Cristaria Plicata Research Articles

Contents of five trace elements in different tissues of four species of mussels in Lake Chaohu and their spatial variation

蚌类在湿地生态系统元素的富集与转化过程中发挥重要作用.以巢湖常见扭蚌（Arconaia lanceolata）、三角帆蚌（Hyriopsis cumingii）、褶纹冠蚌（Cristaria plicata）和圆顶珠蚌（Unio douglasiae）为对象，分析其内脏团、外套膜（包含鳃，下同）和斧足中5种微量元素（Cu、Zn、As、Cd、Pb）的含量.结果表明：5种元素在4种蚌体内均有检出，除Zn在圆顶珠蚌组织间表现为外套膜>内脏团>斧足外，4种蚌体组织间5种微量元素含量均表现为内脏团 > 外套膜 > 斧足；4种蚌类各微量元素平均含量均表现为Zn > Cu > As > Pb > Cd；Cu和Pb在4种蚌类中的平均含量表现为扭蚌 > 褶纹冠蚌 > 圆顶珠蚌 > 三角帆蚌，扭蚌各组织中Pb含量是其他3种蚌类的2.62~6.99倍，Zn的各平均含量表现为圆顶珠蚌 > 扭蚌 > 三角帆蚌 > 褶纹冠蚌，As表现为圆顶珠蚌 > 三角帆蚌 > 褶纹冠蚌 > 扭蚌，Cd表现为扭蚌 > 圆顶珠蚌 > 三角帆蚌 > 褶纹冠蚌，Cd在圆顶珠蚌和扭蚌中的含量是三角帆蚌和褶纹冠蚌的2.75~6.08倍.不同种类之间微量元素含量的差异大于同一种类微量元素含量的空间差异.微量元素污染较重的河口区蚌体组织具有较高的微量元素含量，污染较轻的河口中蚌体组织各微量元素含量也相对较低，表明蚌类可作为巢湖水体微量元素污染监测的指示生物.4种蚌类中Pb、Cd、As含量均未超出国家食品安全标准的限定值.;Mussels play an important role in the enrichment and transformation of elements in wetland ecosystems. In this study, Arconaia lanceolata, Hyriopsis cumingii, Cristaria plicata, and Unio douglasiae were used to analyze the content of five trace elements (Cu, Zn, As, Cd, Pb) in different tissues (visceral mass, mantle containing gills, foot ). The results showed that all five elements were detected in four species of mussels. The average content of each element in the tissues of the four species of mussels was visceral mass > mantle > foot, except for the average content of Zn in the tissues of U. douglasiae was shown as mantle > visceral mass > foot. The average content of each trace element in the four species of mussels was Zn>Cu>As>Pb>Cd; The average contents of Cu and Pb in the four species of mussels were expressed as A. lanceolata > C. plicata > U. douglasiae > H. cumingii. The content of Pb in the tissues of A. lanceolata was 2.62-6.99 times of the other three mussels. The average content of Zn is expressed as U. douglasiae > A. lanceolata > H. cumingii > C. plicata, As is expressed as U. douglasiae > H. cumingii > C. plicata > A. lanceolata, Cd appears as A. lanceolata > U. douglasiae > H. cumingii > C. plicata, the content of Cd in U. douglasiae and A. lanceolata is 2.75-6.08 times of H. cumingii and C. plicata. The difference in the content of trace elements between different species is greater than the spatial difference in the content of trace elements of a certain kind. Mussels in the estuary of Lake Chaohu, where the trace element is polluted heavily, have a higher content of trace elements and the contents of trace elements in tissues in estuaries with less pollution are also relatively low, indicating that mussels can be used as indicator organisms for monitoring of trace element pollution in Lake Chaohu. The contents of Pb and Cd in the four mussels did not exceed the limit of the national food safety standards, but the safety risks caused by As accumulation in H. cumingii and U. douglasiae were not excluded, and large quantities of food were not recommended.

