• The Korean Journal of Malacology
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• v.27 no.3
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• pp.253-259
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• 2011

Boring behaviour and drilling mechanism were investigated by visual observations. In this study, of two kinds of holes (the outer and inner holes) which are formed by drilling of boring gastropod Lunatia fortunei (Naticidae), the diameters of the outer holes are broader and larger than those of the inner holes, and their holes look like the crater in shape, as seen in all valves of bivalves bored by Naticidae species. Two kinds of glands (the accessory boring gland and accessory salivary gland) on the foots of boring gastropods have been investigated. Of them, it has been confirmed that only the accessory salivary glands on the foots secreted sulphuric (acidic) components in the mucus (secretion), while the accessory boring glands on the foots did not secrete their components. In this study, we confirmed that L. fortunei possess the accessory boring gland on the foot, as seen in most species in Naticidae. Accoeding to the results of the experiment of the blue litmus paper tests of the mucus (secretions) secreted from the accessory boring gland the color of the blue litmus paper did not turn red in color because chemical components of mucus (secretion) secreted from the accessory boring gland on the foot of L. fortunei (boring gastropod) were not acidic components. It is supposed that the mucus, which is secreted from the accessory boring gland, contained gelatin-like substances or enzymes without acidic components, as already reported in Naticidae species. Therefore, these substances may be involved in softening the surface of the valves of M. veneriformis. Consequently, it is assumed thar L. fortunei bores holes through the shells of molluscs by means of following 3 methods: (1) a softening of the calcareous shells of M. veneriformis with chemical secretions (including gellatin-like substances or enzyme except for acidic components) from the accessory boring glands, (2) mechanical rasping with the radula, (3) a combination of both. In this study, particularly, acidic components, which are involved in softening the surface of the shells, are not associated with the boring mechanism of L. fortunei because chemical acidic components were not detected in the mucus (secretion), as found in Naticidae species.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.205-211
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• 2011

This study presents physiological rates of oxygen consumption, ammonia excretion, feeding rates, O/N ratio and assimilation efficiency of the blood cockle, Scapharca subcrenata, determined from specimens collected in Yeoja bay on the south coast of Korea. Physiological parameters were measured monthly under static, laboratory controlled conditions with ambient conditions, and measurements were performed seasonally in order to estimate scope for growth and its probable sources of variation. Oxygen consumption and ammonia excretion rates have been increased as temperature increased with the highest value of August, 2008. Feeding rate was the highest during April whereas the lowest was during August which is a period of gametogenesis with minimum biomass of phytoplankton around sampling area. Assimilation efficiency was not significantly different seasonally and O/N ratio decreased during July to August. The scope for growth was negative during high temperature months(July to August), reflecting the high temperature and low feeding rate, and had its highest positive values during spring and autumn. Data on the physiological parameters and scope for growth of Scapharca subcrenata obtained in this study will be used to assess the carrying capacity for blood cockle cultivation.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.199-204
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• 2011

We studied possibility of the sowing culture at the bottom after intermediate culture as a method for raising the survival of the Purplish Washington clam, Saxidomus purpuratus. The pearl net ($35cm(W){\times}35cm(B){\times}20cm(H)$) for S. prupuratus spat during the period of intermediate culture (hanging culture) from April to October in 2010. The pearl net (100 inds./net) was installed at two stations (Namhae and Pohang) being about 3-4 m in water depth. After hanging culture, S. prupuratus spat sowed in the bottom of the Gangjin Bay. The survivals (%) of intermediate culture of this species at Namhae station and Pohang station were 73% and 74%, respectively. Daily growth rate of mean shell length and mean weight in Namhae station were higher than those in Pohang station. After sowing at the bottom of the Gangjin Bay, its survival (%) showed 73.98% in January 2011. These results suggested the possibility of the intermediate culture as hanging culture for raising survival rate of S. prupuratus.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.277-291
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• 2012

