Cristaria Plicata Research Articles

Cloning and expression of selenoprotein W from pearl mussels Cristaria plicata

Selenoprotein W (SelW) is a selenocysteine containing protein with redox activity involved in the antioxidant response. In this study, a selenoprotein W was cloned from pearl mussel Cristaria plicata (designated as CpSelW), and the expression patterns were characterized in tissues after Aeromonas hydrophila challenged. The full-length cDNA of cpSelW was of 858bp, containing a 5' untranslated region (UTR) of 145bp, a 3' UTR of 455bp with a poly (A) tail, and an open reading frame (ORF) of 258bp encoding a polypeptide of 85 amino acids with the predicted molecular mass of 9.277kDa, which shared 61% identity with SelW from Gallus gallus. A tertiary structure model generated for the CpSelW displayed a β-α-β-β-β-α secondary structure pattern, which was similar to mouse SelW protein 3D structure. The mRNA of CpSelW was constitutively expressed in tested tissues of healthy mussel, including mantle, gill, hemocytes, muscle, and hepatopancreas, and it was highly expressed in hepatopancreas. After mussels were stimulated by A. hydrophila, the mRNA expression of CpSelW in hemocytes at 6, 12 and 24h, in gill at 12h and in hepatopancreas at 24h was significantly down-regulated.

CLONING AND PROKARYOTIC EXPRESSION PEROXIREDOXIN 6 GENE IN CRISTARIA PLICATA

Peroxiredoxin 6 has glutathione peroxidase and phospholipid enzyme A2 double activity and plays an important role in antioxidant protection and metabolism of lung surface-active material.Cristaria plicata is one of the most important freshwater mussels for pearl production in China.In this study,a Prx6 homologue-CpPrx6 in Cristaria plicata,was cloned by utilizing reverse transcriptase polymerase chain reaction and rapid amplification of the cDNA ends.A phylogenetic tree was constructed based on the amino acid sequence of CpPrx6 using neighbor-joining method and MEGA 4.1 software.The three-dimensional structure of CpPrx6 was constructed using the Swiss-model.The expression patterns,both in tissues and towards microorganism A.hydrophila stimulation,were then characterized by real-time fluorescence quantitative PCR.The results showed that the full length cDNA of CpPrx6 contained a 5'-untranslated region(UTR) of 71 bp,an open reading frame of 657 bp that encoded 218 amino acids,and a 3'-UTR of 889 bp with a 29 bp polyadenylic acid tail.The predicted molecular mass and estimated isoelectric point(pI) of CpPrx6 were 24.24 kD and 6.33,respectively.No signal peptide,the transmembrane region,mitochondria,lysosomes,peroxisomes and nuclei localization sequence were found and contained 1 potential N-linked glycosylation site(N9FTA) in CpPrx6,which suggested that it is a cytosolic protein.The deduced amino acid sequence of CpPrx6 shared 70%—72% overall similarity with known Molluscan Prx6.The conserved peroxidase catalytic center "PVCTTE" and a lipase motif "GKSWA" were observed in the sequence,the tertiary structures of CpPrx6 contained 6 α-helixes and 12 β-sheets,the catalytic center "PVCTTE" located in fifth α-helix,three conserved residues His22,Asp134 and Ser28 together formed the catalytic center of the phospholipase A2,indicating that it was a member of 1-Cys Prx.Phylogenetic analyses showed that CpPrx6 sequence clustered together with the other Molluscan Prx6 sequences.The mRNA transcript of CpPrx6 was detected in most C.plicata organs,such as haemocyte,mantle,adductor muscle,hepatopancreas and gill,with the highest expression level found in gill.After injection of Aeromonas hydrophilai,the expression levels of CpPrx6 significantly increased in hepatopancreas at 6h and 12h,in haemocytes and gills at 12h(6h,P0.05;12h,P0.01),respectively.The expression levels then returned to normal at 24h.This suggested that CpPrx6 perhaps played an important role in resistance to oxidative stress and basic immunization of C.plicata.According to the ORF,designed site(KpnI and EcoRI) primers,the CpPrx6 gene was subcloned into a vector pET-32a(+) and transformed into Escherichia coli BL21(DE3),the constructed recombinant expression plasmids were induced by the chemical inducer IPTG.The expression products were analyzed by SDS-PAGE.The results indicated that recombination CpPrx6 was successfully expressed in E.coli.The expressed protein had a molecular weight of 40 kD.

