• Journal of Animal Reproduction and Biotechnology
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• v.35 no.3
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• pp.223-231
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• 2020

Karyotype analysis is a major work in the process of triploid abalone production for the purpose of productivity and quality improvement. However, the metaphase spreads for karyotype analysis have been prepared just from the larvae at trochophore stage, which has restricted the spectrum of sample correction inhibiting more efficient analysis. Here, we investigated the feasibility of preparing metaphase spreads from the larvae at veliger stage that is the next developmental stage of trochophore. For this, diploid and triploid larvae at trochophore and veliger stages from Pacific abalone (Haliotis discus hannai) were subjected to metaphase spread preparation and its efficiencies were measured and compared each other. As the results, although the efficiencies of metaphase spread preparation were significantly lower in the larvae at veliger stage compared to the ones at trochophore stage regardless of ploidy status, we found that the preparation of metaphase spreads, which showed the clear chromosomal images containing the normal number of chromosomes, was possible from the veliger stage larvae. On the other hands, all larvae used in this study regardless of developmental stage and ploidy did not show colchicine sensitivity. Moreover, no significant difference was observed in cell cycle distribution of the cells comprising larvae between two developmental stages regardless of ploidy status. These suggested that the details of protocol to prepare metaphase spreads from abalone larvae should be optimized depending on its developmental stages. Taken together, we demonstrated the feasibility of preparing metaphase spreads from H. discus hannai veliger stage larvae for karyotype analysis.

• Development and Reproduction
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• v.17 no.4
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• pp.337-343
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• 2013

Post-thawed larval rearing in Pacific oyster Crassostrea gigas was performed to investigate the survival rate with time course in three kinds of larvae cryopreserved. The highest survival rate and larval activity index (LAI) of post-thawed larvae were obtained from the permeation in 0.2 M sucrose and 2.0 M ethylene glycol (EG) at $-1^{\circ}C/min$ in freezing speed showing the survival rates just after thawing of 63.8% in trochophore, 84.1% in D-shaped veliger and 56.3% in early umbo veliger. In post-thawed larval rearing with food supply, the larvae lasted their lives until 24 hours in trochophore, 75 hours in D-shaped veliger and 57 hours in early umbo veliger. The results suggested that each larval stage post-thawed revealed no more further development to subsequent respective stage.

• Ocean and Polar Research
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• v.37 no.1
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• pp.37-47
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• 2015

The effects of low salinity (fertilization success and larval survival) on the limpet Cellana grata were studied at early stages of development using the marine bioassay technique. It was shown that, under normal conditions for development from fertilization to the post veliger stage, the salinity must be not less than 20.0~35.0 psu. However, the fertilization rate and larval survival of C. grata was obviously reduced at 5.0 psu and 10.0 psu, respectively. Mass mortality was estimated to occur at <20.0 psu (48-h $EC_{50}=19.54psu$) and the survival rate of normal veliger larvae decreased with experimental time during exposure. No observed effective concentration (NOEC) and lowest observed effect concentration (LOEC) of post veliger were estimated at 30.0 psu and 25.0 psu, respectively, during 48-h exposure. The tolerance limits of the test species to salinity revealed various concentration ranges of salinity, which may reflect the physiology and ecology of the initial development stages of C. grata. These results demonstrate that reduced salinity is detrimental to the reproductive success and larval survival of C. grata, and if salinity is lowered by natural or anthropogenic sources during spawning, this would lead to decreased reproductive success and larval settlement.

