• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.641-645
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• 2003

Spermatogenesis, ultrastructure, and sperm morphology of the Pacific oyster (Crassostrea gigas) were investigated with TEM and SEM. C. gigas sperm were primitive consisting of a head midpiece and tail. Sperm size (head and midpiece) was about 1.78 ${\mu}m$. Sperm morphology was similar to a sharp of a small water jar with a rough surface. Sperm had both anterior nuclear fossa (anf) and posterior nuclear fossa (pnf). Acrosome forms had a hat-like shape. The axial rod was projected in front of the acrosome. C. gigas sperm had four large mitochondria in the midpiece.

• Animal Systematics, Evolution and Diversity
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• v.11 no.2
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• pp.235-242
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• 1995

The nucleotide sequence variation of mitochondria1 DNA were investigated by eight restriction endonucleases from two oyster species, Crassostrea gigas collected from two localities of South Korea and one locality of Japan and C. nippona collected from one locality of South Korea. The total mtDNA size in the oyster, C. gigas, from the three localities was approximately 18 kb and that in C. nippona was 22 kb. The restriction fragment patterns of mtDNA in C. gigas from the three localities by BamHI, BgII, and XhoI digestions were identical to one another. The degree of mtDNA sequence divergence of C. gigas between the two localities in Korea was 2% and that between Korean and Japanese C. gigas was 5%. The amount of sequence divergence between the two species of oysters was 42%.

• Analytical Science and Technology
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• v.22 no.5
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• pp.360-368
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• 2009

Tributyltin (TBT) use has been prohibited by the IMO (International Maritime Organization), as well as Korea, since 2003. This prohibition has affected a gradual reduction in TBT use in maritime environs (seawater, sediment, and biosamples) in several countries. In this study, Crassostrea gigas (oyster) and Tapes philippinarum (manila clam) were chosen and measured for butyltin compound concentrations to verify TBT pollution levels since its 2003 ban. Specimens were taken directly from farms for concentration measurement, where Crassostrea gigas and Tapes philippinarum are cultivated, as well as prevalent locations predicted to have been polluted. Concentrations of MBT, DBT, and TBT of Crassostrea gigas were measured to be N.D -N.D., N.D. -N.D., and N.D. -60.21 ng Sn $g^{-1}$ (wet wt), respectively. Regarding Tapes philippinarum, MBT, DBT, and TBT were N.D. -12.27 ng Sn $g^{-1}$ (wet wt), N.D. -45.95 ng Sn $g^{-1}$ (wet wt), and N.D.-7.30 ng Sn $g^{-1}$ (wet wt), respectively. For this research, a correlative study was conducted to determine butyltin compound concentration in Crassostrea gigas at the locations where measurements were made in 1994 to determine to what extent TBT pollution level decreased. A decrease in all 7 sites was observed. In 4 of the 7 samples, butyltin compounds were measured to be below the detection limit, while that of the Tapes philippinarum did not appear high compared to foreign research data.

• Environmental Analysis Health and Toxicology
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• v.25 no.4
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• pp.287-294
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• 2010

Objectives : The aim of this study was to verify the intersexuality of Crassostrea gigas and Ruditapes philippinarum in southern coastal waters of Korea. Methods : Specimens of Crassostrea gigas (n=363) were collected from six areas of Tongyeong, Geoje and Yeosu. Ruditapes philippinarum (n=221) was collected from five areas of Yeosu. The sex ratio and intersexuality were determined after observing gonad preparations. Results : The rate of intersexuality in Crassostrea gigas was 16.25%, with females (24.79%; n=30/121) exhibiting a higher rate than males (11.98%; n=29/242). The rate of intersexuality in Ruditapes philippinarum was 24.43%, with females (37.76%; n=37/98) exhibiting a higher rate than males (13.82%; n=17/123). Conclusions : The results of this study suggest that intersexuality is induced by aquatic pollutants such as endocrine disrupting chemicals (EDCs).

• Microbiology and Biotechnology Letters
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• v.7 no.3
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• pp.175-179
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• 1979

The present work was conducted in order to survey bacterial flora inhabiting in Crassostrea gigas. The Crassostrea gigas, sea water and mud of its living environments were sampled at Goseong bay, Gyungnam and Dolsan, Yeochon-gun, Chungnam at the period of from December 1978 to February 1979. The obtained results are summarized as follows: 1. The range of bacterial counts found in Crassostrea gigas, sea water and mud was respectively 10$^4$~10$^{6}$ , 10$^{5}$ ~10$^{6}$ and 10$^3$~10$^4$. 2. Among the bacterial 382 strains isolated from the those sample sources, Vibrio genus was 43.5％, Pseudomonas 16.7％, Moraxella 11.5％ and Flavobacterium-cytophaga 8.9％. 3. Among 173 strains classified as Vibrio genus, 56％ of them was found in Crassostrea gigas, 54％ in mud and 25％ in sea water. 4. Pseudomonas type I was found only in sea water and type III/IV found in sea water, mud and Crassostrea gigas. Especially type III/IV was found much in sea water.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.5
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• pp.469-476
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• 2018

