• The Korean Journal of Malacology
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• v.30 no.3
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• pp.211-218
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• 2014

Spermatid differentiations during spermiogenesis and sperm ultrastructures in male Mercenaria stimpsoni were investigated by transmission electron microscopic observations. In the early stage of the spermatid during spermiogenesis, a few granules and a proacrosomal granule, which is formed by the Golgi complex, become a proacrosomal vesicle. Consequently, it becomes an acrosome by way of the process of acrosome formation. The morphologies of the sperm nucleus type and the acrosome of this species have a curved cylindrical type and cap shape, respectively. The spermatozoon is approximately $48-51{\mu}m$ in length including a curved cylinderical sperm nucleus (about $4.18{\mu}m$ long), an acrosome (about $0.52{\mu}m$ in length) and tail flagellum ($42-45{\mu}m$ long). As some ultrastructural characteristics of the acrosomal vesicle, the peripheral parts of two basal rings show electron opaque part (region), while the apex part of the acrosome shows electron lucent part (region). These charateristics of the sperm belong to the family Veneridae in the subclass Heterodonta, unlike a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part (region). Therefore, it is easy to distinguish the families or the subclasses by the acrosome structures. Exceptionally, In particular, a cylinder-like nucleus of the sperm is curved (the angle of the nucleus is about $80^{\circ}$), as seen in some species of Veneridae (range from $0^{\circ}$ to $80^{\circ}$). The number of mitochondria in the midpiece of the sperm of this species are four, as one of common characteristics appeared in most species except for a few species in Veneridae in the subclass Heterodonta. Cross-sectioned axoneme of the sperm tail flagellum shows a 9+2 structure.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.295-298
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• 2014

Finless porpoise is the one of porpoises in Korean waters that frequently observed in the coastal area. This study reported parasite infection cases of stranded finless porpoise, Neophocaena asiaeorientalis which was stranded on the Saemangeum Dyke on the west coast of Korea 21 May, 2012. The finless porpoise was male, and estimated at 8 years old. Parasites were found in abdominal cavity, skull and lung. The parasites were identified as nematode, trematoda and lungworm. Nematoda in abdominal cavity was Crassicauda sp. Trematoda found in the skull was indentified Nasitrema sp. Lungworm in lung seemed one of genus Pseudaliids. Anisakis spp. has not been found.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.281-293
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• 2014

The biogeography and diversity patterns of the marine bivalve molluscan fauna of the East Sea coast of South Korea are analyzed. The total species richness of the continental Korean bivalve fauna, excluding insular regions (Dok-do and Ullung-do), is 304, and from north to south the species richness of bivalves increases showing a clear gradient: Gangwon, 143 species ${\rightarrow}$ Gyeongbuk, 131 ${\rightarrow}$ Gyeongnam, 183. A zonal-geographical analysis of the entire fauna shows that the great majority are warm-water mollusks, constituting 77% (subtropical, 37%, tropical-subtropical, 30%, subtropical-boreal, 10%), The number of boreal (low-boreal, widely distributed boreal and circumboreal) species is lower, 19%, whereas boreal-arctic mollusks have only 4%. This demonstrates that the bivalve molluscan fauna of the eastern coast of Korea is subtropical, and has more affinities to the fauna of the East China Sea than to the northern East Sea. Separate analysis by provinces shows the increasing role of warm-water mollusks from north to south. While tropical-subtropical and subtropical species constitute 47% (68 species) in Gangwon, their dominance increases to 71% (93 species) in Gyeongbuk, and to 80% (148 species) in Gyeongnam. The Gyeongnam bivalve fauna is the most diverse in species composition and has the largest number of "endemics" (species known only from this province), 46%. The Gangwon fauna also contains many "endemics", up to 40%, while Gyeongbuk is an intermediate zone with low "endemicity", only at one-fifth of the regional fauna, and has the most species in common among the three provinces.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.273-279
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• 2014