• The Korean Journal of Malacology
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• v.32 no.1
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• pp.37-43
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• 2016

This study was carried out to determine the optimal water temperature for the embryonic development and laboratory culture of larvae of an intertidal mud snail, Nassarius festivus. The embryos and hatched veliger larvae of N. festivus were incubated at six different temperatures (5, 10, 15, 20, 25 and $30^{\circ}C$). Developmental time for each stage decreased as water temperature increased. The elapsed time to develop to the veliger larva at 15, 20, 25 and $30^{\circ}C$ was 559, 155, 131 and 103 hrs, respectively. At 5 and $10^{\circ}C$, embryo developed to veliger larvae but failed to hatch out of the egg capsule. In contrast, all embryos successfully hatched in the temperature range from 15 to $30^{\circ}C$. The biological minimum temperature during the embryonic development of N. festivus was estimated to be $9.5{\pm}0.4^{\circ}C$. The cumulative water temperatures for blastula, gastrula and veliger stages were calculated as $111{\pm}84$, $486{\pm}185$, $1,164{\pm}72^{\circ}C$, respectively. Temperature also affected the larval survival. Five days after hatching, more than 84% of larvae survived at all experimental temperatures. However, survival began to decrease after 6 days. It was 0% at $30^{\circ}C$. Survival of larvae incubated for 8 days was higher at 15 and $20^{\circ}C$ than other experimental temperatures. We therefore suggest that the optimal range of temperature for embryonic development and larval survival of N. festivus is $15-20^{\circ}C$.

• Environmental Engineering Research
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• v.22 no.1
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• pp.108-115
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• 2017

Chlorination has been the most common antifouling method, but alternatives are under searching. In this article, we report how the hydrogen peroxide could enhance the effect of chlorination to prevent fouling by inhibiting larvae settlement and abatement of mussel colonization or by extinct of them; through marine mussel Mytilus edulis. The addition of hydrogen peroxide shows synergic effect on the veliger larvae (up to 19 folds) and effectively reduces required time of mussel mortality by 8-22%. For resolution of micro- and macro-fouling caused by the marine mussel, as well as diminishing of time and conventional chlorine dose could be important factor in favour of environment and economics.

• Development and Reproduction
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• v.18 no.1
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• pp.25-31
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• 2014

This study was investigated spawning behavior, structure of egg masses and egg development in Aplysia kurodai inhabiting the coastal waters of Jeju Island, Korea. The mating and courtship behavior of A. kurodai occurred in the form of unilateral copulating with chain formation. In chain copulation, only the first animal acted as a female; the second and succeeding animals acted as males (sperm donors) to the animals in front and as females to the animals behind. The fertilized eggs were packaged in capsules that are embedded in jelly to form a cylindrical string called an egg masses. The number of capsule per cm of the egg masses was 55 to 60 capsules and each capsule within the egg masses held 15 to 25 eggs. After spawning, the egg masses were bright yellow or orange in color. This egg masses color not changed until embryos developed into trochophore stage. Thereafter, as embryo developed from trochophore stage to veliger stage the egg masses color became brownish. The fertilized eggs were spherical, with a diameter of approximately $80{\pm}1{\mu}m$ at spawning. At 5 to 6 days after spawning, the embryo developed into trochophore stage and began to rotate within the egg capsule. In the trochophore stage, the precursor of the velum, called the prototroch or prevelum, developed. At 10 days after spawning, the prevelum is transformed into the velum, and the trochophore developed into veliger stage. Between 10 to 15 days after spawning, the veligers broke out of the egg capsule, and hatched as free-swimming larvae.

• Development and Reproduction
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• v.15 no.4
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• pp.301-308
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• 2011

The tolerance evaluation for abalone Haliotis discus hannai embryos was performed using different concentrations of cryoprotective agents (CPAs): dimethyl sulfoxide, ethylene glycol and propylene glycol added to 0.2 M sucrose, respectively. 4-cell, trochophore and veliger were exposed in each CPA with different concentration for 10, 20 and 30 minutes of immersion time. Developmental rates were increased with decreased concentration of every CPA and decreased immersion time, and differed from types of CPA. Developmental rates of veliger in all the CPAs were higher than those of 4-cell and trochophore. The developmental rates and larval activity indices in ethylene glycol were comparatively higher than those in other CPAs and the effective CPA and its concentration for the cryopreservation of the abalone embryos was suggested as 2.0 M ethylene glycol with equilibration time of 30 minutes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.2
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• pp.131-136
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• 2001

