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Peptides in shrimp hemolymph play an important role in the innate immune response. Analysis of hemolymph will help to detect and identify potential novel biomarkers of microbial infection. We used magnetic bead-based purification (ClinProt system) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) to characterize shrimp hemolymph peptides. Shrimp serum and plasma were used as the source of samples for comparative analysis, and it was found that serum was more suitable for shrimp hemolymph peptidomic analysis. To screen potential specific biomarkers in serum of immune-challenged shrimps, we applied magnetic bead-based MALDI-TOF MS to serum samples from 10 immune-challenged and 10 healthy shrimps. The spectra were analyzed using FlexAnalysis 3.0 and ClinProTools 2.1 software. Thirteen peptide peaks significantly different between the two groups were selected as candidate biomarkers of lipopolysaccharide (LPS)-infection. The diagnostic model established by genetic algorithm using five of these peaks was able to discriminate LPS-challenged shrimps from healthy control shrimps with a sensitivity of 90% and a specificity of 100%. Our approach in MALDITOF MS-based peptidomics is a powerful tool for screening bioactive peptides or biomarkers derived from hemolymph, and will help to enable a better understanding of the innate immune response of shrimps.

Both smithsonite and calcite are calcite-group minerals which are isomorphous with one another. They are similar in many physical and chemical properties, and may partially or fully replace one another, which make the separation of smithsonite from calcite inefficient and ineffective in flotation. The present study was undertaken to investigate the solubility properties of individual calcite and smithsonite minerals and their mixtures, and establish correlation between solution chemistry and flotation behavior. Solution chemical calculations show that the species distribution of smithsonite and calcite was strongly affected by solution pH value. With the increase of pH, the measured solubility of calcite is very close to the theoretical value, while that of smithsonite is less than the theoretical value, illustrating that surface precipitations of zinc hydroxide and hydrozincite are possible. In the mixed system, solution chemical calculations show that the conversion from smithsonite and calcite to hydrozincite and zinc hydroxide is spontaneous. The flotation behavior of smithsonite and calcite was studied with the supernatants, and XPS analysis was conducted to detect surface properties. Both simulation results and experimental data show that surface conversion from calcite to zinc species has a vital influence on the separation of smithsonite from calcite by flotation.

Mollusc shell matrix proteins (SMPs) are important functional components embedded in the shell and play a role in shell formation. A SMP (Pif177) was identified previously from the nacreous layer of the Japanese pearl oyster Pinctada fucata, and its cleavage products (named pfPif97 and pfPif80 proteins) were found to bind to the chitin framework and induce aragonite crystal formation and orient the c axis. In this study, a homologue of pfPif177 was cloned from the mantle of the Pacific oyster Crassostrea gigas, containing the homologue of pfPif97 only and not pfPif80. This finding hints at the large divergence in gene structure between the two species. This homologue (cgPif97) shares characteristics with pfPif97, and suggests that the biological functions of these two proteins may be similar. The expression pattern of cgPif97 in different tissues and development stages indicates that it may play an important role in shell formation of the adult oyster. The morphology of the inner shell surface was affected by injected siRNA of cgPif97 and the calcite laths of the shell became thinner and narrower when the siRNA dose increased, suggesting that the cgPif97 gene plays an important role in calcite shell formation in C. gigas. In conclusion, we found evidence that the Pif177 gene evolved very fast but still retains a similar function among species [Current Zoology 59 (1): 109–115, 2013].

The Pacific oyster (Crassostrea gigas) is globally distributed and is one of the most commercially and ecologically important marine organisms. However, little is known about the genome of this species. In this study, a C. gigas fosmid library was constructed that contains 459,936 clones with an average insert size of approximately 40 kb, representing 22.34-fold haploid genome equivalents. End sequencing generated 90,240 fosmid end sequences (FESs) with an average length of 384.27 base pairs (bp), covering approximately 2.58% of the Pacific oyster genome. The FESs were subsequently assembled and annotated, resulting in 6332 sequences with predicted open reading frames >= 300 and 1,189,100 bp repeats. Furthermore, a total of 3200 microsatellite repeats were identified, and dinucleotide repeats were found to occur most abundantly, with AG and AAT being the most abundant repeat class of dinucleotides and trinucleotides. We also found that the repeat number was generally negatively proportional to the repeat element length. Microsatellites composition between the transcribed sequences and genomic sequences was shown to be different. Point mutations of microsatellite were non-random and underwent strong selection stress. Overall, a comprehensive sequence resource for the Pacific oyster was created, including annotated transposable elements, tandem repeats, protein coding sequences and microsatellites. These initial findings will serve as resources for further in-depth studies of physical mapping, gene discovery, microsatellite marker developing and evolution studies.

The effect of Zn2+ on calcite flotation and the effect of lattice ions on calcite flotation in presence of Zn2+ were investigated through microflotation tests, zeta potential measurements, and surface analysis. The results show that Zn species inhibit the interaction between the reagents and calcite through the formation of surface precipitation coating on the calcite surface, when the concentration of Zn2+ is higher than 10−5 mol/L. The effect of Zn species on calcite flotation can be decreased with the increase of Ca2+, instead of CO 3 2 - . In presence of Ca2+ and CO 3 2 - , the change of floatability suggests that Zn species can be desorbed with an optimum ratio of Ca 2 + / CO 3 2 - . The zeta potential measurements and surface analysis show the existence of a mixture of hydrozincite and zinc hydroxide products on mineral surface, and zinc surface coating can be desorbed due to the strong chemical adsorption of Ca2+ and the formation of hydrozincite in the bulk solution.

To determine whether genetic improvement could be attained through a selective breeding programme, divergent selection for shell length was conducted in a base population of the Manila clam, Ruditapes philippinarum. The 10% largest and 10% smallest clams were selected as parents for the upward-selected and downward-selected lines, respectively. Equal numbers of clams were randomly chosen to serve as parents for the control line before the selection. The selected and control lines were reared under the same environmental conditions at larvae, juvenile, and grow-out stages. The values of standardized responses to selection (SR) and realized heritability ( at the age of 360 d were 0.268 and 0.165 for the upward-selected line and 0.341 and 0.260 for the downward-selected line, respectively. Asymmetric differences were evident between the upward-selected and downward-selected lines in both SR and . Performance in shell length is improved by 3.55% in the upward-selected line after one generation, indicating that mass selection for shell length in a base population of the Manila clam, R. philippinarum, is effective and encouraging.