The mass mortalities have been occurring of Korean scallop Patinopecten yessoensis from 1997's to now in Korea east sea. Cages behavior and interference effect (common name; curtain effect) between scallop cages were investigated in culture grounds on the eastern coastal waters of Korea for understand to mechanism of rising about mass mortalities of Korean scallop quickly. The first experiment was carried out in circulating water channel to assess inclination angel from relationship between velocity and cages interval, velocity with culture cages position. An angle of inclination of scallop culture cages were 94.6 to 92.3 degree under a several velocity which were from 0.1 m/s and 131.9 to 118.1 degree under 0.5 m/s with cages interval were 1 m, 94.3 to 91.0 degree under velocity is 0.1 m/s and 133.2 to 122.4 degree under 0.5 m/s with cages interval were 1.5 m and 94.6 to 96.4 degree under velocity is 0.1 m/s and 131.7 to 131.8 under 0.5 m/s with cages interval were 2 m. The second experiment was designed to prove the tank test. Velocities were measured inside and outside of the scallop culture ground at eastern sea of Korea. The velocity of inside of the culture was the slowest as 0.1m/s. In this result, interference between former cage and after cage was occurred.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.259-271
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• 2014

This study was conducted to investigate the impact of sand addition to an intertidal for the development of the Manila clam habitat on benthic community structure. For this, we focused on the spatio-temporal changes in the surface sediment condition and benthic community structure including Manila clam before and after the event. Study site was the lower part of Ojjeom tidal flat in Gonam-myeon, Taean-gun where sand added to on July 2010. We set three stations at each of sand adding area (experimental plot) and non sand-adding area (control plot) and did sampling works ten times from June 2010 to October 2011. Directly after the event, surface sediments changed to very coarse sand, but the state was not maintained over two months because of seasonal sedimentation and finally got back to the original grain sizes in eight months. The number of species and density were temporarily reduced right after the event and polychaetes such as Sternaspis scutata, Ampharete arctica were most negatively affected by the event. However, the number of species and density quickly recovered from the reduction in four to six weeks owing to the recolonization by the existing species and species in the vicinity of the plot. However, despite the recovery of ecological indies, species composition was continuously changed from one to another, thereby community structure stayed unstable condition, especially in some stations with finer sediment in their original condition. After sand addition, density of Manila clam was prominently increased at only one station with coarser sediment in its original condition.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.189-196
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• 2014

A significant production decrease has been witnessed for the Pacific oysters, Crassostrea gigas farmed in the western coastal waters of Korea, presumably by the loss of physiological viability. We evaluated the viability in terms of health indicators, the condition indices and hemocyte apoptosis rates of the oysters inhabiting two representative farming sites, Incheon and Taean each with different environmental variables. In our monthly measurements for the whole year 2013, the indicators were location specific. The condition indices of Incheon were highly variable, 1.67-8.58%, while those of Taean were less, 2.28-5.57%. The condition indices decreased during the spawning seasons, July and September in common. The two oysters exhibited also differed in the apoptotic activities of hemocyte, highly active, 4.03-30.15% for Incheon oysters and less active, 2.87-17.48% for Taean oysters. One thing we could identify was the two measurements were adverse during the critical seasons of spawning, reminiscent of being a useful tool for a health indicator for the oysters. Similar trend was also observed in the time when change in temperature was extreme. The findings in this study are highly indicative of health indicators for the oyster aquaculture.

• The Korean Journal of Malacology
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• v.30 no.3
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• pp.169-175
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• 2014

PAHs (Polycyclic Aromatic Hydrocarbons: PAHs) is the hydrophobic inorganic material composed of carbon and hydrogen that is easily adsorbed biological organisms in the ocean. Bivalves is the indicator of environment monitoring because of reflect growth, physiological response of bivalve followed their habitat environment. The aim of research is understand the change of oysters (Crassostrea gigas) physiological response under exposed PAHs concentration for control, 1, 10 and $100{\mu}g/L$. We investigated induced immune change response for oyster hemocyte and effect of tissue RNA/DNA ratio for mantle, gill and adductor muscle individually. As a result of experiment change of immune response the oyster hemocyte when exposed PAHs showed that viability and adhesion is no significant difference (ANOVA test, p < 0.05). However phagocytosis decreased under the over $10{\mu}g/L$ of PAHs concentration and ROS increased with the increase of PAHs concentration. The change of RNA/DNA ratio is R/D ratio decreased with the increase of PAH concentration in adductor muscle. However gill and mantle showed no change of R/D ratio with PAHs concentration. The oysters when exposed inorganic pollutant that decreased of physiological condition and damaged protein synthesis of adductor muscle.

