Hee-Do Jeung

Popular edible seaweed, Gelidium amansii prevents against diet-induced obesity

The popular edible seaweed, Gelidium amansii is broadly used as food worldwide. To determine whether G. amansii extract (GAE) has protective effects on obesity, mice fed a high-fat diet (HFD) treated with GAE (1 and 3 %) were studied. After 12 weeks of GAE treatment, body weight was greatly decreased in mice fed a high-fat diet. This effect could be due to decreased adipogenesis, as evidenced by the fact that GAE suppressed adipogenic gene expression in adipocytes. In addition, blood glucose and serum insulin levels were reduced by GAE treatment in mice fed a high-fat diet, suggesting improvement in glucose metabolism. GAE supplementation also led to a significant decrease in total cholesterol and triglyceride levels. These data are further confirmed by H&E staining. Our findings indicate that Gelidium amansii prevents against the development of diet-induced obesity, and further implicate that GAE supplementation could be the therapeutical option for treatment of metabolic disorder such as obesity.

Cloning and localization of MCdef, a defensin from Manila clams (Ruditapes philippinarum)

A defensin-like peptide was previously detected in hemocytes of Manila clams (Ruditapes philippinarum). In the current study, we cloned and characterized this defensin, designated MCdef. Cloning produced a full-length gene sequence of 201 bp predicted to encode a 66-amino-acid precursor protein maturing to a 44-amino-acid residue. Amino acid sequence analysis showed that MCdef is similar to defensins from marine mollusks and ticks. Phylogenetic analysis suggested that MCdef is closely related to defensins from Mytilus galloprovincialis (Mediterranean mussel) and Crassostrea gigas (Pacific cupped oyster). The three-dimensional structure of MCdef was modeled using the solution structure of C. gigas defensin as a template. With the exception of three variable loop areas, the modeled structure of MCdef was identical to that of C. gigas defensin. MCdef antiserum was raised against a synthetic MCdef peptide and verified by Western blotting using recombinant MCdef. RT-PCR analysis demonstrated high levels of MCdef mRNA in hemocytes and adductor, foot, gill, mantle, palp, and siphon tissues of Vibrio tapetis-infected Manila clams, whereas in V. tapetis-uninfected Manila clams, the level of MCdef mRNA was low in adductor, palp, and siphon tissues and even lower in the other tested tissues. Immunohistochemical analysis revealed high MCdef expression was detected in the gill, the mantle, and the digestive tubules of the diverticulum of V. tapetis-infected Manila clams. Minimum inhibitory concentration (MIC) of the purified rMCdef was determined. MCdef showed highest activity against Streptococcus iniae and Staphylococcus aureus.

Molecular and histological identification of Marteilioides infection in Suminoe Oyster Crassostrea ariakensis, Manila Clam Ruditapes philippinarum and Pacific Oyster Crassostrea gigas on the south coast of Korea

The oyster ovarian parasite Marteilioides chungmuensis has been reported from Korea and Japan, damaging the oyster industries. Recently, Marteilioides-like organisms have been identified in other commercially important marine bivalves. In this study, we surveyed Marteilioides infection in the Manila clam Ruditapes philippinarum, Suminoe oyster Crassostrea ariakensis, and Pacific oyster Crassostrea gigas, using histology and Marteilioides-specific small subunit (SSU) rDNA PCR. The SSU rDNA sequence of M. chungmuensis (1716 bp) isolated from C. gigas in Tongyoung bay was 99.9% similar to that of M. chungmuensis reported in Japan. Inclusions of multi-nucleated bodies in the oocytes, typical of Marteilioides infection, were identified for the first time in Suminoe oysters. The SSU rDNA sequence of a Marteilioides-like organism isolated from Suminoe oysters was 99.9% similar to that of M. chungmuensis. Marteilioides sp. was also observed from 7 Manila clams of 1840 individuals examined, and the DNA sequences of which were 98.2% similar to the known sequence of M. chungmuensis. Unlike Marteilioides infection of Pacific oysters, no remarkable pathological symptoms, such as large multiple lumps on the mantle, were observed in infected Suminoe oysters or Manila clams. Distribution of the infected Manila clams, Suminoe oysters and Pacific oysters was limited to small bays on the south coast, suggesting that the southern coast is the enzootic area of Marteilioides infection.

An assemblage of mollusks associated with the high latitude scleractinian coral Alveopora japonica (Eguchi 1968) in Jeju Island, off the south coast of Korea

Corals reefs and communities support a wide range of flora and fauna. The complete richness and abundance of faunal communities in either coral reefs or communities is not fully understood. This is especially true for high-latitude coral communities. In this work, we carried out an analysis of an Alveopora japonica associated mollusk assemblage, in Jeju Island, Korea. A. japonica is one of the major coral species present in high abundance (88–155 colonies m-2), with a high recruitment rate (7.8 juvenile corals m-2 yr-1) in Jeju Island, and may serve as a habitat for other benthic organisms. In 2012, a total number of 579 A. japonica colonies with sizes ranging between 15.1-346.7 cm2 in the surface area were collected from a 1m× 10m quadrat installed at a depth of 10 m at Keumneung, on the northwest coast of Jeju Island. Numerous benthic invertebrates were found to be associated with A. japonica colonies. Twenty-seven bivalves and gastropods were identified, including a boring mytilid, Lithophaga curta, and an arcid, Barbatia stearnsi. A zonalgeographical examination of the distribution ranges of these mollusks revealed a majority of warmer water species. Our observations also showed that A. japonica may be providing a habitat to grazing gastropod, Turbo cornutus, and encrusting Spondylidae and Chamidae bivalves. A. japonica forms a coral carpet with a distinct assemblage of bivalves. It is thought that the presence of these mollusks species in the coral indicates its use as a nursery for juvenile species, a ready food supply of organic detritus, and a refuge from predators.

