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Crassostrea Gigas (crassostrea + giga)
Kinds of Crassostrea Gigas Selected AbstractsEffects of exposure to oxamyl, carbofuran, dichlorvos, and lindane on acetylcholinesterase activity in the gills of the Pacific oyster Crassostrea gigasENVIRONMENTAL TOXICOLOGY, Issue 4 2010Gerardo A. Anguiano Abstract Acetylcholinesterase (AChE) activity has been used to test the exposure of mollusk bivalves to pesticides and other pollutants. The Pacific oyster Crassostrea gigas is a species with a worldwide distribution, and it has a high commercial value. The use of this species as a bioindicator in the marine environment, and the use of measurements of AChE activity in tissues of C. gigas require prior evaluation of organisms exposed to several toxic compounds in the laboratory. In our study, the effects of pesticides on AChE activity in the gills and mantle tissues of C. gigas were analyzed by exposing animals to organophosphate (dichlorvos), carbamate (carbofuran and oxamyl), and organochlorine (lindane) pesticides. Adult Pacific oysters were exposed to several concentrations (0.1,200 ,M) of dichlorvos, carbofuran, and oxamyl for 96 h, and lindane (1.0 and 2.5 ,M) was applied for 12 days. In gill tissues, all pesticides analyzed caused a decrease in AChE activity when compared to the control unexposed group. The mean inhibition concentration (IC50) values were determined for dichlorvos, carbofuran, and oxamyl pesticides. Dichlorvos had the highest toxic effect, with an IC50 of 1.08 ,M; lesser effects were caused by oxamyl and carbofuran, with IC50s of 1.67 and 3.03 ,M, respectively. This study reports the effects of pesticides with several chemical structures and validates measurement of AChE activity in the gill tissues of C. gigas for use in environmental evaluations or food quality tests. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 327,332, 2010. [source] Mobility and potential toxicity of sediment-bound metals in a tidal estuaryENVIRONMENTAL TOXICOLOGY, Issue 4 2005O. Geffard Abstract Sediment toxicity in the Gironde Estuary, France, a site contaminated by such trace metals as Cd, Cu, and Zn, was examined monthly from March to October 1997, using concurrently geochemical procedures to assess the mobility of contaminants and ecotoxicity tests with invertebrate larvae (the oyster Crassostrea gigas, the sea urchin Paracentrotus lividus, and the copepod Tigriopus brevicornis). Higher mobility of Cd than of Cu and Zn was shown by desorption tests. Both the gross concentrations of Cu and Zn in the sediment and the mobility of these metals showed a temporal evolution, and changes in the toxicity of the sediment to invertebrate larvae generally were observed concomitantly. Little damage was registered in the spring, and greater damage was found in the summer and fall. Positive correlations were shown between mortality in copepods or abnormalities in oyster larvae with the quantities of metals remobilized from sediment at pH 4. On the contrary, no clear temporal trend was shown for total PAH levels in sediment. These correlations and previous toxicological data suggest that sediment-bound metals, particularly Cu and Zn, possibly play a role in biological responses. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 407,417, 2005. [source] Use of Caged Nucella Lapillus and Crassostrea Gigas to Monitor Tributyltin-Induced Bioeffects in Irish Coastal Waters,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2009Michelle Giltrap Abstract Caging studies have been previously reported to be useful for providing valuable information on biological effects of mollusks over short periods of time where resident species are absent. The degree of imposex in caged dog whelk (Nucella lapillus), was measured using the vas deferens sequence index (VSDI) and the Relative Penis Size Index (RPSI) and the extent of shell thickening in caged Pacific oyster (Crassostrea gigas) was investigated at t = 0 and t = 18 weeks. Nucella lapillus, when provided with mussels as a food source at the control site at Omey Island on the west Irish coast, did not demonstrate imposex features, whereas those transplanted to port areas did. Dunmore East exhibited the highest level of imposex (3.25 VDSI and 2.37 RPSI). Shell thickening was evident in C. gigas transplanted to Dunmore East, with low effects evident at the control location, Omey Island, and Dublin Bay at t = 18 weeks. Dry weight whole-body concentrations of organotins were most elevated in all species held at Dunmore East compared with other locations. Greatest ,15N and ,13C enrichment was observed within the tissues of the predatory N. lapillus in all three test sites. Increased assimilation in the Dublin Bay oysters might have been influenced by the presence of more nutrients at this