Copper/Zinc Superoxide Dismutase from the CladoceranDaphnia magna: Molecular Cloning and Expression in Response to Different Acute Environmental Stressors

The copper/zinc superoxide dismutase (Cu/Zn-SOD) is a representative antioxidant enzyme that is responsible for the conversion of superoxide to oxygen and hydrogen peroxide in aerobic organisms. Cu/Zn-SOD mRNAs have been cloned from many species and employed as useful biomarkers of oxidative stresses. In the present study, we cloned Cu/Zn-SOD cDNA from the cladoceran Daphnia magna, analyzed its catalytic properties, and investigated mRNA expression patterns after exposure to known oxidative stressors. The full-length Cu/Zn-SOD of the D. magna (Dm-Cu/Zn-SOD) sequence consisted of 703 bp nucleotides, encoding 178 amino acids, showing well-conserved domains that were required for metal binding and several common characteristics. The deduced amino acid sequence of Dm-Cu/Zn-SOD showed that it shared high identity with Daphnia pulex (88%), Alvinella pompejana (56%), and Cristaria plicata (56%). The phylogenetic analysis indicated that Dm-Cu/Zn-SOD was highly homologous to D. pulex. The variation of Dm-Cu/Zn-SOD mRNA expression was quantified by real-time PCR, and the results indicated that the expression was up-regulated after 48-h exposure to copper, un-ionized ammonia, and low dissolved oxygen. This study shows that the Dm-Cu/Zn-SOD mRNA could be successfully employed as a biomarker of oxidative stress, which is a common mode of toxicity for many other aquatic hazardous materials.

Expression analysis of i-type lysozyme gene from Cristaria plicata and enzymatic activity analysis

Expression analysis of i-type lysozyme gene from Cristaria plicata and enzymatic activity analysis

Cloning and expression of heat shock protein 90 gene of fresh water mussel: Cristaria plicata

Cloning and expression of heat shock protein 90 gene of fresh water mussel: Cristaria plicata

Gene identification and recombinant protein of a lysozyme from freshwater mussel Cristaria plicata

Lysozymes are important proteins to bivalve in the innate immune responses against bacterial infections, and provide nutrition as digestion enzymes. A new LYZ1 from the freshwater mussel Cristaria plicata was cloned by rapid amplification of cDNA ends (RACE) and nested PCR method. The full-length cDNA sequence of CpLYZ1 was 763 bp. The cDNA contained a 5′-terminal untranslated region (UTR) of 21 bp, a 3′- terminal UTR of 259 bp with a 29 bp poly(A) tail, a tailing signal (AATAAA) and the open reading frame of 483 bp. The CpLYZ1 cDNA encoded a polypeptide of 160 amino acids with a predicted molecular mass of 17.8 kDa, and a theoretical isoelectric point of 6.07. The comparison of the deduced amino acid sequences with LYZs from other species showed that the enzyme belonged to i-type lysozyme. The mRNA transcript of CpLYZ1 could be detected in all the examined tissues with the highest expression level in hepatopancreas. The expression levels of CpLYZ1 in hemocytes, hepatopancreas and gill significantly increased after Aeromonas hydrophila challenge. The expression level of CpLYZ1 in hemocytes sharply decreased from 6 h to 24 h and significantly increased at 48 h, and was the highest level in hepatopancreas at 24 h, and was the maximum level in gill at 48 h. Furthermore, the recombinant CpLYZ1 was induced to be expressed as an inclusion body form by IPTG at 37 °C for 4 h, and then was purified by using the Ni2+ affinity chromatography. The relative enzyme activity of the recombinant CpLYZ1 was influenced on pH and temperature. The optimal pH and temperature was 5.5 and 50 °C, respectively. Against Escherichia coli, A. hydrophila, Staphyloccocus aureus, Bacillus subtilis, Streptococcus sp. and Staphylococcus epidermidis, the recombinant CpLYZ1 had bacteriolytic activity.