Next-generation sequencing (NGS) technology is being applied to an increasing number of non-model species and has been used as the primary approach for accurate genotyping in genetic and evolutionary studies. However, inferring genotypes from sequencing data is challenging, particularly for organisms with a high degree of heterozygosity. This is because genotype calls from sequencing data are often inaccurate due to low sequencing coverage, and if this is not accounted for, genotype uncertainty can lead to serious bias in downstream analyses, such as quantitative trait locus mapping and genome-wide association studies. Here, we used high-coverage reference data sets from Crassostrea gigas to simulate sequencing data with different coverage, and we evaluate the influence of genotype calling rate and accuracy as a function of coverage. Having initially identified the appropriate parameter settings for filtering to ensure genotype accuracy, we used two different single-nucleotide polymorphism (SNP) calling pipelines, single-sample and multi-sample. We found that a coverage of 15× was suitable for obtaining sufficient numbers of SNPs with high accuracy. Our work provides guidelines for the selection of sequence coverage when using NGS to investigate species with a high degree of heterozygosity and rapid decay of linkage disequilibrium.

Animals with trochophore larvae belong to Trochozoa, one of the main branches of Bilateria. In addition to exhibiting spiral cleavage and early cell fate determination, trochozoans typically undergo indirect development, which contributes to the most unique characteristics of their ontogeny. The indirect development of trochozoans has provoked discussion regarding the origin and evolution of marine larvae and is interesting from the perspective of phylogeny-ontogeny correspondence. While these phylo-onto correlations have an hourglass shape in Deuterostomia, Ecdysozoa, plants and even fungi, they have seldom been studied in Trochozoa, and even Lophotrochozoa. Here, we compared the ontogenetic transcriptomes of the Pacific oyster, Crassostrea gigas (Bivalvia, Mollusca), the Pacific abalone, Haliotis discus hannai (Gastropoda, Mollusca), and the sand worm Perinereis aibuhitensis (Polychaeta, Annelida) using several complementary phylotranscriptomic methods to examine their evolutionary trajectories. The results revealed the late trochophore stage as the phylotypic phase. However, this basic pattern is accompanied with increased use of new genes in the trochophore stages which marks specific adaptations of the larval body plans.

Background: Reduced-representation sequencing technology is widely used in genotyping for its economical and efficient features. A popular way to construct the reduced-representation sequencing libraries is to digest the genomic DNA with restriction enzymes. A key factor of this method is to determine the restriction enzyme(s). But there are few computer programs which can evaluate the usability of restriction enzymes in reduced-representation sequencing. SimRAD is an R package which can simulate the digestion of DNA sequence by restriction enzymes and return enzyme loci number as well as fragments number. But for linkage mapping analysis, enzyme loci distribution is also an important factor to evaluate the enzyme. For phylogenetic studies, comparison of the enzyme performance across multiple genomes is important. It is strongly needed to develop a simulation tool to implement these functions. Results: Here, we introduce a Perl module named RestrictionDigest with more functions and improved performance. It can analyze multiple genomes at one run and generate concise comparison of enzyme performance across the genomes. It can simulate single-enzyme digestion, double-enzyme digestion and size selection process and generate comprehensive information of the simulation including enzyme loci number, fragments number, sequences of the fragments, positions of restriction sites on the genome, the coverage of digested fragments on different genome regions and detailed fragments lengths distribution. Conclusions: RestrictionDigest is an easy-to-use Perl module with flexible parameter settings. With the help of the information produced by the module, researchers can easily determine the most appropriate enzymes to construct the reduced-representation libraries to meet their experimental requirements.

As a benthic filter feeder of estuaries, the immune system of oysters provides one of the best models for studying the genetic and molecular basis of the innate immune pathway in marine invertebrates and examining the influence of environmental factors on the immune system. Here, the molecular function of molluscan TANK-binding kinase-1 (TBK1) (which we named CgTBK1) was studied in the Pacific oyster, Crassostrea gigas. Compared with known TBK1 proteins in other model organisms, CgTBK1 contains a conserved S-TKc domain and a coiled coil domain at the N- and C-terminals but lacks an important ubiquitin domain. Quantitative real-time PCR analysis revealed that the expression level of CgTBK1 was ubiquitous in all selected tissues, with highest expression in the gills. CgTBK1 expression was significantly upregulated in response to infections with Vibrio alginolyticus, ostreid herpesvirus 1 (OsHV-1 reference strain and μvar), and polyinosinic:polycytidylic acid sodium salt, suggesting its broad function in immune response. Subcellular localization showed the presence of CgTBK1 in the cytoplasm of HeLa cells, suggesting its potential function as the signal transducer between the receptor and transcription factor. We further demonstrated that CgTBK1 interacted with CgSTING in HEK293T cells, providing evidence that CgTBK1 could be activated by direct binding to CgSTING. In summary, we characterized the TBK1 gene in C. gigas and demonstrated its role in the innate immune response to pathogen infections.

Alternative splicing (AS) is thought to enhance transcriptome diversity dramatically and play an important role in stress adaptation. While well studied in vertebrates, AS remains poorly understood in invertebrates. Here, we used high-throughput RNA-sequencing data to perform a genome-wide survey of AS in the Pacific oyster (Crassostrea gigas), an economically important mollusk that is cultivated worldwide. This analysis identified 8223 AS events corresponding to 4480 genes in the Pacific oyster, suggesting that about 16 % of oyster multiexonic genes undergo AS. We observed that a majority of the identified AS events were related to skipped exons (37.8 %). Then Gene Ontology analysis was conducted to analyze the function of the genes that undergo AS and the genes that produce more than five AS isoforms. After that, the expression of AS isoforms facing temperature, salinity, and air exposure challenge were examined. To validate our bioinformatic-predicted results and examine whether AS affects stress adaptation, we selected heat-shock protein 60 (HSP60) and HSP90 genes, both of which experience AS, for reverse transcription PCR (RT-PCR). We also performed quantitative real-time PCR (qRT-PCR) to determine the relative expression of each AS isoform among different stress adapted populations. Our study indicates that AS events are likely complex in the Pacific oyster and may be related to stress adaptation. These results will complement the predicted gene database of C. gigas and provide an invaluable resource for future functional genomic studies on molluscs.

Genomic and transcriptomic studies have revealed a sophisticated and powerful apoptosis regulation network in oyster, highlighting its adaptation to sessile life in a highly stressful intertidal environment. However, the functional molecular basis of apoptosis remains largely unexplored in oysters. In this study, we focused on a representative apoptotic gene encoding voltage-dependent anion channel 2 (VDAC2), a porin that abounds at the mitochondrial outer membrane. This is the first report on the identification and characterization of a VDAC gene in the Pacific oyster, Crassostrea gigas (CgVDAC2). The full length of CgVDAC2 was 1,738 bp with an open reading frame of 843 bp that encoded a protein of 281 amino acids. A four-element eukaryotic porin signature motif, a conserved ATP binding motif, and a VKAKV-like sequence were identified in the predicted CgVDAC2. Expression pattern analysis in different tissues and developmental stages as well as upon infection by ostreid herpesvirus 1 revealed the energy supply-related and immunity-related expression of CgVDAC2. CgVDAC2 was co-localized with mitochondria when it was transiently transfected into HeLa cells. Overexpression of CgVDAC2 in HEK293T cells suppressed the UV irradiation-induced apoptosis by inhibiting the pro-apoptotic function of CgBak. RNA interference induced reduction in CgVDAC2 expression showed a promoted apoptosis level upon UV light irradiation in hemocytes. The yeast two-hybrid system and co-immunoprecipitation assay indicated a direct interaction between CgVDAC2 and the pro-apoptotic protein CgBak. This study revealed the function of VDAC2 in oyster and provided new insights into its involvement in apoptosis modulation and host defense in mollusks.