Cardiac Activity in the Bivalve Mollusc Cristaria plicata from the River Songhua (China)

Cardiac Activity in the Bivalve Mollusc Cristaria plicata from the River Songhua (China)

Effects of replacing fish meal with mussel (Cristaria plicata) meat on growth, digestive ability, antioxidant capacity and hepatic IGF-I gene expression in juvenile Ussuri catfish (Pseudobagrus ussuriensis)

An 8-week feeding trial was implemented to evaluate the effects of replacing fish meal (FM) with mussel (Cristaria plicata) meat (MM) on growth, digestive ability, antioxidant capacity and hepatic insulin-like growth factor I (IGF-I) gene expression of juvenile Ussuri catfish (Pseudobagrus ussuriensis). Three isonitrogenous and isolipidic diets were formulated to include 0, 177.5 and 355.1 g/kg of MM, accordingly, replacing 0% (M0, control), 50% (M1) and 100% (M2) of FM protein, respectively. The results showed that the final body weight, weight gain, specific growth rate and feed intake were gradually decreased with dietary MM protein levels increased, but there were no significant difference between M0 and M1 groups (p > 0.05). The protein efficiency ratio was increased significantly with dietary MM inclusion (p < 0.05). The apparent digestibility coefficient of dry matter, crude lipid and gross energy gradually increased with increasing dietary MM protein levels, but the apparent digestibility coefficient of crude protein was not significantly affected by MM protein supplementation (p > 0.05). Fish fed diet, M0 and M1 remained unaffected significantly on activities of alpha-amylase and pepsin (p > 0.05), but fish fed diet M2 had the highest activities of alpha-amylase and pepsin. Fish fed diet M1 or M2 had significantly lower hepatic total antioxidant capacity, superoxide dismutase and the higher malondialdehyde level compared to fish fed diet M0. In addition, no significant difference was observed in hepatic IGF-I gene expression level for fish fed diet M0 and diet M1, and fish fed diet M2 showed significantly lower hepatic IGF-I gene expression level. Therefore, we can conclude that MM protein can successfully substitute 50% of FM protein without significantly negative effect on growth, nutrient utilization, and hepatic IGF-I gene expression for juvenile Ussuri catfish, but the antioxidant capacity was negatively affected in the present study, what is more, the total replacement of FM by MM in diet may result in the inhibition of the growth and antioxidant capacity of fish.

Identification and expression of cathepsin B from the freshwater mussel Cristaria plicata.

Cathepsin B plays crucial roles in host immune defense against pathogen infection. In present study, a cathepsin B gene from the freshwater mussel, Cristaria plicata (CpCathB) was cloned and characterized. The full-length cDNA of CpCathB was 1825 bp, and contained a 5' untranslated region (UTR) of 36 nucleotides, an open reading frame (ORF) of 1044 bp and a 3' UTR of 745 bp with a poly (A) tail. The deduced CpCathB protein was encoded as a preproenzyme with 347 amino acid residues and predicted molecular weight of 38.55 kDa. Sequence alignment revealed that CpCathB protein shared 56% - 60.7% identity comparison with other species. The predicted tertiary structure of CpCathB protein was highly similar to that of human. The CpCathB mRNA was expressed in hemocytes, hepatopancreas, adductor muscle, gills and mantle tissues of healthy mussels, and the highest expression level was in hepatopancreas. The transcripts of CpCathB were increased in hemocytes and hepatopancreas from mussels after Aeromonas hydrophila challenge. Moreover, the recombinant CpCathB was expressed in the Escherichia coli Rosetta-gami (DE3) strain. The maximum titer of the anti-CpCathB polyclonal antibodies was 1:640,000.The CpCathB protein had a higher expression in hepatopancreas and mantle and a lower level in hemocytes.

