• Fisheries and Aquatic Sciences
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• 제20권8호
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• pp.16.1-16.8
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• 2017

The exportation of cultured olive flounder (Paralichthys olivaceus) in Korea has been recently decreasing due to the infections with a myxozoan parasite Kudoa septempunctata, and there is a strong demand for strict food safety management because the food poisoning associated with consumption of raw olive flounder harbouring K. septempunctata has been frequently reported in Japan. The life cycle and infection dynamics of K. septempunctata in aquatic environment are currently unknown, which hamper establishment of effective control methods. We investigated sea water and marine invertebrates collected from olive flounder farms for detecting K. septempunctata by DNA-based analysis, to elucidate infection dynamics of K. septempunctata in aquaculture farms. In addition, live marine polychaetes were collected and maintained in well plates to find any possible actinosporean state of K. septempunctata. The level of K. septempunctata DNA in rearing water fluctuated during the sampling period but the DNA was not detected in summer (June-July in farm A and August in farm B). K. septempunctata DNA was also detected in the polychaetes Naineris laevigata intestinal samples, showing decreased pattern of 40 to 0%. No actinosporean stage of K. septempunctata was observed in the polychaetes by microscopy. The absence of K. septempunctata DNA in rearing water of fish farm and the polychaetes N. laevigata intestinal samples during late spring and early summer indicate that the infection may not occur during this period. N. laevigata was suspected as the possible alternate invertebrate host of K. septempunctata, but the actinosporean stage was not found by well plate method and further studies will be necessary. This research provides important baseline information for understanding the infection dynamics of K. septempunctata in olive flounder farms and further establishment of control strategies.

• 한국어병학회지
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• 제28권2호
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• pp.79-85
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• 2015

동해안에서 어획된 청자갈치 (Bothrocara hollandi)의 체측 근육에 유백색의 불투명한 시스트를 형성하고 있는 점액포자충이 발견되었다. 시스트를 마쇄하여 광학현미경으로 관찰해본 결과, 원형에 가까운 점액포자충의 성숙 포자가 관찰되었다. 성숙 포자의 평균 길이는 $11.9(11.0{\sim}13.5){\mu}m$, 평균 폭은 $11.6(10.7{\sim}13.6){\mu}m$, 평균 두께는 $7.8(6.9{\sim}8.8){\mu}m$이었다. 극낭의 평균 길이는 $4.4(3.2{\sim}5.3){\mu}m$이었으며, 평균 폭은 평균 $3.3(2.4{\sim}4.2){\mu}m$이었다. 감염숙주와 성숙포자의 형태학적 특징, 각 부위의 측정값으로부터 본 연구에서 발견된 점액포자충은 Myxobolus aeglefini Auerbach 1906으로 동정하였다. 또한 18S rDNA sequences를 이용한 계통분석 결과 M. albi와 M. groenlandicus와 같은 분지에 속하는 것이 확인되었으며 각각 97.7%와 96.9%의 상동성을 나타내었다.

• Parasites, Hosts and Diseases
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• 제51권3호
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• pp.369-373
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• 2013

The present study was performed to trace the decisive evidence for mixed infection of 2 Myxobolus species, M. episquamalis and Myxobolus sp., in the gray mullet, Mugil cephalus, from Korean waters. Mullets with whitish cyst-like plasmodia on their scales were collected near a sewage plant in Yeosu, southern part of Korea, in 2009. The cysts were mainly located on scales and also found in the intestine. The spores from scales were oval in a frontal view, tapering anteriorly to a blunt apex, and measured $7.2{\mu}m$ (5.8-8.0) in length and $5.3{\mu}m$ (4.7-6.1) in width. Two polar capsules were pyriform and extended over the anterior half of the spore, measuring $3.5{\mu}m$ (2.3-4.8) in length and $2.0{\mu}m$ (1.5-2.2) in width. In contrast, the spores from the intestine were ellipsoidal, $10.4{\mu}m$ (9.0-11.9) in length and $8.4{\mu}m$ (7.3-10.1) in width. The polar capsules were pyriform but did not extend over the anterior half of the spore, $3.7{\mu}m$ (2.5-4.5) in length and $2.2{\mu}m$ (1.8-2.9) in width. The nucleotide sequences of the 18S rDNA gene of the 2 myxosporean spores from scales and intestine showed 88.1% identity to each other and 100% identity with M. episquamalis and 94.5% identity with M. spinacurvatura from mullet, respectively. By the above findings, it is first confirmed that mullets from the Korean water are infected with 2 myxosporean species, M. episquamalis and Myxobolus sp.