• Journal of Marine Life Science
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• v.1 no.2
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• pp.95-108
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• 2016

This study was performed to investigate the community structure of macrobenthic assemblages in the Environmental Conservation area, Korea. Benthic animals were collected by van Veen grab sampler at spring (May) and summer (August) 2009. The total species number and mean density were 195 species 5.6 m^-2 and 667 individuals m^-2, respectively. Polychaetes were the most dominant faunal group in species (96 species) and abundance (431 individuals m^-2). The major dominant species were the polychaetes Lumbrineris longifolia (76±224 individuals m^-2), Mediomastus californiensis (42±117 individuals m^-2), Tharyx sp.3 (26±110 individuals m^-2), the bivalvia Theora fragilis (54±78 individuals m^-2) and the amphipod Eriopisella schellensis (70±146 individuals m^-2). Based on the cluster and nMDS ordination analysis, macrobenthic communities were divided into three faunal groups. The first group was characterized by high abundance of the polychaeta Sternaspis scutata and the amphipod Ampelisca cyclops iyoensis, which is located by most stations of Hampyeong Bay and St. 4 of Deungnyang Bay. The second group was numerically dominated by the polychaeta Capitella capitata at St. 4 and St. 5 in Gamak Bay where was most pollutant area. Finally, the third group was dominated by the polychaetes Heteromastus filiformis, Tharyx sp.3 and the amphipod Sinocorophium sinensis. Therefore, geochemical characteristics such as the bay shape and pollution gradient may be important factors controlling of the macrobenthic community structure in Environment Conservation Area.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.177-190
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• 2009

Species composition and abundance of marine organism in the Nakdong River estuary were investigated seasonally from November 2007 to November 2008. During the study period, a total of 169 species, 93 families, and 6 taxa were collected in the study area. Species included were 2 species in Bivalvia, 11 in Cephalopoda, 43 in Crustecea, 8 in Echinodermata, 6 in Gastropoda, and 99 in Pisces. The seasonal dominant species in number of individuals were Acropoma japonicum in autumn, Apogon lineatus in winter, Siphonalia spadicea fuscolineata in spring, and Crangon hakodatei in summer. Dominant species in abundance were Chelidonichthys spinosus in autumn, Liphius litulon in winter and spring, and Raja kenojei in summer. The number of species and their abundance, the species composition, and the diversity indices fluctuated with seasons. The organisms were divided into 17 groups by seasonal variation using a self-organizing map.

• Development and Reproduction
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• v.12 no.1
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• pp.41-49
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• 2008

Ultrastructural changes occurring during the course of development and degeneration of oocytes in female Ruditapes philippinarum (Adams & Reeve, 1850) are described for clams collected from Gomso Bay, Korea. During the early stages of oogenesis, desomosome-like gap junctions localized between the early vitellogenic oocyte and the follicle cells. Vitellogenesis occurs through a process of autosynthesis, involving the combined activity of the Golgi complex, mitochondria and rough endoplasmic reticulum, and heterosynthesis in which extraovarian precursors are incorporated into oocytes by endocytotic activity, involving the basal region of the early vitellogenic oocytes prior to the formation of the vitelline envelope. The follicle cells appear to play an integral role in vitellogenesis and oocyte degeneration: phagocytosis and intracellular digestion of products originating from oocyte degeneration. These functions can permit a transfer of yolk precursors necessary to vitellogenesis, and they can accumulate nutrients in the cytoplasm, as glycogen and lipids, which can be employed by the vitellogenic oocyte. During the period of oocyte degeneration, follicle cells may have lysosomal system for breakdown, and resorb various phagosomes in the cytoplasm for nutrient storage. But follicle cells probably are not the major source of yolk precursors in vitellogenesis.

• The Korean Journal of Malacology
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• v.19 no.1
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• pp.9-17
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• 2003

The gonad index (GI), reproductive cycle with gonad developmental phases, first sexual maturity and the sex ratio of the jedo venus, Protothaca jedensis, on the coastal waters of Boryeong, Korea were investigated by histological study. Samples were collected from the subtidal zone of Boryeong, Korea from January to December, 1999. Monthly changes in the gonad index in femal and male clams gradually increased from February and reached the maximum in May, and then the values rapidly decreased from June and reached the minimum in November as seen in variations of the reproductive cycle. The spawning period of this species was once a year between May and July, there was a spawning peak between June and July when seawater temperature was over 20$^{\circ}C$. The reproductive cycle of this species in female and male clams can be classified into five successive stages: early active stage (December to March), late active stage (February to June), ripe stage (April to July), partially spawned stage (May to July) and spent/inactive stage (July to January). Percentages of first sexual maturity of female and male clams of 30.1-35.0 mm in shell length were 52.6% and 60.0%, respectively, and 100% for the clams over 45.1 mm in shell length. The sex ratio of individuals > 30.1 mm in shell length was 1:1 (X$^2$ = 0.40, p > 0.05).

