• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.597-599
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• 2000

This study was performed to find out the cryoprotectants for cryopreservation of trochophores and early D-shaped larvae of surf clam, Spisula sachalinensis. Dimethyl sulfoxide (DMSO), ethylene glycol, 1,2-propanediol and methanol were used as cryoprotectant Each cryoprotectant was made to 1.0 M, 2.0 M, 3.0 M with dilution of 0.2 M fructose and 0.2 M sucrose. The trochophoers and early D-shaped larvae were immersed in each preparation for 10 minutes to reach equilibration and cryopreserved in liquid nitrogen. Survival rates of post-thawed trochophores and early D-shaped larvae in 2.0 M DMSO with 0.2 M sucrose were the highest as $91.4{\%}\;and\;78.9{\%}$, respectively.

• Journal of Aquaculture
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• v.17 no.2
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• pp.97-102
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• 2004

We examined the effects of stimulants including sunlight and UV-irradiation on the spawning induction and early development of the noble scallop, Chlamys nobilis. The sunlight stimulation resulted in nuch faster spawning induction (100% success within 40 minutes) compared to UV-irradiation (100% success within 70 minutes). Early development of the scallop larva took place between 15$^{\circ}C$ to 3$0^{\circ}C$. The time to reach the early D-shaped stage was 63.5, 31.5, 18.5 and 17.0 hours at 15, 20, 25 and 3$0^{\circ}C$, respectively. The correlations between the water temperature-(WT) regimes and the time (t) required for each developmental stage are as follows. 2 cell stage: 1/t=0.0606WT-0.6194 ($r^2$=0.9791) 8 cell stage: 1/t=0.0304WT-0.3453 ($r^2$=0.9941) Morula: 1/t=0.0100WT-0.1049 ($r^2$=0.9663) Trochophore: 1/t=0.0058WT-0.0618 ($r^2$=0.9848) D-shaped larva: 1/t=0.0030WT-0.0282 ($r^2$=0.9731) These correlations indicated that the biological minimum temperature of the species is around 10.44$^{\circ}C$. The highest survival rate up to D-shaped larva at different water temperature was observed at $25^{\circ}C$.

• The Korean Journal of Malacology
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• v.1 no.1
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• pp.13-18
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• 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 $260{\mu}m$.

• Development and Reproduction
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• v.5 no.1
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• pp.35-38
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• 2001

This study was peformed to find out the optimum larval stage among trochophore, early Dshaped larva, late D-shaped larva, early umbo and late umbo stages for cryopreservation of surf clam, Spisula sachalinensis larvae. Dimethyl sulfoxide (DMSO)and ethylene glycol were used as cryoprotectant, The larvae were immersed to cryoprotectants for 10 minutes and thereafter, cryopreserved in liquid nitrogen. Survival rates of trochophores frozen-thawed in 2.0 M dimethyl sulfoxide and 2.0 M ethylene glycol were the highest as 97.4% and 85.0%, respectively and post-thaw survival rates were decreased with the larval growth.

• The Korean Journal of Malacology
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• v.1 no.1
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• pp.5-12
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• 1985

The maturity of gonads, early development of the fertilized egg, spawning period, and morphogenesis of larvae in Limnoperua fortunei were studied from October, 1981 to November, 1982 as on attempt to identify its life cycle. 1) Active motility of its sperm was observed at late May, and matured egg could be found at late June. 2) It was estimated that the spawning was occured from late August. This species was belong to the short-term breeder because it finished its spawning within 20 days. 3) It has free-living trochophore and D-shaped larva stage. The shell lengths of early, middle, and D-larval stage were $140.0{\mu}m$, $167.6{\mu}m$ and $210.0{\mu}m$, respectively. The shell heigths of each stage were $97.3{\mu}m$, $137.6{\mu}m$ and $178.2{\mu}m$, respectively.

• The Korean Journal of Malacology
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• v.18 no.2
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• pp.77-82
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• 2002

This study was performed to find out the optimal kind of additive and concentration of ethylene glycol (EG) as the cryoprotectant on the D-shaped larvae of arkshell, Scapharca broughtonii. The larvae in straws was carried in the programed freezer set uo at 0$^{\circ}C$, frozen to -12$^{\circ}C$ by the freezing rate of -1$^{\circ}C$/min, held for 10 minutes, seeded at -12$^{\circ}C$, finally refrozen to -35$^{\circ}C$ by the freezing rate of -1$^{\circ}C$/min and then directly plunged into liquid nitrogen. The survival of larvae frozen in 1.0 M and 2.0 M ethylene glycol added with 0.5 M sucrose were high (50.5 ${\pm}$ 1.3% and 51.9 ${\pm}$ 1.7%, respectively) in the early D-shaped larvae cryopreserved in 1 M and 2 M ethylene glycol diluted with 0.2 M and 0.5 M fructose, glucose and sucrose. In the late D-shaped larvae were cryopreserved according to five concentrations of ethylene glycol added with 0.5 M sucrose, the survival of larvae frozen in 2.0 M ethylene glycol was the highest as 51.9 ${\pm}$ 1.7%. The morphological differences in cells between unfrozen and frozen-thawed D-shaped larvae were not found by the scanning and transmission electron microscopy.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.6
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• pp.485-491
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• 2004