To investigate effects of inbreeding on the fitness related traits in the hermaphroditic bay scallop Argopecten irradians irradians, six groups of offspring with inbreeding coefficients (F) ranging from 0.041 to 0.75 were created by self-fertilization and mass-mating using parents with different inbreeding history. Fitness-related traits of hatching success, larval survival, and size in shell length at days 10, 50, and 160 were studied and compared. All fitness-related traits were significantly affected by inbreeding levels. Compared with their counterpart control of mass-mating line, the line experienced successive two generations of self-fertilization produced significantly lower inbreeding depression for almost all tested traits than those only experienced one generation of self-fertilization. Regression analysis indicated that exponential decrease in both hatching success and larval survival with F (P

The effect of the smithsonite/water interface properties on the floatability of the mineral without and in the presence of sodium carbonate was examined through zeta potential measurements, microflotation tests, and the concentration of Zn2+ ions measurement, in the pH range from 7 to 11. The isoelectric point value of the mineral was achieved at pH 8.0, and the species Zn2+, OH−, HCO3−, CO32−, and H+, as well as the reabsorption of hydrolysis products would determine the smithsonite–solution interface properties. Smithsonite presents high floatability with sodium oleate (1.5 × 10−4 mol/L) between pH 7.0 and 8.0. Above pH 8.0, the smithsonite floatability decreases abruptly, and the polymeric zero-charged Zn(II) hydrolyzed species [ Zn ( OH ) 2 ( H 2 O ) 2 ] n 0 is proposed for depressing the floatability of smithsonite. With the sodium carbonate added into the solution, the isoelectric point value of the mineral was achieved at pH 8.2. The smithsonite interface, having more surface cation sites and zinc species in the Stern layer, gives rise to the floatability in the pH range from 7.0 to 8.7. Due to the formation of Zn(CO3)22−, the decrease of the concentration of the hydrolyzed species [ Zn ( OH ) 2 ( H 2 O ) 2 ] n 0 makes smithsonite more floatable than that without the Na2CO3 at 8.7

The heritability of larval and juvenile growth in natural and cultured populations of the Manila clam Ruditapes philippinarum was estimated using an unbalanced nested design and an artificial fertilization technique. A total of 33 full-sib families and 10 half-sib families were obtained from the natural population in Shihe (Dalian, Liaoning Province in the north-eastern part of China), whereas 11 half-sib families and 33 full-sib families were generated from the cultured population in Putian (Fujian Province in the south-eastern part of China). The offspring from each family were reared under the same hatchery and nursery conditions. Results from these studies led to estimates indicating a significantly greater influence due to the dam component compared with the sire component for both natural and cultured populations, which was mainly due to maternal effect. We found that the heritability estimates obtained from the intra-group correlation of sire half-sib were precise and unbiased. The narrow-sense heritabilities of shell length for the Manila clam in the natural population (NP) at larval (at the age of 9days) and juvenile (at the age of 30days) stages were 0.22 +/- 0.11 and 0.39 +/- 0.14, respectively, whereas those in the cultured population (CP) were 0.17 +/- 0.09 and 0.87 +/- 0.24 respectively. The heritabilities of both NP and CP at 3 days were not significantly different from zero, and were -0.03 for NP and -0.14 for CP. These results suggest that selection should be highly effective in Manila clam, and that selecting either a natural or a cultured population for producing faster growing larvae and juveniles should be successful. Selective breeding could thus be used to develop high-quality seed that would facilitate the development of a shorter culture cycle and higher yields.

In this study, we cloned and characterized the myostatin (MSTN) gene from a cultivated strain of bay scallop, Argopecten irradians, "Zhongkehong", and named it as the Ai-MSTN gene. The Ai-MSTN cDNA sequence was 3553 bp, contained three exons with 1380 bp in the open reading frame encoding 459 amino acids, and was 2014 bp longer than one previously reported. Analysis of its genomic structure and expression profiles indicated that the sequence of MSTN was 12473 bp (Genbank: JN684902) containing 3 exons and 2 introns, which was conserved with its vertebrate and invertebrate homologs. In silico analysis revealed that the promoter region of Ai-MSTN contained several muscle specific regulatory elements. The 3D structure of Ai-MSTN was similar to that of the known mouse MSTN. Ai-MSTN was expressed not only in the digestive gland, pericardium, gill, adductor muscle, gonad and mantle of the bay scallop, but also in its hemolymph, which was firstly reported in mollusks. These findings provide genomic and protein information and expression profiles of the Ai-MSTN gene and lay the groundwork for further investigations of its functional significance in this economically important sea food, bay scallops. (C) 2012 Elsevier B.V. All rights reserved.

Pacific abalone (Haliotis discus hannai Ino) aquaculture is a thriving industry in China. This study describes a novel submerged cage culture system for abalone rearing in Fujian, South China. The cage consisted of five vertical slots that were oriented perpendicular to the flow of water. The slots were separated by six vertically connected plastic plates for abalone attachment and shelter at the bottom of the cage. Experiment 1 was designed to determine the appropriate stocking density at the start of the abalone sea-based production cycle. Eight-month-old hatchery reared and size-graded juveniles were transferred to the sea-based culture system. For different stocking densities, shell length of juveniles obtained in this novel culture system on 2, 3.5 and 5months, respectively, was compared with shell lengths obtained in a traditionally multi-tier basket culture system. In Experiment 2, daily growth rates (DGRs) in shell length and biomass in terms of wet weight of 2-year-old abalones reared in cage and tiered basket culture systems were compared over a 6-month period. Results of Experiment 1 showed that growth of abalone in the cage culture system is density-dependent; the mean final shell length of juveniles obtained was 6.715.9% higher than in tiered baskets system even at the same initial stocking density. In Experiment 2, DGRs in shell length of 53.8378.38mday1 obtained in cage system were significantly higher than that in tiered baskets (P

We conducted an investigation of heavy metal concentrations in Manila clams (Ruditapes philippinarum) and surface sediments after the Dalian Port oil spill. Samples were collected from three mariculture zones (Jinshitan, Dalijia, and Pikou) along the Dalian coast. Heavy metal concentrations in R. philippinarum were consistent and ranked in decreasing order of Zn > Cu > As > Cr > Pb > Cd > Hg, while concentrations in surface sediments were ranked as Zn > Cr > Cu > Pb > As > Cd > Hg, respectively. Bioaccumulation of Zn, Cd, and Hg had obviously occurred in R. philippinarum. Statistically significant correlations (p < 0.05) between concentrations of Pb, Cd, and Hg in R. philippinarum and in surface sediments were observed. Except for Cr and As, heavy metal concentrations in R. philippinarum were well within the legal limits for human consumption.