Spatial variation in the annual reproductive cycle of Turbo (Batillus) cornutus (Gastropoda: Trochidae) at Jeju Island, Korea

The annual reproductive cycle of the top shell Turbo cornutus from Jeju Island was investigated in two populations using histology. In the northern population, gametogenesis commenced in January as the surface water temperature reached 14 °C, while in the southern population gametogenesis began a month earlier, as the water temperature remained at 17 °C. Ripe top shells first appeared in June and spawning continued from June to October when water temperatures were between 20 and 24 °C. Histology indicated that the spawning period of the southern population was a month earlier and lasted longer (June–October) than in the northern population (July–September). The percentage gonad area of animals in the southern population in March and April was significantly higher than in the northern population (p < 0.05), suggesting that the gonads of the southern population matured earlier. The observed earlier maturation and the subsequent spawning of the top shells from the south coast of Jeju Island could be associated with the warmer water temperature and more favorable environmental conditions. The major spawning period of top shells observed in this study from July to September suggested that the currently implemented period of the fishing closure from June to August needs to be re-evaluated to protect more spawning adults in late summer.

Quantitative assessment of reproductive effort of the Manila clam Ruditapes philippinarum in a lagoon on Jeju Island (Korea) using enzyme-linked immunosorbent assay

We investigated gonad development and reproductive effort (RE) of the Manila clam Ruditapes philippinarum at Jeju Island, Korea. Gonad maturation and RE were determined using histology and an indirect enzyme-linked immunosorbent assay (ELISA). In June 2006, most of the clams (80%) in the lagoon were in the resting stage. Spawning clams first appeared in late July, and most clams spawned from early August to mid-September. The condition index increased gradually from early July to late August, then declined from early to mid-September, suggesting that spawning occurred during this period. The gonadosomatic index assessed by ELISA also increased dramatically from June (0.9), peaked in early August (19.7) then declined from late August to mid-September, indicating that clams at the study site had only one spawning pulse during the spawning period. Spawning at Jeju Island was one month later than Manila clams on the west coast of Korea. The delayed spawning and low RE of the clams could be in part, be explained by lower food availability, as the level of chlorophyll-a recorded in this study was much lower than that found in water from the west and south coast.

Cytochemical Measurement of Lysosomal Responses in the Digestive Cells of Wild Pacific Oyster, Crassostrea gigas on the South Coast of Korea

??이매패류의 소화맹낭은 고도로 발달된 리소솜 시스템을 지니고 있어 소화작용과 함께 오염물질의 해독과 배출작용을 담당한다. 따라서 소화맹낭의 리소솜 시스템은 환경 변화에 민감하게 반응한다고 알려져 있다. 이 연구에서는 동결절편을 이용한 조직학적 방법으로 조간대에 서식하는 참굴 소화맹낭의 리소솜 활동을 측정하였다. 참굴은 2010년 6월 광양만 내만의 초남대교, 차면리와 외만의 신덕리, 평산리 조간대에 서식하는 굴을 채집하였다. 제작된 동결 절편을 이용하여 lysosomal membrane stability(LMS) 및 lipofuscin(LF) 축적, neutral lipid(NL) 축적, 소화맹낭 위축도(digestive gland atrophy, DGA)를 평가하였다. 비만도 및 소화맹낭 위축도는 내만에 서식하는 참굴이 다른 지역에 비해 유의적으로 낮았다(P<0.05). LMS는 내만이 외만에 비해 짧은 리소솜 막 불안정화 시간을 보였지만 지역별 통계적인 유의차는 없었다. LF 축적은 내만에 서식하는 참굴이 유의적으로 높은 축적을 보였지만(P<0.05), NL 축적의 경우 외만에 서식하는 참굴이 유의적으로 높은 축적을 보였다(P<0.05). DGA와 LF의 경우 내만과 외만에서 뚜렷한 차이를 보였고, 이는 환경오염의 수준과 관련 있을 것으로 사료된다. 따라서 이 두 가지 분석항목은 연안환경평가에서 좋은 biomarker로 사용될 수 있을 것으로 기대된다.

Phylogenetic, histological and age determination for investigation of non-native tropical black-lip pearl oyster, Pinctada margaritifera , settled in jeju, Korea

This study reports the first finding of tropical blacklip pearl (BLP) oyster, Pinctada margaritifera, in Korean waters. One BLP oyster was found and sampled from Beom-seom islet (33°13′N, 126°33′E) in the southern coast of Jeju Island, Korea in February, 2011. The taxonomic status of the specimen was confirmed by nucleotide sequences of the mitochondrial gene cytochrome oxidase I and 28S ribosomal DNA. Oxygen isotopic analysis (δ18Osh) and histology were used to determine the specimen’s age and reproductive stage, which were 3.5 years and ripe male, respectively. This BLP oyster most likely originated in an area in the subtropics or tropics, such as the Okinawa archipelagic or Micronesian regions. We suggest that intensive monitoring surveys are necessary for confirming the northward expansion of BLP oyster in Korean waters in the near future.