• Journal of fish pathology
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• v.18 no.1
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• pp.39-48
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• 2005

Pathogenicity of Vibrio tapetis, the causative bacterium of 'brown ring disease (BRD)' was evaluated in Manila clams (Ruditapes philippinarumi by artificially 0.1 $m\ell$ infection of $1.0\times10^5$cells and $1.0\times10^8$ cells at 20 $^{\circ}C$. A PCR assay based on 16S rRNA to detect the bacteria in clam tissues was established. Accumulative mortality of clams infected with $1.0\times10^7$cells and $1.0\times10^4$ cells per an individual of the bacteria was 67.5% and 7.5%, respectively. However, the deposit of brown pigment in the inner shells by accumulation of chonchiolin was not found. The bacteria were not be able to re-isolate from the infected clams by the conventional agar plate method but were easily detected by PCR assay established in this experiment. In clams artificially infected with 10 species of Vibrio, a 414bp for V. tapetis was detected in PCR assay. The specific band in the clams infected with $1.0\times10^4$cells per an individual of V. tapetis was detected only in gills one day after the infection but never be found in any tissues including gills three days after the infection. In the case of clams infected with $1.0\times10^8$cells per an individual of V. tapetis the specific band was detected in gills and intestine one day after the infection, in all tissues three days after the infection, and then in gills and adductor muscle nine days after the infection. The PCR assay was applied to detect V. tapetis in manila clam, surf clam (Mactra veneriformis), oyster (Crassostrea gigas) and Thomas' rapa whelk (Rapana venosa) taken from Taean and Gochang from April to July 2004. The infection rates were detected to 23.1% and 9.4% in the oyster and surf clam, while manila clam and Thomas' rapa whelk were not found.

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.297-302
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• 2010

Water temperature, salinity and density on egg development of the sunray surf clam, Mactra chinensis were investigated for artificial seedling production. The required time from fertilization to D-shaped larvae were 33.8 hours in $18^{\circ}C$, 20.6 hours in $23^{\circ}C$, 18.2 hours in $28^{\circ}C$ and 15.0 hours in $33^{\circ}C$. The development duration was reduced with increasing temperature. The relationships between temperature and the required time from egg to each developmental stage were described as follows: 2-cell, 1/h = 0.1051WT - 1.4782; 8-cell, 1/h = 0.037WT - 0.3686; gastrula, 1/h = 0.008WT - 0.0521; trochophore, 1/h = 0.0041WT - 0.0235; D-shaped larva, 1/h = 0.0024WT - 0.0102. Biological minimum temperature for the egg development was estimated to be $8.0^{\circ}C$ in average. The possible range of temperature for the development of D-shaped larvae was $18-28^{\circ}C$ and optimum of water temperature for the development of egg was $23^{\circ}C$. The possible range of salinity for the development of D-shaped larvae was 20-35 psu and optimum of salinity for the development of egg was 30-35 psu over 25 psu at least. The density of fertilized egg was below 40 per 1 ml in rearing seawater for elevating the development rate from fertilized egg to D-shaped larva.

• Korean Journal of Food Science and Technology
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• v.24 no.6
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• pp.541-546
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• 1992

In order to develop low salt fermented hen clam sauce with high stability, the effects of citric acid pretreatment and fermentation temperature were examined. The VBN contents of surf clam sauce treated with citric acid (SCA) were lower than those of control and the same sauces added alcohol at two temperature conditions ($5^{\circ}C$ and room temperature) during fermentation. The maximum $NH_2-N$ contents of control and SCA during fermentation at $5^{\circ}C$ were 501.3 and $618.4{\sim}691.6\;mg/100g$, respectively, and the pH of those showed $5.61{\sim}6.24$ and $2.43{\sim}3.21$. The total creatine contents of control and SCA, respectively, were $36.8{\sim}27.6\;mg/100g$ ranges. As the time of treatment with citric acid was longer, the degradation of ATP, ADP and AMP in the SCA was faster. In the control, the Ala content was $19.6{\sim}23.02%$ and was highest level among all free amino acids. As fermenting term was longer, among the free amino acids, Ala and Gly were large amounts in control and SCA, respectively, and Gly was slowly increased in SCA during fermentation. As the results of organoleptic test, the tastes of SCA showed good score than control.