Ferritin is a ubiquitous protein that plays an important role in iron storage and iron-withholding strategy of innate immunity. In this study, three genes encoding different ferritin subunits were cloned from bay scallop Argopecten irradians (AiFer1, AiFer2 and AiFer3) by rapid amplification of cDNA ends (RACE) approaches based on the known ESTs. The open reading frames of the three ferritins are of 516 bp, 522 bp and 519 bp, encoding 171,173 and 172 amino acids, respectively. All the AiFers contain a putative Iron Regulatory Element (IRE) in their 5'-untranslated regions. The deduced amino acid sequences of AiFers possess both the ferroxidase center of mammalian H ferritin and the iron nucleation site of mammalian L ferritin. Gene structure study revealed two distinct structured genes encoding a ferritin subunit (AiFer3). Quantitative real-time PCR analysis indicated the significant up-regulation of AiFers in hemocytes after challenged with Listonella anguillarum, though the magnitudes of AiFer1 and AiFer2 were much higher than that of AiFer3. Taken together, these results suggest that AiFers are likely to play roles in both iron storage and innate immune defense against microbial infections. (C) 2011 Elsevier Ltd. All rights reserved.

Crassostrea sikamea and C. ariakensis are two oysters from Asia that are sympatric and differ slightly in their environmental preference. They can hybridize in one direction, although the fertilization level and survival of hybrid larvae to spat are low. To understand the possible effects of salinity on cross-fertilization and the survival of hybrid larvae, we conducted hybridization experiments at four salinities (20, 25, 30 and 35 ppt). At all salinities, about 10% of C. sikamea eggs were fertilized by C. ariakensis sperm, while the reciprocal cross completely failed to fertilize. Survival of fertilized eggs to D-stage in the hybrid cross (C. sikamea female x C. ariakensis male, SA) was significantly (P

New analytical expressions for electrical potential distribution and surface charge density/surface potential relationship ( σ / ψ 0 ) are derived by approximately solving a Poisson–Boltzann equation describing the electrical potential distribution around a colloidal particle with planar, cylindrical, or spherical shape and immersed in a general electrolyte solution. Application scopes of these new expressions are limited to small reduced radius of the colloidal particle, and are complementary with those of previous expressions available in literature, which advisably apply for larger reduced radius without solitary exception. For the new expressions for σ / ψ 0 relationship, the accuracy is summarized as follows: in the case of the cylindrical colloidal particle and if top limit of a reduced surface potential is fixed as 5.5, top limits of a reduced colloidal radius are respectively not larger than 0.1, 0.034 and 0.008 for 3:1, 2:1 and 1:1 type electrolyte solutions; whereas in the case of the spherical colloidal particle and if top limit of the reduced surface potential is fixed as 6.5, top limits of the reduced colloidal radius are, respectively, not larger than 0.49, 0.39, and 0.29 for 3:1, 2:1 and 1:1 type electrolyte solutions. In the case of the planar colloidal particle immersed in a general electrolyte solution, an exact expression for ( σ / ψ 0 ) relationship is obtained.

For genetic analysis and linkage mapping of bay scallop (Argopecten irradians), a set of 120 novel simple sequence repeat markers were developed from microsatellite-enriched libraries and expressed sequence tags. An inter-subspecies hybrid bay scallop family (CC5) of 46 progeny was analyzed as the reference population to confirm polymorphism and test the segregation patterns of these loci. A total of 104 microsatellite markers were polymorphic in the reference family, among which 36 in female, 28 in male, and 40 in both parents, respectively. Linkage analysis allowed mapping these markers to 15 linkage groups, which is close to the haploid chromosome number of bay scallop (n = 16). Analysis of the 40 markers segregating in both parents showed a higher recombination rate in the female parent, with the average of female-to-male recombination ratio of 1.09:1 between linked pairs of markers. When null alleles were considered, there were 17 loci showing segregation distortion at the 5% significance level using the chi-square test. The microsatellite markers developed in this study provide a useful resource for future linkage mapping and quantitative loci analysis in A. irradians.

The influence of surface dissolution on flotation separation of fine ilmenite from titanaugite was investigated through infrared spectroscopic (FT-IR) analysis and X-ray photoelectron spectroscopy (XPS) test. The results show that surface dissolution in weak acid solution is helpful to enlarge the floatability difference between ilmenite and titanaugite. In weak acidic solution, as sodium oleate mainly interacts with Fe which results in ilmenite flotation, and surface dissolution is beneficial to its oxidation, the floatability of ilmenite after surface dissolution is increased; meanwhile, sodium oleate interacts with Ca and Mg which results in titanaugite flotation, and the quantities of Ca and Mg on the surface of titanautite are decreased due to the surface dissolution, so the floatability of titanaugite after surface dissolution is depressed. For an ilmenite ore obtained from Panzhihua with TiO2 grade of 8.41%, flotation after surface dissolution treatment could increase TiO2 grade of rough concentrate from 26.7% to 31.73%.

Bindin is a major protein packaged as insoluble granules in sperm acrosomes. It may be responsible for species-specific recognition and binding of sperm to a glycoprotein receptor on the surface of eggs. The putative functional region of bindin is a fucose-binding lectin (F-lectin) domain. We cloned a novel bindin gene from the Kumamoto oyster Crassostrea sikamea by 3` and 5` RACE. The full-length cDNA of C. sikamea bindin was 1,134 bp, with a 774-bp open reading frame encoding 257 amino acids. The deduced amino acid sequence contained a putative signal peptide of 24 amino acids. The length of the bindin genomic DNA we obtained was 5,353 bp, containing 4 exons and 3 introns. We studied F-lectin repeats of the bindin gene from 3 species of Crassostrea to detect the relationship between them and found 11, 2, and 5 haplotypes from C. sikamea, Crassostrea angulata, and Crassostrea gigas, respectively. Phylogenetic trees showed a closer relationship between C. gigas and C. angulata than between C. gigas and C. sikamea. Two haplotypes of C. angulata fell into 2 different clades, one in the C. gigas clade and the other in the C. sikamea clade. Deduced amino acid sequences and hydropathy plots were considerably similar among these species, indicating the close resemblance in the tertiary structure of bindin proteins. To test for selection, we compared the number of nonsynonymous substitutions and synonymous substitutions per nucleotide site among the 18 F-lectin haplotypes. This analysis identified 7 positively selected positions (P > 95%) among 18 haplotypes from the 3 species, all located on the F-lectin binding face around the 3 residues that are specifically involved in binding fucose (H37. R64, and R70). We hypothesize that these 7 clustered amino acids may be related to species recognition and thus could impose selective pressure on bindin divergence.