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.261-271
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• 2011

The gametogenic cycle, the spawning season and the biological minimum sizes in female and male Protothaca (Notochione) jedoensis were investigated by quantitative statistical analysis. In females, monthly changes in the percents of the follicle areas to the ovarian tissue areas and the percents of the oocyte areas to the ovarian tissue areas increased in February and reached the maximum in April, and then gradually decreased from May to July, with the spawning peak between June and July. In males, monthly changes in the percents of the testicular tissue areas to total tissue areas and the percents of the spermatogenic stage areas to the testicular tissue areas increased in February and reached the maximum in April, and then showed a rapid decrease from May to July. From these data, it is apparent that the number of spawning seasons in female and male P. (N.) jedoensis occurred once a year, from May to July. Therefore, P. (N.) jedoensis in both sexes showed a unimodal gametogenic cycle during the year. Compared the gametogenic cycle by quantitative statistical analysis in 2007 with the previous qualitative results of this species, the results of the gametogenic cycle calculated by quantitative statistical analysis showed some differentiations in the spawning seasons evaluated by the gonad index by qualitative histological analysis. The intervals of the beginning of two spawning seasons showed one month between the results of quantitative and qualitative analyses. The biological minimum sizes (considering to 50% of group sexual maturity) in female and male clams by quantitative analysis of this species are 32.01 mm in shell length in females and 30.58 mm in males, respectively. According to the mean shell length fitted to von Bertalanffy's equation, 30.58 and 32.01 mm in shell length were considered to be two years old. Therefore, we assume that both sexes of this population begin reproduction from two years of age.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.11 no.4
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• pp.152-157
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• 2006

Samples of Meretrix lusoria were collected monthly from the tidal flat of Simpo, Puan-gun, Chollabuk-do, west coast of Korea from April 2004 to March 2005. Age of M. lusoria was determined from the rings on the shell. 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 variations in the marginal index (MI') of the shell, it is assumed that the ring of this species was formed once a year during the period of February to April. The relationship between shell length (SL) and shell height (SH; mm) was highly correlated with shell height as the following equation: SH = 0.8103 SL + 0.5145 $(r^2=0.991)$. The shell length (SL) - shell width (SW) relation was also expressed by the following equation: SW = 0.4897 SL + 0.0315 $(r^2=0.976)$. Shell length (SL; mm) and total weight (TW; g) was expressed by the following equation: $TW=2.9195\times10^{-4}\;SL^{2.9547}\;(R^2=0.991)$. Shell length (SL) and shell height (SH; mm) was highly correlated with shell height as the following equation: $SH=0.8103\;SL+0.5145\;(R^2=0.991)$ The shell length (SL) - shell width (SW) relation was also expressed by the following equation: $SW=0.4897\;SL+0.0315\;(R^2=0.976)$. Growth curves for shell length and total weight fitted to the von Bertalanffy's growth curve were expressed respectively as: $SL_t=104.9[l-e^{-0.2235(t+0.7677)}],\;TW_t=280.8[l-e^{-0.2235(t+0.7677)}]^{2.9547}$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.778-784
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• 2017

We investigated the possibility of a bio-monitoring system for predicting toxic dinoflagellates (Genus Alexandrium) by the measuring shell valve movements(SVMs) of Pacific oyster, Crassostrea gigas (Mollusca: Bivalvia) using the Hall element sensor. We then described the SVMs of Pacific oyster exposed to the toxic algae under laboratory conditions. Pacific oyster used for experiment were fed Isochrysis galbana until they stabilized and kept under hunger conditions for three days to prevent the influence of food before the experiment. Pacific oyster were exposed to the toxic dinoflagellate, A. fundyense, and the potentially toxic dinoflagellate, A. affine. When Pacific oyster were exposed to A. fundyense, SVMs increased over 10 times/hr at low cell densities of 20 cells/mL. SVMs increased again at $14.1{\pm}5.7times/hr$ at 500 cells/mL, and $27.9{\pm}11.1times/hr$ at the high cell density of 5,000 cells/mL. However, in the presence of A. affine, SVMs increased at $6.7{\pm}3.9times/hr$ until 300 cells/mL, while they increased greatly to $15.3{\pm}10.8times/hr$ at 1,000 cells/mL. The SVMs of Pacific oyster indicated differences depending on species for toxic dinoflagellates. Therefore, the SVMs of Pacific oyster could be useful for A. fundyense, but would bedifficult to apply for A. affine.