Identification and characterization of two distinct sigma-class glutathione-S-transferase from freshwater bivalve 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. In this study, two distinct sigma-class GST (CpGSTσ1 and 2) cDNA sequences were cloned from freshwater bivalve Cristaria plicata. The full length cDNA of CpGSTσ1 and 2 was 826 bp and 1609 bp, which encoded 213 and 248 amino acid residues, respectively. Their transcripts were expressed in all detected tissues and the highest expression level was in hepatopancreas from C. plicata. The expression level of CpGSTσ1 and 2 in hepatopancreas and hemocytes showed a significantly increased trend after bacterial challenge. The recombinant CpGSTσ1 was successfully expressed as a soluble form in Escherichia coli DE3. The specific activity of recombinase toward CDNB was 46.965 ± 0.082 μmol/min/mg, and its optimum temperature and pH was 37 °C and 9.0, respectively. The recombinant of CpGSTσ1 could bear 6 M urea and 8% SDS, when the concentration of urea was 8 M and its activity was only below 20%. The results might provide a better perspective on the mechanisms of resistance to bacterial infection in molluscs.

Microcystin induction small Maf protein involve in transcriptional regulation of GST from freshwater mussel Cristaria plicata

The small Mafs, MafF, MafG and MafK play critical roles in morphogenesis and homeostasis through associating with Cap “n” Collar family of transcription factors. In this study, we tried to identify a small Maf protein in the freshwater mussel Cristaria plicata. The MafK cDNA of C. plicata, designated as CpMafK, was cloned from the hemocytes using degenerate primers by the rapid amplification of cDNA ends PCR. The full length cDNA of CpMafK is 2170 bp, which includes an open reading frame of 570 bp, encoding 189 amino acids. CpMafK possesses four conserved domains and shows a low level (54–63%) of sequence similarity to small Mafs from other species. The results of Real-time quantitative PCR revealed that CpMafK mRNA was constitutively expressed in tissues, and the highest expression level was in hepatopancreas. After microcystin challenge, the expression levels of CpMafK mRNA were up-regulated in hemocytes and hepatopancreas. The cDNA of CpMafK was cloned into the plasmid pET-32, and the recombinant protein was expressed in Escherichia coli BL21(DE3). CpMafK could combine to the promoters of CpGST1 and CpGST2 with high-affinity in vitro. Therefore, CpMafK could regulate the expression of detoxification.

Seasonal variation of a population Unionicola penicillatus (Unionicolidae) from the freshwater bivalve Cristaria plicata (Unionidae) in Poyang Lake, eastern China

The water mite Unionicola penicillatus (Wen, Gao &amp; Zhu) (Acari: Unionicolidae) was collected in freshwater bivalve Cristaria plicata (Unionidae). The population variation of U. penicillatus was investigated in 504 bivalves during the period from August 2013 to July 2014 in Poyang Lake, East China. The results indicated that the overall prevalence and abundance of U. penicillatus was 9.52% and 1.58±10.38. The highest prevalence was 58.70% in September. The highest abundance levels were observed when the length of bivalves was in 220–300 mm. The number of U. penicillatus in a host was not correlated with the sex of bivalves. The outer and inner gills of bivalves were the preferred sites of U. penicillatus.

鳥取県における特定希少野生動物カラスガイCristaria plicata 個体群の現状 : 幼生と宿主魚類の関係に着目して

鳥取県における特定希少野生動物カラスガイCristaria plicata 個体群の現状 : 幼生と宿主魚類の関係に着目して

Discovery and natural history of the mussel leech Batracobdella kasmiana (Oka, 1910) (Hirudinida: Glossiphoniidae) in Russia