Relative growth and composition of larval development stages in brood pouch of the melania snail, Semisulcospira libertina libertina were investigated based on monthly field samples for a year. Total number of specimens examined was 1,200. Size values (mean$\pm$S. D.) of shell height (SH), shell diameter (SD), total weight (TW), meat weight (MW) and shell weight (SW) were $15.96\pm3.41\;mm$, $7.82\pm1.38\;mm$, $0.55\pm0.31\;g$, $0.24\pm0.15\;g$ and $0.39\pm0.23\;g$, respectively, Water temperature (WT) of the sampling site varied from $1.3^{\circ}C\;to\;22.5^{\circ}C$. Relative growth equations among SH, SD, TW, MW and SW of S. libertina libertina specimens pooled were as follows: SD=0,3583SH+2.1648 $(R^2=0.8391)$, $TW=0.0005SH^{2.4853}\;(R^2=0.8391)$,$MW:\;0.0005SH^{2.849}\;(R^2= 0.8391)$ and $SW=0.0004SH^{2.3798}\;(R^2=0.7057)$. Female S. libertina libertina had larvae in its brood pouch throughout the year, Average number of larvae in the brood pouch varied from $91\pm33(July)$ to $396\pm174\;(November)$, decreasing in spring and increasing in autumn. In the monthly composition of larval stage in the brood pouch, trochophore, pre-veliger, veliger and juvenile showed maximum as $66.7\%$ in May, $70.7\%$ in November, $60.9\%$ in February and $13.9\%$ in January, respectively. Percent composition of the juveniles decreased in spring and autumn. In conclusion, S. libertina libertina is likely to have two main parturition periods, March to May and September and October.

• The Korean Journal of Malacology
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• v.2 no.1
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• pp.26-29
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• 1986

Corbicula fluminea, one of the 2 species in the family Corbiculidae living in the Lake Uiam, was used as an experimental material and the embryonic development and the structure of glochidia of this species were investigated. This freshwater mussels was oviparous, but some ovoviviparous: incubated their youngs in the inner-demibranchs or outer-demibranchs, however, chiefly used the inner-demibranchs as brood-pouch. The average time required from a fertilized egg to two-cell stage, veliger stage, and glochidium was 76 minutes, 3 hours, and 17 hours, respectively, The mean size of glochidium was $168{\mu}m$ in shell height, $195{\mu}m$ in shell lengh, $114{\mu}m$ in hinge legth and the form of glochidium was D-type and had no hooks or hooklets for attaching to fish like Unioidae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.7 no.1
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• pp.1-6
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• 1974

Meretrix lusoria is one of the most favorite edible bivalves inhabiting wide inter-tidal flats along the western coast of Korea. Over the period of July to September 1973, some specimens from a tidal flat near AnMyun Island were submerged in sea water with various concentrations of ammo-mum hydroxide added and careful observations were made on their fertilization, early development, and metamorphosis of the larvae. The highest rate of fertilization was demonstrated by individuals treated with 1/1000 normal solution of ammonium hydroxide, and their fertilized eggs followed normal development, i. e., two cell stage in 1.2 hours after fertilization, gastrula stage after 4.7 hours, and trochophore stage after 5.6 hours. Within 24 hours after fertilization M. lusoria larvae have acquired the form of early straight-hinge veliger with the mean prodissoconch I length of $112\mu$. It takes seven days to get the umbo stage with the mean shell length of $172\mu$ and twenty days to get the metamorphosing stage with the mean shell length of $232\mu$. The larvae were cultured to the metamorphosing stage with the shell length of $272\mu$ in the laboratory condition. The relationship between the shell length (L) and the shell height (H) in veliger stage is shown as H=1.02325L-24.46425 with a significant difference.