• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.2
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• pp.138-145
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• 2018

The diet composition of Takifugu niphobles was studied with 587 specimens collected in the eelgrass bed of Jangpyeong-ri, Tongyeong, Korea, using a seine net, monthly from May 2016 to April 2017. The standard length (SL) of the specimens ranged from 0.7 to 9.0 cm. The stomach contents analysis indicated that T. niphobles consumed mainly amphipods (%IRI: 91.0 %). In addition, T. niphobles fed on small quantities of copepods, polychaetes, insects, bivalves and crabs. T. niphobles consumed mainly amphipods over all size class. Smaller individuals (less than 4 cm SL) fed mainly on amphipods and copepods. The proportion of copepods decreased, as body size increased, whereas the consumption of polychaetes increased gradually. The seasonal variation in the diet composition of T. niphobles was significant. Amphipods were most common prey in all seasons. Copepods decreased from summer to spring gradually whereas the consumption of polychaetes increased in autumn.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.614-621
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• 2010

A indigenous freshwater bivalve Unio douglasiae was introduced to compare the differences in the efficacy of algal bloom control and the appearances of mussel-mediated adverse effects between two different reservoirs such as mesotrophic (Shingu r.) and hypertrophic (Seokmun r.). We constructed the study mesocosm in the shore of each reservoir, stocked the mussel at density of $30indiv./m^3$ for 7 days, and measured daily the phytoplankton density and water quality. In mesotrophic reservoir, even though approximately 38% of suspended solids and chlorophyll-a was reduced by stocked bivalves for the first 3 days, algal density, ammonia and soluble reactive phosphorus gradually increased with increasing mussel death. In hypertrophic reservoir, mussels strongly inhibited suspended solids and chlorophyll-a by the termination of study with no increase of mussel death and nutrient, especially ammonia concentration. In both reservoirs, a strong selectivity showed mussels preferred to diatom rather than cyanobacteria and green algae without algal density and nutrient level. Our results indicate that an introduction of freshwater bivalve U. douglasiae is more strategic to improve water quality of hypertrophic than mesotrophic reservoir, but many preliminary studies on the treatment method and the selection of target water system are required.

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.311-316
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• 2010

Spermatid differentiations during spermiogenesis and mature sperm ultrastructure in male Crassostrea nipponica were investigated by transmission electron microscope observations. The morphology of the spermatozoon of this species has a primitive type and is similar to those of other bivalves. Mature spermatozoa consist of broad, cap-shaped acrosomal vesicle and an axial rod in subacrosomal materials on an oval nucleus showing deeply invaginated anteriorly, two triplet substructure centrioles surrounded by four spherical mitochondria, and satelite fibres, which appear near the distal centriole. The acrosomal vesicle of spermatozoa of C. nipponica resemble to those of other investigated ostreids. Especially, two transverse bands (stripes) appear at the anterior region of the acrosomal vesicle, unlikely 2-3 transverse bands (stripes) in C. gigas. It is assumed that differences in this acrosomal substructure are associated with the inability of fertilization between the genus Crassostrea and other genus species in Ostreidae. Therefore, we can use sperm morphology in the resolution of taxonomic relationships within the Ostreidea. The sperm is approximately $48-50{\mu}m$ in length including an oval sperm nucleus (about $1.0{\mu}m$ in length and $1.41{\mu}m$ in width), an acrosome (about $0.48{\mu}m$ in length and 0.30 in width) and tail flagellum ($46-48{\mu}m$). The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9 + 2 structure. These morphological charateristics of acrosomal vesicle belong to the family Ostreidae in the subclass Pteriomorphia.