The purpose of this study was to collect basic data that could be used in the manufacture of two kinds of canned oyster Crassostrea gigas. The steamed oyster was prepared by shucking after boiling for 6 min at $105^{\circ}C$ and then washing and dewatering. The roasted oyster was prepared by baking steamed oyster at $140^{\circ}C$ for 20 min. The manufacturing methods of canned seasoned boiled oyster and canned seasoned roasted oyster were as follows. The boiled or roasted oyster (50 g) was added to a can (RR-90) along with a mixture of seasoning sauce 40 and then seamed using a vacuum seamer under 20 cm Hg after pre-exhausting at $90^{\circ}C$ for 20 min. The two kinds of canned oyster products produced under sterilization of Fo 12 min were tested for cultured bacteria, external appearance, proximate composition, pH, VBN (Volatile basic nitrogen), TBA (Thiobarbiuric aicd) value, amino-N, salinity, color value sensory evaluation, etc. Results showed that the canned seasoned roasted oyster had higher overall acceptability than the canned seasoned boiled oyster. The reason for this was judged to be that the process of roasting at $140^{\circ}C$ for 20 min influenced the sensory evaluation.

• Korean Journal of Environmental Biology
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• v.27 no.3
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• pp.279-284
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• 2009

In order to understand food sources-metabolism for the pacific oyster (Crassostrea gigas), the stable isotope ratios of carbon (${\delta}^{13}C$) and nitrogen (${\delta}^{15}N$) of its gut, gill, and muscle as well as potential food sources (particulate organic matter, sedimentary organic matter, benthic microalgae, seagrass detritus) were determined in Dongdae Bay. Average ${\delta}^{13}C$ and ${\delta}^{15}N$ values reflect that oysters primarily fed on sedimentary organic matter as opposed to suspended organic matter during summer and winter seasons. However, the relatively enriched $^{15}N$ values of particulate organic matter (>$250{\mu}m$) and sedimentary organic matter in the summer may be due to the photosynthetic incorporation of $^{15}N$-enriched nitrogen (DIN) or the spawning events of bivalves. Specific oyster tissues (gut, gill, and muscle) revealed different metabolic pathways, which were determined through analysis of ${\delta}^{13}C$ and ${\delta}^{15}N$ in each organ. The present results suggest the determination of carbon and nitrogen stable isotopes to be a useful approach in ecological research related to the food sources- metabolism of Crassostrea gigas.

• 한국해양학회지
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• v.15 no.1
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• pp.8-16
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• 1980

The seed of Japaness oyster, Crassostrea gigas(Thunberg), cultivated along the southerncoast of Korea have been transplanted and cultivated in both the Seonyu island and the Eocheong island of the western coast of Korea. The present study was carried out to investigate the growth of transplanted oysters, environmental factors influencing their fatness, and differences of two areas between the Seonyu island and the Eocheong island during the period from April to November, 1978. The results obtained were as follows: 1. Maximum height of the shell was 69.2mm (58.4mm on the average) in the island of Seonyu and 64.8mm(53.2mm) in the island of Eocheong, respectively. 2. The fatness of the oysters measured in the island of Seonyu (5.2g/month) was greater than in the island of Eocheong (2.5g/month) 3. The shell height was increased with high temperature while, the shell fatness with low temperature. 4. The growth rate of the transplanted seed oysters was twice as much as that of native ones in the western coast of Korea. 5. Environmental conditions of Seonyu island were more favorable in cultivating oysters than those of the Eocheong island.

• Journal of Aquaculture
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• v.16 no.3
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• pp.196-201
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• 2003

Sessile organisms such as the oyster Crassostrea gigas have been given much attention as a potential biomonitoring indicator to assess the impact of toxicants on aquatic organism. In this study, we exposed cells isolated from gill of oyster (Crassostrea gigas) to hydrogen peroxide in vitro. In addition oysters were in vivo exposed to pyrene and benzo(a)pyrene at various concentrations for 2 weeks. Comet assay was used to detect DNA single strand breaks and to investigate the application of this technique as a tool for aquatic biomonitoring. Hydrogen peroxide increased DNA single strand break with increasing concentration after 30 minutes exposure in vitro. Pyrene and benzo(a)pyrene caused DNA damage only at very high concentration (100 $\mu\textrm{g}$/L or 1000 $\mu\textrm{g}$/L) at two week exposure in vivo. DNA damage was relatively higher at hemocyte than at gill. It suggested that metabolized PAHs are transferred to hemolymph from digestive gland which have a relatively high enzyme activity, and attacked the DNA of hemocyte, while gill accumulated PAHs without degrading them to their metabolites due to low enzyme activity at gill. Both in vitro and in vivo exposure experiments showed that the comet assay is an effective tool on screening whether the organism are exposed to genotoxic contaminants.

• The Korean Journal of Malacology
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• v.31 no.1
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• pp.43-48
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• 2015

Oxygen isotope ratios (${\delta}^{18}O$) of three Pacific oyster (Crassostrea gigas) specimens from the Neolithic Yeondae-do shell midden site, Tongyeong, Korea, were analyzed to determine the seasonality of shellfish gathering and site occupation. Oxygen isotope samples were taken from the left valve hinge sections of the specimens. Oxygen isotope values ranged between -0.1 ‰ and -2.4 ‰, between -0.2 ‰ and -2.9 ‰, and between 0.3 ‰ and -2.8 ‰ in oyster specimen #one, #two and #three, respectively. The isotope profiles showed seasonal temperature cycles, providing information related to the seasonality of shellfish gathering and site occupation. Hinge-edge oxygen isotope values of the specimens showed decreasing trends after passing through maximum values (winter), indicating that they formed during spring. Thus it can be assumed that during spring season, oysters were gathered and the site was occupied.