Toll-like receptor (TLR) signaling pathway was an important and evolutionarily conserved innate immune pathway. Evolutionary lineage of this pathway in the Lophotrochozoans is still less understood. In this study, we cloned a novel TLR, a key component of TLR pathway, from Crassostrea gigas, and named it CgToll-1. The 4343 base pairs full-length cDNA was assembled with the 3' and 5' RACE (rapid amplification of cDNA ends) PCR results, and containing a 3540 bp open reading frame, which encoding a putative TLR protein of 1179 amino acid residues. Real-time reverse transcription polymerase chain reaction analysis revealed that the highest CgToll-1 expression level was in hemolymph, and the expression pattern in hemolymph dramatically increased in the presence of bacteria Vibrio anguillarum. Furthermore, TLR pathway core genes of mollusks were searched and compared with model invertebrates. Phylogenetic trees of two downstream genes (I kappa B, Rel) showed that mollusks genes were closer to Drosophila melanogaster than Strongylocentrotus purpuratus, while three upstream genes (MyD88, IRAK, TRAF6) showed the opposite propensity. We have also detected that these two downstream genes were significantly more conservative than the three upstream genes based on amino acid sequence alignment. We found no significant difference between the codon usage biases of TLR pathway genes. This study suggests that CgToll-1 was a constitutive and inducible protein and thus could play an important role in the immune responses against bacterium infection. Besides, comparative analysis of TLR pathway showed that gene loss and divergence might exist during evolution in invertebrate. (C) 2010 Elsevier Ltd. All rights reserved.

Native oyster reefs once dominated many estuaries, ecologically and economically. Centuries of resource extraction exacerbated by coastal degradation have pushed oyster reefs to the brink of functional extinction worldwide. We examined the condition of oyster reefs across 144 bays and 44 ecoregions; our comparisons of past with present abundances indicate that more than 90% of them have been lost in bays (70%) and eco regions (63%). In many bays, more than 99% of oyster reefs have been lost and are functionally extinct. Overall, we estimate that 85% of oyster reefs have been lost globally. Most of the world's remaining wild capture of native oysters (> 75%) comes from just five ecoregions in North America, yet the condition of reefs. in these ecoregions is poor at best, except in the Gulf of Mexico. We identify many cost-effective solutions for conservation, restoration, and the management of fisheries and nonnative species that could reverse these oyster losses and restore reef ecosystem services.

The effect of sodium hexametaphosphate (SHMP) on the separation of serpentine from pyrite and its mechanism were studied systematically through flotation tests, sedimentation tests, surface dissolution, ζ potential tests, adsorption measurements, and infrared spectroscopic analyses. The results show that the SHMP could significantly reduce the adverse effect of serpentine on the flotation of pyrite and make the mixed sample of pyrite and serpentine more disperse in the alkaline condition, thus improve the adsorption of xanthate on pyrite. The action mechanism of the SHMP is that it lowers the pH value at the isoelectric point of serpentine and enhances the negative charge through the dissolution of magnesium from the surface of serpentine and adsorbing on the surface of serpentine. It changes the total interaction energy between serpentine and pyrite from gravitational potential energy to repulse potential energy, according to the calculation of the EDLVO theory.

Molluscs are an extraordinarily diverse group of animals and to discriminate them based on one molecular marker/gene is very difficult because of the too fast or slow rate of nucleotide substitution. In the study, the tropomyosin cds (coding sequences) of 43 animal species were analyzed, the results of which suggested that the tropomyosin gene was a nice marker gene to phylogenetic analysis of molluscs, even for all the studied animals. In addition, InDels (insertions and deletions) in tropomyosin cds of turbo cornutus were also studied and one segment repeat, which probably happened recently and was of functional importance, was found.

To resolve the taxonomic status of a small cupped oyster from southern China, we collected and sequenced oysters from 20 sites in China along with sister species from other parts of the world. A total of 187 oysters were sequenced for 2 fragments belonging to the mitochondrial 16S rRNA and cytochrome oxidase I (COI) genes. Sequence analyses of both gene fragments indicate that the small cupped oyster from southern China is the same species as Crassostrea angulata from Portugal. C. angulata has a wide distribution in southern China, ranging from Zhejiang to Hainan, with the Yangtze River separating it from Crassostrea gigas in northern China. The wide distribution and high gene diversity in China support the suggestion of a historical transfer of C. angulata from China to Europe. Sequence divergence between C. angulata and C. gigas, 1.05–1.32% in 16S and 2.22–3.37% in COI, is higher than that between the most divergent populations of a Crassostrea species (C. virginica, 0.51% in 16S and 2.04–2.22%...

In order to improve the yield of bay scallop Argopecten irradians by exploiting geographic subspecies heterosis, crosses between and within two subspecies, the northern A. i. irradians (Lamarck) and the southern A. i. concentricus (Say), were created and the offspring were cultured under the same environmental conditions. The two parental populations were collected from Bohai Bay in northern China and Beibu Bay in southern China, which were distinct in particular shell colours. The results indicated that the shell colour of bay scallop was inheritable and could be used as a morphological mark to distinguish hybrid and purebred individuals. At harvest, hybrid offspring always produced a significantly higher yield than purebred offspring. Positive heterosis was achieved for shell length, shell height, shell width, total weight and adductor weight, which was 5.02, 5.22, 3.88, 7.53 and 9.47 respectively. Hybrid gain was 10.86% for shell length, 10.48% for shell height, 9.77% for shell width, 34.90% for total weight and 41.69% for adductor weight, respectively, and all were significantly > 5%. The present study reveals that it is effective for improving yield by hybridization between different geographic subspecies in the bay scallop.

