• The Korean Journal of Malacology
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• v.13 no.2
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• pp.131-141
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• 1997

전북 김제시 심포에서 1994년 1월부터 12월까지 월별로 채집된 백합 Meretrix lusoria의 생식세포형성과정 및 생식주기를 , 조직학적으로 조사한 결과는 다음과 같다. 백합은 자웅이체이고 난생을 하며, 생식소는 내장낭의 간중장선의 하부로부터 족부의 근육부근까지 분포하며, 성숙되면 팽대되지만 방란, 방정 후에는 위축된다. 생식소는 많은 난자형성여포들과 정자형셩여포들로 구성되어 있다. 여포에는 호산성 세포와 미분화간충직들이 들어 있는데, 이들은 초기 생식세포의 영양물질로 제공되고 있으며, 생식소가 발달함에 따라 점차 소실된다. 초기활성기의 난원세포는 직경 10$\mu\textrm{m}$ 내외이며, 초기 난모세포는 난병을 여포벽에 부착한 채 성장을 하여 70$\mu\textrm{m}$ 내외의 완숙란으로 된다. 정원세포가 성장을 하여 정보세포, 정세포를 거쳐 변태를 마친 정자는, 정자형성소낭의 중앙 내강에 정자속을 형성한다. 방란, 방정을 마친 생식소는, 일부 미방출된 생식세포가 퇴화 흡수되면서 비활성기를 지나 이듬해 수온상승과 더불어 새로운 발달을 시작한다. 생식주기는 연속적인 5단계로 구분할 수 있는데, 초기 활성기(1-3월), 후기 활성디 (2-5월), 완숙기(4-8월), 부분 방출기(6-9월), 퇴화 및 비활성기(9-2월)로 구분할 수 있다. 산란은 6월 (22$^{\circ}C$)부터 9월 ($25^{\circ}C$)까지 지속되지만, 산란성기는 7월(27$^{\circ}C$)-8월(28$^{\circ}C$)이다. 생식소지수는 1월에 0.58을 나타내며 5월에 4.60으로 최대값을 나타낸 후, 6월부터 점차 감소하기 시작하여 12월과 1월에는 1.0미만에 머무른다.

• 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.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.20 no.2
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• pp.171-181
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• 2004

Partial sequences of the mitochondrial cytochrome oxidase subunit Ⅰ(mtCOI) gene of veneroid clams were obtained to eluciadate molecular phylogeny. A total of nine veneroids and one corbiculid were collected from southern and western sea of Korea. The mtCOI sequences of the clams obtained from the present study and three veneroids sequences from GenBank were analyzed by maximum parsimony and neighbor-joining methods. The subfamilies Samarangiinae, Dorsiniinae, Cyclinae, Meretricinae and Chioninae were monophyletic, but Pitarinae was paraphyletic. One transitions and two transversions among two samples of Ruditapes philippinarum and a R. variegata were observed.

• Ocean and Polar Research
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• v.32 no.3
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• pp.247-254
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• 2010

Single cell PCR analysis and light and scanning electron microscopic techniques were utilized to identify free living bivalve larvae in the coastal waters of Tae-an, on the west coast of Korea. Through DNA sequencing, venerid clam larvae were isolated and identified as Ruditapes philippinarum (99% similarity) and Meretrix lusoria (99%). Under microscopic observation, the D-veliger stage of R. philippinarum exhibited symmetrical shoulder angles and an elliptical ventral form. In contrast, M. lusoria displayed asymmetrical shoulder angles and a round ventral form in the umbonal stage. Size of the R. philippinarum larvae was $156{\pm}22{\mu}m$ in length, $126{\pm}12{\mu}m$ in height, $92{\pm}14{\mu}m$ in width with a length: height ratio of 1.23. Meretrix lusoria was $202{\pm}44{\mu}m$ in length, $161{\pm}35{\mu}m$ in height, $96{\pm}38{\mu}m$ in width with a length: height ratio of 1.25. Experimental results indicate that morphological and molecular characteristics provide evidence for the larval identification of these two venerid clam larvae species in nature.