• The Korean Journal of Malacology
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• v.26 no.1
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• pp.51-62
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• 2010

The ultrastructures of germ cells and the accessory cells during spermatogenesis and mature sperm ultrastructure in male Gomphina veneriformis, which was collected on the coastal waters of Yangyang, East Sea of 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 four mitochondria surrounding the centrioles. Accessory cells are observed to be connected to adjacent germ cells, they contain a large quantity of glycogen particles and lipid droplets in the cytoplasm. Therefore, it is assumed that they are involved in the supplying of the nutrients for germ cell development, while any phenomena associated with phagocytosis of undischarged, residual sperms by lysosomes in the cytoplasm of the accessory cells after spawning was not observed in this study. The morphologies of the sperm nucleus type and the acrosome shape of this species have a cylindrical and modified long cone shape, respectively. In particular, the axial filaments in the lumen of the acrosome, and subacrosomal granular materials are observed in the subacrosomal space between the anterior nuclear fossa and the beginning part of axial filaments in the acrosome. The spermatozoon is approximately $50-55{\mu}m$ in length including a long sperm nucleus (about $7.80{\mu}m$ in length), an acrosome (about $1.13{\mu}m$ in length) and tail flagellum ($40-45{\mu}m$). 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 charateristics of sperm morphology of this species in the family Veneridae are (1) acrosomal morphology, (2) the number of mitochondria in the midpiece of the sperm,. The axial filament appears in the acrosome as one of characteristics seen in several species of the family Veneridae in the subclass heterodonta, unlikely the subclass pteriomorphia containing axial rod instead of the axial filament. As some characteristics of the acrosome structures, 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 belong to the family Veneridae in the subclass heterodonta, unlikely 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. The number of mitochondria in the midpiece of the sperm of this species are four, as one of common characteristics appeared in most species in the family Veneridae.

• The Korean Journal of Malacology
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• v.29 no.2
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• pp.129-137
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• 2013

This study was conducted to find out the changes of survivorship, respiration and organ structure of Mactra veneriformis exposed to copper (Cu). Experimental period was four weeks. Experimental groups were composed of one control condition and three copper exposure conditions (0.025, 0.050 and 0.100 mg/L). The results of the study confirmed that copper induces reduction of survival rate and respiration rate and histopathology of organ structure of the bivalve. In the copper concentration of 0.100 mg/L, mortality was 100% after Cu exposure of 3 weeks. Respiration rate was observed exposure groups lower than control decline by 75%. Histological analysis of organ system illustrated expansion of hemolymph sinus, disappearance of epidermal layer and degeneration of connective tissue layer of the mantle. Also, histological degenerations as epithelial necrosis and hyperplasia of mucous cells are recognized in the gill and it was observed expansion of hemolymph sinus, disruption of epithelial layer, decrease of mucous cell and degeneration of connective tissue layer in the foot. In the digestive diverticulum, it was showed atrophy of basophilic cell and degeneration of epithelial cell in the digestive tubules, and as the concentration of copper increased the accumulation of lipofuscin increased.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.6
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• pp.399-412
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• 2005

This study investigated the composition and the distribution of the benthic polychaeta community in the semi-enclosed Yoja Bay on the southern coast of Korea and was designed to deduce temporal changes in the community with the comparison of the previous studies. In YoJa Bay, benthic polychaetous community structure was investigated on the base of the samples from 87 stations. The surface sediment was mainly composed of fine-grained sediment, mixed clayey silt and silty clay. The total benthic macrofaunal density was $387 indiv./m^2$, and the density was higher in the middle bay, and in the mouth of bay than in the inner bay. scapharca subcrenata (Bivalvia) and amphipods (Crustacea) were important species in the inner and the middle of the bar, respectively. Benthic polychaetes were comprised of 72 species with a mean density of $149 indiv./m^2$. Their distributions showed higher densities in the mouth of bay than in the rest of bay. The dominant species over 1.0 percentages were composed of the 20 species, and they occupied $84.5\%$ of the total density. The most dominant species was Sternaspis scutata ($13.6\%$), fallowed fly Heteromastus filiformis ($9.8\%$), Polynoidae indet. ($8.3\%$), Sigambra tentacuzata ($7.1\%$) and others. The cluster analysis revealed that the study area was divided into three station groups. At the station group YI located in the inner bay, the most dominant species was Heteromastus filiformis . At the station group YII in the middle bay, the dominant species was Sternaspis scutata. And at the station group YIII in the mouth of bay, the dominant species was Paraiacydonia paradoxa. Whereas Sternaspis scutata and Mediomastus sp. were the dominant species in the past study, Heteromastus filiformis and Tharyx sp. appeared newly to be the dominant species, even if their low densities that in the past. These facts mean that Yoja Bay be maintained yet as little polluted area compared to other bays on the coast of Korea, but needed some caution of marine environmental management.