We conducted a complete diallel cross among three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino to determine the heterosis and the combining ability of growth traits at the spat stage. The three populations were collected from Qingdao (Q) and Dalian (D) in China, and Miyagi (M) in Japan. We measured the shell length, shell width, and total weight. The magnitude of the general combining ability (GCA) variance was more pronounced than the specific combining ability (SCA) variance, which is evidenced by both the ratio of the genetic component in total variation and the GCA/SCA values. The component variances of GCA and SCA were significant for all three traits (P

The shell length, height, and width, live body weight, and edible tissue weight of Manila clam of 1, 2, and 3 years of age were measured, and their correlation coefficients were calculated. The shell morphological traits were used as independent variables, and live body weight or edible tissue weigh used as a dependent variable for calculating the path coefficients, correlation index and determination coefficients. The results showed that the correlation coefficients between each shell morphological trait and the live body weight or edible tissue weight were all highly significant ( P R 2 ) of morphological traits against the live body weight of clams of all ages and edible tissue weight of 1-year-old clams were larger than 0.85, but R 2 of morphological traits against the edible tissue weight of 2- and 3-year-old clams was smaller than 0.85, indicating that some other factors might be associated with the edible tissue weight of 2- and 3-year-old clams. Multiple regression equations were obtained to estimate shell length X 1 (cm), shell height X 2 (cm), shell width X 3 (cm) against live body weight Y (g), edible tissue weight Z (g): for 1-year-old clams: Y = −4.317 + 0.18 X 1 + 0.147 X 2 , ( X 1 X 2 Z = −1.011 + 0.095 X 2 , ( X 2 Y = −15.119 + 0.249 X 1 + 0.176 X 2 + 0.688 X 3 , ( X 1 X 3 Z = −4.248 + 0.198 X 1 , ( X 1 X 3 Y = −25.013 + 0.415 X 1 + 1.184 X 3 , ( X 1 X 3 Z = −7.082 + 0.119 X 1 + 0.332 X 3 , ( X 1 X 3

In order to improve the production and accurately estimate response to selection, divergent selection for growth in shell height was conducted in a cultured population of the Japanese scallop Patinopecten yessoensis. Applying the same selection intensity +/- 1.756 in upward and downward directions, three groups including two selected groups of Fast and Slow and one non-selected Control group were created, which were reared under the same environmental conditions at any stage. Differences always significantly existed among the three groups (P Control > Slow. The average standardized response to selection (SR), realized heritability (h(R)2) and genetic gain (GG) was 0.473%, 0.269% and 7.85% for the Fast group and 0.381%, 0.217% and 6.60% for the Slow group respectively. Moreover, significant differences (P < 0.05) were detected between the fast and the slow lines in both SR and h(R)2, providing evidence for an asymmetric response in two directions. Performance in shell height is improved by 7.85% in the fast line after one generation selection, suggesting that mass selection for faster growth in a cultured population of the Japanese scallop is effective.

A study was conducted to investigate the impact of starvation on different sizes of Manila clam Ruditapes philippinarum (0.66 ± 0.11, 2.12 ± 0.38, and 11.65 ± 0.84 mm in shell length, respectively) in the summer of 2008. Different size clams were starved for 7, 15, 30, 45, and 60 d, respectively, and followed by refeeding for 30 d. During the study, the water temperature ranged 26.2–28.4 °C, salinity 22–24‰, and pH 7.80–8.12. Compensatory growth occurred in the smallest size-group after 7 and 15 d of starvation, respectively. The point-of-no-return (PNR50) was determined to be 18.7 d. However, no compensatory growth was noted in the medium size-group, and the PNR50 for this group was 25.2 d. The complete compensatory growth was observed for the largest size-group following food depravation for 7 and 30 d, respectively. In the same group, over-compensatory growth occurred 15 d post-starvation. The PNR50 for the largest size-group was 46.3 d. The survival rate of different groups decreased as the starvation time prolonged. To discuss the change in body biochemical composition of individuals in the process of starvation and refeeding, the biochemical composition of the largest group individuals at different stages was determined. There were no significant differences in moisture and ash concentrations of the largest size-group during starvation and refeeding (P > 0.05). The relative body protein content increased as the starvation period prolonged and the level returned to normal after refeeding. The lipid content of the clam at the end of starvation was significantly lower than the initial level (P

Mineralogical analyses of the saprolitic laterite material have been characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal analysis, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). Results showed that the saprolitic laterite material consists mainly of nickel-substituted lizardite showing the pebble-like morphology and traces of magnetite and phlogopite. Leaching results showed that as much as 84.8% nickel could be leached under the experimental conditions of 10% (v/v) H 2 SO 4 , 90 °C reaction temperature, leached within 5 min, particle size d 50 = 25 μm, stirring at 500 rpm and liquid to solid ratio 3:1. The kinetics of nickel and magnesium leaching from the saprolitic laterite material have been investigated in a mechanically stirred reactor and the activation energies were determined to be 53.9 kJ mol −1 for nickel and 59.4 kJ mol −1 for magnesium respectively, which are characteristic for a chemical reaction controlled process. The similarity of the activation energies of nickel and magnesium leaching from the saprolitic laterite material by sulphuric acid means that nickel in lizardite is loosely bound within the octahedral layer and almost all of the nickel could be leached simultaneously with magnesium but without complete decomposition of the silicate structure.

Through leaching from residue directly and leaching after a roasting treatment, respectively, the experimental research on sulfuric leaching of vanadium from residue of stone coal that came from power generation was conducted. Factors which influence the leaching of vanadium such as concentration of sulfuric acid, leaching temperature, leaching time and liquid-to-solid ratio were investigated in both processes. In the process of direct leaching, to achieve a leaching rate of 74.49%, H 2 SO 4 concentration of up to 5.4%, leaching temperature of 90 °C and leaching time of 8 h were necessary reaction factors. The results show that after a roasting treatment at the optimum condition of 950 °C at 1 h, 76.88% vanadium can be leached under the experimental condition of 0.45% of H 2 SO 4 , 30 °C for 1 h with a liquid-to-solid ratio of 2 mL/g. Leaching after an oxidation roasting treatment is an efficient way to leach vanadium from the residue of stone coal, which has some advantages, such as high recovery, low economic cost and less impurities in leaching solution.

The effects of reaction time, reaction temperature, stirring speed and flowrate of CO2 gas on desilication rate and loss rate of vanadium were studied. The results indicated that desilication rate increases with the increase of flowrate of CO2 gas and reaction time. Reaction temperature and stirring speed have little effect on desilication rate, while influence the loss rate of vanadium significantly. Under the condition of reaction time of 2 h, reaction temperature of 95 °C, stirring speed of 180 r/min, flowrate of CO2 gas of 60 mL/min and aging time of 2 h, desilication rate is more than 96% and the loss rate of vanadium is about 4.24%. The residue of desilication process can be processed for silicon materials, such as high-grade hydrated silica, which commonly known as white carbon black. In addition, with this carbonation method, leaching regents NaOH can be recycled by simple treatments.