location. Surficial sediment organotin levels were most elevated in the Dunmore East <2-mm fraction (22,707 ,g tributyltin/kg dry weight), whereas low organotin levels were determined from Dublin and Omey Island sediments. The valuable application of cost-effective caging techniques to deliver integrated biological effects and chemical measurements in the absence of resident gastropod populations in potential organotin/tributyltin hotspot locations is discussed. [source] Butyltin accumulation in two marine bivalves along a pollution gradient,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2008Chuan-Ho Tang Abstract In the present study, we describe a field survey regarding the effect of ambient water conditions in the accumulation of tributyltin (TBT) and its metabolites in green mussels (Perna viridis) and Pacific oysters (Crassostrea gigas). The results showed that following the changes in TBT pollution levels, the accumulation of butyltins exhibited clear differences between oysters and mussels. The ratio of TBT to total butyltin (TBT:,BT) decreased from 0.87 to 0.31 with increasing TBT burdens in the oysters. This status suggests that following the increases of TBT burdens, the metabolic rates of TBT were clearly enhanced in oysters; however, this phenomenon was not shown in mussels. The TBT:,BT remained relatively constant at approximately 0.7 in the mussels despite the TBT burdens. Because of this phenomenon, the opposite status of different TBT burdens between oysters and mussels were present at different TBT pollution levels. These observations may provide valuable insight when evaluating or comparing TBT pollution in the environment using oysters and/or mussels as bioindicators. [source] Subchronic organismal toxicity, cytotoxicity, genotoxicity, and feeding response of pacific oyster (Crassostrea gigas) to lindane (,-HCH) exposure under experimental conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2007Gerardo Anguiano Abstract This study evaluated organismal toxicity, cytotoxicity, and genotoxicity and the filtration rate in response to different concentrations of subchronic lindane (gamma-hexachlorocyclohexane [,-HCH]), exposure (12 d) in adult Pacific oysters Crassostrea gigas. Oysters were exposed in vivo in laboratory aquaria to 10 different concentrations (0.0,10.0 mg/L) of ,-HCH. The median lethal concentration (LC50) after 12 d was calculated as 2.22 mg/L. Cytotoxic effects were observed in hemocytes, where the mean cell viability was significantly decreased at 1.0 mg/L of ,-HCH after 12 d. Genotoxicity of ,-HCH measured by single cell gel electrophoresis assay, in hemocytes was evident at 0.7 mg/L of ,-HCH after 12 d. After 4 h of exposure to ,-HCH, filtration rates were reduced compared with controls to 65.8 and 38.2% at concentrations of 0.3 and 0.7 mg/L, respectively, and after 11 d of exposure, filtration rates were reduced to 60.4 and 30.9% at concentrations of 0.1 mg/L and higher. These results show the subchronic effects of ,-HCH at different concentrations and effect sensitivities are categorized as filtration rate < genotoxicity < cytotoxicity < mortality. The relevance of integral toxicity evaluation, considering different endpoints from molecular, cellular, and individual levels is discussed. [source] Metallothionein gene expression and protein levels in triploid and diploid oysters Crassostrea gigas after exposure to cadmium and zincENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2006Véronique Marie Abstract Quantitative real-time polymerase chain reaction (PCR) was used to compare for the first time the differential expression of metallothionein (MT) isoform genes, together with biosynthesis of the total MT proteins, in the gills of triploid and diploid juvenile Pacific oyster Crassostrea gigas in response to cadmium (Cd) and zinc (Zn) exposure. Oysters were exposed to Cd (0.133 ,M), Zn (15.3 ,M), and Cd+Zn for 14 d. Results showed similar response capacities to metal exposures in the two populations. No significant difference was revealed in terms of MT gene expression, MT protein synthesis, and Cd accumulation. However, triploid oysters bioaccumulated Zn 30% less efficiently than diploid oysters. Among the three MT isoform genes, CgMT2 appeared to be more expressed than CgMT1, whereas CgMT3 appeared to be anecdotal (106 times lower than CgMT2). CgMT2 and CgMT1 gene expression levels were increased sevenfold in the presence of Cd, whereas Zn appeared to have no effect. A twofold increase in MT protein levels occurred in response to Cd exposure. Discrepancies between mRNA and protein levels suggest that in C. gigas MT are regulated at the transcriptional level, as well as at the translational level. [source] Genetic indicators of herbicide stress in the pacific oyster Crassostrea gigas under experimental conditionsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2000Dario Moraga Abstract This study examined use of the oyster Crassostrea gigas as a bioindicator of experimental pollution caused by two concentrations of five pesticides (atrazine, isoproturon, alachlore, metolachlore, and diuron) used in agricultural and urban activities. The effect of these pesticides on the genetic structure of the marine bivalve was studied as part of an environmental biomonitoring project. This research was performed on two natural estuarine populations sampled along the French Atlantic coast as part of an ongoing monitoring program to survey the ecosystem of Brittany using two approaches: identifying the genetic markers based on the alleles and genotypes associated with pollution effects, and searching for a correlation between these markers and the sensitivity or tolerance of individuals under stress conditions. Results indicate a differential survival of individuals subjected to the various pollutants examined. The sensitivity of alleles and genotypes to environmental stress can be assessed based on the significant differences in allele and genotype frequencies observed between resistant and sensitive individuals when subjected to the pesticides. This genetic study included examination of five enzyme systems (Ak, Pgi, Cap, Pgm, and Mdh) involved in physiologic processes. A total of six alleles and five genotypes at three loci (Ak, Pgi, and Pgm) were identified as being markers of resistance or sensitivity. It is hypothesized that these markers could be used as potential genetic markers in estuarine ecosystem monitoring. [source] Characterization of chitinase-like proteins (Cg -Clp1 and Cg -Clp2) involved in immune defence of the mollusc Crassostrea gigasFEBS JOURNAL, Issue 14 2007Fabien Badariotti Chitinase-like proteins have been identified in insects and mammals as nonenzymatic members of the glycoside hydrolase family 18. Recently, the first molluscan chitinase-like protein, named Crassostrea gigas (Cg)-Clp1, was shown to control the proliferation and synthesis of extracellular matrix components of mammalian chondrocytes. However, the precise physiological roles of Cg -Clp1 in oysters remain unknown. Here, we report the cloning and the characterization of a new chitinase-like protein (Cg -Clp2) from the oyster Crassostrea gigas. Gene expression profiles monitored by quantitative RT-PCR in adult tissues and through development support its involvement in tissue growth and remodelling. Both Cg -Clp1- and Cg -Clp2-encoding genes were transcriptionally stimulated in haemocytes in response to bacterial lipopolysaccharide challenge, strongly suggesting that these two close paralogous genes play a role in oyster immunity. [source] Structural and functional evidence for a singular repertoire of BMP receptor signal transducing proteins in the lophotrochozoan Crassostrea gigas suggests a shared ancestral BMP/activin pathwayFEBS JOURNAL, Issue 13 2005Amaury Herpin The transforming growth factor , (TGF-,) superfamily includes bone morphogenetic proteins, activins and TGF-,sensu stricto (s.s). These ligands, which transduce their signal through a heteromeric complex of type I and type II receptors, have been shown to play a key role in numerous biological processes including early embryonic development in both deuterostomes and ecdyzozoans. Lophochotrozoans, the third major group of bilaterian animals, have remained in the background of the molecular survey of metazoan development. We report the cloning and functional study of the central part of the BMP pathway machinery in the bivalve mollusc Crassostrea gigas (Cg- BMPR1 type I receptor and Cg- TGF,sfR2 type II receptor), showing an unusual functional mode of signal transduction for this superfamily. The use of the zebrafish embryo as a reporter organism revealed that Cg- BMPR1, Cg- TGF,sfR2, Cg- ALR I, an activin Type I receptor or their dominant negative acting truncated forms, when overexpressed during gastrulation, resulted in a range of phenotypes displaying severe disturbance of anterioposterior patterning, due to strong modulations of ventrolateral mesoderm patterning. The results suggest that Cg- BMPR1, and to a certain degree Cg- TGF,sfR2 proteins, function in C. gigas in a similar way to their zebrafish orthologues. Finally, based on phylogenetic analyses, we propose an evolutionary model within the complete TGF-, superfamily. Thus, evidence provided by this study argues for a possible conserved endomesoderm/ectomesoderm inductive mechanism in spiralians through an ancestral BMP/activin pathway in which the singular, promiscuous and probably unique Cg- TGF,sfR2 would be the shared type II receptor interface for both BMP and activin ligands. [source] Molecular identification and expression study of differentially regulated