvolatile organic salts being considered as an environmentally friendly potential replacement for volatile organic compounds in industry. In two greenhouse experiments, we factorially crossed four concentrations of 1-N-butyl-3-methylimidazolium bromide (bmimBr; experiment 1: 0 or 10 mg/L; experiment 2: 0, 1, or 100 mg/L) with the presence or absence of the snail Physa acuta in aquatic mesocosms. Experimental results were weighted by their respective control (no bmimBr or P. acuta) and combined for statistical analysis. When both bmimBr and snails were present, chlorophyll a abundance and algal biovolume were higher than would be expected if both factors acted additively. In addition, snail growth rates, relative to those of controls, declined by 41 to 101% at 10 and 100 mg/L of bmimBr. Taken together, these two results suggest that snails were less efficient grazers in the presence of bmimBr, resulting in release of algae from the grazer control. Snails stimulated periphyton primary production in the absence, but not in the presence, of bmimBr, suggesting that bmimBr also can indirectly alter ecosystem function. These findings suggest that sublethal contaminant levels can negatively impact communities and ecosystem processes via complex interactions, and they provide baseline information regarding the potential effects of an emergent industrial chemical on aquatic systems. [source] Lethal and non-lethal effects of multiple indigenous predators on the invasive golden apple snail (Pomacea canaliculata)FRESHWATER BIOLOGY, Issue 10 2004Nils Carlsson Summary 1. We investigated the individual and combined effects of two predators (the climbing perch, Anabas testudineus, and the wetland crab, Esanthelphusa nimoafi) indigenous to wetlands in Laos, on the behaviour and survival of the invasive South American golden apple snail (Pomacea canaliculata). The snail is considered a pest, consuming large amounts of rice and other aquatic vegetation in the region. 2. Snail avoidance reactions to released predator chemical cues were investigated in aquaria while the effects of predators on a mixed snail population were studied in field enclosures that contained native aquatic plants (Salvinia cucullata, Ludwigia adscendens and Ipomoea aquatica). 3. In the aquaria experiment, neonate (2,3 mm) and medium-sized snails (8,10 mm) responded to fish chemical cues by going to the surface, whereas adult snails (35,40 mm) went to the bottom. In contrast, no size class of snails reacted to chemical cues released by crabs. 4. In the field experiment, fish reduced the abundance of neonate snails, and crabs reduced the abundance of all size classes. The effect of the combined predators could not be predicted from the mortality rate observed in single predator treatments. The survival of neonate and medium-sized snails was greater and of adults less than expected. The presence of predators did not affect egg production. Snails consumed significant amounts of plants despite the presence of predators. 5. Our findings suggest that some indigenous Asian predators have lethal and sublethal effects on P. canaliculata that depend on snail size and predator type. When in the presence of several predators the response of snails to one predator may either increase or decrease the vulnerability of snails to the others. [source] Multiple predator-avoidance behaviours of the freshwater snail Physella heterostropha pomila: responses vary with riskFRESHWATER BIOLOGY, Issue 3 2000Thomas M. McCarthy Summary 1We examined the predator-avoidance behaviour, exhibited in response to chemical cues, of two populations of the snail Physella heterostropha pomila. Snails were subjected to four treatments simulating different degrees of predation risk: control water (low risk), or water from tanks containing nonforaging crayfish (intermediate risk), crushed conspecifics (high risk) or crayfish consuming conspecifics (high risk). Data were analysed using three-way ANOVA models (population × predator chemicals × injured conspecific chemicals). 2Physella increased its avoidance behaviour as risk increased. Crayfish cue elicited a significantly greater response than from controls. Cues from injured conspecifics elicited the strongest response. 3Physella exhibited several types of avoidance behaviour, including burial into the substratum, moving to the water surface, and crawling out of the water. The type of cue present influenced response type. Cues from crayfish reduced burial and increased movement to the water surface or out of the water. Cues from injured-conspecifics significantly increased crawling completely out of the water. 