• The Korean Journal of Malacology
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• v.20 no.1
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• pp.75-84
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• 2004

Reproductive cycle, the condition index, sex ratio of the Pacific oysters, Crassostrea gigas were investigated by histological and morphometric data. The specimens were collected in the two oyster farms of Geoje and Namhae, Gyeongsangnam-do, Korea, from November 1995 to October 1996. Growth of shell length in two regions was similar, but growth of total weight of the oyster in Namhae was faster than that in Geoje oyster farm. The spawning periods in female and male clams were from July to October in Geoje and from June to October in Namhae oyster farm. Ripe oocytes were approximately 50 m in diameter. The reproductive cycle of in females and males in Geoje and Namhae oyster farms can be divided into five successive stages: early developing, late developing, ripe, partially spawned and spent/inactive. Monthly changes in gonad developmental phases showed somewhat different patterns between female and male clams except for the spawning period. On the whole, however, monthly changes in the gonad developmental phases showed a similar pattern in the same sex. The sex ratios of females to males in Geoje and Namhae oyster farms were not significantly different from a 1:1 sex ratio ($x^2$ = 0.55 (p > 0.05) in Geoje and $x^2$ = 0.27 ( p > 0.05) in Namhae). Artificial induction of maturation by heating of adult oysters (two-year-old) was investigated from 17 January to 18 March in 1996. Maturity at the fixed water temperature group of $20^{\circ}C$ was 80%, it showed the highest maturity of experimental groups cultured for five weeks. The survival (%) of Crassostrea gigas in the raised water temperature experimental groups (15, 20, $25^{\circ}C$) were over 98.5%, as similar to the control group (100%). But, the survival of C. gigas in the fixed water temperature experimental groups (15, 20, 25, $30^{\circ}C$) were decreased with the increase of the water temperatures. In the fixed water temperature experimental group of $30^{\circ}C$, the survival was 51.1%. Base on these results, the fixed water temperature of $20^{\circ}C$ was the best condition for artificial induction of sexual maturation.

• Journal of Life Science
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• v.12 no.1
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• pp.49-54
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• 2002

Development of a rapid method possessing the requisite sensitivity and specificity for virus monitoring is necessary for protection of the shellfish-consuming public. Oysters tissue usually contains virus particles in relatively small concentrations along with various other substances that can interfere with detection steps. Therefore, the critical point concerning the detection of viruses in shellfish tissues resides in the processing of samples. The current study demonstrated the possibility of purifying small amounts of virus particles at the interface of a 10/50% sucrose gradient after a single round of sucrose gradient ultracentrifugation. We could detect HAV and poliovirus simultaneously from oyster tissues by using two different sets of primer. Furthermore, the method showed a high level of virus recovery rate (>95%) as determined by plaque assays of the final samples. Taken the advantages of the simple and sensitive methods, it was possible to detect 2 pfu of HAV in 5 g of oyster digestive tissues within 24h.

• Korean Journal of Food Science and Technology
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• v.6 no.4
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• pp.209-213
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• 1974

Pigments were extracted by aqueous acetone from the boiled canned oyster colored during storage and then the components were separated by thin layer chromatography. Totally eleven pigments could be isolated including one yellow, one red, five orange or reddish orange and four green components, and their UV-visible spectra were measured. It can be envisioned from the electronic spectral study and color reaction on the indivisual pigments isolated from the brown acetone extracts that the green pigments as well as most of the yellow orange ones may be porphyrin derivatives originated probably from the chlorophyll and some of the orange pigments contains ketocarotenoids. In particular, the pigment of band 8 which is expected to be pheophytin a or its derivatives and the carotenoid band 7 seem to be the major pigment. The close resemblance of the chromatogram of the colored muscle extract to that of the viscera suggests that the brown coloring material is probably originated from the viscera pigments.

• Fisheries and Aquatic Sciences
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• v.25 no.5
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• pp.287-297
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• 2022

The objective of this study was to evaluate the probability of norovirus foodborne illness by raw oyster consumption. One hundred fifty-six oyster samples were collected to examine the norovirus prevalence. The oyster samples were inoculated with murine norovirus and stored at 4℃-25℃. A plaque assay determined norovirus titers. The norovirus titers were fitted with the Baranyi model to calculate shoulder period (h) and death rate (Log PFU/g/h). These kinetic parameters were fitted to a polynomial model as a function of temperature. Distribution temperature and time were surveyed, and consumption data were surveyed. A dose-response model was also searched through literature. The simulation model was prepared with these data in @RISK to estimate the probability of norovirus foodborne. One sample of 156 samples was norovirus positive. Thus, the initial contamination level was estimated by the Beta distribution (2, 156), and the level was -5.3 Log PFU/g. The developed predictive models showed that the norovirus titers decreased in oysters under the storage conditions simulated with the Uniform distribution (0.325, 1.643) for time and the Pert distribution (10, 18, 25) for temperature. Consumption ratio of raw oyster was 0.98%, and average consumption amount was 1.82 g, calculated by the Pert distribution [Pert {1.8200, 1.8200, 335.30, Truncate (0, 236.8)}]. ₁F₁ hypergeometric dose-response model [1 - (1 + 2.55 × 10^-3 × dose)^-0.086] was appropriate to evaluate dose-response. The simulation showed that the probability of norovirus foodborne illness by raw oyster consumption was 5.90 × 10^-10 per person per day. The annual socioeconomic cost of consuming raw oysters contaminated with norovirus was not very high.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.145-145
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• 2003