genes in the Pacific oyster Crassostrea gigas in response to pesticide exposureFEBS JOURNAL, Issue 2 2005Arnaud Tanguy The effects of pesticide contamination on the metabolism of marine molluscs are poorly documented. We investigated the response of a marine bivalve, the Pacific oyster, Crassostrea gigas, using a suppression subtractive hybridization method to identify up- and down-regulated genes after a 30-day exposure period to herbicides (a cocktail of atrazine, diuron and isoproturon, and to the single herbicide glyphosate). A total of 137 unique differentially expressed gene sequences was identified, as well as their associated physiological process. The expression of 18 of these genes was analyzed by RT-PCR under laboratory experimental conditions. The metabolic functions they are associated with include xenobiotic detoxification, energy production, immune system response and transcription. This study provides a preliminary basis for studying the response of marine bivalves to long-term herbicide exposure in terms of regulated gene expression and characterizes new potential genetic markers of herbicide contamination. [source] Condition-specific competition allows coexistence of competitively superior exotic oysters with native oystersJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008Frederick R. Krassoi Summary 1Trade-offs between competitive ability and tolerance of abiotic stress are widespread in the literature. Thus, condition-specific competition may explain spatial variability in the success of some biological invaders and why, in environments where there is small-scale environmental variability, competitively inferior and superior species can coexist. 2We tested the hypothesis that differences in abiotic stress alter the outcome of competitive interactions between the native Sydney rock oysters Saccostrea glomerata and exotic Pacific oysters Crassostrea gigas by experimentally testing patterns of intra- and interspecific competition across a tidal elevation gradient of abiotic stress at three sites on the east coast of Australia. 3At low and mid-intertidal heights, exotic C. gigas were able to rapidly overgrow and smother native S. glomerata, which grew at c. 60% of the exotic's rate. In high intertidal areas, where C. gigas displayed about 80% mortality but similar growth rates to S. glomerata, the native oyster was not affected by the presence of the exotic species. 4Asymmetrical effects of the exotic species on the native could not be replicated by manipulating densities of conspecifics, confirming that effects at low and mid-intertidal heights were due to interspecific competition. 5Our results suggest that the more rapid growth of C. gigas than S. glomerata comes at the cost of higher mortality under conditions of abiotic stress. Thus, although C. gigas may rapidly overgrow S. glomerata at low and mid tidal heights, the native oyster will not be competitively excluded by the exotic due to release from competition at high intertidal elevations. 6The success of trade-offs in explaining spatial variation in the outcome of competitive interactions between C. gigas and S. glomerata strengthen the claim that these may be a useful tool in the quest to produce general predictive models of invasion success. [source] The top 27 animal alien species introduced into Europe for aquaculture and related activitiesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2010D. Savini Summary The information extracted from IMPASSE, DAISIE, FishBase, and FAO-DIAS inventories of alien species were used to draw a list of the 27 most utilized animal alien species for aquaculture and related activities (e.g. stocking, sport fishing, ornamental purposes) in Europe. Three variables have been considered to assess their negative ecological impacts when these species escape from aquaculture facilities: (i) their distribution across Europe (including non-EU Member States); (ii) evidence of their environmental impact in the wild; and (iii) evidence of their being vectors of non-target alien species and other hitchhikers (e.g. pathogens). Drivers of use and mechanisms of dispersal in the wild have been also considered and reviewed. Twenty of the species are freshwater fishes: alien cyprinids and salmonids have been introduced into Europe mainly for food production, sport fishing and ornamental purposes. The most widespread species are the goldfish Carassius auratus and the rainbow trout Oncorhynchus mykiss, established in 29 and 28 European countries, respectively. Notwithstanding their successful distribution in Europe, only the Gibel carp Carassius gibelio and the peneid shrimp Marsupenaeus japonicus were found to have environmental impact in all the countries of establishment. Crayfish and predatory fishes (e.g. catfishes and salmonids) cause major environmental