• The Korean Journal of Malacology
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• v.13 no.2
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• pp.185-192
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• 1997

1990젼 3월부터 1991년 2월까지 전라북도 군산시 내초도 연안에 서식하는 동죽의 성장을 조사하였다. 1.조사해역의 연간 수온분포는 2.0-26.3$^{\circ}C$이고, 간석지 온도는 0.7-36.2$^{\circ}C$이었다. 2. 동죽의 패각에 나타나는 윤문은 연 1회 형성되며 윤문 형성시기는 3-4월로 조사되었다. 3. 초륜 형성기간은 9개월(0.75년)로 나타났다. 4. 각장(SL: mm)과 체중(TW: G)간의 관계는 TW=1.090 x $10^{-4}$ S $L^{3.2798}$( $r^{2}$=0.99)이었으며, 각장과 각고(SH:mm)간의 관계는 SH=0.865 SL + 0.250( $r^{2}$=0.99)이고, 각장과 각폭(SW: mm) 간의 관계는 SW=0.599 SL - 0.203 ( $r^{2}$=0.98; 각장 22 mm미만), SW=0.724 SL - 2.796( $r^{2}$=0.91; 각장 22 mm이상)이었다.5. 연령(t)에 대한 각장(S $L_{t}$ )의 Bertalanffy성장식은 $L_{t}$ =51.399(1- $e^{0.585}$8(t+0.064)이고, 연령(t)에 대한 체중 (T $W_{t}$ )의 Bertalanffy성장식은 $W_{t}$ =44.467(1- $e^{0.585}$8(t+0.064)$^{3}$로 나타났다.타났다.

• Journal of fish pathology
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• v.18 no.1
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• pp.49-58
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• 2005

Hemacolor stain, histopathological observation and FTM incubation assay were applied to detect Perkinsus sp. infection in Manila clams (Ruditapes philippinarumi taken from culture beds at Tean and Gochang from March 2002 to August 2003. The prevalency was 100% in the clams from Gochang and 20-70% from Tean. Of the three methods, histopathological observation was the most effective to detect the infection. And the parasites was most abundant in gills. When PCR assay was applied to detect Perkinsus sp. for four species of Mollusc such as manila clam, surf clam (Mactra veneriformis), oyster (Crassostrea gigas) and Thomas' rapa whelk (Rapana venosa) taken from Tean and Gochang from April to July 2004, the parasites were detected from all the species at the infection rates of 95%, 62%, 46.9% and 10% in that order. The infection rate was much higher in the species burrowing in the bottom sediments than those attaching on the tidal rock. The results suggest that Perkinsus sp. may affect almost all the molluscs inhabiting western coastal areas of Korea.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.51-63
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• 2013

To assess the effect of environmental factors on the sustainability of cultured production shellfish, we investigated the habitat characteristics of tidal flat (Namhae-po in Taean). We measured the physiochemical parameters (temperature, salanity, pH, dissolved oxygen and nutrients) and the geochemical characteristics (chemical oxygen demand, ignition loss, C/N ratio and C/S ratio). Surface sediments were collected from several site of tidal flat to examine the geochemical characteristics of both the benthic environment and heavy metal pollution. The grain size for research area of tidal flat were similar at the ratio of silt and clay in comparison with the other site of it. The C/N ratio was more than 5.0, reflecting the range arising from the mix of marine organism and organic matter. The C/S ratio (about 2.8) showed that survey area had anoxic or sub-anoxic bottom conditions. The enrichment factor (Ef) and index of accumulation rate (Igeo) of the metals showed that those research areas can be classified as heavily polluted, heavily to moderately polluted, or more or less unpolluted, respectively. Adult surf clam (Mactra veneriformis) density was highest at St. 2 (middle part of the Namhae-po), on the other hand, surf clam spat density was highest at St. 3 (lower part of the Namhae-po). Heavy rain, terrigenous suspended clay with fresh water from neighboring agricultural land, and severe high air temperature during summer could be thought as detrimental causes of spat and adult mortality in Namhae-po tidal flat. We suggested that the growth of shellfish in the tidal flat was effected by the various environmental conditions, so an improvement in the cultured method was needed.