Aquaculture is challenged by a number of constraints with future efforts towards sustainable production. Global climate change has a potential damage to the sustainability by changing environmental surroundings unfavorably. The damaging parameters identified are water temperature, sea level, surface physical energy, precipitation, solar radiation, ocean acidification, and so on. Of them, temperature, mostly temperature elevation, occupies significant concern among marine ecologists and aquaculturists. Ocean acidification particularly draws shellfish aquaculturists' attention as it alters the marine chemistry, shifting the equilibrium towards more dissolved CO2 and hydrogen ions ($H^+$) and thus influencing signaling pathways on shell formation, immune system, and other biological processes. Temperature elevation by climate change is of double-sidedness: it can be an opportunistic parameter besides being a generally known damaging parameter in aquaculture. It can provide better environments for faster and longer growth for aquaculture species. It is also somehow advantageous for alleviation of aquaculture expansion pressure in a given location by opening a gate for new species and aquaculture zone expansion northward in the northern hemisphere, otherwise unavailable due to temperature limit. But in the science of climate change, the ways of influence on aquaculture are complex and ambiguous, and hence are still hard to identify and quantify. At the same time considerable parts of our knowledge on climate change effects on aquaculture are from the estimates from data of fisheries and agriculture. The consequences may be different from what they really are, particularly in the temperature region. In reality, bivalves and tunicates hung or caged in the longline system are often exposed to temperatures higher than those they encounter in nature, locally driving the farmed shellfish into an upper tolerable temperature extreme. We review recent climate change and following environment changes which can be factors or potential factors affecting shellfish aquaculture production in the temperate region.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.259-267
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• 2012

Due to the oil spill incident in December 2007, every facility of oyster culture was removed in western coast especially in Taean and Seosan. To restore oyster resources in Taean and Seosan, we brought oyster seeds from southern area and monitored their growth. In addition we monitored the culture environment throughout the year, and observed the number of oyster larvae and attached spats on collectors during summer. The factors of water environment were appropriate for oyster culture in both study area. The growth of shell height was larger in Uihang-ri, Taean than Jungwang-ri, Seosan. Spawning was more intensive in a short time in Jungwang-ri, Seosan than Uihang-ri, Taean. The number of oyster larvae and spats of collectors were much more in Jungwang-ri, Seosan than Uihang-ri, Taean. This study showed that transplantation of healthy oyster seeds from southern area can be a way of restoration of oyster resources in western coast. In addition, systematic approaches are necessary by building a better understanding of regional characteristics to restore and enlarge the oyster culture farms in western coast. In summary Uihang-ri, Taean will be appropriate for cultivation farms and Jungwang-ri, Seosan for seedling grounds to increase oyster culture productivity.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.175-180
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• 2011

The investigated amounts according to microalgae for stable supply of artificial seed of the hard clam, Meretrix petechialis and also observed the effect according to the repower of the microalgae after the specified period starvation. The stage of specimen used in the test was the D-shaped larva. The microalgae was Chaetoceros calcitrans, Isochrysis galbana and Nannochloris oculata. When the mixture of Chaetoceros calcitrans, Isochrysis galbana and Nannochloris oculata or alone C. calcitrans as food was supplied with 3,000-5,000 cells/ind., it turned to be the most effective. When the food was provided after starvation for some period, the shell length of D-shaped larva was grown to over $192.5{\mu}m$ at fourth day from the initial feeding. The survival rate tended to be lower, the longer the starvation period.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.245-254
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• 2012

This project analyzes distinct qualities of pearl cultured in Tongyeong by physical, chemical and optical test. The result is to provide scientific data for the value of pearl from Korean seawater. It divides one year pearl, which is used as a sample in the project, into white, natural blue and yellow gold colors, and then it has been divided into A, B and C based on the quality of the last results. A chemical experiment demonstrates that the higher quality has lower protein content of less than 10%. In another test called heavy metal content test, there is no big difference among classes. In the characterization of spectroscopy, it shows 280 nm peak indicated the conchiolin. It is clear that 407 nm, 430 nm and 460 nm peak are White group that are not in processed condition.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.273-282
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• 2011