4The two populations differed in the type and degree of response exhibited. One population exhibited significantly greater ,reactivity' (i.e. any avoidance behaviour) in response to foraging crayfish, and more burial and crawl-out behaviours were exhibited in high-risk treatments. [source] Nocturnal swimming, aggregation at light traps, and mass spawning of scissurellid gastropods (Mollusca: Vetigastropoda)INVERTEBRATE BIOLOGY, Issue 1 2007Carole S. Hickman Abstract. Thousands of minute scissurellid gastropods (Vetigastropoda: Scissurellidae) were observed and collected at floating light traps in Moorea, French Polynesia, where a mass spawning event occurred on November 11, 2002. More than 20,000 live snails were recovered from the traps, and epidemic spawning continued in the laboratory, where clouds of white sperm and red-orange eggs were broadcast into the water. No aggregations of this magnitude have been reported previously in vetigastropods, nor is the capacity for sustained swimming known from other vetigastropod taxa. Snails had emerged from a local benthic habitat of coral sand and swum through ,2 m of water to reach the traps. Scanning electron micrographs of the ornate shells confirm the identity of the most abundant species as Scissurella spinosa, with lesser numbers of Sinezona plicata. Our observations indicate that scissurellids are not exclusively benthic and that they are not rare, even though they have seldom been collected and studied alive. Because little is known about the basic biology and anatomy of scissurellids and because their position within the basal Gastropoda is poorly resolved, we include information on the design and construction of inexpensive light traps to promote comparative investigation of other poorly known species. [source] Effect of Dietary Protein Sources on Growth and Body Composition of Snail, Semisulcospira gottscheiJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2010Sang-Min Lee A feeding experiment was conducted to determine a dietary protein source for juvenile snail, Semisulcospira gottschei. Eight experimental diets (designated as 1,8) were formulated to contain 31% casein, 42% fish meal, 31% blood meal, 39% meat meal, 46% corn gluten meal, 57% soybean meal, 50% cottonseed meal with 23% casein, and 50% wheat flour with 6% casein, respectively, as dietary sole protein sources. Snails (37 ± 3.4 mg/snail) were randomly distributed into 25 L aquaria (20 L water each) in a recirculating aquarium system at a density of 100 juveniles per aquarium. Three replicate groups of snails were fed one of the experimental diets ad libitum once in every 2 d for 12 wk. At the end of the feeding experiment, survival of snails ranged from 77 to 89%, and was not significantly different among the treatments. Snails fed Diet 7 containing 25.3% crude protein deriving from cottonseed meal and casein grew faster than did snails fed other diets, except for snails fed Diet 6 containing soybean meal as a protein source. Growth of snails fed diets containing blood meal, corn gluten meal, and meat meal was the least of snails fed any diet. Crude protein, crude lipid, and ash contents of whole body varied remarkably with dietary protein source. The present findings suggest that dietary protein source could affect the body weight and proximate composition of snails. Cottonseed meal and soybean meal might be a more preferable dietary protein source for snail juvenile compared with other ingredients tested. [source] Deep-sea hydrocarbon seep gastropod Bathynerita naticoidea responds to cues from the habitat-providing mussel Bathymodiolus childressiMARINE ECOLOGY, Issue 1 2007Sharmishtha Dattagupta Abstract Bathynerita naticoidea (Gastropoda: Neritidae) is a numerically dominant heterotrophic gastropod found at hydrocarbon seep sites on the upper Louisiana slope of the Gulf of Mexico. Snails of this species are commonly associated with beds of the methanotrophic mussel Bathymodiolus childressi (Bivalvia: Mytilidae), and their population structure mirrors that of the mussels they are found among. Previous studies have shown that these snails feed on bacteria and decomposing periostracum on the B. childressi shell. We predicted that B. naticoidea might be attracted to cues specific to its preferred habitat, such as dissolved methane, mucus from conspecific snails, or metabolites produced by B. childressi mussels. To examine this, we used a flow-through Y-maze system to investigate the behavior of B. naticoidea exposed to these potential cues. We found that the nerite is not attracted to methane, but is strongly attracted to seawater conditioned with B. childressi. The attractant appears to be specific to this type of mussel, and is not a soluble cue produced by conspecific snails. [source] Contrasting mtDNA diversity and population structure in a direct-developing marine gastropod and its trematode parasitesMOLECULAR ECOLOGY, Issue 22 2009DEVON B. KEENEY Abstract The comparative genetic structure of hosts and their parasites has important implications for their coevolution, but has been investigated in relatively few systems. In this study, we analysed the genetic structure and diversity of the New Zealand intertidal snail Zeacumantus subcarinatus (n = 330) and two of its trematode parasites, Maritrema novaezealandensis (n = 269) and Philophthalmus sp. (n = 246), using cytochrome c oxidase subunit I gene (COI) sequences. Snails and trematodes were examined from 11 collection sites representing three regions on the South Island of New Zealand. Zeacumantus subcarinatus displayed low genetic diversity per geographic locality, strong genetic structure following an isolation by distance pattern, and low migration rates at the scale of the study. In contrast, M. novaezealandensis possessed high genetic diversity, genetic homogeneity among