牡蛎养殖技术

太平洋牡蛎具有体型大、生长快、味美、产量高、适应性强等优点,是浅海养殖的优良品种之一。本文概述了太平洋牡蛎的人工养殖技术,同时介绍了一种牡蛎的室内控温育苗技术;旨在为牡蛎养殖单位的生产实践提供参考。     

Folic acid and cyanocobalamin effects on the expression of genes involved in DNA methylation of the oyster Crassostrea gigas

The microalga Chaetoceros calcitrans was cultured with three concentrations of vitamin B12 (cyanocobalamin) to supplement the feed for the oyster Crassostrea gigas. In two additional assays, vitamins B12 and B9 (folic acid) were dissolved in the water to increase the methyl donors necessary for the one‐carbon cycle and DNA methylation. Microalgae did not present differences in their concentration of vitamins, and no correlation was found between the concentration of vitamin supplement and the vitamin concentration in oysters; however, changes in the expression of genes involved in the DNA methylation were found. The expression of proton‐coupled folate transporter (PCFT) was lower in oysters supplemented with Vit. B9. The expression of proton‐coupled folate transporter (PCFT) was lower in oysters supplemented with Vit. B9., however, the expression of genes implicated in the release of the methyl used to maintain methylation such as methionine synthase (MS) and DNMT1 expression was high, suggesting faster transportation of Vit. B9. The methylenetetrahydrofolate reductase (MTHFR), implicated in the reduction of folic acid, was lower in oysters supplemented with Vit. 9 and B12 dissolved in the water. DNA methyltransferase DNMT1A, involved in DNA maintenance, was higher in oyster supplemented with Vit. B9, but the expression of DNMT1B was not different. In conclusion, the supplementation with folic acid increases the expression of genes implicated in the maintenance of DNA methylation in C. gigas.     

Characterization of the quantitatively major collagen in the mantle of oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

ABSTRACT:   A quantitatively major collagen was isolated from the pepsin-solubilized collagen preparation of the mantle by differential salt precipitation and phosphocellulose column chromatography, and its constituent α components (α1 and α2) were purified by phosphocellulose column chromatography. The subunits were demonstrated to be genetically distinct from each other by peptide mapping and amino acid analysis. The amino acid composition calculated from those of the α1 and α2 components in 2 : 1 ratio coincided well with that of the major collagen from the mantle. These results suggest that the major collagen in the mantle of the oyster may have a heterotrimer structure (α1)₂α2.     

Suspended culture evaluation of Pacific oyster Crassostrea gigas in a tropical estuary

The growth and survival of Crassostrea gigas were evaluated in hanging culture in the Chone River estuary (Bahía de Caráquez), Manabí province, Ecuador. Oyster seeds (~10 mm) were confined in lantern nets at a density equal to the occupation of half the surface of the basket base, until reaching commercial size (80 mm). A sample for oyster biometric, parasitic and bacterial analysis was obtained monthly. Temperature, salinity, oxygen concentration, seston and phytoplankton biomass were determined. At the end of the study, the oysters were analysed for heavy metal concentration. The commercial oyster production was extrapolated to estimate the possible economic performance of a family production module (a 7 × 7 m bamboo raft). The results show a great biological feasibility of culture of C. gigas with harvests of commercial size oysters in only 5 months and acceptable survivals (accumulated >70%, after 3 weeks of crop seed selection). The heavy metal concentrations and the parasitological and bacteriological analyses did not indicate levels of contamination. The economic projections suggest that, even with a profitability of 57%, the initially invested capital could be recovered within the first harvest.     

Genetic parameters of growth and survival in the Pacific oyster Crassostrea gigas

The Pacific oyster Crassostrea gigas is a representative bivalve mollusc that is widely cultured in the world and is the largest molluscan group cultured in China. In order to assess the feasibility of improving survival of C. gigas through genetic selection, the heritability and genetic correlations for growth and survival traits between different life stages were examined. Genetic parameters were estimated based on intraclass correlations of 49 full‐sib families (29 half‐sib families) in larvae (4 and 20 days after fertilization) and spat (140 days after fertilization) stages. The heritability for growth traits in larvae and spat was 0.30–0.86 and 0.53–0.59, respectively, and varied with ages. The heritability of survival was low in larvae (0.13 ± 0.05 and 0.17 ± 0.04, respectively for 4 and 20 days after fertilization) but medium (0.39 ± 0.07) in spat, suggesting that selection for increasing spat survival was feasible. The genetic correlation between growth traits within age was medium to high and positive (ranging from 0.47 to 0.96, respectively, between shell length (SL) and shell height (SH) at 20 days and between SL and SH at 140 days after fertilization), suggesting that selection to improve single growth trait will cause positive response in another growth traits in C. gigas. The genetic correlations between survival and growth traits at 140 days were low but positive (ranging from 0.23 to 0.27, respectively, between survival and SH and between survival and SL at 140 days after fertilization), suggesting that selection for survival may not have a negative response in growth. Overall, this study suggests that survival traits should be taken as improving target of next selection breeding programme in C. gigas.     

