• Journal of fish pathology
• /
• v.19 no.3
• /
• pp.243-251
• /
• 2006

The internal defense system of mollusks consists of circulating haemocytes. In order to understand the morphological characterization of haemocytes, light and electron microscopy were carried out in oyster, Crassostera gigas. Four types of haemocytes were recognized: type Ⅰ small hyalinocytes, type Ⅱ large hyalinocytes, type Ⅲ large granulocytes and type Ⅳ small granulocytes. Additionally, the activities of alkaline phosphatase (ALP), acid phosphatase (ACP), peroxidase (POD), α-naphthyl acetate esterase, β-glucuronidase, PAS, sudan black B and oil red O in haemocytes were analysed by immunocytochemical methods. The results indicate that enzymatic activities were abundant and more active in granulocytes than in hyalinocytes. After incubation with haemoctyes and Vibrio FKC, phagocytic index and percentage of phagocytic cell were and shown to be increased from 15 to 120 min. In addition, the enzymatic activities were higher than those of controls: ALP, ACP, α-naphthyl acetate esterase and β-glcuronidase, indicating that these enzymes can be related with phagocytosis in oyster.

• Journal of Life Science
• /
• v.18 no.7
• /
• pp.1015-1018
• /
• 2008

To analyze the population genetic structure of the oyster Crassostrea gigas Thunberg, 34 specimens werecollected from Gamak bay in March, 2007. Total genomic DNA was extracted from each sample and PCR was performed to identify haplotypes of oyster by using HCO2918 and LCO1491 primers. Four kinds of haplotypes (CR1, CR2, CR3, and CR4) were identified. Among these group, CR3 showed the highest relative frequency at 73% than any other of haplotypes. On the basis of hierarchical genetic structure, the population of Gamak showed a higher genetic relationship with Namhae, but the genetic distance between southern and western coasts was negative and no statistical significance was found (p>0.05). Consequently, the oyster from Korea coast is determined to be both homogenous and large.

• The Korean Journal of Malacology
• /
• v.28 no.1
• /
• pp.21-28
• /
• 2012

The combined effects of water temperature and salinity on the settlement rate and density (spats/$cm^2$) of Crassostrea gigas pediveliger larvae were studied under the hatchery conditions. Four water temperatures (20.0, 23.0, 26.0 and $29.0^{\circ}C$) were tested at three salinities (20.0, 30.0 and 40.0). The optimum water temperature by salinity conditions were $29.0^{\circ}C$ and 20.0, 30.0 which significantly (P < 0.05) the highest mean (${\pm}S.D$) larval settlement rate of $43.1{\pm}0.1%$, $42.1{\pm}0.1%$, respectively. But the combination of water temperatures and salinities for settlement density was not effected, but each factor as water temperature ($29.0^{\circ}C$), salinity (40.0) was shown significantly high and low settlement density, respectively (P < 0.05). The statistics result of settlement density frequency was appeared: mode ($1.2-2.3spats/cm^2$), Mean ($1.9-2.4spats/cm^2$), Range ($3.0-5.8spats/cm^2$) and the lowest variance was obtained 0.4 at water temperature $20.0^{\circ}C$ by salinity 30.0, but $29.0^{\circ}C$ by 20.0 was the highest (1.1). The best condition at this results for the larvae setting under the artificial seed collection of C. gigas was $29.0^{\circ}C$ and 20.0-30.0.

• The Korean Journal of Malacology
• /
• v.30 no.4
• /
• pp.343-351
• /
• 2014

We determined the effects of neuroactive compounds known as synthetic larval settlement inducers on the settlement of the Pacific oyster C. gigas pediveliger on the larval collector. Six types of the inducers, serotonin (5-HT), ${\gamma}$-amino butyric acid (GABA), L-3,4-dihydroxyphenylalanine (L-DOPA), norepinephrine, epinephrine and methyl bromide (MB) were tested. All the chemicals induced larval settlement, MB being the most effective with settlement rate of $42.7{\pm}2.7%$, followed by GABA ($35.4{\pm}2.0%$), 5-HT ($29.1{\pm}2.2%$), L-DOPA ($19.2{\pm}2.1%$), epinephrine ($15.2{\pm}0.9%$), and norepinephrine ($11.0{\pm}1.2%$). The chemicals ${\gamma}$-amino butyric acid and methyl bromide were also better in terms of settled density on the collector with their respective density of $1.97{\pm}1.42$ and $2.37{\pm}1.86ind/cm^2$, reminiscent of being most effective candidates for a larval settlement inducer in the oyster hatchery.

• The Korean Journal of Malacology
• /
• v.28 no.1
• /
• pp.45-54
• /
• 2012

We investigated environmental characteristics of the tidal flat oyster aquafarms to clarifyeffects of the tidal flat environmental factors on growth and mortality of the tidal flat oyster Crassostrea gigas by the Net Bag Rack Culture System in two districts in Western Korea. In this study, we have carried out the basic environmental investigation on growth of the single tidal flat, water quality and sediments, etc. in Taean and Seosan districts, Choongcheongnam-do, where the single tidal flat oyster aquaculture have been performed by the net bag rack culture system. In June 2011 when the final survey carried out at the two districts in western Korea, the mortality in Seosan district was higher than that in Tae-an district. Judging from the results of growth and mortality of the single tidal flat oysters investigated at two sites of Jinsan-ri in Taean and Chang-ri in Seosan districts, two results of Taean district showed higher growth and lower mortality than those of Seosan district. It is assumed that the proper acceptable density possible for growth of the tidal flat seeds and the secure of economics, in case of plastic cultivate net with the size of $50{\times}80cm$, are about 200 individuals. In this study, It was clarified that selection of the suitable sites, the input into the net bag of high quality oyster seeds and selective dispersion in the optimal density of the single tidal flat oyster have an effect on growth and mortality of the tidal flat oyster.