Spawning induction, egg development and larval growth of ark shell (Tegillarca granosa) (L.) were investigated. The most effective method of spawning induction was steady temperature increasing from$4^{\circ}C\;to\;28^{\circ}C$ with irradiation of sea water by UV after T. granosa was exposed to air at $4^{\circ}C$ Optimum condition for larval roaring was under the 32.4 psu and two temperature $regimes:\;28{\pm}1^{\circ}C\;and \;25{\pm}1^{\circ}C$. Fertilized eggs was demersal isolated eggs, and egg diameter was $60{\mu}$. D-shaped larvae appear about 20 hr after hatching with $94.1{\mu}$ in shell length and $86.7{\mu}$ in shell height. Ten days were required from hatching to umbo larva stage, of a mean shell length $125.2{\mu}$. On 25th day, the larva grew to $450{\mu}$ in shell length and began to settle on the bottom. Effect of temperature between $25^{\circ}C$ (control group) and $28^{\circ}C$ on larval growth was not different. Survival rate of larvae settled on the bottom was about $19{\%}$ in both temperatures conditions $(25^{\circ}C\;and\;28^{\circ}C)$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.1
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• pp.62-67
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• 1999

Infection rates of oyster ovarian parasite, Marteiliodes chungmuensis and productivity of the oyster shellstock infected with the parasite were investigated at the main seed collection areas in the southern coast of Korea where the extreme bad seed collection of oyster occurred in 1992 and 1993 to evaluate the cause of the bad seed collection. Additionally, the bacterial flora of the sea water and oyster lana were examined to identify the shellfish larva pathogenic bacteria like Vibrio sp. and Pseueomonas sp. In August 1992 to September 1993, infection rate of oyster ovarian parasite, M. chungmuensis at Tongyong, Kyongsangnam province, and Yosu, Chollanam province where the bad seed collection occurred, were $11.8\~100\%$ and $14.3\~100\%$, respectively. But the parasite was not detected in the shellstock collected at Daechon, Chungchongnam province. While a virus-like particle was identified in the cytoplasm of the egg infected by the parasite. The parasite infected egg was not able to fertilize completely. Uninfected egg in the gonad contaminated by the parasite could be able to fertilize but showed an abnormal development till D-shaped larva and then, died of necrosis after D-shaped lana. And some lana developed from low lipid content egg could not develop to the spat and died after the early umbo stage. The predominant bacteria in the oyster lana collected at bad seed collection areas were Pseudomonas sp. and Pseudomonas like bacteria and the occupancy rates were $53.3\~87.1\%$.

• The Korean Journal of Malacology
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• v.30 no.4
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• pp.311-319
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• 2014

Early sexual maturation through temperature stimulation was induced in female and male of yezo scallop. Gonadosomatic index (GSI) in female showed $9.12{\pm}2.9$ in January, $14.89{\pm}2.9$ in February and $21.3{\pm}1.4$ in March in experiment I. GSI in experiment I showed a significant increase (P < 0.05) and in experiments II and III were not show significant variations (P > 0.05). It also showed significant between the control and the experiments I, II, and III in February (P < 0.05) measurements. Experiment I has showed good results in sexual maturation and spawning when compared with other experiments II and III and the control. Histological observation showed that ovary condition was in a growing stage in all the experiments I, II, and III. In February, ovary condition through histological observation was a late mature stage in all the experiments I, II, and III except the control of a growing stage. GSI and gonad weight were $4.4{\pm}0.88$ and 2.8 g, respectively in November whereas it was $15.1{\pm}2.8$, and 11.7 g, respectively in January and $21.7{\pm}5.4$, and 19.4 g, respectively in February after rearing at a water bath of $12^{\circ}C$ depending on the condition of experiment I. It was possible early releasing of eggs and sperms of yezo scallop in February instead of the middle of April to the end of May being spawning period. Fertilized eggs have become a gastrula stage through a spiral cleavage and then become a trochophore larvae after 36 hours. After 10 days, D-shaped larvae have changed into an umbo stage larvae and attached to juveniles in the post larvae after 20-23 days.

• The Korean Journal of Malacology
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• v.29 no.4
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• pp.263-272
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• 2013

The development of swift's scallop Chlamys swiftii, reared in the laboratory, has been examined through the investigation of morphological characteristics in fertilized egg, larvae and juvenile. Eggs were fertilized with a dilute sperm solution to improve the survival of fertilized eggs. Developing larvae were maintained at a temperature of $16{\pm}0.5^{\circ}C$ and salinity concentration of 33 ppt. We have investigated the fertilization rates and egg number spawned at several stimulating conditions such as sunlight exposure, air dry, seawater temperature rise ($5^{\circ}C$) and seawater temperature rise ($5^{\circ}C$) after exposure of air dry for spawning induction of swift's scallop Chamys swiftii. Stimulation treated with sunlight exposure and seawater temperature rise ($5^{\circ}C$) have shown the spawning number of 700,000-900,000 and 700,000-800,000 per individual, respectively while stimulation treated with seawater temperature rise ($5^{\circ}C$) after exposure of air dry have shown the high spawning number of 1,000,000-1,500,000 per individual. Survival rate of D-shaped larvae of swift's scallop put into the different seawater temperatures of $8^{\circ}C$, $12^{\circ}C$, $16^{\circ}C$, $20^{\circ}C$ and $24^{\circ}C$ has been 4.1%, 11.6%, 32.7%, 18.6% and 3.2%, respectively. Fertilized eggs with the diameter of $72{\mu}m$ developed into trochophore larvae of $103{\pm}3.8{\mu}m$ shortly after 35 hours and to D larvae of $129{\pm}10.4{\mu}m$ shell length within 72 hours. It took 336 hours to become initial Umbo-stage larva of $145{\pm}16.8{\mu}m$ shell length. Post larvae, which have been $197{\pm}13.6{\mu}m$ shell length, spontaneously have settled in the attachment substances. It have required 528 hours from fertilized eggs to early attached juvenile to become initial juvenile size of $245{\pm}15.8{\mu}m$ shell length.