• Ocean and Polar Research
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• v.40 no.1
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• pp.15-22
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• 2018

In the present study, we investigated temporal variation in the reproductive effort and biochemical contents in adult Manila clam Ruditapes philippinarum at Shi-Heung-Ri beach on the east coast of Jeju Island. Gonad-somatic index (GSI), a ratio of the egg mass to the total biomass determined using ELISA increased dramatically from late May to June (7.1% to 19.5%). In mid-July, GSI dropped to 15.1%, indicating spawning on a small scale during this period. GSI also declined dramatically from late August (15.5%) to September (4.3%), suggesting that massive spawning occurred during this period. A positive correlation was observed between clam size and potential fecundity, while potential fecundity ranged between 1.19-8.40 million eggs/clam. Total proteins and lipids in the tissue increased from late spring to mid-summer, coinciding with an increase in GSI. Protein, lipid and carbohydrate contents in the tissue were lowest in January, indicating that clams were suffering from poor nutritional circumstances, which may be associated with poor food supply from the environment. Monthly increase and/or decrease in the body weight were closely related to gonad maturation and subsequent spawning, which was also linked to temporal changes in the contents of protein, lipid and carbohydrates in the tissue.

• Korean Journal of Food Science and Technology
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• v.6 no.1
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• pp.36-41
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• 1974

Gracilaria verrucosa and Gelidium amansii collected from Wando, Yeosoo and Namhae districts Gracilaria sp. imported from Manila, and Ecklonia cava from Cheju island were investigated to raise the extraction yield of agar or alginic acid. The results are summarized as follows. In agar extraction from domestic seaweeds, Gelidium sp. showed 8-10% yield increase by gamma-irradiation whereas Gracilaria sp. exhibited no effect. In Manila seaweed, gamma-irradiation (1.5 Mrad) caused 25-30% increase in agar extraction and the properties of agar sample by these methods were acceptable. In alginic acid extraction from Ecklonia sp., gamma-irradiation (0.3 Mrad) showed 6% yield increase.

• Acta Via Serica
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• v.3 no.2
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• pp.73-90
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• 2018

The Silk Road tied the globe together for the first time by producing an early globalization phenomenon. Some consider that the ancient Silk Road disintegrated around the $18^{th}$ century CE due to the fall of the Muslim empires and the kingdoms between Asia and Europe. However, the maritime trade among East Asia and the Spanish dominion on the American continent reactivated the ancient Silk Road on some levels, and maintained trade dynamics until the $19^{th}$ century. This was possible because of Mexican silver and trade spots. Notwithstanding its historical background, Mexico seems so far away from the new Silk Road, or the Belt and Road Initiative in the $21^{st}$ century. Thus, this paper analyzes Mexico's historic and current role concerning the Silk Road. First, I conceptualize and compare the ancient Silk Road and Belt and Road Initiative through the lens of complex interdependence theory. I propose that, unlike the ancient Silk Road, the Belt and Road Initiative is a case of an induced complex interdependence. Second, I study the Manila Galleons' dynamics in order to trace the ancient ties with the Silk Road. I emphasize Mexican silver's contribution to East Asian economies and the importance of Mexico's role in the East Asia-Spanish trade. Consequently, I analyze Mexico's position in the Belt and Road Initiative. Finally, I present some concluding remarks about Mexico's role in the Silk Road.

• Asian Journal for Public Opinion Research
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• v.12 no.2
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• pp.122-141
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• 2024

Drawing on mere exposure effect, we proposed that more exposure to a city, as measured by the number of channels of exposure, would increase familiarity, city image, and intention to visit that city. We conducted a survey of university students in seven Asian countries, asking them about a total of 14 cities, at least one from each of the surveyed countries. Exposure was found to be a significant antecedent and was most powerful when mediated by familiarity. Some types of exposure were stronger than others. Personal exposure, in the form of having visited a city or knowing someone who has, was the strongest type of exposure, with more than double the effect of media exposure. Social media, which is difficult to classify as either personal or media, was assessed separately and had a much smaller effect. The mere exposure effect exists whether the intention to visit a city is related to pleasure (tourism) or business.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.109-117
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• 2002

Detection of protozoan parasites Perkinsus sp. and P. atlanticus was developed in this study using a specific polymerase chain reaction (PCR) to diagnose the presence of those organisms that causes extensive mortalities of marine shellfishes. The PCR was conducted together with fluid thioglycollate medium (FTM) method and 2 M NaOH lysis method. For the test, Manila clams, Ruditapes philippinarum, were collected from four coastal locations in Korea including Wando Island, Gimnyeong, Sungsan and Sogwipo in Jeju. In addition, trophozites of Perkinsus sp. cultivated in vitro and the granular ark clam, Tegillarca granosa, taken from Gangjin on the south coast of Korea, were used as positive and negative controls, respectively. Expected DNA bands were detected in the samples from Wando Island, Sungsan and the in vitro cultured Perkinsus sp. when the probes specific for the genus Perkinsus and P. atlanticus were used. The samples were also positively diagnosed by the FTM and 2 M NaOH methods. In contrast, the Manila clams from Gimnyeong and Sogwipo, and the granular arks clams from Gangjin showed no detectable signs of infection with the PCR, the FTM method and the 2 M NaOH lysis method. On the other hand, being amplified by p. atlanticus specific primer, it is suggested that the protozoan parasite Perkinsus sp. found in the Korean Manila clam is P. atlanticus. Finally the PCR- based assay developed in the present study can be used in detection of Perkinsus infection and discrimination of Peykinsus species in quarantine stations or laboratories due to the high sensitivity and specificity as well as its rapid detection.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.6
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• pp.723-730
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• 2016