Application of sperm cryopreservation in selective breeding of the Pacific oyster,Crassostrea gigas (Thunberg)

The robustness of Pacific oyster, Crassostrea gigas (Thunberg), sperm cryopreservation in the context of selective breeding based on family lines was investigated. Irrespective of egg density, high fertilization success was achieved with cryopreserved sperm when sperm:egg ratios of 1000:1 to 10 000:1 were used. Variation among replicate runs on the same oyster batches was minimal, indicating that cryopreservation and larval rearing procedures were repeatable. Twenty independent single male–female crosses were made to assess the utility of cryopreserved sperm in selective breeding. The fertility of unfrozen sperm was generally a poor predictor of cryopreserved sperm fertility. Based on D‐larval yields, 17 of the 20 crosses were likely to yield adequate spat for selective breeding (>10⁵ D‐larvae from 1 million eggs), two were marginal (5 × 10⁴ D‐larvae) and one was inadequate (4 × 10³ D‐larvae). An alternative fertilization strategy to improve D‐yield from a given number of sperm was then tested. Fertilizing 10 million eggs at a sperm:egg ratio of 200:1 increased the total D‐yield when compared with fertilizing 1 million eggs at a sperm:egg ratio of 2000:1 for the same male–female pair. We conclude that, despite wide variation in fertility, cryopreserved sperm is useful for family production.     

福建漳浦太平洋牡蛎微卫星等位基因比较

本文采用Ucdcg153、157、202微卫星分子标记对福建漳浦从广东饶平引人的太平洋牡蛎育苗亲贝进行等位基因比较.两组样品(Cg♀和cg♂)携带的等位基因在微卫星重复区间及其附近存在高度相似的变异特征.这些特征区间分别是:Ucdcg153 23～40位碱基区间,Ucdcg157 73～100位碱基区间,Ucd-cg2...     

太平洋牡蛎不同组织DNA甲基化的F-MSAP分析

采用荧光标记的甲基化敏感性扩增多态性(F-MSAP)技术对太平洋牡蛎(Crassostrea gigas)的6个组织进行全基因组CCGG位点甲基化水平的检测。结果表明: 鳃、闭壳肌、外套膜、唇瓣、性腺、消化盲囊6个组织的甲基化水平分别为: 31.77%、36.41%、32.00%、36.47%、32.77%和37.92%。甲基化模式分为全甲基化和半甲基化, 在太平洋牡蛎中, 全甲基化模式与总体甲基化水平一致, 消化盲囊、唇瓣、闭壳肌组织的甲基化水平较高, 而鳃、外套膜、性腺组织的甲基化程度较低; 半甲基化位点显著少于全甲基化位点, 并且不同组织间的半甲基化位点不存在显著性差异, 而从全甲基化位点及总甲基化水平分析, 不同组织之间甲基化水平差异显著。太平洋牡蛎中存在组织特异性甲基化片段和非组织特异性甲基化片段, 但却只在一个或部分个体中出现, 没有发现在所有研究个体中都存在的甲基化差异片段, 这可能与牡蛎较高的杂合度相关。对实验样品进行的荧光标记的扩增片段长度多态性(F-AFLP)分析发现, 样品间的确存在较大的遗传差异, 基于以上结果可以推测基因组甲基化水平可能与个体遗传背景相关联。

     

Heritability estimates for nutritional quality‐related traits of the Pacific oyster,Crassostrea gigas

Pacific oysters, Crassostrea gigas, are the most abundantly harvested shellfish in the world and are ecologically significant. The content of nutrients, including protein, glycogen, lipid, zinc (Zn), and selenium (Se), is important for oyster meat quality, but heritability estimates of such traits have rarely been reported. In this study, 64 full‐sib families were generated using a nested mating design. Finally, 18 full‐sib families, of which there were nine half‐sib families, with each containing 2 full‐sib families, were sampled for heritability estimates. The narrow‐sense heritabilities of glycogen, protein, lipid, Zn, and Se contents were 0.29 ± 0.02, 0.38 ± 0.02, 0.58 ± 0.08, 0.02 ± 0.02, and 0, respectively. Negative genetic correlations existed between both glycogen and protein content (?0.95 ± 0.004) and between lipid and protein content (?0.59 ± 0.05), whereas a positive correlation was observed between lipid and glycogen content (0.16 ± 0.06). Weak genetic and phenotypical correlations (r = 0–0.2) were observed between shell height and nutritional quality traits. These data demonstrated that glycogen, protein, and lipid content can be chosen in a selective breeding program, but glycogen and lipids cannot be selected together with protein. Furthermore, performing indirect selective breeding for quality traits by selecting traits related to growth is impossible. This study provides information for the development of breeding strategies for oyster quality traits.     