The mussel leech Batracobdella kasmiana (Oka, 1910) (Hirudinida: Glossiphoniidae) inhabits the mantle cavity of large freshwater mussels (Sawyer 1986; Lai &amp; Chen 2010). This specific lifestyle is unusual in leeches although a few additional parasitic species from mussels have been reported (Grizzle &amp; Brunner 2009). The known localities of B. kasmiana are situated in Japan (Honshu), continental China and Taiwan (Oka 1910, 1917; Gee 1919; Yang 1996; Yamauchi et al. 2008; Lai &amp; Chen 2010). The majority of records were reported from continental China, in which this species is widely distributed across the eastern half of the country from Yunnan to Beijing (Yang 1996). It has never been mentioned as a member of the Russian fauna (Lukin 1976). A few naiad species in the family Unionidae are known hosts of B. kasmiana, including Sinanodonta spp., Cristaria plicata (Leach, 1815), and Nodularia douglasiae (Griffith and Pidgeon, 1833) (Oka 1917; Yang 1996; Yamauchi et al. 2008). The biology and ecological preferences of this leech species are poorly known (Yang 1996; Yamauchi et al. 2008; Lai &amp; Chen 2010).

Molecular cloning, expression and antioxidative activity of 2-cys-peroxiredoxin from freshwater mussel Cristaria plicata

Peroxiredoxins (Prxs) play an important role against various oxidative stresses by catalyzing the reduction of hydrogen peroxide (H2O2) and organic hydroperoxides to less harmful form. A 2-cys peroxiredoxin, designated as CpPrx, was cloned from hemocytes of freshwater mussel Cristaria plicata. The full length cDNA of CpPrx is 1247 bp, which includes an open reading frame (ORF) of 591bp, encoding 196 amino acids. CpPrx possesses two conserved cysteine residues (Cys49, Cys170). The deduced amino acid sequence of CpPrx showed a high level (67–74%) of sequence similarity to 2-Cys Prxs from other species. The results of real-time quantitative PCR revealed that CpPrx mRNA was constitutively expressed in tissues, and the highest expression levels were in hepatopancreas and gills. After peptidoglycan (PGN) and Aeromonas hydrophila challenge, the expression levels of CpPrx mRNA were up-regulated in hemocytes and hepatopancreas. The cDNA of CpPrx was cloned into the plasmid pET-32, and the recombinant protein was expressed in Escherichia coli BL21(DE3). Comparison with DE3-pET-32 and DE3 strain, the cells of DE3-pET-32-CpPrx exhibited resistance to the concentration of 0.4, 0.8 and 1.2 mmoL/L H2O2 in vivo.

An improved method for in vitro culture of glochidia in freshwater mussel Cristaria plicata (Mollusca, Bivalvia)

We established an improved method for in vitro culture of glochidia in freshwater mussel Cristaria plicata and compared the transformation percentage in L-15 basic medium supplemented with different plasma from host fish or two non-host fish species. The results showed that the metamorphosis rate of glochidia cultured with host fish plasma and non-host fish plasma was all above 96%. High-density lipoprotein and low-density lipoprotein (LDL) levels were significantly lower in host fish plasma than in non-host fish plasma (P 0.05). The method developed herein not only provides a simplified in vitro culture method for glochidia at a reduced cost, but it also improves the culture efficiency. The method and medium composition may be further improved in studies investigating the long-term growth of juvenile mussels, and it would greatly benefit artificial breeding and germplasm resource preservation for this important species.

Transcriptome analysis of the freshwater pearl mussel (Cristaria plicata) mantle unravels genes involved in the formation of shell and pearl.