The effects of starvation on larval growth, survival, and metamorphosis of Manila clam Ruditapes philippinarum at the temperature of 19.6–21.6 °C, the salinity of 34‰ and pH of 8.0 were investigated from May 18 to July 18, 2006. In this study, the early, middle and late umbo-veliger larvae with the shell lengths of 100, 140, and 190 μm were subject to temporary food deprivation for up to 4.5, 20, and 25d at 0.5, 4, 5d intervals, followed by refeeding for the remaining of a 24, 20, 25d period, respectively. The results suggested that the larvae should have shown considerable tolerance to starvation due to their endogenous and exterior nutrition material, for larvae and time to the point-of-no-return (PNR: the threshold point during starvation after which larvae could no longer metamorphose even if food is provided) were calculated to be 4.25, 17.54, and 22.17d. As the starvation period prolonged, the mean shell length of larvae starved got close to constants at 1.5, 4, and 15d after starvation, which were different for larvae at different stages when starvation began, survival of larvae decreased, and was lower in treatments starved earlier in development than those starved later, for the early, middle and late umbo-veliger larvae, after 4.5, 20 and 25d of starvation period, few larvaes were alive. After starvation period, the alive larvaes were able to metamorphose and had a capability of compensatory growth when refeeding was given. Starvation not only affected metamorphosis rate, but also caused the delay in the time to metamorphosis and the decrease in the metamorphosed sizes. For example, for the continuously-fed larvae, duration to metamorphosis was 20.7d, for larvae with a size of 100-μm starved for up to 4d, larvae with a size of 140-μm starved for up to 16d, larvae with a size of 190-μm starved for up to 20d, duration to metamorphosis were 29.7, 31.7, and 37.7d, the delay in duration to metamorphosis were 9, 11, and 17d, respectively. Furthermore, importance of nutrition material for maintaining larval survival during starvation and the compensatory growth on larvae at the same feeding time were discussed.

TO understand possible reproductive interaction between Crassostrea ariakensis (Fujita, 1913) and C. sikamea (Amemiya, 1928), which coexist ill estuaries of China and Japan, we conducted 2 X 2 factorial crosses between the two species. Asymmetry in fertilization success was observed where C. sikamea eggs can be fertilized be C. ariakensis the receprocal cross resulted in no fertilization. Fertilization Success ill C.sikamea female X C. ariakemvis male (SA) crosses was lower than that in the two intraspecific crosses and produced larvae that had similar growth the rate as their maternal species during the first nine days because of maternal effects. After that, genome incompatibility casted negative effects on the growth and survival of the hybrid larvae. Most hybrid larvae died during metamorphosis. but a small number of spat survived. Genetic analysis revealed that the survived SA spat contained DNA from both species and were the hybried. This study demonstrates that hybridization between C. ariakensis and C. sikamea is possible in one direction.

Superoxide dismutases are an ubiquitous family of enzymes that function to efficiently catalyze the dismutation of superoxide anions. Two unique and highly compartmentalized bay scallop Argopecten irradians superoxide dismutases: MnSOD and ecCuZnSOD, have been molecularly characterized in our previous study. To complete characterize the SOD family in A. irradians, a novel intracellular copper/zinc SOD from the A. irradians (Ai-icCuZnSOD) was obtained and characterized. The full-length cDNA of Ai-icCuZnSOD was 1047 bp with a 459 bp open reading frame encoding 152 amino acids. The genomic length of the Ai-icCuZnSOD gene was about 4279 bp containing 4 exons and 3 introns. The promoter region containing many putative transcription factor binding sites were analyzed. Furthermore, quantitative reverse transcriptase real-time PCR (qRT-PCR) analysis indicated that the highest expression of the Ai-icCuZnSOD was detected in gill and the expression profiles in hemocytes of bay scallops challenged with bacteria Vibrio anguillarum and lipopolysaccharide (LPS) were different. The result presented an increased expression after injection with LPS whereas no significant changes were observed after V. anguillarum injection. A fusion protein containing Ai-icCuZnSOD was produced in vitro. The rAi-icCuZnSOD is a stable enzyme, retaining more than 80% of its activity between 10 and 60 degrees C and keeping above 88% of its activity at pH values between 5.8 and 9. Ai-icCuZnSOD is more stable under alkaline than acidic conditions. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.

Extracellular superoxide dismutase (ECSOD) is a major extracellular antioxidant enzyme that protects organs from damage by reactive oxygen species (ROS). We cloned a novel ECSOD from the bay scallop Argopecten irradians (AiECSOD) by 3' and 5' RACE. The full-length cDNA of AiECSOD was 893 bp with a 657 bp open reading frame encoding 218 amino acids. The deduced amino acid sequence contained a putative signal peptide of 20 amino acids, and sequence comparison showed that AiECSOD had low degree of homology to ECSODs of other organisms. The genomic length of the AiECSOD gene was about 5276 bp containing five exons and six introns. The promoter region contained many putative transcription factor binding sites such as c-Myb, Oct-1, Sp1, Kruppel-like, c-ETS, NF kappa B, GATA-1, AP-1, and Ubx binding sites. Furthermore, tissue-specific expressions of AiECSOD and temporal expressions of AiECSOD in haemocytes of bay scallops challenged with bacteria Vibrio anguillarum were quantified using qRT-PCR. High levels of expression were detected in haemocytes, but not in gonad and mantle. The expression of AiECSOD reached the highest level at 12 h post-injection with V. anguillarum and then returned to normal between 24 h and 48 h post-injection. These results indicated that AiECSOD was an inducible protein and that it may play an important role in the immune responses against V anguillarum. Crown Copyright (C) 2008 Published by Elsevier Ltd. All rights reserved.

During winter months, a novel overwintering mode of transferring juvenile abalones to open seawaters in southern China rather than keeping them in closed land-based nursery systems in northern China is a popular practice. The initial size, stocking density and sorting are among the first considerations when establishing an abalone culture system. This study aimed to investigate the effects of these factors on the growth of juvenile Pacific abalone, Haliotis discus hannai Ino, during overwintering. Juvenile abalones were reared in multi-tier basket form for overwintering in open seawaters in southern China for 106 days. The daily growth rates (DGRs) in the shell length of all experimental groups ranged from 67.08 to 135.75 mu m day(-1), while the specific growth rates (SGRs) were 0.2447-0.3259% day(-1). Variance analysis indicated that both DGRs and SGRs in shell length were significantly affected by the initial body size and stocking density. Furthermore, the effects of stocking density on DGRs and SGRs varied with the initial size. However, sorting abalones according to their initial sizes may not be necessary in practice as sorting did not alter growth significantly at all densities in this study. Factors potentially affecting abalone growth such as genetic control and intraspecific competition were discussed.

Sulfuric acid leaching process was applied to extract nickel from roasting-dissolving residue of a spent catalyst, the effect of different parameters on nickel extraction was investigated by leaching experiments, and the leaching kinetics of nickel was analyzed. The experimental results indicate that the effects of particle size and sulfuric acid concentration on the nickel extraction are remarkable; the effect of reaction temperature is mild; while the effect of stirring speed in the range of 400–1 200 r/min is negligible. Decreasing particle size or increasing sulfuric acid concentration and reaction temperature, the nickel extraction efficiency is improved. 93.5% of nickel in residue is extracted under suitable leaching conditions, including particle size (0.074–0.100) mm, sulfuric acid concentration 30% (mass fraction), temperature 80 °C, reaction time 180 min, mass ratio of liquid to solid 10 and stirring speed 800 r/min. The leaching kinetics analyses shows that the reaction rate of leaching process is controlled by diffusion through the product layer, and the calculated activation energy of 15.8 kJ/mol is characteristic for a diffusion controlled process.