impacts in Europe by outcompeting native species and altering habitat structure. Alien crayfish, Procambarus clarkii and Pacifastacus leniusculus, are responsible for the largest range of impacts (i.e. crayfish plague dissemination, bioaccumulation of pollutants, community dominance, competition and predation on native species, habitat modifications, food web impairment, herbivory and macrophytes removal). Cyprinids (e.g. herbivorous carps) are vectors of diseases and parasites, while salmonids (e.g. Salvelinus fontinalis) often cause genetic impairment of native stocks by hybridization. The importation of alien farmed (target) species frequently leads to the introduction of associated non-target species. The cultures of the Pacific cupped oyster Crassostrea gigas and Manila clam Ruditapes philippinarum were responsible for the introduction of the largest number (60) of non-native invertebrates and algae, often attached to packaging material, fouling the shell or parasitizing bivalve tissues. [source] Effect of High-Pressure Processing on Vibrio parahaemolyticus Strains in Pure Culture and Pacific OystersJOURNAL OF FOOD SCIENCE, Issue 4 2002H. Calik ABSTRACT Different strains of Vibrio parahaemolyticus (Vp) in broth cultures and Vp-inoculated live Pacific oysters (Crassostrea gigas) were subjected to high-pressure processing (HPP) at 241, 276, 310, and 345 MPa. Results showed Vp numbers were reduced by HPP in both pure culture and whole oysters. Vp inactivation was dependent on time and pressure. Optimum conditions for reducing Vp in pure culture and oysters to nondetectable levels were achieved at 345 MPa for 30 and 90 s, respectively. Resistance variations were detected between Vp in pure culture and in oysters. HPP proved to be an efficient means of reducing Vp in oysters. [source] Identification and characterization of 18 novel polymorphic microsatellite makers derived from expressed sequence tags in the Pacific oyster Crassostrea gigasMOLECULAR ECOLOGY RESOURCES, Issue 3 2009C. SAUVAGE Abstract We report the development of 18 new polymorphic microsatellite DNA markers derived from Crassostrea gigas expressed sequences tags. Genotyping of 48 wild adult oysters sampled from Marennes-Oléron bay (France) revealed 12 to 48 alleles per locus. Observed and expected heterozygosity levels ranged from 0.64 to 1 and from 0.77 to 0.97, respectively. The development of these new markers creates a useful complementary tool for population genetics studies, parentage analysis and mapping in Pacific oyster, a species of major aquacultural and ecological importance. [source] QTL for resistance to summer mortality and OsHV-1 load in the Pacific oyster (Crassostrea gigas)ANIMAL GENETICS, Issue 4 2010C. Sauvage Summary Summer mortality is a phenomenon severely affecting the aquaculture production of the Pacific oyster (Crassostrea gigas). Although its causal factors are complex, resistance to mortality has been described as a highly heritable trait, and several pathogens including the virus Ostreid Herpes virus type 1 (OsHV-1) have been associated with this phenomenon. A QTL analysis for survival of summer mortality and OsHV-1 load, estimated using real-time PCR, was performed using five F2 full-sib families resulting from a divergent selection experiment for resistance to summer mortality. A consensus linkage map was built using 29 SNPs and 51 microsatellite markers. Five significant QTL were identified and assigned to linkage groups V, VI, VII and IX. Analysis of single full-sib families revealed differential QTL segregation between families. QTL for the two-recorded traits presented very similar locations, highlighting the interest of further study of their respective genetic controls. These QTL show substantial genetic variation in resistance to summer mortality, and present new opportunities for selection for resistance to OsHV-1. [source] Characterization of 20 single nucleotide polymorphism markers in the Pacific oyster (Crassostrea gigas)ANIMAL GENETICS, Issue 6 2009J. Bai No abstract is available for this article. [source] Transcriptome response of the Pacific oyster (Crassostrea gigas) to infection with Vibrio tubiashii using cDNA AFLP differential displayANIMAL GENETICS, Issue 5 2009N. Taris Summary We used qualitative complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) differential display analysis and real-time, quantitative PCR (RT-qPCR) to identify genes in the Pacific oyster Crassostrea gigas, whose transcription either changes in response to exposure to a pathogenic bacterium (Vibrio tubiashii) or varies between families known to differ in sensitivity to heat stress, before and at 12 and 36 h after bacterial exposure at a temperature of 25 °C. These conditions simulate those associated with summer mortality syndrome, a poorly understood cause