Cristaria plicata, a bivalve widespread in Eastern Asia fresh water, is utilized as the freshwater pearl mussel in China. With a high economic value in pearl production, it is also an ideal object used for the studies on biomineralization in freshwater. In the research, we performed a large-scale sequencing of Cristaria plicata mantle transcriptome using Illumina HiSeq™ 2500, obtaining 98,501 unigenes with 67,817,724 bases. 22.28 and 16.64% of the unigenes were annotated in the NR and Swiss-Prot databases, respectively. Most of the annotated unigenes were homologous with proteins of Crassostrea gigas (47.4%) and some were similar to proteins of Aplysia californica (16.7%). Here, we identified 109 homologous unigenes of 15 decided shell matrix proteins, including nacrein, Pif, perlucin, tyrosinase (Tyr), PfN44, PUSP1, chitinase, shell matrix protein, MSI80, fibronectin type III, AmOxCo, perlwapin, BMSP, PfCHS1 and CaLP. Two other mantle transcriptomes of Pinctada margaritifera and Pinctada fucata were also analyzed to perform a biomineralization protein comparison of the three molluscan transcriptomes. All the three compared mollusks shared four proteins, including nacrein, Pif, Tyr and PfCHS1. It was also discovered that Cristaria plicata shared more biomineralization proteins with Pinctada fucata than that with Pinctada margaritifera. Our study explored a whole draft of mantle transcriptome of freshwater mussel and unraveled genes involved in the formation of shell and pearl, making it possible to identify massive novel biomineralization proteins in mollusks.

Systematics and distribution of Cristaria plicata (Bivalvia, Unionidae) from the Russian Far East.

The number of anodontine bivalve species placed in the genus Cristaria (Bivalvia, Unionidae) from the Russian Far East is still not stable among authors. Some recognize only one valid species Cristaria plicata (Leach, 1815) while others accept two additional species, Cristaria tuberculata Schumacher, 1817 and Cristaria herculea (Middendorff, 1847). In the present study, these taxonomic doubts are addressed using analyses of mitochondrial DNA sequences and shell morphometry. No significant differences have been revealed by the COI DNA sequences or the main statistical morphometric indices from the three Cristaria forms. In the specimens analysed, changes in shell morphometry with age suggest that original descriptions of the different forms may be attributed solely to differences in age and sex. We consider that Cristaria plicata, Cristaria tuberculata and Cristaria herculea from the Russian Far East should be considered as a single species, namely Cristaria plicata (Leach, 1815), with Cristaria tuberculata and Cristaria herculea as junior synonyms. The geographic range of Cristaria plicata and its conservation status are also presented here.

Sequencing, De Novo Assembly, and Annotation of the Transcriptome of the Endangered Freshwater Pearl Bivalve, Cristaria plicata, Provides Novel Insights into Functional Genes and Marker Discovery.

BackgroundThe freshwater mussel Cristaria plicata (Bivalvia: Eulamellibranchia: Unionidae), is an economically important species in molluscan aquaculture due to its use in pearl farming. The species have been listed as endangered in South Korea due to the loss of natural habitats caused by anthropogenic activities. The decreasing population and a lack of genomic information on the species is concerning for environmentalists and conservationists. In this study, we conducted a de novo transcriptome sequencing and annotation analysis of C. plicata using Illumina HiSeq 2500 next-generation sequencing (NGS) technology, the Trinity assembler, and bioinformatics databases to prepare a sustainable resource for the identification of candidate genes involved in immunity, defense, and reproduction.ResultsThe C. plicata transcriptome analysis included a total of 286,152,584 raw reads and 281,322,837 clean reads. The de novo assembly identified a total of 453,931 contigs and 374,794 non-redundant unigenes with average lengths of 731.2 and 737.1 bp, respectively. Furthermore, 100% coverage of C. plicata mitochondrial genes within two unigenes supported the quality of the assembler. In total, 84,274 unigenes showed homology to entries in at least one database, and 23,246 unigenes were allocated to one or more Gene Ontology (GO) terms. The most prominent GO biological process, cellular component, and molecular function categories (level 2) were cellular process, membrane, and binding, respectively. A total of 4,776 unigenes were mapped to 123 biological pathways in the KEGG database. Based on the GO terms and KEGG annotation, the unigenes were suggested to be involved in immunity, stress responses, sex-determination, and reproduction. A total of 17,251 cDNA simple sequence repeats (cSSRs) were identified from 61,141 unigenes (size of >1 kb) with the most abundant being dinucleotide repeats.ConclusionsThis dataset represents the first transcriptome analysis of the endangered mollusc, C. plicata. The transcriptome provides a comprehensive sequence resource for the conservation of genetic information in this species and enrichment of the genetic database. The development of molecular markers will assist in the genetic improvement of C. plicata.

