• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.503-504
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• 2000

바지락포자충 Perkinsus는 미국과 유럽 등지에서 굴과 바지락에 기생하며 고수온기 숙주의 대량 폐사를 유발하는 원생동물로 이에 대한 연구가 활발하게 진행중인 패류질병이다. Choi 와 Park (1997)은 1990년대 초반부터 나타난 여름철 바지락 대량 폐사 원인 중의 하나로 바지락포자충을 폐사 원인 생물로 추정한 바 있다. 이 연구는 1997년부터 진행중인 우리 나라 전 해역에 대한 바지락포자충 감염현장 조사의 일환으로, 경남지역에 분포하는 바지락의 바지락포자충 감염에 대한 조사 보고이다. (중략)

• Korean Journal of Environmental Biology
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• v.19 no.1
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• pp.79-86
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• 2001

The apicomplexan parasite, Perkinsus sp., has been reported as a causative pathogen responsible for the mass mortality of the Manila clams, Ruditapes philippinarum in European countries as well as in Korea. Prevalence, infection intensity, histopathologic features and zoosporulation of Perkinsus found in the Manila clams distributed along the coast of Cheju Island were investigated in this study. Clams were collected from nine different beaches along the Cheju Island from May to July in 2000. Ray's Fluid Thioglycollate Medium (RFTM) and Choi's NaOH lysis methods were applied in the diagnosis and quantification of the Perkinsus infection. Prevalence, percentage infection of the parasite examined was 100% in Pyosun, 70% in Sungsan, 63% in Kumneong, 33% in Jongdalri, 21% in Iho, 17% in Moslpo, and 14% in Seogwipo. No Perkinsus was found in the clams collected from Kimnyong and Yongmeo-ri. Infection intensity as a number of Perkinsus cells per gram tissue wet weight (twwt), was 98,430 cells/g twwt in Pyosun, 78,553 cells/g twwt in Sungsan, 18,980 cells/g twwt in Kumneong, 4,290 cells/g twwt in Jongdalri, 1,527 cells/g twwt in Iho, 1,069 cells/g twwt in Moslpo, and 853 cells/g twwt in Seogwipo. Histological preparation of the infected tissues revealed trophozoites of Perkinsus sp., ranged from 5 to 10 ${\mu}{\textrm}{m}$, in diameter mostly distributed in the digestive gland and the gill filaments. Zoospores were discharged from the hypnospore via discharging tube about 2 days after incubated in filtered and aerated seawater. In general, the prevalence and infection intensity of Perkinsus in Cheju Island were much lower than that reported from the western and southern coast of Korea.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.10a
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• pp.251-252
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• 2001

현재 곰소만에는 크고 작은 111개의 바지락 양식장 (98년 기준)이 허가되어 있는 곳으로 우리나라 바지락 총생산의 약 30％를 차지하는 대표적인 바지락 생산지이다. 그런데 곰소만의 경우, 바지락 양식장의 모든 위치는 만의 중앙부를 기준으로 모두 동쪽에 분포하고 있다. 이러한 사실은 바지락 양식장이 어떤 지형적 특징에 의존하고 있음을 시사한다 (이 등, 2001). 본 연구에서는 곰소만의 지형 특징을 토대로 그곳에서의 퇴적작용을 이해한 후, 지형적으로 구분되는 대표적인 곳에서 중형저서생물인 하르팍티쿠스 요각류의 분포를 조사하여 바지락형성 장소의 지형학적ㆍ생물학적 특성을 고찰하였다. (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.252-253
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• 2003

바지락포자충 Perkinsus는 미국과 유럽 등지에서 굴과 바지락에 기생하며 고수온기숙주의 대량 폐사를 유발하는 원생동물로 이에 대한 연구가 활발하게 진행 중인 패류질병이다. Choi 와 Park (2001), Choi et at.(2002)은 우리나라 전 연안과 일본 Isahaya Bay에 서식하는 바지락에서 Perkinsus를 검출하고 이들의 감염도와 조직병리학적 특성을 보고한 바 있다. (중략)

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2000.05a
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• pp.245-246
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• 2000

연안 간석지에 잠입하여 생활하는 바지락은 체내에 함유되어 있는 사니질이 많아, 식용으로 이용시 사전에 토사시켜야 하는 번거로움이 있을 뿐 아니라 폐사할 경우에는 토사처리가 불가능하므로 바지락의 경제성 높은 이용을 위한 토사처리의 간편성이 요구되고 있다. 이와 관련하여 패류의 토사처리를 위한 연구로는 염분도에 의한 방법(Macmillan and Rodman, 1971 ; Westbroek 1976 ; Mishra and Srdikar, 1990) 등이 보고되어 있으나 체계적으로 보고되어 있지 못한 실정이다. 따라서 본 연구는 바지락의 토사를 위한 간편법으로서 수온과 염분도별, 바지락의 최적 토사량을 측정하였고 최종적으로 소화맹낭의 잔여 사니도 계측하였다. (중략)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.3
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• pp.303-309
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• 1999