of massive mortalities in cultured Pacific oysters in North America, Asia and Europe. Using 32 AFLP primer pairs, we identified 92 transcript-derived fragments that are qualitatively differentially expressed. We then cloned and sequenced 14 of these fragments, designed fragment-specific primers and quantified their transcription patterns using RT-qPCR. Most of the differences in transcription patterns between stress-tolerant and stress-sensitive families were evident before bacterial exposure, and genes that responded to bacterial exposure did so in parallel between stress-sensitive and stress-tolerant families. blast searches of sequence databases revealed that these fragments represent genes involved in immune response as well as genes related to metabolic processes. Our data support the hypothesis that family level differences in resistance to stress in Pacific oysters are largely attributable to constitutive differences in gene transcription or ,general vigour' that are detectable before and maintained after infection, rather than being due to induced responses at the transcriptome level. [source] Association among growth, food consumption-related traits and amylase gene polymorphism in the Pacific oyster Crassostrea gigasANIMAL GENETICS, Issue 6 2008A. Huvet Summary To examine further a previously reported association between amylase gene polymorphism and growth in the Pacific oyster Crassostrea gigas, ecophysiological parameters and biochemical and molecular expression levels of ,-amylase were studied in Pacific oysters of different amylase genotypes. Genotypes that previously displayed significantly different growth were found to be significantly different for ingestion and absorption efficiency. These estimated parameters, used in a dynamic energy budget model, showed that observed ingestion rates (unlike absorption efficiencies) allowed an accurate prediction of growth potential in these genotypes. The observed association between growth and amylase gene polymorphism is therefore more likely to be related to ingestion than to absorption efficiency. Additionally, relative mRNA levels of the two amylase cDNAs were also strongly associated with amylase gene polymorphism, possibly reflecting variation in an undefined regulatory region, although no corresponding variation was observed in specific amylase activity. Amylase gene sequences were determined for each genotype, showing the existence of only synonymous or functionally equivalent non-synonymous polymorphisms. The observed associations among growth, food consumption-related traits and amylase gene polymorphism are therefore more likely to be related to variation in the level of amylase gene expression than to functional enzymatic variants. [source] Bioinformatic mining of EST-SSR loci in the Pacific oyster, Crassostrea gigasANIMAL GENETICS, Issue 3 2008Y. Wang Summary A set of expressed sequence tag-simple sequence repeat (EST-SSR) markers of the Pacific oyster, Crassostrea gigas, was developed through bioinformatic mining of the GenBank public database. As of June 30, 2007, a total of 5132 EST sequences from GenBank were downloaded and screened for di-, tri- and tetra-nucleotide repeats, with criteria set at a minimum of 5, 4 and 4 repeats for the three categories of SSRs respectively. Seventeen polymorphic microsatellite markers were characterized. Allele numbers ranged from 3 to 10, and the observed and expected heterozygosity values varied from 0.125 to 0.770 and from 0.113 to 0.732 respectively. Eleven loci were at Hardy,Weinberg equilibrium (HWE); the other six loci showed significant departure from HWE (P < 0.01), suggesting possible presence of null alleles. Pairwise check of linkage disequilibrium (LD) indicated that 11 of 136 pairs of loci showed significant LD (P < 0.01), likely due to HWE present in single markers. Cross-species amplification was examined for five other Crassostrea species and reasonable results were obtained, promising usefulness of these markers in oyster genetics. [source] Assessment of metabolic and immune changes in postspawning Pacific oyster Crassostrea gigas: identification of a critical period of vulnerability after spawningAQUACULTURE RESEARCH, Issue 9 2010Yan Li Abstract This study investigates the vulnerable period in postspawning Pacific oysters (Crassostrea gigas) through physiological and immunological assessments. After spawning, the oyster condition index reduced by 50% and required 70 days to recover to the prespawning level. The mantle glycogen reduced quickly while the reduction in tissue protein occurred slowly. The mantle tissue also lost more protein than gills. The analysis of adenylate energy charge indicated that oysters were stressed in the first 8 days after spawning. As a result of spawning, haemocyte phagocytosis was reduced and remained