Domestic Manila clam production has been reduced due to coastline changes and environmental degradation, but aquaculture industry is facing difficulties caused by an increase in imports. It is important to recognize the integral habitat environment in order to do sustainable aquaculture. The habitat environment of Manila clams (Ruditapes philippinarum) is closely related to the productivity of aquaculture farms. This study investigated 3 indexes, survival (sediment type, hydrodynamic), growth (Chlorophyll a, DIN, DIP) and environment (water temperature, dissolved oxygen, sediment chemical oxygen demand, ignition loss) as indicators of habitat characteristics for a tidal flat farm in Geunso Bay (Pado and Beopsan) from June 2015 to May 2016. As a result, Pado (maximums.; sand 48.76 %, hydrodynamic 10.59 cm/s, Chlorophyll a 12.70 ug/L, exposure time 3 hours, DO 18.65 mg/L) had a higher sand content, faster current speed, more abundant nutrients and DO, providing more favorable conditions for Manila clams than Beopsan (maximums.; sand 37.40 %, hydrodynamic 6.02 cm/s, Chlorophyll a 6.41 ug/L, exposure time 7 hour, DO 14.81 mg/L). In fact, Pado showed a higher density than Beopsan. This study considered the habitat environments of Pado and Beopsan to provide a basis for optimal management practices and potential suitable sites in Geunso bay.

• The Korean Journal of Malacology
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• v.27 no.4
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• pp.291-297
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• 2011

In an attempt to improve the substrate condition for Manila clam (Ruditapes philippinarum) culture, crushed oyster (Crassostrea gigas) shells were spread on the muddy tidal flat of Namseong-ri, Podu-myeon, Goheung-gun, Jeollannam-do in April 2008. To test the suitability of the crushed oyster shell added substrate, seed clams were transplanted from Taehwa river estuary in Ulsan city in June 2008. Over 23 months of sampling, the mean grain size and the sorting in the experimental site containing the crushed oyster shell were significantly higher than the control site. The ignition loss, water content, chemical oxygen demand (COD) and acid-volatile sulfide (AVS) level were also significantly higher in the crushed oyste shell added substratum. Survival of the clams transplanted to the crushed oyster shell added substratum was significantly higher and all the clams transplanted to the normal muddy substratum died in August 2009, 13 months after the transplantation. At the end of the experiment in April 2010, the transplanted clams reached 36.10 mm in shell length and 8.92 g in total weight with survival of 43.5%. Our study suggested than crushed oyster shell added in the mud dominant substratum greatly improved living condition and survivability of clams.

• Journal of Aquaculture
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• v.11 no.2
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• pp.183-191
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• 1998

To substitute fromzed and freeze-dried food for live food in the development of the artificial seedling production of bivalve larvae, the dietary value of live T. suecica was compared with those of freeze-dried T. suecica, frozed T. suecica, live T. suecica (50%)+frozen T. suecica (50%), and live T. suecica (50%)+freeze-dried T. suecica (50%) in the rearing of oyster (Crassotrea gigas) and hen clam (Mactra chinensis) larvae, and manila clam (Tapes philipninarum) spats. Oyster larvae fed live T. suecica showed the highest growth (shell hight $231.9^{\mu}$m) and survival rate (72.6%) and those fed freeze-dried T. suecica showed the lowest growth (shell height $168.9^{\mu}$m) and survival rate (35.3%). However, in the hen clam larvae, there were not significantly different among diet group in growth and survival rate. The small spats of manila clam fed live t. suecica or live T. suecica (50%)+freeze-dried T. suecica (50%) showed higher growth and survival rate than those fed other diet group. In the case of large spats of manila clam, live T. suecica and live T. suecica (50%)+frozen T. suecica (50%) showed better growht. But, survival rates were not different among diet groups. Dietary valuse of frozen and dried T. suecica were different on species and growth stage, and frozen and freeze-dried T. suecica can be partially used as substitute food for T. suecica live T. succica in shellfish hatchery.

• Journal of fish pathology
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• v.18 no.3
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• pp.247-258
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• 2005

To understand responses of bivalve tissues to various injurious agents, histopathological observation was done in the Manila clam, Ruditapes hilippinarum, during 240 hours after an intramuscular injection of N-methyl-N-nitro-N-nitrosoguanidine (MNNG). Some histopathological changes were observed with the epithelia of stomach, midgut, hindgut, digestive diverticula and gonads after injecting MNNG. The earliest degenerative changes were recognized in the epithelium of midgut 12 hours after the injection. Partial or complete, epithelial destruction was constantly accompanied by the massive infiltration of a mononuclear, necrotic cell group including hemocytes. At 144 hours later, gonads showed the necrotic desquamation of their germinal epithelia. Nearly all of the infiltrated cells within the destructive epithelium were suggested to be hemocytes, from the binding property with a hemocyte-specific lectin, Ricinus communis (RCA-1). From these results it was concluded that the epithelium of digestive system is vulnerable to parenteral MNNG and hemocytes might be deeply involved in this MNNG-induced destruction of the digestive epithelium.

• 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.