• The Korean Journal of Zoology
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• v.8 no.1
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• pp.1-7
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• 1965

The short-necked clam is distributed widely in Korean tidal flats and it is a much an important bivalve quantitatively as to control the production of the tidal flat. The shell of this clam tends to show remarkable morphological variations depending on the habitat. Under a seemingly favorable condition for the growth , the color pattern of shell of the clam is clear and obvious and having less weight and elongated shape, the ratios of shell length to both height and width are small . On the contrary , when the environment appears to be an unfavorable one, the shell is found to be heavy and stunted with smudgy color pattern. If this correlation between could be a basis for the judgement in suitability of growth environment for the clam. In the Ikawazu Bay, Japan, it is revealed that the elongated shell is produced from the coast outside of the Bay (1) , the stunted from the esturay (2) and the intermediate from the floodgate area (3) and the middle of the Bay (4). Followings are the results obtained from the morphological investigation of the claim in this Bay. 1. Relationship between the shell length and the largest shell rib length is linear and between the shell length and the shell width is also linear but with a critical point at the shell length of 17-20 mm. The ratio between the width and the largest rib length at a given shell length increases with the order of 1, 3, 4, and 2. 2. A gradual decreases of the ratio of the shell length to the largest rib length is observed when the former is less than 17-18 mm, and this ratio increases with the shell of longer. Also there is a different range of this ratio in each different location ; the greatest range in 2, the smallest in 1 and 4 being in between. 3. A similar biometric finding is apparent with the ratio between the length and width of the shell and the order in value is 2, 4, 1 and 3. 4. The ratios between the length and the largest rib length of elongated and stunted shell are 0.84-0.86 and 0.89-0.92, respectively , and those between the length and width are 0.40-0.51 and 0.49-0.58, respectively. 5. Generally , the elongated short necked clam shells are products of the tidal flat of good circulation of sea water with high salinity and smaller fluctuations of salinity and temperature within a day. The stunted shells are produced for tidal flats of opposite of above conditions.

• The Korean Journal of Malacology
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• v.29 no.3
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• pp.207-216
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• 2013

Changes in density of manila clam, Ruditapes philippinarum to environment, catch and recruitment were studied in a few stations (Seonjae, Seongam, Hwangdo and Padori) in the West coast area of Korea from January, 2007 to December, 2009. Water temperature, salinity, dissolved oxygen and pH in the study stations were 0.8 to $31.2^{\circ}C$, 22.1 to 33.7 psu, 5.0 to 12.0 mg/L and 7.39 to 8.99, respectively. The concentrations of dissolved inorganic nitrogen, phosphate and silicate were 0.016 to 1.281 mg/L, 0.004 to 0.093 mg/L and 0.016 to 1.617 mg/L, respectively. Chlorophyll-a ranged from 0.2 to 12.1 ${\mu}g/L$, respectively. Substrata were mainly composed of muddy sand and very poorly sorted in Padori, muddy sand and well sorted in Seonjae and Hwangdo, gravelly muddy sand and poorly sorted in Seongam. Density was high in Seonjae and Seongam, but low in Hwangdo and Padori. In clam culture station, in which spat was naturally produced without sowing seedlings, the living density was decreased by increasing of death and a catch of shellfish, and recruitment was changed. Also, Density affected condition factor and shape of clam. Condition factor was the highest in Hwangdo, in which temperature in the winter and chlorophyll-a were high, and was the lowest in Padori. In the shape of clam, the shape in Seongam was a elongated form, but in Padori was a stunted form.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.6
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• pp.823-833
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• 2020

The Manila clam Ruditapes philippinarum, is an important marine bivalve that is widely distributed along the west and north coasts of South Korea. It has been used in a variety of Korean foods owing to its superior umami taste. In the present study, we developed a flavoring with an excellent sensory preference from Manila clam using extrusion cooking processing. Optimization of extrusion cooking conditions was performed using response surface methodology (RSM). Barrel temperature (X1, 140-160℃) and screw speed (X2, 400-560 rpm) of the extruder were chosen as independent variables. The dependent variable was overall acceptance (Y, points). The estimated optimal conditions were as follows: overall acceptance (Y): X1=140℃ and X2=560 rpm. The indicated value of the dependent variable overall acceptance (Y) under the optimal conditions was 8.94 points, which was similar to the experimental value (8.82 points). Overall acceptance of the Manila clam flavoring was related to its umami and Manila clam tastes. The electronic nose and tongue results successfully segregated different clusters of the samples between the lowest and highest sensory scores. The sample with the highest sensory score had higher sourness, umami, and sweetness intensities, and the lowest sensory scored sample showed more off-flavor compounds.