at a low level for 3 days. In contrast, the reduction of haemolymph antimicrobial activity did not occur until 3 days after spawning and continued to decline until day 8. This immunesuppression was not directly correlated to the changes in haemocyte density. Our study suggests that the first 8 days after spawning are a critical period for oyster survival due to the loss of energy and low immunity. This study further improves our understanding of the coincidence between spawning and summer mortality in oyster aquaculture. [source] SHORT COMMUNICATION: Discovery and evaluation of exon-primed intron-crossing (EPIC)-PCR markers for the Pacific oyster (Crassostrea gigas)AQUACULTURE RESEARCH, Issue 9 2010Qi Li First page of article [source] Impact of a native predatory whelk on cultivated oysters (Crassostrea gigas) crops in San Quintin Bay, MexicoAQUACULTURE RESEARCH, Issue 4 2009Laura F Rodriguez Abstract San Quintin Bay (Baja, California, Mexico) is extensively utilized by artisanal farmers to cultivate Pacific oysters (Crassostrea gigas) using a rope/rack system. A large juvenile oyster mortality event was significantly correlated with the presence of native predatory whelks, Macron trochlea. Surveys, field and lab experiments were performed to identify the predatory behaviour of the whelk, determine factors affecting oyster mortality, and quantify the impact on oyster farmers. Macron trochlea was found to be a voracious, active predator, which can consume ,4 juvenile oysters day,1. Juvenile oysters suffer significantly higher mortality in the presence of whelks. Macron trochlea has the largest impact on small oysters. Once oysters grow to >30 mm they reach a size refuge above which there is much lower mortality. At average growth rates, an oyster can escape predation after ,3 months. But, in areas of highest whelk densities, at average predation rates, whelks could consume the standing crop of juvenile oysters in approximately 43 days. For the artisanal oyster farmers of San Quintin this represents a substantial economic loss, which was unaccounted for previously. Farmers can reduce loss to whelk predation by seeding juvenile oysters in low whelk density areas until oysters reach the size refuge. [source] Short-term physiological response of the Pacific oyster, Crassostrea gigas, on exposure to varying levels of polycyclic aromatic hydrocarbonAQUACULTURE RESEARCH, Issue 15 2007Mu-Chan Kim Abstract In the present study, we investigate the short-term adaptive physiological strategies to polycyclic aromatic hydrocarbon (PAH) of Pacific oysters, Crassostrea gigas, by exposing the oysters to varying levels of PAH (0, 50, 100 and 200 ,g L,1) for 7 days with a 3-day acclimation period under laboratory conditions. The filtration rate (FR) and respiration rate (R) increased significantly at 50 ,g L,1 PAH and decreased at 100 and 200 ,g L,1 compared with the control. The absorption efficiency (Abs. eff.) was significantly impaired at 200 ,g L,1 PAH. Ammonia excretion (E) increased with increasing PAH levels, with a significant elevation at 200 ,g L,1. Although a significantly elevated FR was observed, oysters exposed to 50 ,g L,1 PAH showed scope for growth (SFG) similar to the control. This indicates that even at nominal levels, PAH contamination is a possible cause of reduced oyster production because of increased food demand. The oysters exposed to 200 ,g L,1 PAH showed negative SFG values, which could be a possible cause of growth stagnation or even mortality when the exposure is chronic. [source] Studies on triploid oysters in Australia: farming potential of all-triploid Pacific oysters, Crassostrea gigas (Thunberg), in Port Stephens, New South Wales, AustraliaAQUACULTURE RESEARCH, Issue 6 2005J A Nell Abstract Triploid Pacific oysters Crassostrea gigas farmed in Port Stephens, NSW had an exceptionally fast growth rate and reached a whole weight of 55 g in 13 months versus 20 months for diploids. Mortality of the triploids (24.5±2.94%) was significantly lower (P<0.05) than that of the diploids (40.0±2.26%) over the duration of the experiment (July 2002,February 2004). Unfortunately, this advantage was offset by discoloration of the meats of the triploids when they were in better condition than the diploids over summer (October 2003,March 2004). However, discoloration of meat of triploids had cleared up by April 2004 and neither did they suffer this problem from April,September 2003. The triploids also had a lower peak condition than the diploids. Oysters in peak meat condition, i.e. spawning condition, are preferred for the half shell trade in Australia and in this study, there was at least a six-month period prior to discoloration, when the triploids were large enough and had sufficient meat condition for marketing on the half shell. [source] | ||||||||||||||||