• Journal of the korean society of oceanography
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• v.36 no.4
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• pp.109-123
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• 2001

The importance of phytoplankton, benthic vegetation, vascular marsh plants (primarly Phragmites communis and Salix gracilstyla) and riverine particulates inputs to the coastal bay food web was studied in Kwangyang Bay, Korea using stable carbon isotope ratios. Vascular marsh plants (${\delta}^{13}$C=-27.4${\pm}$0.8%o) and riverine particulates (-26.0${\pm}$0.8%o) were isotopically distinct from phytoplankton (-20.7${\pm}$0.8%o), microphytobenthos (-14.2${\pm}$0.6%o) and seagrass (8.8%o). The ${\delta}^{13}$C values of consumers in the study site ranged from -20.2 to -11.3olo suggesting the assimilation of carbon derived from both phytoplankton and benthic vegetation (including algae and seagrass), The relative importance of both pelagic and benthic origins of food sources was likely to vary depending on feeding habit of the consumers. The isotopic difference between pelagic and benthic consumers indicated that plankton-derived carbon was used mostly by pelagic consumers, but the carbon derived from intertidal benthic vegetation was incorporated into food webs through benthic consumers. The ${\delta}^{13}$C values of consumers in the present study differed noticeably from published values of the phytoplankton-based ecosystem, particularly in the $^{13}$C enrichment of benthic grazers, deposit-feeders and demersal feeders of fishes. This tendency of the $^{13}$C enrichment was also found in suspension-feeding bivalves. Taking the biomasses of benthic vegetation into consideration, benthic microalgae was likely to account for the consumer $^{13}$C enrichment. Role of terrestrially derived riverine carbon was limited to the riverine system and was not evident within the bay systems. Phragmites, despite their important biomass, appeared to be of little importance as consumer diet.

• Development and Reproduction
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• v.14 no.1
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• pp.7-11
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• 2010

This study attempted to verify the possibility of using germ cell aspiration (GCA) method as a non-fatal technique in studying the life-history of equilateral venus, Gomphina veneriformis (Veneridae) and granular ark, Tegillarca granosa (Arcidae). Using twenty-six gauge 1/2" (12.7mm) needle, GCA was carried out in equilateral venus through external ligament. In granular ark, GCA was performed by preventing closure of the shells by inserting a tongue depressor between the shells while still open. The success rate of sex identification using the GCA method was 95.6% for the equilateral venus (n=650/680) and 94.3% for the granular ark (n=707/750). Mortality of equilateral venus, which spent 33 days under wild conditions, was 13.8% (n=90/650) while the mortality of granular ark, which spent 390 days under wild conditions, was 2.4% (n=17/707). Although we believe that GCA does not appear to cause death in equilateral venus or granular ark, the success rate in employing of this methodology may differ depending on the level of proficiency of the researcher and reproductive stage of the bivalve. This study concludes that GCA is a convenient non-fatal methodology, which can be employed to identify sex and investigate gonadal maturity in Gomphina veneriformis and Tegillarca granosa.

• The Korean Journal of Malacology
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• v.26 no.1
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• pp.33-43
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• 2010

The ultrastructure of germ cells during spermatogenesis and some characteristics of sperm morphology in male Mytilus coruscus, which was collected on the coastal waters of Gyeokpo in western Korea, were investigated by transmission electron microscope observations. The morphology of the spermatozoon has a primitive type and is similar to those of other bivalves in that it contains a short midpiece with five mitochondria surrounding the centrioles. The morphologies of the sperm nucleus type and the acrosome shape of this species have an oval and modified cone shape, respectively. In particular, the axial rod is observed between the nucleus and acrosome of the sperm. The spermatozoon is approximately $45-50{\mu}m$ in length including a sperm nucleus (about $1.46{\mu}m$ in length), an acrosome (about $3.94{\mu}m$ in length) and tail flagellum (approximately $40-45{\mu}m$). The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure. Some special charateristics of sperm morphology of this species in the genus Mytilus are (1) acrosomal morphology, (2) the number of mitochondria in the midpiece of the sperm, and (3) the existence of a satellite. The axial rod appears in the acrosome and sperm nucleus as one of the characteristics seen in several species of the subclass Pteriomorphia, unlikely the subclass Heterodonta containing axial filament instead of the axial rod. The number of mitochondria in the midpiece of the sperm of this species in the family Mytilidae are five, as one of common characteristics appeared in most species in the family Mytilidae. Most of Mytilus species contain a satellite body which is attached to the proximal centriole in the middle piece of the sperm, as one of common characteristics of sperm morphology in the family Mytilidae.