• The Korean Journal of Malacology
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• v.24 no.1
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• pp.67-72
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• 2008

This study investigated the proximate composition in the muscle and viscera of five commercially valuable Korean Veneridae, Protothaca jedoensis, Ruditapes philippinarum, Saxidomus purprratus, Cyclina sinensis and Meretrix lusoria. The proximate analysis revealed that the moisture, crude protein and carbohydrate of muscle in higher than viscera. As results, except for the crude lipid and carbohydrate there was little significant differences among the moisture, protein and crude ash. The crude lipid contents was highest in the viscera of Meretrix lusoria, while lowest in the muscle of Ruditapes philippinarum. The carbohydrate content of viscera in the Meretrix lusoria, Ruditapes philippinarum and Protothaca jedoensis were $3.61{\pm}0.45%$, $3.45{\pm}1.4%$ and $3.39{\pm}0.07%$, respectively.

• The Korean Journal of Malacology
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• v.24 no.1
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• pp.11-24
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• 2008

GDNA was isolated from the jedo venus clam (Protothaca jedoensis, Lischke) from Boryeong (jedo venus clam from Boryeong JVCB) and Wonsan (jedo venus clam from Wonsan; JVCW) located in the West Sea and the East Sea of Korean Peninsula, respectively and we performed clustering analyses, DNA polymorphisms and the populations genetic variations. In the present study, the seven decamer primer generated the one hundred and eleven major/minor specific bands in JVCB population and ninety four-specific bands in JVCW population. Seven primers generated the unique shared bands to each population of one hundred and seventy-six, on average of 25,1, in JVCB population from Boryeong and three hundred thirty, on average of 47,1, in JVCW population from Wonsan, respectively. The dendrogram obtained by the seven oligonucleotides primers, indicates two genetic clusters. Especially, two Protothaca between the individual WONSAN no. 12 and BORYEONG no. 10 showed the longest genetic distance (0.537) in comparison with other individuals used. Accordingly, RAPD analysis showed that the JVCB was a little more genetically diverse than the JVCW population. This result implies the genetic similarity owing to rearing in the same and/or similar circumstances or inbreeding within the JVCW population. So to speak, JVCB population may have high levels of genomic DNA variability owing to the introduction of the wild individuals from the other sites to sampling sites although it may be the geographically diverse distribution of this species. However, it was confirmed that it did not appear like that really in this study. We feel convinced that RAPD analysis discovered a significant genetic distance between two Protothaca population pairs (P<0.001). The existence of population discrimination and genetic diversity between two Protothaca populations was identified by RAPD analysis.

• The Korean Journal of Malacology
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• v.17 no.1
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• pp.13-18
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• 2001

The relationship between shell length and ring radius in each ring group was expressed as a regression line. Therefore, there is a correspondence in each ring formation. Based on the monthly variation of the marginal index (Ml') of the shell, it is assumed that the ring of this species was formed once a year during the period of August to October, and the main period of the annual ring formation was August through September. The relationship between shell length (SL) and total weight (TW) was expressed by the equation TW = 2.2476 $\times$ 10$^{-5}$ SL$^{3.536}$ ($r^2$= 0.90). Shell length (SL) and shell height (SH; mm) were highly correlated with the equation SH = 0.7545 SL - 0.0145 ($r^2$= 0.93). The shell length (SL)-shell width (SW) relation was expressed by the equation SW = 0.5336 SL- 2.4253 ($r^2$= 0.87). Growth curves for shell length and total weight fitted to the von Bertalanffy's equation were expressed as follows: SL$_{t}$ =60.02[1 - e$^{-0.6458(t-0.3895)}$ ], Twt = 43.63[1 - e$^{0.6458(t-0.3895)}$ ]$^{3.536}$ .