collection sites and high migration rates. Genetic diversity and migration rates were typically lower for Philophthalmus sp. compared to M. novaezealandensis and it displayed weak to moderate genetic structure. The observed patterns likely result from the limited dispersal ability of the direct developing snail and the utilization of bird definitive hosts by the trematodes. In addition, snails may occasionally experience long-distance dispersal. Discrepancies between trematode species may result from differences in their effective population sizes and/or life history traits. [source] Spatial and temporal population genetic structure of four northeastern Pacific littorinid gastropods: the effect of mode of larval development on variation at one mitochondrial and two nuclear DNA markersMOLECULAR ECOLOGY, Issue 10 2009HYUK JE LEE Abstract We investigated the effect of development mode on the spatial and temporal population genetic structure of four littorinid gastropod species. Snails were collected from the same three sites on the west coast of Vancouver Island, Canada in 1997 and again in 2007. DNA sequences were obtained for one mitochondrial gene, cytochrome b (Cyt b), and for up to two nuclear genes, heat shock cognate 70 (HSC70) and aminopeptidase N intron (APN54). We found that the mean level of genetic diversity and long-term effective population sizes (Ne) were significantly greater for two species, Littorina scutulata and L. plena, that had a planktotrophic larval stage than for two species, Littorina sitkana and L. subrotundata, that laid benthic egg masses which hatched directly into crawl-away juveniles. Predictably, two poorly dispersing species, L. sitkana and L. subrotundata, showed significant spatial genetic structure at an 11- to 65-km geographical scale that was not observed in the two planktotrophic species. Conversely, the two planktotrophic species had more temporal genetic structure over a 10-year interval than did the two direct-developing species and showed highly significant temporal structure for spatially pooled samples. The greater temporal genetic variation of the two planktotrophic species may have been caused by their high fecundity, high larval dispersal, and low but spatially correlated early survivorship. The sweepstakes-like reproductive success of the planktotrophic species could allow a few related females to populate hundreds of kilometres of coastline and may explain their substantially larger temporal genetic variance but lower spatial genetic variance relative to the direct-developing species. [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] Variation in multiple paternity and sperm utilization patterns in natural populations of a simultaneous hermaphrodite land snailBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010SANDRA KUPFERNAGEL Mating frequency has important implications for patterns of sexual selection and sexual conflict, and hence for issues such as the maintenance of genetic diversity and speciation. We assessed the level of multiple paternity and sperm utilization patterns in four natural populations of the simultaneous hermaphrodite land snail Arianta arbustorum using four polymorphic microsatellite loci. A total of 1088 offspring from 26 wild-caught snails were genotyped to determine the number of fathers siring each brood and paternity skew in succeeding clutches. Multiple paternity was detected in the offspring of all 26 mother snails examined with the contribution of two to six fathers. The four populations examined differed in the level of multiple paternity. Snails in the population with the highest density of adults showed the highest level of multiple paternity, whereas snails in the population with the lowest density exhibited the lowest value of multiple paternity. Highly skewed paternity patterns were found in the progeny of 15 (57.7%) of the 26 mother snails. The number and identity of fathers siring the offspring of single mothers also varied among successive clutches. Furthermore, genetic analyses indicate a low level of self-fertilization in one of the four populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99, 350,361. [source] Tandem Exploitation of Helix pomatia Glycosyltransferases: Facile Syntheses of H-Antigen-Bearing OligosaccharidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2007Hagen Bretting Prof. Abstract Snails from the family Helicidae produce in their albumen glands a highly branched galactan, which consists almost exclusively of D - and L -galactose. The D -Gal residues are glycosydically ,(1,6)- or ,(1,3)-linked, whereas the L -Gal moieties are attached ,(1,2). Up until the present time, two ,(1,6)- D -galactosyl transferases and one ,(1,2)- L -galactosyl transferase have been identified in a membrane preparation of these glands. These were used to synthesise various oligosaccharides by successive addition of the NDP-activated (NDP=nucleoside-5,-diphosphate) D -Gal or L -Fuc moieties, up to a heptasaccharide by starting from the disaccharide D -Gal-,(1,3)- D -Gal-,(1,OMe. Even larger oligosaccharides up to a tridecasaccharide were obtained by starting with the hexasaccharide D -Gal-[,(1,3)- D -Gal]4 -,(1,4)- D -Glc as an acceptor substrate. This