Sequence variation of the mitochondrial 12S rRNA gene among Unionicola (Wolcottatax) arcuata (Acari: Unionicolidae) from freshwater mussels in China

Unionicola (Wolcottatax) arcuata (Wolcott, 1898) (Acari: Hydrachnidia: Unionicolidae) commonly occurs in parasitic association with Cristaria plicata (Leach), Anodonta woodiana elliptica (Heude) or Anodonta woodiana pacifica (Heude) during one or more stages of its life cycle. The mitochondrial 12S rRNA gene was sequenced and analysed from U. arcuata obtained from nine populations of these freshwater mussels from six large lakes in the middle and lower reaches of the Yangtze River, China. The 382 base sequence alignments for these nine populations of U. arcuata had two gaps and contained 51 (13.4%) variable nucleotides. The pairwise divergences among U. arcuata sequence data ranged from 0 to 10.9%, with the lowest intraspecific divergences (0–0.5%) observed among U. arcuata obtained from the same host species and the highest intraspecific divergences (6.7–10.9%) found among U. arcuata from different species of hosts. The results of sequence alignment and divergence were consistent with the heterogeneity in sequence data of the 12S rRNA gene observed in other studies of acarines. Maximum parsimony and maximum likelihood analyses each yielded a single tree with the same topology and high bootstrap support. The gene trees indicate three major clades, with U. arcuata from C. plicata, A. woodiana elliptica and A. woodiana pacifica each forming a distinct clade. Overall, the results of this study indicated that host association, rather than patterns of geographic distribution, plays an important role in the degree of genetic divergence among populations of U. arcuata.

Mitochondrial genome of the cockscomb pearl mussel Cristaria plicata (Bivalvia, Unionoida, Unionidae)

The complete mitochondrial genome sequence of the cockscomb pearl mussel Cristaria plicata, which is an endangered species in South Korea, was sequenced. The circle genome (15,708 bp in size) consists of 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. There were 26 noncoding regions (NCs) found throughout the mitogenome of C. plicata, ranging in size from 2 to 327 bp, and the two largest NC regions, NC286 and NC326, were found between ND5 and tRNAGln (286 bp) and between tRNAGlu and ND2 (326 bp), respectively. The 13 mitochondrial protein-coding genes of a female individual of C. plicata collected from Korea (15,708 bp) were compared to those of the Chinese individual (15,712 bp) published before. The result showed that ND3 is the most conserved with 100% nucleotide similarity, and each of the other protein-coding genes has ca. 99%, respectively. The two largest NCs among 26 NCs have totally 98% nucleotide similarity between Korean and Chinese ones.

Chemical analysis of a polysaccharide from Cristaria plicata (Leach)

A polysaccharide (MPS) isolated from Cristaria plicata (Leach) consisted of d-glucose. Its structural characteristics were investigated by High Performance Liquid Chromatography (HPLC), infrared analysis, gas chromatography-MS, total acid hydrolysis, methylation analysis, periodate oxidation and Smith degradation. The results indicated that the polysaccharide of C. plicata (Leach) has the weight-average molecular weight of about 2.97 × 106 Da. The structure of the polysaccharide was composed of glucose with α-(1 → 4)-linkages with short exterior chains. The fundamental information obtained from this work is beneficial to the interpretation in the relationship of the polysaccharide structure and its biological functions, and suggests that the polysaccharide from mussel may contribute to be used as a dietary supplement for health foods and therapeutics.

Cloning, identification and functional characterization of a pi-class glutathione-S-transferase from the freshwater mussel Cristaria plicata

