• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.684-689
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• 2017

We examined the possibility of developing an early monitoring system using the shell valve movement activity of Pacific oyster (Crassostrea gigas) for early detection of low salinity water in coastal areas. At salinity levels of 30 psu and 20 psu, SVMs were detected $7.32{\pm}3.21times/hr$ and $7.11{\pm}3.90times/hr$, respectively, The patterns and times of SVMs were not significantly different between the two experiment phases. However, at 10 psu and 5 psu, shell valves were observed to be permanently closed in all experiments. Under combined condition (Group 1: temperature $15^{\circ}C$ ${\times}$ salinity 15 psu), SVMs were observed from 20 psu to 30 psu over a 2 - 3 hr period, and then remained closed. In Group 2 (temperature $30^{\circ}C$ ${\times}$ salinity 15 psu), SVMs were observed, which indicated that the physiological condition of the oysters reached a critical point. Thus, it may be possible to utilize SVMs as an early warning signal for low salinity water.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.6
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• pp.647-655
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• 2018

This study collected basic data on two types of canned roasted oyster Crassostrea gigas. Oysters Crassostrea gigas were immersed at $105^{\circ}C$ for 6 min and then washed and dehydrated before pre-drying. Roasted oysters were prepared by baking boiled oysters at $140^{\circ}C$ for 20 min. The canned roasted oyster added with tomato sauce was prepared as follows. An aluminum can was filled with 50 g of roasted oyster and 40 g of mixed seasoning sauce, degassed at $90^{\circ}C$ for 3 min and vacuum-sealed using a double seamer under a 20 cmHg vacuum. The canned roasted oyster added with tomato paste sauce was prepared similarly by adding the same amount of tomato paste sauce instead of tomato sauce. Microbial growth, appearance, proximate composition, pH, volatile basic nitrogen (VBN), thiobarbituric acid (TBA) value, amino-N, salinity, color value, texture, free and total amino acids, and minerals were measured in the two products. A sensory evaluation indicated that the canned roasted oyster added with tomato paste sauce had preferable characteristics over the canned roasted oyster sauce added with tomato sauce.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.489-494
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• 2010

The nutritional demand of oyster larva (Crassostrea gigas) were investigated to determine the optimal culture conditions and improve micro-algae utilization. Changes in nutrients and shell growth were examined in fed and 96-h (48 h in late umbone stage) oysters at four larval stages. Shell growth increased significantly in D shape larvae, regardless of feeding variations. No growth was observed in starved larvae, except in shell length of umbone (to 11.9 ${\mu}m$). Fed larvae showed significant growth in all development stages (P < 0.05). During starvation, lipids were most significantly decreased in all larval stages (by 76.8%, 68.3%, 76.3%, and 40.3%, respectively), followed by protein (41.1%, 31.1%, 33.1%, 16.7%) and nitrogen-free extracts (40.8%, 24.3%, 36.9%, 20.1%), Gross energy (kcal/g) consumption in each larval stage was 49.6%, 35.1%, 39.1%, and 20.4%, respectively. Our results indicate that lipids are the most important energy source during the early larval development stages of C. gigas.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.5
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• pp.1075-1082
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• 2014

Monthly Screening of Pacific oyster, Crassostrea gigas, was surveyed by PCR for Ostreid herpesvirus(OsHV-1) infections from 2012 to 2013 in Korea. It was showed positive results in one hatchery in April and May 2012 and in oyster farming areas from August to November in 2013. The obtained sequences showed 99.3~99.5% homology with OsHV-1 ${\mu}var$(Accession Number: HQ842610) and 96.2~96.3% homology with OsHV isolated from Korea(Accession Number: AY509253).