• The Korean Journal of Malacology
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• v.26 no.1
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• pp.19-31
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• 2010

Seogundo is a small island adjacent to the southern coast of Jeju Island and connected to it by a boulder beach at low tide Surveys of this area were conducted from 2001 to 2009 to enumerate the mollusks there and also to examine their diversity, relative abundance, and ecological relationships. Both the boulder beach itself and several large tide pools were studied, including the coarse sand substrate and several species of seaweed and coralline algae found in the tide pools. Of the 121 species obtained or observed, there were 97 gastropods, 16 bivalves, and 8 polyplacophorans. Live specimens were obtained for about half of those species. About one third were found on rocky substrate, with the most common species being Nodilittorina radiata and Nerita japonica in the upper intertidal zone, N. radiata and Littorina brevicula in the middle intertidal, and Turbo (Lunella) coronata coreensis and Acanthopleura japonica in the lower intertidal and shallow subtidal. The seaweeds and coralline algae contained about 40% of all mollusk species. The most common mollusks in two species of brown seaweed were Ittibittum parcum, Musculus nanus, and Euplica scripta. In a species of red seaweed, Komaitrochus pulcher was the most frequent, as in the coralline algae, along with M. nanus. The coarse sand in the tidepools contained about 25% of the species, with the Cerithiidae having the largest number. A sample of beach drift contained 17 species, with Bittium aleutaceum and Rissoina (Phosinella) pura being most common. Most species, about 60%, were found in a variety of habitats, especially the marine flora; few species exhibited any habitat preferences. Biographically, Jeju Island is part of the Warm Temperate Northwest Pacific Province and the East China Sea ecoregion with a strong faunal affinity with southern Japan, eastern China, and northeastern Taiwan. Zonal-geographical groupings reveal that the fauna is mainly subtropical-low boreal, preferring moderately warm water, with a somewhat smaller number of tropical-subtropical species.

• 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.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.

• Fisheries and Aquatic Sciences
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• v.7 no.3
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• pp.141-147
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• 2004

Sixteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in seventy marine organisms (40 species) from the Korean coast. PAHs were present in all the organisms. The level of total PAHs in the organisms varied from 0.45 to 224 ng/g dry weight and the carcinogenic PAHs varied from 0.05 to 49.8 ng/g dry weight. The PAHs residues according to the marine organisms showed a highest content in bivalve species, and followed by crustaceans, cephalopods, fish and gastropods. Human dietary intake of total PAHs through marine organism in Korea was estimated to be 4.12 ng/kg body weight/day and 0.67 ng/kg body weight/day for carcinogenic PAHs. The relative contributions of individual species to the total dietary intake of PAHs were in the order of bivalves $(53.4{\%})$, fish $(21.9{\%})$, crustaceans $(15.3{\%})$, cephalopods $(8.8{\%})$ and gastropods $(0.6{\%})$. Daily dietary intake of $PAH_{TEQ}$ expressed as a TEQ value was estimated to be 0.13 pg TEQ/kg body weight/day, which did not exceed a tolerable daily intake (TDI) proposed by the KFDA and the WHO as well as the UK toxicity committee. Lifetime cancer risk due to ingestion of marine species by the Korean adult was evaluated using the equation estimating exposure of food ingestion. Although approximately $23{\%}$ of cumulative frequency of the sampled marine species exceeded the cancer risk guideline, lifetime cancer risk associated with marine organism consumption was negligible. Results indicate that dietary intake of PAHs through the consumption of the Korean marine organisms seems to be safe for human ingestion with negligible cancer risk.