Identification and counting of Pacific oyster Crassostrea gigas larvae by object detection using deep learning

Natural seedling collection is widely used in the culture of various bivalve species. For successful natural seedling collection, collectors must be installed when larvae appear in the water column at a stage immediately before attachment. Aquaculture farmers generally identify target larvae by morphological features through microscopic examination in a time- and labor-expensive exercise, which also requires a level of expertise to ensure accurate larval identification. We develop a deep-learning-based object-detection technique that ultimately might reduce the time and effort required to accurately identify and count Pacific oyster larvae, render their identification more consistent, and negate the need for expertise. Images of plankton net samples collected in Matsushima and Sendai bays, Japan, were taken using a new photographic device with a CMOS image sensor. Images of oyster larvae identified by an expert were used to create a library of labeled images to train a deep-learning model, which proved to be 82.4% accurate in precision, 90.8% in recall, and 86.4% in F-measure. A further method for estimating larval shell height from the rectangular shape of oyster larval images is also developed. The standardized mean difference in shell height between measurements and estimates is 3.3%. This deep-learning model has the potential to significantly reduce the time and effort required to identify oyster larvae in plankton samples, and thereby costs of this exercise.     

太平洋牡蛎生物沉积作用的研究

2001年3-9月,在自然养殖状态下对太平洋牡蛎的生物沉积及其对物质输运的影响进行了研究。结果显示,太平洋牡蛎能加速海洋中颗粒物质的沉积,太平洋牡蛎的生物沉积率分别为小个体(壳长80～95mm)26.3～69.9mg·ind-1·d-1,中等个体(壳长95～110mm)37.5～83.7mg·ind-1·d-1和大个体(壳长110～125mm)44.1～103.7mg·ind-1·d-1。太平洋牡蛎的生物沉积与其壳长呈正相关线性关系,与其干组织重呈正相关的指数关系,而单位重量的生物沉积则与壳长和干组织重分别为负相关的线性和幂指数关系。海水温度和环境中饵料数量是影响太平洋牡蛎的生物沉积的重要因子。     

Characterization,fluctuation and tissue differences in nutrient content in the Pacific oyster (Crassostrea gigas) in Qingdao,northern China

The Pacific oyster (Crassostrea gigas) is one of the most important aquaculture species worldwide. Its meat quality is vital for consumer satisfaction, and nutrient content, especially glycogen, is closely associated with oyster fatness and meat colour. Fluctuations in nutrient content of short‐term starvation have not been previously reported, and seasonal variation in glycogen content in different tissues has rarely been reported. In the present study, we investigated these important aspects of oyster production and found that short‐term starvation (50 hr) did not significantly alter glycogen, protein or lipid content. The seasonal variation assay showed that glycogen and lipid accumulation was high in autumn and winter and that seawater temperature and protein content were inversely related to glycogen content. Glycogen content of the whole flesh was higher from January to April and was positively related to the condition index before the onset of gametogenesis. Glycogen content was higher in the gonad, labial palp and mantle compared to the gill or adductor muscle. Relative expression of genes encoding proteins involved in glycogen metabolism (glycogen synthase, glycogen phosphorylase, glycogen debranching enzyme and glycogen branching enzyme) was closely associated with the glycogen content in the corresponding tissues. Glycogen content in the gonad was regulated by glycogen metabolic and glycolysis pathway genes (6‐phosphofructo kinase, phosphoglycerate kinase, pyruvate kinase, hexokinase and glucose transporters), and stored glycogen was the main energy source for gametogenesis. These findings contribute to oyster aquaculture management and glycogen improvement and expand our understanding of glycogen metabolism in oysters.     

Effects of developmental stage, seawater concentration and rearing temperature on cryopreservation of Pacific oyster Crassostrea gigas larvae

ABSTRACT: For the development of a stepwise cryopreservation technique for larvae of the Pacific oyster Crassostrea gigas , various conditions were examined. Larvae at 9, 12, 15, 18 and 21 h after insemination were cooled at a rate of −1°C/min (seeding at −8°C for 15 min) and then plunged into liquid nitrogen at −35 or −40°C using 1.5 M dimethyl sulfoxide (DMSO) and 250 mM trehalose as cryoprotectants. Among these larvae, 15 h after insemination (the trochophore stage before formation of the shell gland) showed the highest motility and the best external appearance after thawing. Trochophore larvae were cryopreserved in preservation media containing different dilutions (1/4, 1/6, 1/8, 1/10 and 1/30) of seawater. Larvae preserved in the 1/4 seawater medium showed the highest appearance of shelled larvae 4 days after thawing. Trochophore larvae reared in seawater at 21, 25 or 29°C were cryopreserved for 8 months and then reared at 26°C after thawing. Larvae reared at 25°C showed the highest survival rate and normal larval ratio at day 6 after thawing, although larvae reared at 21°C showed the highest rates until day 4. One larva developed at 25°C succeeded to settle.     