Glutathione-S-transferases (GSTs) are multifunctional phase II detoxification enzymes that catalyze the attachment of electrophilic substrates to glutathione and play an important role in protecting organisms against the toxicity of reactive oxygen species (ROS). The piGST cDNA was cloned and sequenced after rapid amplification of cDNA ends (RACE) from the freshwater mussel Cristaria plicata. The comparison of the deduced amino acid sequences with GSTs from other species showed that the enzymes belonged to the pi-class and the amino acids defining the binding sites of glutathione (G-site) and for xenobiotic substrates (H-site) were highly conserved. The Cp-piGST cDNA is 816 nucleotides (nt) in length and contained a 615 nt open reading frame (ORF) encoding 205 amino acid residues, and has 19 nt of 5′ untranslated region (UTR) and a 3′ UTR of 182 nt including a tailing signal (AATAAA) and a poly (A) tail. The molecular weight of the predicted piGST is 23.4 kDa, with the calculated PI being 5.2. The mRNA transcript of Cp-piGST could be detected in all the examined tissues with highest expression level in hepatopancreas. The expression level of Cp-piGST in hepatopancreas and gill showed similar trend that were significantly increased after bacterial challenge compared to the control group at 12 h. Furthermore, the recombinant Cp-piGST with high enzyme activity was induced to be expressed as a soluble form by IPTG at 20 °C for 8 h, and then was purified by using the native Ni 2+ affinity chromatography. The specific activity of the purified soluble Cp-piGST enzyme into pET30 was 2.396 μmol/min/mg, and which into pET32 was 1.706 μmol/min/mg. The recombinant Cp-piGST had a maximum activity at approximately pH 8.0, and its optimum temperature was 37 °C. The recombinant Cp-piGST enzyme activity became lower gradually with the denaturant concentration increasing.

A catalase from the freshwater mussel Cristaria plicata with cloning, identification and protein characterization

Catalase is an important antioxidant protein which can protect organisms against various oxidative stresses by eliminating hydrogen peroxide. The catalase cDNA of Cristaria plicata（cpCAT） was cloned from the haemocytes using degenerate primers by the method of 3′ and 5′ rapid amplification of cDNA ends PCR. The gene is 4863 bp long and has a total of two introns and three exons. The precise size and location of the introns and exons have been determined. In addition the full-length cDNA of cpCAT contained 2618 bp, The cDNA contained a 5′ untranslated region (UTR) of 136 nucleotides, the 3′ UTR of 979 bp with a canonical polyadenylation signal sequence AATAAA and a polyA tail, and an open reading frame (ORF) of 1503 bp, encoding 501 amino acid residues with 56.86 kDa predicted molecular weight. The theoretical isoelectric point was 6.77. BLAST analysis showed that the deduced amino acid sequence of cpCAT had significant homology to catalases from animals, plants and bacteria. The deduced amino acid sequence of cpCAT had characteristic features of catalase family such as catalytic site motif (61FNRERIPERVVHAKGAG77), heme-ligand signature motif (351RLYSYSDTH359), two glycosylation sites (N145, N436), NADPH binding site and the three catalytic amino acid residues (His72, Asn145 and Tyr355). It had no signal peptide. The phylogenetic tree indicated that cpCAT gene was very close to the gene of scallops, Chlamys farreri. The enzymatic activity of purified recombinant cpCAT was 11194.4 ± 40.4 U/mg, it might resist against H 2O 2. The recombinant enzyme held higher thermal stability, the optimum temperature was 25 °C, it retained more than 82% activity between 25 and 60 °C. The stability of the recombinant enzyme were higher between pH 5 and 10, and the optimal pH value was 7.0. When cpCAT was treated with 2–4moL/L urea and 1%–3% SDS, the activity was also stable, it kept more than 80% activity.

Copper and zinc interaction on water clearance and tissue metal distribution in the freshwater mussel, Cristaria plicata, under laboratory conditions

Copper and zinc interaction on clearance from water and distribution in different tissues was investigated for the freshwater mussel, Cristaria plicata, under laboratory conditions. Clearance rate of Cu or Zn from water was highly dependent on exposure concentration. Interaction effect was most evident at 300 μg·L−1 Cu exposure and depressed the Zn clearance rate significantly (p<0.05). However, the presence of 100 μg·L−1 and 300 μg·L−1 Zn hardly affected the Cu clearance rate. The 300 μg·L−1 Cu presence enhanced Cu accumulation in each tissue most significantly (p<0.01), but caused Zn content to decrease in the gills by 62% (p<0.05), viscera by 49% (p<0.05) and foot by 31% (p<0.05), and increase in the mantle by 97% (p<0.05) and the muscles by 243% (p<0.05) for different Zn exposure treatments. The response of metal accumulation in various tissues of the test mussels indicated that Zn transferred from the gills, viscera and foot to the mantle and muscles might be one of the important characteristics of the Zn regulatory mechanism by leading to a narrow range of Zn concentration in the different tissues.

