• The Korean Journal of Malacology
• /
• v.15 no.1
• /
• pp.49-55
• /
• 1999

Mass mortality of the horned turban shell, Batillus cornutus was investigated using histological and bacteriological methods. Some pathogenic bacteria were isolated from mortal or inactive individuals. The pathogenic agents causing mortality of the horned turban shells were as Vibrio alginolyticus and V. anguillarum. Laboratory experiment indicated that optimal growth temperature of two bacteria was 25 to 30$^{\circ}C$ and 3% of NaCl. Histological examination of the horned turban shells showed that gill necrosis is one of the major symptom of infected individuals. It was believed that sudden increase of those two bacterial agents due to environmental change cause mortality of horned turban shells.

• The Korean Journal of Malacology
• /
• v.15 no.1
• /
• pp.63-69
• /
• 1999

Electrophoretic analysis was carried out to elucidate genetic relationships of four Korean scallops, Patinopecten yessoensis, chlamys ferreri ferreri, Chlamys swifti and Amusium japonicum japonicum, and of a Chinese population of C. ferreri ferreri purchased form a market. Glucose phosphate isomerase banding pattern was highly varied among eight loci. Three populations of C. ferreri ferreri were more closely clustered in a dendrogram within the range of Nei＇s genetic similarity values of 0.730-0.830. P. yessoenensis and Chlamys swifti were clustered with genetic similarity value of 0.647. These two clusters were lineated at the value of 0.598. A. japonicum japonicum was clustered with other three species at value of 0.541.

• The Korean Journal of Malacology
• /
• v.15 no.2
• /
• pp.115-119
• /
• 1999

We investigated the processes of egg and larval developments for aquaculture technique development of seedling production fo the flat oyster, Ostrea denselamellosa. Teo flat oyster of larviparous type was different from the pacific oyser (ovivarous type) because their larvae (trochophore and prodissoconch larvae) in the gill released into the seawater. The process of egg development was observed by artificial fertilization at $25^{\circ}C$, using a dissecting method. The sizes of Unfertilized eggs ranged from 80 to 90 $\mu\textrm{m}$ and fertilized eggs with globule-shape was 90-100 $\mu\textrm{m}$. The Polar body appeared after fertilization and egg cleavage began within 1 hour, reaching the blastula stage after 10 hours. The trochophore in the gill appeared 2-3 days after fertilization and grew to the prodissoconch larvae (130 140 $\mu\textrm{m}$) having a complete shell after 1-2 days. The shell of prodissoconch larvae grew to 205 220 $\mu\textrm{m}$ after 10 hours, and then they became umbo stage larvae showing oval in shape. The velum of umbo stage larvae was degenerated about 17-20 days after fertilization and grew into a pediveliger with a developed foot, at this time, the shell length size was 320 360 $\mu\textrm{m}$.

• The Korean Journal of Malacology
• /
• v.15 no.2
• /
• pp.121-125
• /
• 1999

The present study aimed to elucidate whether and intestinal fluke, Gymnophalloides sp. exist in Gogunsan-gundo located at western part of Korean Peninsula; about 100 km apart from Gunsan city, Jeollabuk-do, Korea. The survey was carried out Two times each in 1997 and 1998, examining stool samples by means of formalin-ether concentration method. Results are summarized as follows : of 411 fecal samples examined, Gymnophalloides sp. positives were 19 (8.9%); 9.5% inMunyeodo, 1% in Seonyudo, but none in Jangjado. The positive cases did not show any specific clinical complaints. Prevalence rate of Gymnophalloides seoi metacercariae from oysters, Crassostrea gigas were 80.8%

• The Korean Journal of Malacology
• /
• v.25 no.2
• /
• pp.93-96
• /
• 2009

Unexpected mass mortality has been one of the drawbacks in front of the stable production of Japanese scallop (Patinopecten yessoensis) on the Gangwon coasts of the East Sea. The preliminary data from our routine observation revealed that the mortality appeared to be related to variation of water temperature in the farming site and the degree of the mortality was dependent on scallop strain. The present study performed to verify the preliminary findings exhibited that the mortality was closely related to daily temperature variation rather than monthly variation. Daily temperature variation was particularly damageable to the scallop during the temperature elevation period. Scallops from hatchery seeds (Chinese strain) were more tolerant against the temperature variation over those from wild seeds. The hatchery scallop gain of the temperature tolerance was probably due to their larval experience to higher temperature in the hatchery as well as their maternal genetic acclimation to upper temperature extreme of the Chinese environment which was recently found.