Molecular cloning and functional characterization of a novel i‐type lysozyme in the freshwater mussel Cristaria plicata

The freshwater bivalve Cristaria plicata, which is widely distributed in Eastern Asia, is a key species in the pearl culture industry. In this study, a novel invertebrate-type lysozyme, designated as CpLYZ2, was cloned from hemocytes of C. plicata. This lysozyme shares high sequence identity and is homologous to a previously identified lysozyme CpLYZ1 isolated from C. plicata and with HcLyso3 isolated from Hyriopsis cumingii. The full-length cDNA of CpLYZ2 is 913 bp long, which includes an open reading frame (ORF) of 486 bp, a 3' untranslated region (UTR) of 389 bp and a 5' UTR of 38 bp. The ORF encodes a putative polypeptide of 161 amino acids with a predicted molecular mass of 18.2 kDa and a theoretical isoelectric point of 6.56. CpLYZ2 mRNA transcripts can be detected in hemocytes, hepatopancreas, muscle, gills and mantle tissues, the greatest expression being observed in the gills. CpLYZ2 expression in hemocytes, hepatopancreas and gills increased significantly after the mussel was challenged with Aeromonas hydrophila. Furthermore, the optimal pH and temperature for enzyme activity of the recombinant CpLYZ2 were 5.5 and 50°C, respectively. The recombinant lysozyme protein exhibited bacteriolytic activity against Escherichia coli, A. hydrophila, Staphylococcus aureus, Bacillus subtilis, Streptococcus sp. and Staphylococcus epidermidis. The findings of this study help to elucidate immune responses in molluscs and will thus expedite disease management of these key freshwater species, in turn boosting pearl culture in eastern Asia.

Are Cristaria herculea (Middendorff, 1847) and Cristaria plicata (Leach, 1815) (Bivalvia, Unionidae) separate species?

The number of species in the freshwater mussel genus Cristaria Schumacher, 1817 recognized from Far East Russia has varied over the last several decades. While some authors consider the occurrence of only one species, Cristaria plicata (Leach, 1815), widespread in East Asia, others, recognize two separate species Cristaria herculea (Middendorff, 1847) and Cristaria tuberculata Schumacher, 1817 from Far East Russia, distinct from C. plicata. For the present study, freshwater mussels, identified as C. herculea, were collected in the Upper Amur basin (Transbaikalia, Russia). The shell morphology and the whole soft body anatomy were analysed in detail and compared with previously published information on other Cristaria spp.. Additionally, a cytochrome oxidase subunit 1 (CO1) gene fragment was sequenced from foot tissue samples of selected animals, collected from the same region, and compared with published data. Based upon morphological similarities of glochidia and adult morphology and anatomy as well as the mitochondrial DNA sequence analysis, we consider C. herculea as a synonym of C. plicata. Further analysis of Far East Russia C. herculea and C. tuberculata specimens using both molecular and morphological characters should be carried in the future to enhance our knowledge about the taxonomy within the Cristaria genus. Moreover, a comprehensive revision of the genus Cristaria is needed, restricting the type locality and comparing topotypic specimens for both C. plicata and C. tuberculata, and including all recognized Cristaria species.

Determination of the complete mitochondrial genome sequence of mussel Cristaria plicata (Leach)

In the present study, the total mitochondrial genome of a freshwater mussel Cristaria plicata (Leach) was sequenced and determined. The mitogenome is 15,710 bp in length. It consists of 13 protein-coding genes, 22 tRNA genes and 2 rRNA genes. The total base composition is: 36.49% A, 27.23% T, 23.21% C, and 13.07% G with an A+T rich feature (63.72%). These results provide useful data to study of the genetics, systematics and conservation of mussel C. plicata (Leach).