Morphology and phagocytic ability of hemocytes from Cristaria plicata

Cristaria plicata is one of the most important freshwater mussels for pearl production in China, whose hemocytes were characterized using light, phase contrast and electron microscopy. In accordance with the presence or the absence of granules in the cytoplasm, two main types of hemocytes were recognized, granulocytes and agranulocytes. The granulocytes possessed cytoplasmic granules, while agranulocytes had none or a few cytoplasmic granules. In addition, in line with the diameter of granulocytes and cytoplasmic granules, granulocytes were further divided into large and small granulocytes. According to the diameter of agranulocytes and the different N/C ratios, agranulocytes could also be divided into hyalinocytes and lymphoid hemocytes. The mean concentration of the hemocytes of C. plicata was about (2.37 ± 0.51) × 10 6 cell mL −1. The two main cell types were small granulocytes (56.60% ± 1.41) and hyalinocytes (36.80% ± 2.11), while large granulocytes (4.20% ± 0.23) and lymphoid hemocytes (2.40% ± 0.12) were of the minority. With the rise of water temperature, total hemocyte counts showed a significant increase. The hemocytes presented different tinctorial properties for Wright's staining in smears. Small granulocytes and hyalinocytes exhibited acidophils and basophils, while large granulocytes and lymphoid hemocytes showed only acidophils and basophils respectively. Three types of hemocytes, large granulocytes, small granulocytes and hyalinocytes, could phagocytize yeast and Bacillus subtilis cells. Small granulocytes appeared to be more efficient in phagocytosis than large granulocytes and hyalinocytes, and large granulocytes showed to be more efficient than hyalinocytes. Water temperature had a great effect on the phagocytic ability of hemocytes.

Sympatric variability of isotopic baselines influences modeling of fish trophic patterns

Stable isotope signatures of freshwater snails and mussels have been established as a convenient baseline measurement at the primary consumer level for food-web coupling studies. We measured δ15N and δ13C of primary consumers, including mussels (Anodonta woodiana, Cristaria plicata, and Unio douglasiae), snails (Bellamya aeruginosa and Hippeutis sp.), and zooplankton from the same habitat within a shallow eutrophic lake. Primary consumers showed positive relationship between δ15N and δ13C, indicating a linkage between planktonic and benthic habitats in this system. The variation in isotope ratios was higher in short-lived primary consumers (zooplankton) compared with the long-lived primary consumers (mussels and snails), suggesting limited availability of short-lived primary consumers as isotopic baselines in aquatic food-web assessment. Significant differences in isotope ratios were also found among three species of mussels, and when using these mussels separately as pelagic baselines to calculate trophic position and contribution of planktonic and benthic sources of fishes, bias and even misestimates were observed. This finding suggests that caution is needed when multiple primary consumers coexist in the same habitat, and it is important to assess potential effects of different baselines used.

Contributions of Pelagic and Benthic Dietary Sources to Freshwater Mussels: Evidence from Stable Carbon Isotope Analysis

ABSTRACT In Gonghu Bay of Lake Taihu, tissue of five mussel species showed δ13C values similar to or slightly below that of pelagic suspended particulate organic matter (SPOM). This indicated that mussels in this area either fed non-selectively and so reflected available carbon in the pelagic habitat or selected for phytoplankton. The situation was the same for Anodonta woodiana woodiana and Cristaria plicata in Meiliang Bay; however, for the remaining three species, Hyriopsis cumingii, Arconaia lanceolata, and Lamprotula rochechouarti, tissue had intermediate δ13C values, falling between those for pelagic SPOM and benthic sediment organic matter (SOM), suggesting a possible preferential selection of phytoplankton from the pelagic SPOM but more likely reflecting local differences in pelagic SPOM and benthic SOM composition and available organic carbon sources. The mixing model showed that pelagic SPOM accounted for over 98% of carbon incorporated by all mussels in Gonghu Bay and two mussels in Meiliang Bay, suggesting the dietary importance of pelagic food sources for mussels. Less than 50% of the assimilation in H. cumingii, A. lanceolata, and L. rochechouarti came from the pelagic carbon sources in Meiliang Bay, which suggested that these species consumed a mix of benthic and pelagic derived carbon sources.

