• The Korean Journal of Malacology
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• v.17 no.1
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• pp.63-70
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• 2001

The distribution and seasonal changes of the intertidal macrobenthos community was performed on five intertidal rocky stations of Hwasoon at Jeju Islands September 1999 to August 2000. The macrobenthos was composed of six phyla, 13 classes, 24 orders, 49 families, and 97 species. The dominant species of the upper zones were Nodilittorina exigua, Notoacmea schrenckii, Liolophura japonica and Patelloida saccharina. Those of the middle zones were Monodonta labio, Chthamalus challengeri, Siphonalia japonica and Liolophura japonica. Those of the lower zones were Siphonalia sirius, Patelloida saccharina, Chthamalus challengeri, and Liolophura japonica. The community dominance indices of the upper zones were much higher than those of the middle and lower zones. Species diversity and evenness in all investigated zones were highest in station 1 and lowest in staton 3. But, species richness was highest in station 1 and lowest in station 4.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.33-40
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• 2005

Occurrence and prevalence of Marteilioides chungmueasis have been reported in several waters around Tongyeong but no report has been made for Pukman bay. Therefore, we investigated that the prevalence and infection intensities in Pukman Bay at the inside and the outside areas which are hydrographically divided by tidal current. Furthermore, various environmental parameters were investigated in order to elucidate effective parameter for parasitic infection. Infection rates of Marteilioides chungmuensis in adult oysters were ranged 3.3-20.0% at the inside area during September 2002 through January 2003, and 3.3-30.9% at the outside area during August 2002 through January 2003. External manifestation of infected oyster consisted of abnormal egg masses with nodular appearance in the soft tissue. Histopathological symptoms included massive hemocytic infiltration within or around the follicle wall and atrophic epithelium of digestive diverticula. For the environmental parameters, comparative study made differences between two side of the Bay during the infection period: inside > outside for SS while inside < outside for chlorophyll-a. A positive relationship was observed between chlorophyll-a and infection period, which might indicate the difference in food availability between two areas. The prevalence of ovarian parasite Marteilioides chungmuensis, therefore, was highly associated with food availability. Pearson's correlation analysis was made between environmental parameters and infection prevalence. Significance was observed in water temperature (p < 0.05), suspended solids (p < 0.01) and chlorophyll-a (p < 0.05). A principle component analysis showed that infection of the ovarian parasite, Marteilioides chungmuensis, exhibited effects of seasonality (component I = 55.2%) and chemical/physical environmental factors (component II = 24.4%). These results clearly indicate that the infection of ovarian parasite, M. chungmuensis in the Pacific oyster Crassostrea gigas is closely associated with seasonality and food availability.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.47-56
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• 2005

A series of radiotracer experiments were employed to quantitatively compare the biokinetics of uptake from the dissolved phase (influx rates), uptake from the various types of food source (assimilation efficiency), and loss (efflux) of Ag between Potamocorbula amurensis and Macoma balthica. Simultaneously, influx rates of dissolved Cd in both clams were determined to compare with those of Ag. Effects of salinity on influx rates were evaluated in these 2 euryhaline species, as were effects of clam size. Influx rate of Ag and Cd (${\mu}g g^{-1}$ [dry wt.] $d^{-1}$) increased linearly with metal concentrations. Influx rates of Ag in both clams were 3 to 4 times those of Cd. Absolute influx rates of the 2 metals were 4 to 5 times greater in P. amurensis than M. balthica, probably because of differences in biological attributes (i.e. clearance rate or gill surface area). As salinity was reduced from 20 to 2.5 psu, the influx rate of Cd in P. amurensis increased 4-fold and that of Ag increased 6-fold, consistent with expected changes in speciation. Weight-specific metal influx rates (${\mu}g g^{-1}$ [dry wt.] $d^{-1}$) were negatively correlated with the tissue dry weight of the clams, but most rate constants determining physiological turnover of assimilated metals were not affected by clam size.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.57-64
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• 2005

Samples of Corbicula japonica Prime of Jujin estuary in Gochang were collected from July 2000 to September 2001. Age of C. japonica 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 variation of 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 and March. The relationship between shell length (SL; mm) and total weight (TW; g) was expressed by the following equation: TW = 1.0942 ${\times}10^{-4}SL^{3.3217}$ ($r^2$ = 0.9905). Shell length (SL) and shell height (SH; mm) was highly correlated with shell height as the following equation: SH = 0.9174 SL - 0.9935 ($r^2$ = 0.9885). The shell length (SL) - shell width (SW) relation was also expressed by the following equation; SW = 0.5925 SL - 1.1706 ($r^2$ = 0.9726). Growth curves for shell length and total weight fitted to the von Bertalanffy's growth curve were expressed as: $$SL_t = 46.4861[1-e^{-0.3383(t+0.0958)}]$$, $$TW_t = 34.54[1-e^{-0.3383(t+0.0958)}]^3.3217$$.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.1-11
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• 2005

Reproductive cycle, first sexual maturity, spawning amount related with the size and spawning interval in female Ruditapes philippinarum were investigated by histological observation and the analysis of morphometric data during artificial spawning induction. Ruditapes philippinarum is dioecious and oviparous. The reproductive cycle of this species can be subdivided into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (May to October), and spent/inactive stage (August to February). The spawning period was once a year between May and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. Percentages of first sexual maturity of female clam of 15.1-20.0 mm in shell length were 56.3%, and 100% for the clams > 25.1 mm. The mean number of the spawned eggs increased with the increase of size classes (shell length). In case of spawning induction by the same size class, the number of spawned eggs were gradually decreased with the increase of spawning frequencies (the first, second, and third spawnings). In the experiments of artificial spawning induction during the spawning season, the interval of each spawning was estimated to be 15-17 days (average 16.5 days).