• The Korean Journal of Malacology
• /
• v.24 no.3
• /
• pp.189-197
• /
• 2008

In order to develop the sustainable ecological management, short-necked clams, Ruditapes philippinarum, were collected from Yoengi coast in Tongyoeng, Korea. The growth of the clam was estimated as: $L_f=68.08{\cdot}(1-e^{-0.145(t+0.324)})$ from ring radius composition of shell. Instantaneous co-efficiency of total mortality and natural mortality were calculated as: 0.991/year and 0.494/year, respectively. The age of the clams from the first capture was estimated to be 3.28. The total biomass was estimated to be 212 MT in the fisheries area (6.4 ha). Applied by these parameters, the annual recruit biomass and the current yield per recruit were calculated to be 649.5 individual/$m^2$ and $0.7\;g/m^2$, respectively. The current fishing intensity was much lower for maximum sustainable yield and acceptable biological catch. Although higher yield per recruit could be achieved by increasing fishing intensity, it is favorable to retain the current fishing intensity because of the unique fishing attitude on Yeongi coast in Tongyoeng, Korea.

• The Korean Journal of Malacology
• /
• v.24 no.3
• /
• pp.199-203
• /
• 2008

Thirty one marine molluscan species were added to the malacofauna of Dokdo Island, Korea based on the samples collected from April 2006 to August 2008 with SCUBA diving. As a result, one hundred six marine molluscan species were recorded from Dokdo Island hitherto.

• The Korean Journal of Malacology
• /
• v.24 no.2
• /
• pp.97-104
• /
• 2008

The gonad index, reproductive cycle and first sexual maturity of Sinonovacula constricta collected from Simpo, Kimje-gun, Korea were investigated by histological analysis. The gonad index(GI) in both sexes of S. constricta increased from April and reached a maximum in July when the water temperature rapidly increased. And then, the GI values gradually decreased by spawning from August through October. Monthly variations in the GI showed a close relationship with ovarian development. The reproductive cycle in females and males can be classified into five successive stages: early active stage(March to June), late active stage(May to July), ripe stage(July to September), partially spawned stage(August to October), spent/inactive stage(October to March). The percentage of first sexual maturations in female and male clams of 50.1-60.0 mm in shell length was over 50%, and for clams over 70.1 mm in shell length, it was 100%. Because harvesting clams < 50.1 mm in shell length could potentially cause a drastic reduction in recruitment, a measure including a prohibitory fishing size should be taken for adequate improved fisheries resource management.

• The Korean Journal of Malacology
• /
• v.1 no.1
• /
• pp.13-18
• /
• 1985

The metamorphosis and the growth of larva in Limnoperna fortunei were studied from October, 1981 to December, 1983. 1) The larva of this species is observed in the three different stages in the form of D-shaped. The shell length of the larva in the early stage is $130.44{\mu}m$ to $143.60{\mu}m$ and in the middle stage $161.67{\mu}m$ to $184.11{\mu}m$. In the late stage the length size of the larva increases up to $194.55{\mu}m$ to $208.45{\mu}m$. The shell height is $103.19{\mu}m$, to $119.47{\mu}m$, $126.51{\mu}m$ to $157.63{\mu}m$ and $136.87{\mu}m$ to $176.35{\mu}m$ in the three stages respectively. Thus the growth ratio of shell length to shell height is 1:0.75. 2) The metamorphosing stage begins when the shell height becomes larger than $210{\mu}m$ and the shell length exceedes $260{\mu}m$.

• The Korean Journal of Malacology
• /
• v.9 no.2
• /
• pp.23-29
• /
• 1993

전복, Nordotis discus의 1$0^{\circ}C$와 2$0^{\circ}C$의 수온구에서 개체크기별 대사와 폐사에 미치는 부니의 영향에 대한 결과는 다음과 같다.1. 수온 -염분별 산소소비율의 일반적 경향은 고온-고염분에서 큰개체보다는 작은개체에서 그 비율리 높게 나타났다.2. 염분별 두 수온간의 온도계수 (Q $_{10)}$ 는 작은 개체에서 1.2-2.9의 병위를 큰개체의 경우 1.5-3.4의 범위를 나타내었으나 개체크기에 관계없이 유사한 양상을 보였다.3. 부니의 농도별 사망율은 작은 개체의 경우 처리 96시간후 2$0^{\circ}C$수온에서 부니 농도1000ppm에서 가장 높았고. 큰 개체의 경우 50ppm에서 가장 낮았다.4. 96시간-반치사농도(LC$_{50}$)는 1$0^{\circ}C$의 경우, 큰개체에서 1076.58 ppm, 작은 개체에서 812.55 ppm이었으며, 2$0^{\circ}C$의 경우는 큰개체에서 698.28 ppm, 작은 개체에서 546.74ppm으로 나타났다.5. 부니의 영향으로 인한 호흡산소소비량은 개체크기에 관계없이 1$0^{\circ}C$에서 보다 2$0^{\circ}C$에서 더욱 높았으며, 1000ppm에서 70% 이상의 감소율을 나타내었다.