Isolation and characterization of 18 polymorphic microsatellite loci from freshwater pearl mussel (Cristaria plicata)

Cristaria plicata was an important freshwater mussel for pearl culture in China. 18 polymorphic microsatellite markers were isolated and characterized using (CA)15-enriched genomic library of C. plicata. These loci showed high levels of genetic polymorphism testing on 60 individuals sampled from Poyang Lake of Jiangxi Province, China. The number of alleles per locus ranged from 4 to 18. The expected (HE) and observed heterozygosities (HO) were 0.7232–0.8961 and 0.0000–1.0000, respectively. Four microsatellite loci were significantly deviated from Hardy–Weinberg equilibrium and no linkage disequilibrium was found. These microsatellite loci will be useful for assessment of genetic diversity and population structure in C. plicata.

An introduction to directions in freshwater mollusk conservation: molecules to ecosystems

Previous articleNext article No AccessArticlesAn introduction to directions in freshwater mollusk conservation: molecules to ecosystemsAlan D. Christian and John L. HarrisAlan D. Christian1Department of Biological Sciences and Environmental Sciences Program, Arkansas State University, P.O. Box 599, State University, Arkansas 72467 USA*E-mail addresses: [email protected] Search for more articles by this author and John L. Harris2Environmental Division, Arkansas Highway and Transportation Department, P.O. Box 2261, Little Rock, Arkansas 72203 USA, and Department of Biological Sciences, Arkansas State University, P.O. Box 599, State University, Arkansas 72467 USA&dagger:[email protected] Search for more articles by this author PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Volume 27, Number 2June 2008 Article DOIhttps://doi.org/10.1899/08-025.1 Views: 49Total views on this site Citations: 7Citations are reported from Crossref Journal History This article was published in the Journal of the North American Benthological Society (1986-2011), which is continued by Freshwater Science (2012-present). © 2008 by The North American Benthological SocietyPDF download Crossref reports the following articles citing this article:Isabel Porto-Hannes, Lyubov E. Burlakova, David T. Zanatta, Howard R. Lasker Boundaries and hybridization in a secondary contact zone between freshwater mussel species (Family:Unionidae), Heredity 126, no.66 (Apr 2021): 955–973.https://doi.org/10.1038/s41437-021-00424-xYan-Ling Cao, Xiong-Jun Liu, Rui-Wen Wu, Tao-tao Xue, Long Li, Chun-Hua Zhou, Shan Ouyang, Xiao-Ping Wu Conservation of the endangered freshwater mussel Solenaia carinata (Bivalvia, Unionidae) in China, Nature Conservation 26 (Apr 2018): 33–53.https://doi.org/10.3897/natureconservation.26.25334Xue-Yan Ma, Hai-Bo Wen, Jun Zou, Wu Jin, Dan Hua, Ruo-Bo Gu, Pao Xu An improved method for in vitro culture of glochidia in freshwater mussel Cristaria plicata (Mollusca, Bivalvia), Hydrobiologia 595 (Jan 2017).https://doi.org/10.1007/s10750-016-3012-3Andrew T. Harris,1 Daelyn A. Woolnough,2 and David T. Zanatta3 Insular lake island biogeography: using lake metrics to predict diversity in littoral zone mollusk communities, Journal of the North American Benthological Society 30, no.44 (Jul 2015): 997–1008.https://doi.org/10.1899/11-020.1Michael A. Martinez, David L. Rogowski Use and Apparent Partitioning of Habitat by an Imperiled Springsnail (Hydrobiidae) and a Cosmopolitan Pond Snail (Physidae), The Southwestern Naturalist 56, no.22 (Jun 2011): 216–223.https://doi.org/10.1894/F11-JS-34.1Daniel J. Hornbach, Mark C. Hove, Benjamin D. Dickinson, Kelly R. MacGregor, Jill R. Medland Estimating population size and habitat associations of two federally endangered mussels in the St. Croix River, Minnesota and Wisconsin, USA, Aquatic Conservation: Marine and Freshwater Ecosystems 20, no.33 (May 2010): 250–260.https://doi.org/10.1002/aqc.1081Karel Douda Effects of nitrate nitrogen pollution on Central European unionid bivalves revealed by distributional data and acute toxicity testing, Aquatic Conservation: Marine and Freshwater Ecosystems 20, no.22 (Mar 2010): 189–197.https://doi.org/10.1002/aqc.1076