• Development and Reproduction
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• v.16 no.1
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• pp.47-51
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• 2012

Genomic DNAs (gDNAs) were isolated from the hard clam ($Meretrix$ $lusoria$, Roding, 1798) populations of Gunsan located in the Yellow Sea of the Korean peninsula. Genetic distances among different individuals of the LSCP (light shell color population) population of the hard clam (lane 1-11), GSCP (grey shell color population) population of the hard clam (lane 12-22) and DSCP (dark shell color population) population of the hard clam (lane 23-33), respectively, were generated using Systat version 10 according to the bandsharing values and similarity matrix. The dendrogram, generated by seven reliable oligonucleotides primers, indicates 3 genetic clusters. LSCP population could be evidently discriminated with the other two populations among three populations. The longest genetic distance (0.801) was found to exist between individuals in the two populations, between individuals' no. 33 of the DSCP population and no. 06 of the LSCP population. The higher fragment sizes (>2,000 bp) are much more observed in the GSCP population. Three hard clam populations can be clearly distinguished, especially, by their morphological characters and PCR-based approach.

• The Korean Journal of Malacology
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• v.22 no.2
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• pp.115-124
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• 2006

Gonad index, spermatogenesis and the reproductive cycle of Meretrix petechialis were investigated by cytological, histological observations. Monthly changes in the gonad index coincides the gonadal development. The morphology of the spermatozoon had a primitive type and is similar to that of other bivalves having a short mid-piece with five to six mitochondria surrounding the centrioles. The morphology of the sperm nucleus type and the acrosome shape of this species were cylindrical type and cap-like shape, respectively. The spermatozoon was approximately 40-45 ${\mu}m$ in length including the sperm nucleus length (about 1.50 ${\mu}m$), acrosome length (0.60 ${\mu}m$) and tail flagellum. The axoneme of the tail flagellum consisted of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail showed 9 + 2 microtubular arrangement. The spawning period was from June to September and the main spawning occurred from July to August when seawater temperatures were higher than $20^{\circ}C$. The reproductive cycle of this species could be categorized into five successive stages: early active stage (February to March), late active stage (February to May), ripe stage (April to July), partially spawned stage (June to September), and spent/inactive stage (September to February).

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.167-173
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• 2011

This study was performed to describe the effect of water temperature, salinity and density on the eggs development of the hard clam, Meretrix petechialis. Eggs of Meretrix petechialis were turned out to be demersal isolated eggs of $82.3-86.1{\mu}m$ in an average diameter after spawning. The hatching rate of D-shaped larvae by elapsed time after spawning was the highest in fertilization immediately after spawning and distinguished decrease from 1 hour of spawning. The optimum water temperature for development of D-shaped larvae from fertilization was ranged between $25^{\circ}C$ to $27^{\circ}C$. However, D-shaped larvae was not developed at $33^{\circ}C$ of water temperature. The required time from fertilization to D-shaped larvae were 37.3 hours in $20^{\circ}C$, 20.8 hours in $25^{\circ}C$, and 15.3 hours in $30^{\circ}C$. Biological minimum temperature for the egg development was estimated to be $12.4^{\circ}C$ in average. The range of salinity for the development of eggs were 20.0-37.5 psu, optimum range was estimated to be 27.5-32.5 psu.

• Proceedings of the Malacological Society of Korea Conference
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• 2000.11a
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• pp.18-21
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• 2000

• YAKHAK HOEJI
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• v.39 no.3
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• pp.252-259
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• 1995

Isolation, purification and characterization of biophysicochemical properties of the three new lectins, MLA-I, MLA-II, MLA-III from the hemolymph of Meretrix lusoria have been reported previously. A series of immunochemical studies were investigated in this work. The three lectins were revealed as having partial identity each other by immunodiffusim and immunoelectrophoresis. These results suggest that MLA lectins are isolectins having similar biophysicochemical properties. Particularly, MLA-I proved to be a potent mitogen for murine splenic as well as human peripheral lymphocytes, and the optimum mitogenic dose were 62.5 and 1.95 $\mu\textrm{g}$/ml, respectively.