Molluscan shells may display a variety of colors, which formation, inheritance, and evolutionary significance are not Well understood. Here we report a new variant of the Pacific abalone Haliotis discus hannai that displays a novel orange shell coloration (O-type) that is clearly distinguishable from the Wild green-shelled abalone (G-type). Controlled mating experiments between O- and G-type abalones demonstrated apparent Mendelian segregations (1:1 or 3:1) in shell colors in F(2) families, which support the notion that the O- and G-types are under strict genetic control at a single locus With a recessive o (for orange shell) allele and a dominant G (for green shell) allele. Feeding with different diets caused modifications of shell color within each genotype, ranging from orange to yellow for O-type and green to dark-brown for the G-type, without affecting the distinction between genotypes. A previously described bluish-purple (B-type) shell color was found in one of the putative oo X oG crosses, suggesting that the B-type may be it recessive allele belonging to the same locus. The new O-type variant had no effect on the growth of Pacific abalone on the early seed-stage. This Study demonstrates that shell color in Pacific abalone is subject to genetic control as well as dietary modification, and the latter probably offers selective advantages in camouflage and predator avoidance.

Mineralogical analyses of a saprolitic laterite has been studied by particle size analysis, thermal analysis, X-ray fluorescence (XRF), scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The results showed that the saprolitic laterite consists mainly of nickel-substituted lizardite revealing the elliptic morphology. The fast rate of nickel dissolution from this saprolitic laterite by sulphuric acid at atmospheric pressure has been investigated at different temperatures. As much as 91.3% Ni could be leached after 12 min with 10%(v/v) H 2 SO 4 , particle size d 50 = 25 µm, reaction temperature 90 °C, stirring at 500 rpm and liquid to solid ratio 3:1. Extending the leaching time results in a loss of nickel to the residue. To prevent the re-adsorption of dissolved nickel by re-precipitated amorphous silica, it may be appropriate to leach saprolitic laterites at a lower temperature for a longer time and maintain high free acidity.

Microsatellites were screened in a backcross family of the Pacific oyster, Crassostrea gigas. Fifteen microsatellite loci were distinguishable and polymorphic with 6 types of allele-combinations. Null alleles were detected in 46.7% of loci, accounting for 11.7% of the total alleles. Four loci did not segregate in Mendelian Ratios. Three linkage groups were identified among 7 of the 15 segregating loci. Fluorescence-based automated capillary electrophoresis (ABI 310 Genetic Analyzer) that used to detect the microsatellite loci, has been proved a fast, precise, and reliable method in microsatellite genotyping.

This paper examines the effect of inbreeding level of population on the magnitude of inbreeding depression expressed by comparing them between two cultured populations (A and B) in the hermaphroditic animal of the bay scallop Argopecten irradians irradians. Population A is expected to have less genetic variations and higher inbreeding level due to longer cultured history (20 generations) and less "ancestral" individuals (26 individuals) than population B due to shorter cultured history (4 generations) and more "ancestral" individuals (406 individuals). Two groups within each population were produced, one using self-fertilization and one using mass-mating within the same population. Selfed offspring (AS and BS) from two populations both had lower fitness components than their mass-mated counterparts (AM and BM) and exhibited inbreeding depression for all examined traits, e.g. lower hatching, less viability and slower growth, indicating that inbreeding depression is a common feature in this animal. Fitness components in all traits of offspring from population A significantly differed those from population B and the magnitude of inbreeding depression for all traits in population A with higher inbreeding level was significantly smaller than that in population B with lower inbreeding level, indicating that both fitness components and magnitude of inbreeding depression were significantly affected by inbreeding level of populations and genetic load harbored in population A may be partially purged through inbreeding. Moreover, the magnitude of inbreeding depression in the two populations both varied among traits and life history stages. The present results support the partial-dominance hypothesis of inbreeding depression. (C) 2008 Elsevier B.V. All rights reserved.

Oysters are commonly found on rocky shores along China's northern coast, although there is considerable confusion as to what species they are. To determine the taxonomic status of these oysters, we collected specimens from nine locations north of the Yangtze River and conducted genetic identification using DNA sequences. Fragments from three genes, mitochondrial 16S rRNA, mitochondrial cytochrome oxidase I (COI), and nuclear 28S rRNA, were sequenced in six oysters from each of the nine sites. Phylogenetic analysis of all three gene fragments clearly demonstrated that the small oysters commonly found on intertidal rocks in north China are Crassostrea gigas (Thunberg, 1793), not C. plicatula (the zhe oyster) as widely assumed. Their small size and irregular shell characteristics are reflections of the stressful intertidal environment they live in and not reliable characters for classification. Our study confirms that the oysters from Weifang, referred to as Jinjiang oysters or C. rivularis (Gould, ...

A base population of the bay scallop, Argopecten irradians irradians Lamarck, was produced by crossing two cultured bay scallop populations. After 1 year of rearing, the top 10% truncation selection of the top 10% (i=1.755) was carried out in the base population of about 1300 adults. A control parental group with a an identical number to the select parental group was randomly selected from the entire population before isolation of the select parental group. The result showed that, at the larval stage, the growth rate of larvae in the selected line was significantly higher than that of the control (P < 0.05), and that the genetic gain was 6.78%. Owing to the lower density of control at the spat stage, the mean shell length of the control line was larger than that of the select line at day 100. When the same density was adjusted between two lines in the grow-out stage (from day 100 to 160), the daily growth rate of the selected line was significantly higher than that of the control line (P < 0.05). Survival of the select line was significantly larger than that of the control line in the grow-out stage. In conclusion, the results obtained from this experiment indicate that selective breeding from a base population with a high genetic diversity established by mass spawning between different populations appears to be a promising method of genetic improvement in bay scallop, A. irradians irradians Lamarck.

We constructed genetic linkage maps for the bay scallop Argopecten irradians using AFLP and microsatellite markers and conducted composite interval mapping (CIM) of body-size-related traits. Three hundred seventeen AFLP and 10 microsatellite markers were used for map construction. The female parent map contained 120 markers in 15 linkage groups, spanning 479.6 cM with an average interval of 7.0 cM. The male parent map had 190 markers in 17 linkage groups, covering 883.8 cM at 7.2 cM per marker. The observed coverage was 70.4% for the female and 81.1% for the male map. Markers that were distorted toward the same direction were closely linked to each other on the genetic maps, suggesting the presence of genes important for survival. Six size-related traits, shell length, shell height, shell width, total weight, soft tissue weight, and shell weight, were measured for QTL mapping. The size data were significantly correlated with each other. We subjected the data, log transformed firstly, to a principle component analysis and use the first principle component for QTL mapping. CIM analysis revealed one significant QTL (LOD=2.69, 1000 permutation, P