• Fisheries and Aquatic Sciences
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• v.6 no.4
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• pp.220-224
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• 2003

In order to determined the appropriate processing season of Pacific oyster (Crassostrea gigas), 30 individuals cultured in Kamak Bay on the southern coast of Korea were taken bimonthly 7 times a year, and seasonal variation of edible portion weight, edible portion yield and coefficient of fatness were investigated. There were close relationships between edible portion weight (X) and total weight (Y) and between coefficient of fatness (X) and edible portion yield (Y), which were expressed in regression lines, i.e. Y=0.2709X-1.9094 (r=0.9254) and Y=44.0596X+ 15.1127 (r=0.8485), respectively. From the results of seasonal variation of edible portion weight, yield and coefficient of fatness, the appropriate processing season of raw Pacific oyster was between winter and spring, that is, between December and following April the next year.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.223-228
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• 2011

To understand the role of hemocytes in the shell repair process, a hole was drilled in the right valves of the Pacific oyster, Crassostrea gigas, and the repair process was observed. Histological observations suggested that the exterior surface of the shell was repaired by aggregated hemocytes. The nuclei of the hemocytes were cleary stained in the regenerated shell while appearing fragmented after calcification at the $7^{th}$ day. Globular calcium granules were genegenerated from the hemocytic monolyer after 6 days of incubation which were morphologically and chemically identical with those from prismatic shell. Our finding suggested that the repaired prismatic shell was composed by aggregated hemocytes and that their endogenous calcium component might support the nucleation of calcium biomineralization during shell repair.

• Fisheries and Aquatic Sciences
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• v.6 no.3
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• pp.135-139
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• 2003

During routine survey of Pacific oyster (Crassostrea gigas) collected from Tongyoung area in southern coast of Korea, histological examination revealed that a intracellular microorganisms infected the digestive gland of the oyster. They infected hepatopancreatic cells extensively. The size of intracellular microorganism was of 45 to 86nm in diameter and 200nm to more thar 500nm in length. They were pleomorphic. The morphological characteristic of intracellular microorganisms lacked cell wall and was bounded by the plasma membrane. They contained typical prokaryotic ribosomes and fibrillar DNA-like strands. No additional internal structure has been observed. Based on the lack of cell wall and the cellular localization, the intracellular microorganism is considered as a Mycoplasma-like organism.

• The Korean Journal of Malacology
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• v.27 no.1
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• pp.35-42
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• 2011

In order to understand effect of polycyclic aromatic hydrocarbon (PAH) on shell repair of the Pacific oyster, Crassostrea gigas, shell regeneration experiments were carried out using oysters drilled a hole on the right valve. The change of pH and hemocytic characteristics in both extrapallial fluid and hemolymph were observed during the shell repair. The thickness of mantle tissue was apparently decreased, while necrosis in epithelium and periostracal gland was increased in response to PAH exposure. Our finding suggested that PAH could adversely influence on shell repair.

• Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.15-19
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• 2012

A new cyclic peptide (six-membered amino acid), gamakamide-E (L-Leu-L-Met (SO)-L-Me-Phe-L-Leu-D-Lys-L-Phe), was isolated as a strongly bitter tasting compound from cultured oysters, Crassostrea gigas. The molecular formula of $C_{43}H_{61}N_7O_8S$ was deduced from high resolution fast atom bombardment mass spectrometry (HR FAB-MS) ($[M+H]^+$ m/z 836.4356 ${\Delta}$= -2.4 mmu). Its unique structure including a hydantoin structure was firstly elucidated by nuclear magnetic resonance (NMR) analysis. Stereochemistries of constituent amino acids were determined by chiral high performanced liquid chromatography analysis of natural and synthesized peptides.

• The Korean Journal of Malacology
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• v.32 no.2
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• pp.67-71
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• 2016

In order to obtain a large number of fertilized eggs for seedling production, experiment was carried out examine effects of serotonin on spawning of the Pacific oyster Crassostrea gigas. The shorter response time to initial spawning in case of serotonin injection showed, the higher serotonin injected with 7.6-27 min. The response time to initial sperm releasing showed the same tendency with female. The highest response rates and eggs amount spawned were showed in the highest concentration. The serotonin injection had no effect on frequency of germinal vesicle breakdown (GVBD), fertilization and hatching rate.