• Journal of Marine Life Science
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• v.6 no.2
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• pp.97-105
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• 2021

Tegillarca granosa, is one of the most important fishery resources throughout Asia. However, due to industrialization factories, marine environmental pollution, and global warming, the marine fishery production has drop sharply. In order to understand the genetic factors of the blood clam, which is a major fishery resource on the southern coast of Korea, the whole genome of blood clam was studied. The assembled genome of T. granosa was 915.4 Mb, and 19 chromosomes were identified. 25,134 genes were identified, and 22,745 genes were functionally annotated. As a result of performing gene gain and loss analysis between the blood clam genome and eight other types of shellfish, it was confirmed that 725 gene groups were expanded, and 479 gene groups were contracted. The homeobox gene cluster of blood clam showed a well-preserved genetic structure within lophotrochozoan ancestor. T. granosa genome showed high similarity between three hemoglobin genes with Scarpharca broughtonii. The blood clam genome will provide information for the genetic and physiological characteristics of blood clam adaptation, evolution, and the development of aquaculture industry.

• Journal of the korean society of oceanography
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• v.31 no.3
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• pp.117-122
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• 1996

Oxygen consumption by the Manila clam, Ruditapes philippinarum (Bivalvia: Veneridae) maintained in a culture tank for 7-10 weeks was measured with an automatic intermittent-flow-respirometer (AIFR). There was evidence for an endogenous tidal rhythm of 12.4 h in oxygen consumption, at irregular intervals of between about 7 and 18 hours during experiments of between 22 h 5 min and 70 h 32 min (duration) recording for fasting animals in constant darkness at constant temperatures in the absence of tidal rhythms.

• Fisheries and Aquatic Sciences
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• v.4 no.4
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• pp.208-218
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• 2001

We have investigated the gonad index (GI), gonadal development, reproductive cycle, first sexual maturity, sex ratio, the number of spawned eggs and spawning frequency of the Manila clam, Ruditapes philippinarum. Samples were collected from the intertidal zone of Komso Bay, Korea from January to December in 1999. Monthly changes in the gonad index (GI) and condition index showed a similar pattern in the reproductive cycle. The spawning period was once a year between early June and early October, there was a spawning peak between July and August when seawater temperature was over $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (June to October), and spent/inactive stage (August to March). Percentages of first sexual maturity of female and male clams of l5.1-20.0mm in shell length were $56.3\%$ and $60.0\%$, respectively, and $100\%$ for the clams >25. mm. The sex ratio of individuals >15.1 mm in shell length was about 1:1 $(\chi^2= 0.02,\;p>0.05)$. Number of the eggs released from each clam by the induction increased as the size of clam in terms of shell length increased. Mean number of the eggs from the second induction of the spawning was $75.35-84.30\%$ $(average\;79.81\%)$ of the number of the eggs released in the first spawning. Our data indicated that R. philippinarum in Komso Bay has one major spawning peak with over two minor spawning, and the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.48 no.4
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• pp.555-563
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• 2015

Organic matter and trace metals were investigated in surface sediments of Gomso Bay, where there is dense Manila clam Ruditapes philippinarum farming activity, to evaluate contamination of sediments in intertidal shellfish farming area. We measured mean grain size (Mz), chemical oxygen demand (COD), ignition loss (IL), acid volatile sulfide (AVS), total organic carbon (TOC), and total nitrogen (TN), and trace metals (As, Cd, Cr, Cu, Fe, Hg, Mn, Pb and Zn) in intertidal and sublittoral sediments. The intertidal sediments were mainly composed of coarser sediments (sand, silty sand, and sandy silt), with Mz values ranging from 2.61 to 4.79 Ø. Mz and the content of organic matter in sediments were lower in the intertidal zone than in the sublittoral zone. The mean metal concentrations in surface sediments decreased in the order Fe > Mn > Zn > Cr > Pb > Cu > As > Cd > Hg. The metal concentrations in surface sediments showed a significant positive correlation with Mz and organic matter content, indicating that metal concentrations in the surface sediments of Gomso Bay are controlled by Mz and organic matter. The concentrations of organic matter and trace metals in the study region were lower than or similar to those in other intertidal zones in western coast and much lower than those reported in other shellfish farming areas in Korea. Our results suggest that intertidal Manila clam farming sediments from Gomso Bay are not contaminated by organic matter and trace metals.