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.147-161
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• 2005

To elucidate the phylogenetic relation of the superfamily Veneroidea, we obtained partial 28S rRNA sequences of 14 heterodonts and three pteriomorphs which were collected from Korea and the sequence data of related taxa from GenBank, and analyzed maximum parsimony with PAUP program 750 of the nucleotide positions were variable, 560 of which were informative under conditions of parsimony. Total tree length was 2,765, and consistency index, homoplasy index (HI), and Retention index was 0.4843, 0.5157, and 0.6291, respectively. Intraspecific variation of 28 rRNA of Corbicula fluminea and Sinonovacula constricta was 3.1% and 1.3%, respectively. Pitarinae-Cyclininae-Meretrinae group had a clade and Samaranginae, Chioninae, and Dorsininae were clustered.

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.81-93
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• 2005

Reproductive cycle with the gonadal phases, first sexual maturity, artificial spawning amount by the size and spawning interval of the hard clam, Meretrix lusoria were investigated by histological observations and morphometric data by artificial spawning induction. Meretrix lusoria is dioecious and oviparous. The reproductive cycle of this species can be classified into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (June to September), and spent/inactive stage (September to February). The spawning period was from June to September, and the main spawning occurred between July and August when the seawater temperature exceeds over $20^{\circ}C$. Percentage of first sexual maturity of female and male clams ranging from 40.0 to 45.0 mm in shell length was over 50%, and all clams over 50.0 mm in shell length sexually matured. Female and male clams ranging from 40.0 to 45.0 mm in shell length are considered to be two years old. Therefore, we assume that the hard clams of both sexes begin reproduction from two years of age. The mean number of the spawned eggs increased with the increase of size (shell length) classes. In case of artificial spawning induction, the number of spawned eggs from the clams of a sized class was gradually decreased with the increase of the number of the spawning frequencies (the first, second, and third spawnings). In the experiments of artificial spawning induction during the spawning season, the interval of each spawning was estimated to be 15-18 days (average 17 days).

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.95-105
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• 2005

Gonadosomatic index, reproductive cycle, spermatogenesis and first sexual maturity of Chlamys farreri were investigated by cytological and histological observations, from January 1998 to December 1999. The gonadosomatic index (GSI) rapidly increased in April and reached a maximum in May when seawater temperature rapidly increase. Then the GSI gradually decreased from June to August when spawning occur. Accordingly, monthly changes in the GSI in males coincide with the reproductive cycle. The spermatozoon of Chlamys farreri is the primitive type found in external fertilization species. The head of the spermatozoon is approximately $2.75{\mu}m$ in length including the acrosome measuring about $0.50{\mu}m$ in length, and its tail was approximately $20{\mu}m$, the axoneme of the tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. Five spherical mitochondria around the centriole (the satellite body) appear in the middle piece of the sperm. The spawning period was from June to August and the main spawning occurs from July to August when seawater temperatures are greater than $20^{\circ}C$ The reproductive cycle of this species can be categorized into five successive stages; early active stage (January to March), late active stage (March to April), ripe stage (April to August), partially spawned stage (June to August), and spent/inactive stage (August to January). Over 50% of male scallops attained first sexual maturity between 50.0 and 60.0 mm in shell height, and 100% of those over 60.0 mm in shell height achieved maturity. Accordingly, we assume that male individuals begin reproduction at three years of age.

• The Korean Journal of Malacology
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• v.17 no.1
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• pp.7-12
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• 2001

The age and growth of the short-necked clam, Paphia undalata, was investigated from 546 samples randomly collected in December 2000 in Kwangyang Bay, Korea. Ages were determined from ring radius of shell and the maximum age was observed to be 2 years. The relationship between shell length (SL) and shell height (SH) of Paphia undalata was SL = 0.2105 ＋ 1.7569 $\times$ SH ($R^2$= 0.98), and the shell length (SL)-total weight (TW) relationship was TW = 2.5824 $\times$ 10$^{-4}$ $\times$ S $L^{2.6769}$ ($R^2$= 0.92). The von Bertalanffy growth parameters were estimated by the non-linear method, with values as follows: $L_{\infty}$ = 81.46 mm, K : 0.20/year, $t_{0}$ = -1.19 year. The von Bertalnanffy growth equation was $L_{t}$ = 81.46(1- $e^{-0}$.20(t+1.19)/), $W_{t}$ = 33.68(1- $e^{-0}$.20(t+1.19)/)$^{2.6769}$.

• The Korean Journal of Malacology
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• v.18 no.1
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• pp.1-8
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• 2002

Seasonal changes in biochemical composition of Crassostrea giggas and Scapharca broughtonii in the Kosong bay and Kangjin bay, southern Korea were studied over 12 months in relation to their habitat. In Crassostrea giggas, protein was high during summer in all experimental station, but lipid and carbohydrate were high during winter, and no clear difference was between experimental station. Glycogen content was sharply decreased during summer, and energy content was low but carbohydrate was high during summer. In Scapharca broughtonii, protein was low, but carbohydrate was high during summer. Lipid was high from February to March, glycogen content was low from June to September. Energy content was low during winter and no clear difference biochemical composition was between experimental station of Scapharca broughtonii.