Molecular cloning and characterization of cathepsin L from freshwater mussel, Cristaria plicata

Cathepsin L is one of the crucial enzyme superfamilies and involved in the immune responses. The Cathepsin L cDNA and genome of Cristaria plicata（CpCL） was cloned from the hemocytes using degenerate primers by the rapid amplification of cDNA ends (RACE) PCR. The genomic DNA was 9353 bp long and had a total of six introns and seven exons. The full-length cDNA of CpCL was 1144 bp, the cDNA contained a 5′ untranslated region (UTR) of 34 nucleotides, the 3′ UTR of 108 bp with a canonical polyadenylation signal sequence AATAAA and a polyA tail, and an open reading frame (ORF) of 1002 bp, encoding 333 amino acid residues with 37.65 kDa predicted molecular weight. The theoretical isoelectric point was 8.61. The prepro-cathepsin L was consisted of a typical signal peptide (Met1-Gly20), a pro-region peptide (Leu21-Glu116) and a mature peptide (Tyr117-Val333). Many members of the papain family possessed of a proline residue at position 2 in the mature enzymem, this was also observed in CpCL. The preproprotein included an oxyanion hole (Gln 135), the active center formed by Cys141, His280 and Asn 300, the potential N-glycosylation site (Asn38, Asn 113 and Asn 272) and the conserved GCXGG motifs, which was characteristic of cathepsin, the conserved ERWNIN and GNFD motifs, which were characteristic for cathepsin L. Homology analysis revealed that the CpCL shared 49–87% identity to other known cathepsin L sequences. The phylogenetic tree showed that the CpCL clustered with the invertebrate cathepsin L cysteine proteases, and was closely related to the cathepsin L of Hyriopsis cumingii. The expression of CpCL mRNA was detected in hepatopancreas, hemocytes, mantle, gills and adductor muscle, and the higher expression level was in hepatopancreas. After A. hydrophila stimulation, the expression of the CpCL mRNA was up-regulated in hemocytes and hepatopancreas, and the expression level was significantly lower in gill than one after PBS challenge group.

Ontogenetic changes in the trophic position of a freshwater Unionidae mussel

Freshwater mussels have often been used as indicators of a trophic baseline (i.e., primary consumers) in the food web. To assess the utility of a large filter-feeding mussel, Cristaria plicata, as an isotopic indicator, we compared the carbon (delta C-13) and nitrogen (delta N-15) stable isotope ratios of the mussel with those of its potential food sources, particulate organic matter (POM) and sediment organic matter (SOM). The delta C-13 values of large mussels (shell length > 140 mm, -31 parts per thousand to -29.2 parts per thousand) were similar to those of POM (-30.2 parts per thousand) rather than those of SOM (-27.6 parts per thousand), indicating that mussel carbon was derived mainly from POM (mainly phytoplankton). In contrast, the mussels exhibited 6.3 parts per thousand to 9.0 parts per thousand higher delta N-15 values than did POM. Assuming a previously reported trophic enrichment factor (+3.4 parts per thousand), the trophic level estimate of the mussel ranged from 2.9 to 3.6, indicating that they functioned as secondary rather than primary consumers. Our results also revealed positive correlations between shell lengths and delta N-15 values, suggesting that the mussels changed their trophic position from primary consumer (shell length 140 mm) with growth. A significant inter-annual difference was found in the y-intercepts of the regression lines between shell length and delta N-15, indicating that mussels can reflect inter-annual changes in the isotopic baseline (i.e., primary producers).

Gene characterization and expression of defensin in &lt;I&gt;Cristaria plicata&lt;/I&gt;

Gene characterization and expression of defensin in &lt;I&gt;Cristaria plicata&lt;/I&gt;