tandem exploitation process has high potential for the easy introduction of D -Gal and L -Fuc residues into a great variety of oligosaccharides, which can be used in ligand/acceptor studies. [source] Effect of Dietary Protein Sources on Growth and Body Composition of Snail, Semisulcospira gottscheiJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2010Sang-Min Lee A feeding experiment was conducted to determine a dietary protein source for juvenile snail, Semisulcospira gottschei. Eight experimental diets (designated as 1,8) were formulated to contain 31% casein, 42% fish meal, 31% blood meal, 39% meat meal, 46% corn gluten meal, 57% soybean meal, 50% cottonseed meal with 23% casein, and 50% wheat flour with 6% casein, respectively, as dietary sole protein sources. Snails (37 ± 3.4 mg/snail) were randomly distributed into 25 L aquaria (20 L water each) in a recirculating aquarium system at a density of 100 juveniles per aquarium. Three replicate groups of snails were fed one of the experimental diets ad libitum once in every 2 d for 12 wk. At the end of the feeding experiment, survival of snails ranged from 77 to 89%, and was not significantly different among the treatments. Snails fed Diet 7 containing 25.3% crude protein deriving from cottonseed meal and casein grew faster than did snails fed other diets, except for snails fed Diet 6 containing soybean meal as a protein source. Growth of snails fed diets containing blood meal, corn gluten meal, and meat meal was the least of snails fed any diet. Crude protein, crude lipid, and ash contents of whole body varied remarkably with dietary protein source. The present findings suggest that dietary protein source could affect the body weight and proximate composition of snails. Cottonseed meal and soybean meal might be a more preferable dietary protein source for snail juvenile compared with other ingredients tested. [source] Histopathological alterations in the edible snail, Babylonia areolata (spotted babylon), in acute and subchronic cadmium poisoningENVIRONMENTAL TOXICOLOGY, Issue 2 2005P. Tanhan Abstract Histopathological alterations in 6- to 8-month-old juvenile spotted babylon, Babylonia areolata, from acute and subchronic cadmium exposure were studied by light microscopy. The 96-h LC50 value of cadmium for B. areolata was found to be 3.35 mg/L, and the maximum acceptable toxicant concentration (MATC) was 1.6 mg/L. Snails were exposed to 3.35 and 0.08 mg/L (5% of MATC) of cadmium for 96 h and 90 days, respectively. After exposure the gill, the organs of the digestive system (proboscis, esophagus, stomach, digestive gland, and rectum), and the foot were analyzed for cadmium accumulation. The results showed that most digestive organs had a high affinity for cadmium. The main target organ was the stomach, which could accumulate on average 1192.18 ,g/g dry weight of cadmium. Cadmium was shown to accumulate to a lesser extent in the digestive gland, gill, rectum, esophagus, proboscis, and foot. Histopathological alterations were observed in the gill and digestive organs (proboscis, esophagus, stomach, and rectum). The study showed that the stomach and gill were the primary target organs of both acute and subchronic exposure. Gill alterations included increased size of mucous vacuoles, reduced length of cilia, dilation and pyknosis of nuclei, thickening of basal lamina, and accumulation of hemocytes. The epithelial lining of the digestive tract showed similar alterations such as increased size of mucous vacuoles, reduced length of cilia, and dilation of nuclei. In addition, fragmentation of the muscle sheath was observed. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 142,149, 2005. [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] Transfer of Cd, Cu, Ni, Pb, and Zn in a soil-plant-invertebrate food chain: A microcosm study,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2006Renaud Scheifler Abstract The transfer of Cd, Cu, Ni, Pb, and Zn was evaluated in a soil-plant (lettuce, Lactuca sativa),invertebrate (snail, Helix aspersa) food chain during a microcosm experiment. Two agricultural soils, polluted and unpolluted, were studied. Lettuce was cultivated for eight weeks before introduction of snails into the microcosms (M-snails). In a parallel experiment, snails were exposed to lettuce only (i.e., without soil) in simpler exposure devices called containers (C-snails). Snail exposure duration was eight weeks for both M- and C-snails. No effects on snail survival were found. Both M- and C-snails exposed to polluted soil showed a growth reduction, but only after two weeks of exposure. Time-dependent accumulation in M-snails exposed to the polluted environment showed a regular increase of Cd and Zn concentrations over time and a rapid increase of Pb concentrations within the first two weeks, which then remained stable. Copper and Ni concentrations did not increase during any of the experiments. Concentrations in M- and C-snails were compared to estimate the relative contribution of soil and plant to the total bioaccumulation. The results suggest that the soil contribution may be higher than 80% for Pb, from 30 to 60% for Zn, and from 2 to 40% for Cd. [source] | ||||||||||||||||||||||||||||||||||||||||