Microcystin accumulation in freshwater bivalves from Lake Taihu, China, and the potential risk to human consumption

The potential risk through ingestion of microcystins (MC) in contaminated mollusks has not been well studied. The present paper studied seasonal changes of MC content (determined by liquid chromatography-mass spectrometry) in various organs of three species of bivalves (Cristaria plicata, Hyriopsis cumingii, and Lamprotula leai) in Lake Taihu, China, where toxic cyanobacterial blooms occurred. Coinciding with peaks of seston MC (maximum, 5.7 microg/L) and MC in cyanobacterial blooms (maximum, 0.534 mg/g), most organs showed sharp MC peaks during the summer, indicating both fast uptake and fast depuration by bivalves. Because hepatopancreas and intestine had considerably higher MC content than other organs, they are the most dangerous for human consumption. Both the present and previous studies show that the hepatopancreatic MC and total tissue MC often are correlated in various aquatic invertebrates. During the peak of the cyanobacterial blooms, C. plicata had higher hepatopancreatic MC content than the other bivalves, whereas H. cumingii had higher intestinal MC content than the other bivalves. Estimated daily intakes for humans from the consumption of whole tissues of the three bivalves were 0.48 to 0.94 microg MC-LR equivalent/kg body weight (12- to 23.5-fold the tolerable daily intake value proposed by the World Health Organization), which indicates a high risk for humans consuming these bivalves.

Population dynamics of the water mite Unionicola arcuata (Unionicolidae) in the freshwater bivalve Cristaria plicata (Unionidae) in Poyang Lake, eastern China

Population dynamics of the water mite Unionicola arcuata were investigated in the freshwater bivalve Cristaria plicata during the period from January to December 2002 in Poyang Lake, East China. A pattern of seasonal variation was observed, with prevalence and abundance peaking in early spring and autumn. The number of mites in individual hosts was significantly correlated with the size, but not with the sex, of bivalves. The change in infection level of mites on different infection sites in C. plicata was significant, with >58% of the mites found on the outer and inner gills, indicating that U. arcuata shows site preference.

Seasonal dynamics of the hepatotoxic microcystins in various organs of four freshwater bivalves from the large eutrophic lake Taihu of subtropical China and the risk to human consumption

So far, little is known on the distribution of hepatotoxic microcystin (MC) in various organs of bivalves, and there is no study on MC accumulation in bivalves from Chinese waters. Distribution pattern and seasonal dynamics of MC-LR, -YR and -RR in various organs (hepatopancreas, intestine, visceral mass, gill, foot, and rest) of four edible freshwater mussels (Anodonta woodiana, Hyriopsis cumingii, Cristaria plicata, and Lamprotula leai) were studied monthly during Oct. 2003-Sep. 2004 in Lake Taihu with toxic cyanobacterial blooms in the summer. Qualitative and quantitative determinations of MCs in the organs were done by LC-MS and HPLC. The major toxins were present in the hepatopancreas (45.5-55.4%), followed by visceral mass with substantial amount of gonad (27.6-35.5%), whereas gill and foot were the least (1.8-5.1%). The maximum MC contents in the hepatopancreas, intestine, visceral mass, gill, foot, and rest were 38.48, 20.65, 1.70, 0.64, 0.58, and 0.61 microg/g DW, respectively. There were rather good positive correlation in MC contents between intestines and hepatopancreas of the four bivalves (r=0.75-0.97, p<0.05). There appeared to be positive correlations between the maximum MC content in the hepatopancreas and the delta13C (r=0.919) or delta15N (r=0.878) of the foot, indicating that the different MC content in the hepatopancreas might be due to different food ingestion. A glutathione (GSH) conjugate of MC-LR was also detected in the foot sample of C. plicata. Among the foot samples analyzed, 54% were above the provisional WHO tolerable daily intake (TDI) level, and the mean daily intakes from the four bivalves were 8-23.5 times the TDI value when the bivalves are eaten as a whole, suggesting the high risk of consuming bivalves in Lake Taihu.