The ultrastructural characteristics of germ cells during spermatogenesis and mature sperm morphology in male Pinctada martensii were investigated by transmission electron microscope observation. The morphologies of the sperm nucleus and the acrosome of this species are the oval shape and cone shape, respectively. Spermatozoa are approximately $47-50{\mu}m$ in length including a sperm nucleus (about $1.24{\mu}m$ in length), an acrosome (about $0.60{\mu}m$ in length), and tail flagellum (about $45-47{\mu}m$). The axoneme of the sperm tail shows a 9+2 structure. In P. martensii in Pteriidae, a special substructure showing a thick and wide triangular shape which is composed of electron-dense opaque material (occupied about 50% of all, the upper part of the acrosomal vesicle), appeared in the upper region (part) of the acrosomal vesicle, while the lower region (part) of the acrosomal vesicle is composed of electron-lucent material. Thus, this special structure, which exist in the upper part of the acrosomal vesicle in P. martensii, is somewhat different from those of other subacrosomal vesicle in other families in subacrosomal vesicles. Therefore, we assume that the existence of a special substructure showing a thick and wide triangular shape in the acrosomal vesicle of the spermatozoon can be used as a key characteristic for identification of P. martensii or other species in Pteriidae in subclass Pteriomorphia. The number of mitochondria in the midpiece of the sperm of this species are five (exceptionally sometimes four), as one of common characteristics appear the same number of mitochondria in the same families of superfamilyies. This species in Pteriidae does not contain the axial rod and satellite fibres which appear in the species in Ostreidae in subclass Pteriomorphia. These characteristics can be used for the taxonomic analysis of the family or superfamily levels as a systematic key or tools.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.159-165
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• 2011

The anatomy and ultrastructure of the digestive diverticulum of Saxidomus purpuratus were described using light and electron microscopy. The digestive diverticulum of dark green color was situated on the gonad and connected to stomach by a primary duct. Digestive diverticulum is composed of numerous digestive tubules. The epithelial layer of digestive tubule, which is simple, is composed of basophilic cells and digestive cells. Basophilic cells are columnar in shape, and the electron density is higher than that of the digestive cell. The cytoplasm has a well-developed endoplasmic reticulum, tubular mitochondria, Golgi complex and membrane-bounded granules of high electron density. Digestive cells are columnar in shape, with development of microvilli on the free surface. Pinocytic vasicles, lysosomes and numerous mitochondria were observed in the apical cytoplasm of digestive cells. The results of this study suggest that basophilic cells and digestive cells in the digestive tubule are specialized in the extracellular and intracellular digestions, respectively.

• The Korean Journal of Malacology
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• v.28 no.3
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• pp.187-196
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• 2012

Recently, for the purpose of constructing artificial ecosystem, the public aquarium and experimental mesocosm systems are receiving attention. To design and establish an aquarium and mesocosm system, there is need of several materials for simulating the environment, such as sediments, rocks, and plants. Expecially for sessile mollusks, there must be proper materials to which sessile invertebrates can adhere. Nowadays, many aquariums and mesocosm systems are using dead coral skeletons for sessile mollusks. This study was proceeded to have data on the effect of dead coral skeletons on water qualities with the experiment on the environmental factors. For this purpose, I made glass tank for experiment, chose two types of dead coral skeletons imported from the Indonesia and observed the change of water qualities and decomposition efficiency of TAN (total ammonia-nitrogen), nitrite ($NO_2{^-}$) and nitrate ($NO_3{^-}$). As a result, the lager the surface area was, the more TAN, nitrite and nitrate decomposition rate increased. In addition, coral skeletons covered with crustose algae and bacteria in the tank showed faster TAN, nitrite and nitrate removal rate and stabilization. Accordingly, this experiment suggested that dead coral skeletons could be used as a sub filter for the closed system as well as an adhering plate.