Mass mortality of the Manila clam, Ruditapes philippinarum has been reported all along the west and south coast of Korea for the past several years. As a pathogenic agent, Perkinsus sp., an endoparasitic protozoan has been identified in this study and believed to be responsible for the mass mortalities. Prevalence and infection intensity of Perkinsus sp. was investigated from a Manila clam population inhabiting at Komsoe Bay in the west coast where mass mortality of the clam has been reported. A total of 142 Manila clam, 50 oyster, Crassostrea gigas, 10 ark shell, Scapharca broughtonii, and 5 predatory gastropada, Rapana venosa were examined for the presence and the quantity of Perkinsus sp. Ray's fluid thioglycollate medium method (FTM method) with modified Mackin's infection intensity scale and Choi's quantitative method were used in detecting and quantifying the parasite. All individuals of R. philippinarum examined in this study were infected with Perkinsus sp., indicating $100\%$ prevalence while none of the oysters and the gastropods exhibited the parasite. Six to ten individual hypnospores of Perkinsus sp. were counted from the ark shells. The number of hypnospores in the clam tissues varied from 16,667 to 4,091,667, with a mean number of 1,077,628. Average infection intensity according to Mackin's was 2.87, indicating a moderate infection. A negative correlation was observed between the number of Perkinsus sp. in the tissue and the condition index, a ratio tissue wet weight to shell cavity volume. The clam size and the infection intensity in terms of total number of parasites were positively correlated; the bigger clam, the heavier infection. Such high number of Perkinsus sp. counted in the clams could be enough to cause physiological disturbance of clams, such as retarded growth and reproduction. It is also believed that such a high infection leads mortality of the clam via continuous draining of the energy by metabolic activities and reproduction of the parasites. Correlation between the condition index and the infection intensity observed in this study supports this hypothesis.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2001.05a
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• pp.309-310
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• 2001

국내에서 바지락 양식은 경기도 연안의 간석지에서 1912년에 시작되었다고 보고되어 있으며, 1980년부터 본격적인 양식이 시작되어 1990년에 최고 생산량을 기록하였다. 그러나 최근에는 매립에 의한 서식장 감소, 양식장의 밀식에 따른 자가 오염 및 환경변화 등에 의한 바지락 폐사에 따라 생산량 감소가 야기되어 지속적인 바지락 양식장 유지관리의 중요성이 대두되고 있다. 곰소만 조간대 및 주변 해역에서의 기존연구는 지질학적 특성뿐 만 아니라, 생물학적 특성, 퇴적물의 물리적 특성, 그리고 해역의 수리역학적 특성을 포함한 포괄적인 연구에 관해서는 미흡한 실정이다. (중략)

• The Korean Journal of Malacology
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• v.19 no.1
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• pp.1-8
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• 2003

The present study was performed to describe the influence of water temperature and salinity on the filtration rates of the short-necked clam, Ruditapes philippinarum. The clams were collected at tidal flat near Yeosu city, Cheollanamdo, Korea, from July 2001 to August 2001. Diatoms, Phaeodactylum tricornutum (KMCC B-128), were indoor-cultured by f/2 medium, and were used to measure the filtration rate of the clams. Filtration rates of the clams were measured by indirect method. Cell concentrations of food organisms were determined by direct counting cells using the hemacytometer under the light microscope. The filtration rate of the clams increased with temperatures up to the optimum temperature, circa 25$^{\circ}C$. Above this optimum temperature, the filtration rate decreased drastically. Also the filtration rate of the clams increased with salinity up to 35 psu. The maximal filtration rates of the clams were recorded at 20-25$^{\circ}C$, similar to be known as the optimal temperature for their growth, and 25-35 psu, respectively. The minimal filtration rates of the clams were recorded at 5$^{\circ}C$ and 15 psu. At the similar temperature and salinity, the filtration rate of the younger clams was higher than that of the older ones. Thermal coefficient, Q$_{10}$ values at low temperature range were much higher than those at high temperature range. These results indicate the short-necked clam is more sensitive in cold water. As they grow up, they become more stronger against their ambient environmental changes, such as thermal-shock, salinity changes.

• The Korean Journal of Malacology
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• v.16 no.1_2
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• pp.49-54
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• 2000

The growth of short neck calms, Tapes philippinarum was compared between two areas, Songdo in Kamak Bay and Sudo in Chinhae Bay from April 1999 to March 2000. The short neck clams in Kamak bay grew from 13.84${\pm}$0.04 mm to 35.43${\pm}$1.22 mm in shell length, while those in Chinhae bay grew from 13.84${\pm}$0.04 mm to 31.91 ${\pm}$1.72 mm in 12 months. Shell height, shell breadth and total weight of the short neck clams in Kamak bay were also greater than those from Chinhae bay. Bottom quality of Chinhae bay showed negative skewness, and that of Kamak bay was positive skewness of Chinhae bay seems to be caused by the effect of strong tidal current. This may indicate that Kamak bay is better area than Chinhae bay for the culture of the short neck clams.

• The Korean Journal of Malacology
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• v.29 no.1
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• pp.1-6
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• 2013

This study aimed to evaluate the effects of shaking stress in the hemolymph of the Manila clam Ruditapes philippinarum by quantification of nitric oxide (NO) levels. The clams were divided into 3 groups as follows: clams placed in a plain container (control), clams injected with nitro-L-arginine methyl ester (NAME, an NO inhibitor), and clams in a container filled with nylon fiber at a density of $1kg/m^3$. Subsequently, each group was placed in sea water and shaken at 100 rpm for 6 h. The concentration of NO was quantified by using DAF assay and Griess assay. Both the assays showed that while shaking significantly increased the NO concentration, the NO inhibitor reduced the NO concentration in the hemolymph of the clams tested. In addition, the nylon fiber, which was used as a filler, effectively prevented the increase in NO concentration. This result suggests that measurement of NO concentration is a useful tool for evaluation of physiological stress in marine bivalves. In addition, it should be considered that a filler is necessary when dredge fishing or the suspended clam culture method is developed.