Meiotic chromosome configurations in triploid and heteroploid mosaic males of Crassostrea gigas and Crassostrea ariakensis

Reversion from triploids to diploids or heteroploid mosaics may make the revertants recover reproductive ability and lose their aquacultural advantages. Meiotic chromosomes in triploids and mosaics of Crassostrea gigas and Crassostrea ariakensis were studied. Pachytene spermatocytes showed incomplete trivalent formation, varying 64–72% in C. gigas and 62–69% in C. ariakensis. At metaphase I, trivalents, bivalents and univalents occurred in various combinations. Trivalents occurred in all spermatocytes, ranged 6–10 per spermatocyte and averaged 8.53–8.97 in C. gigas and 8.49–8.95 in C. ariakensis. Univalents and bivalents appeared in 59.2–72.1% of the spermatocytes in C. gigas, and ranged 0.77–1.39 and 1.01–1.51 per spermatocyte respectively. In C. ariakensis, they occurred in 57.5–81% of the spermatocytes, and ranged 0.9–1.32 and 1.03–1.35 respectively. The most common trivalent was formed by a bivalent with the third chromosome attaching to its side to form ‘long‐tail‐cross’ or ‘t’ or ‘frying‐pan’‐shaped configurations that constituted 65.7% and 59.9% of the trivalents in C. gigas and C. ariakensis respectively. Other kinds of trivalent associations included tandem chains (14.7%, 16.5%), closed circles or triangles (5.3%, 9.8%), convergent ‘T’ or ‘Y’ (5.8%, 7.4%) and unclassified configurations (8.5%, 6.4%). Diploid spermatocytes were not observed from mosaics, although they showed considerable proportions of ‘diploid’ cells in their gills.     

Heritability estimates for growth‐related traits in the Pacific oyster (Crassostrea gigas) using a molecular pedigree

Pacific oyster is one of the leading species in world aquaculture, but heritability estimation applying mixed‐family approach has not been actively pursued. In this study, heritability for growth‐related traits in the Pacific oyster was first estimated by creating a single cohort of 45 families in a full‐factorial mating design consisting of nine sires and five dams. A total of 270 offspring were analysed and parentage assignment inferred by six microsatellite markers achieved 100% success. All parents contributed to the spawn and a total of 42 full‐sib families were represented. Using an animal model, heritability estimates at 12 months of age were 0.49 ± 0.25 for shell height, 0.36 ± 0.19 for shell length, 0.45 ± 0.23 for shell width and 0.35 ± 0.17 for wet weight. Genetic correlation between shell height and wet weight was quite high (0.79 ± 0.25), suggesting that direct selection of shell height, which is an easily measurable trait, also improves wet weight. The results obtained in this study indicate that growth‐related traits could be improved by exploiting additive genetic effects through selective breeding.     

5种壳色长牡蛎不同组织常规营养成分分析与评价

对壳黑、壳紫、壳橙、壳金和壳白5种壳色长牡蛎(Crassostrea gigas)不同组织包括闭壳肌、外套膜、鳃、性腺-内脏团的营养成分(水分、总蛋白质、总脂肪、糖原、灰分)进行检测分析,比较它们与普通养殖群体营养成分的差异以及5种壳色长牡蛎各组织间营养成分的差异。结果表明,在闭壳肌中,壳紫长牡蛎的总脂肪含量显著高于壳橙长牡蛎(P0.05),其他组分在6个群体中未表现出显著性差异(P0.05);在外套膜中,壳金长牡蛎总脂肪含量显著高于壳黑、壳橙和普通养殖群体(P0.05),壳白长牡蛎的灰分含量显著高于普通养殖群体(P0.05),其他组分在各群体之间未表现出显著性差异(P0.05);在鳃中,长牡蛎壳橙、壳紫、壳白选育群体的糖原含量显著低于对照组(P0.05),其他组分在6个群体之间没有显著性差异(P0.05)。长牡蛎5种壳色选育群体和普通养殖群体的性腺-内脏团在水分、总蛋白质、总脂肪、糖原和灰分中均无显著性差异(P0.05)。4个组织中水分和灰分均以外套膜和鳃中含量最高,闭壳肌中总蛋白质的含量则在4个组织中居首位,总脂肪和糖原含量均以性腺-内脏团中最高。研究结果表明不同壳色长牡蛎之间以及不同壳色与普通对照群体之间在一些重要营养成分上已表现出分化,这为长牡蛎壳色品系选育提供了重要的参考资料。