To evaluate the effect of PAHs on fertilization and larval development of the Pacific oyster, Crassostrea gigas via in vivo exposure for 30 days. Conditioned C. gigas adult brood stock was taken from oyster farm in May 2003 and raised in flow through tank at 20-22$^{\circ}C$ with feeding equivalently mixed marine microalgae: Chaetoceros simplex, C. gracilis, Isochrysis galbana and Tetrasemis tetrathele. The oysters were exposed to PAHs cocktail at 200ppb (10 species) until they are fully riped with an untreated group. Motility of sperm, Fertilization and The percent of D-shaped larvae was measured under microscope (Olympus BX-50). Fertilization capability using dry sperm and eggs from both non- and PAHs treated brood stocks was significantly reduced at the treated group (P<0.01). In addition to the origin effect, it was obvious that fertilization of eggs from both group were adversely suppressed in consistent with PAHs level (P<0.01). The percent of D-shaped larvae in treated group was significantly reduced comparing to non-treated. The percent was adversely correlated with PAHs level, which was more significantly reduced in treated group. Therefore, it was obvious that PAHs exposure on the Pacific oyster has adverse affects on the sperm as well as larvae in both maternal and acute source.

• 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.

• YAKHAK HOEJI
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• v.50 no.3
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• pp.160-165
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• 2006

Germanium is found in a range of minerals and ores and is present in foods including beans, tomato juice, oysters, tuna and garlic. Germanium is a non-metallic element, which can exist in valence states of 2 and 4. Clinical trials and use in private practices for more than a decade have demonstrated organic germanium's efficacy in treating serious disease including cancer, arthritis and senile osteoporosis. But it was rarely reported that inorganic germanium has biological properties. STB-BM contains mineral complex, rare earth elements and a little amount of Inorganic germanium. The experiment was carried out the anti-obesity effect. To investigate anti-obesity effect of STB-BM, we measured the effect of body weight, fat weight (subcutaneous fat, epididymal fat, visceral fat, kidney fat and total fat) and serum biochemical level in rats fed high fat diets. STB-BM 35 mg/kg suppressed the increasing ratio of body weight, epididymal fat weight, visceral fat weight, total fat weight, triglyceride and LDL-cholesterol (p<0.05).

• Journal of Energy Engineering
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• v.27 no.3
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• pp.48-56
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• 2018

The shell waste biomineralization process has known a tremendous metamorphosis and also the nanostructure with the identification of matrix proteins in oyster shells. However, proteins are represented in minor shell components and they are the major macromolecules that control biocrystal synthesis. Aragonite and calcite were derived from molluscan shells and evaluated the source of carbonate minerals and it helps for the formation of limestone. The oyster shell wastes are large and massive. The paleoecological study of oyster beds has discovered a near-shore and thin Upper Rudeis formation with storm influence during the accumulation of oysters with highly altered by disarticulation, bioerosion, and encrustation. It is possible even in the Paleozoic mollusks provided sufficient carbonate entirely to the source of microcrystalline of limestone. The present review is to discuss paleoecologically a number of oyster shell beds accumulated and sediment to form the different types of limestone during the Middle Miocene time.

• Development and Reproduction
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• v.16 no.4
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• pp.385-388
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• 2012

The sex ratio (F:M) in the same population of oyster, Crassostrea gigas at the commencement of the study (2007) was 1:1.0, but changed to 1:2.8 by the end of the study (2008). The sex reversal rate in two-year-old oysters was 40.2%. Specifically, female to male sex reversal rate was 66.1%, which is higher than the male to female sex reversal rate of 21.1%. The sex reversal pattern of C. gigas appears to go from male ${\Rightarrow}$ female ${\Rightarrow}$ male, and as such is determined to be rhythmical hermaphroditism.

• Korean Journal of Environmental Biology
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• v.22
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• pp.63-70
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• 2004

Tributyltin (TBT) and its degradation products, dibutyltin (DBT) and monobutyltin (MBT) were quantitatively determined in surface sediments and two molluscan species, Pacific oyster (Crassostrea gigas) and rock shell (Thais ctavigera), from Gwangyang Bay, Korea. Butyltin compounds were detectable in almost all sediment and biota samples. Tributyltin concentrations in surface sediment ranged<2∼33 ng g$\^$-1/, which is at a lower end of TBT concentrations in industrialized bays in Korea. However, TBT levels in sediments were related to boating activities around the bay. In biota samples, TBT concentrations were in the range of 178∼2,458 ng g$\^$-1/ toy oyster and 47∼236 ng g$\^$-1/ for rock shell. Relatively high TBT concentrations in biota were found near wharves for fisherboats and harbor areas. About 90∼100％ of the female T. clavigera displayed imposex, and relative penis length index of the imposexed-female was in the range of 20.9∼107.9％. Furthermore, TBT body residue had a significant positive relationship with degree of imposex in T. clavigera. Overall, TBT concentrations in Gwanyang Bay were much lower than other major bays in Korea.