• The Korean Journal of Malacology
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• v.26 no.1
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• pp.91-95
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• 2010

Density-dependant growth and mortality rate of Manila clam Ruditapes philippinarum reared in net cages was investigated in Gomso Bay, Korea where unusually high mortality of clams has been reported. For the experiment, four groups of clam cages were set up with a density of $2,000clams/m^2$ (group A), $1,000clams/m^2$ (group B), $500clams/m^2$ (group C) and $100clams/m^2$ (group D). Mortality and growth of clams in each experimental cage was monitored biweekly from May 2001 to September 2001. Highest mortality in group A was observed in late August, while highest mortality of rest groups was observed in early September. In September, the cumulative mortality in group A was 99%, while it was 93.2% in group B, 91.2% in group C and 88% in group D. Shell growth rate of clams in thecages was found to be density dependent; monthly shell length increase was 0.67 mm in group A, 1.33 mm in group B, 1.63 mm in group C and 1.71 mm in group D. Our study indicated that clam growth and mortality in the Bay is density dependent and the growth and survival rate is negatively correlated with the density.

• The Korean Journal of Pharmacology
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• v.9 no.2
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• pp.29-37
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• 1973

Lampranthus spectabilis is an ornamental plant which belongs to one of the Aizoaceae family as an one-year herb. There are no illustrations on the references that Lampranthus spectabilis has been made use for the purpose of the medicinal plant among the traditional herb doctors and the laymen. However, it has the specific characteristics to be analogous to the Cactaceae family in the botanical classification. Besides, mescaline, the main ingredient of Peyote cactus, demonstrates the sympathomimetic effect as well as the psychotomimetic effect. The authors called our attention to the resemblance to the botanical family between Aisoaceae and Cactaceae, and made a survey whether the alcohol extract of Lampranthus spectabilis might possess any pharmacological effect on the isolated heart of clam or not. The results of the experiment were as follows. 1. Administration of LX to the isolated heart of clam produced an inhibitory effect on the cardiac motility in proportion to its concentration $10^{-4}$, $5{\times}10^{-4}$ and $10^{-3}\;g/ml$ respectively. 2. Administration of LX $5{\times}10^{-4$ and $10^{-3}\;g/ml$ produced the blockade effect on the cardiac motility pretreated with serotonin $10^{-7}$ and $10^{-4}\;g/ml$, as well as with methysergide $10^{-6}$ and $10^{-5}\;g/ml$. 3. Administration of LX $5{\times}10^{-4}\;g/ml$ produced no effect on the cardiac motility pretreated with acetylcholine $10^{-7}\;g/ml$. 4. Administration of LX $5{\times}10^{-4}\;g/ml$ produced the blockade effect on the cardiac motility pretreated with barium chloride $10^{-4}\;g/ml$, as well as with prostaglandin $20\;{\mu}g$. Consequently, it is concluded that the alcohol extract of Lampranthus spectabilis has an effect of depression on the motility of the isolated heart of clam. Its mechanism of action might be due to a direct action on the heart.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.9 no.1
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• pp.35-42
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• 1976

Larval morphogenesis and infection rates of Cercaria pectinata Huet were investigated in regards to histological changes and mortality of the hard clam, Meretrix lusoria $(R\ddot{o}ding)$, in Buan located on the Western Coast of Korea. The trichocerous cercariae, Cercaria pectinata, and its sporocysts parasitize mainly in the tissues of goand, digestive gland and gills of the hard clams. One branched sporocyst grows into a great number of cylindrical sporocysts, and a heavily infected clam possesses 2,000 to 5,000 cylindrical spo ro cysts. Each of them produces approximately 30 to 70 germinal cells and cercariae. Of 2,639 clams examined 347 individuals $(13.2\%)$ were found to be infected. The infection rates showed seasonal variations, the rate being highest $(29.6\%)$ in July, and lowest $(2.0\%)$ in March. Whereas, the infection rates did not change significantly with the changes of size class of the shell. No infection was observed in Meretrix petachialis (Lamarck) collected from Myeong-ji, Kimhae Gun located near Busan. In the iefected clams, the gametogenesis (oogenesis and apermatogenesis) did not undergo completely, therefore the heavily infected clam seemed to be castrated. Also the tissues of the digestive gland and gills were compressed by the multiplication of the parasites. When they were kept in aquariums in the laboratory, high mortality has occurred in the infected clams. All of the 60 infected clams died within 35 days.