• Current Research on Agriculture and Life Sciences
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• v.16
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• pp.31-36
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• 1998

In order to investigate the effect of cytokinins on the cotyledonary variability of somatic embryos in Heracleum moellendorffii Hance., somatic embryos were induced from the immature zygotic embryo on MS medium containing 1.0mg/l 2, 4-D, and then transferred to 2,4-D-free and cytokinin-added medium for somatic embryogenesis after 4weeks culture. Polycotyledonary embryos were formed most abundantly(84.9%) on the 0.2mg/l BA medium as compared with the 0.2mg/l 2ip(42.6%) and kinetin(32.9%) media, and it was proportional to BA concentrations(0.01~0.1mg/l). The rate of polycotyledonary embryo formation increased proportional to the period of BA treatment and also increased more at the globular stage than at the heart, torpedo-shaped and cotyledonary stages.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.559-564
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• 2000

We studied to find out the effect of water temperature on the egg development of pearl oyster, Pincata fucata martensii and Pacific oyster, Crassostrea gigas. The optimum water temperatures for egg development were $20{\~}25^{\circ}C$ in P. fucata martensii and $15{\~}25^{\circ}C$ in C. gigas. The required time from fertilization to D-shaped lana was $41.7\;hours\;at\;20^{\circ}C$ and 27.5 hours at $25^{\circ}C$ in P. fucata martensii, and 35.3 hours at $15^{\circ}C$, 26.3 hours at $20^{\circ}C$ and 17.6 hours at$ 25^{\circ}C$ in C. gigas, respectively. The relationships between the water temperature ($WT:^{\circ}C$) and the required time (h: hour) from fertilization to each developmental stage were given as follows; P. fucata martensii Up to 8-cell $$1/h=0.0463WT-0.6945 (r^2=0.9702)$$ Up to morula $$1/h=0.0196WT-0.2184 (r^2=0.8118)$$ Up to trochophore $$1/h=0.0076WT-0.0802 (r^2=0.8756)$$ Up to D-shaped larva $$1/h=0.0031WT-0.0380 (r^2=0.9075)$$ C. gigas Up to 8-cell $$1/h=0.0210WT-0.1123 (r^2=0.9862)$$ Up to morula $$1/h=0.0143WT-0.1077 (r^2=0.9833)$$ Up to trochophore $$1/h=0.0052WT-0.0218 (r^2=0.9857)$$ Up to D-shaped lawn $$1/h=0.0029WT-0.0170 (r^2=0.9689)$$ Biological minimum temperature for egg development of P. fucata martensii and C. gigas was calculated as $$12.3^{\circ}C and 5.7{\circ}C$$, respectively.

• 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.27 no.4
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• pp.359-369
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• 2011

Twelve species of food microalgae were investigated to clarify the digestion index of Crassostrea gigas larvae using epifluorescence microscopy to choose an appropriate diet for artificial seed production in hatchery. An experiment was conducted using 1 (D shaped stage), 4 (Early umbo stage), 8 (umbo stage) and 12 (Full grown stage) days old larvae. larvae were stocked in 1 L flasks at 5 individuals/mL and fed $10{\times}10^4$ algal cells/mL of each species individually. Prior to larvae were fed for 3 h and then were observed under the microscope to detect ingestion; larvae were then sieved and replaced in 1 L flasks containing filtered seawater and were observed after 3, 5 and 8 h to analyse the digestion index. Values of digestion indices were specific for each alga. No evidence for the ingestion of Thalassiosira weissflogii was evident at all larval development stages tested. Digestion indices of others microalgae were 0.8-99.7% at 4 stage of larval development stages: Chlorella ellipsoidea (0.8-5.4%), Nannochloris oculata (1.4-5.0%), Isochrysis galbana (99.1-99.5%), Pavlova lutheri (99.1-99.5%), I. aff. galbana (99.4-99.5%), Cheatoceros calcitrans (0.0-99.2%), C. gracilis (0.0-99.7%), C. simplex (0.0-95.9%), Phaeodactylum tricornutum (0.0-99.6%), Tetraselmis tetrathele (0.0-99.7%) and Dunaliella tertiolecta (0.0-99.6%), respectively. Therefore, it is assumed that food microalgae showing the high digestion such as I. galbana should be supplied to the early umbo stage larvae, and then after the umbo larval stage, the mixed microalgae with diatoms and light green algae should be supplied to the full grown stage larvae to increase the digestion of their larvae.

• Journal of Plant Biotechnology
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• v.38 no.4
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• pp.258-262
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• 2011

Embryogenic callus was induced from the cultures of immature embryos of Camellia japonica L. on Murashige & Skoog's (MS) solid medium supplemented with 1 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D), and then the embryogenic callus was proliferated on same medium for 4 weeks over. The embryogenic callus was sub-cultured on MS basal medium without 2,4-D to produce coyledonary stage of somatic embryo. The frequency (%) of somatic embryogenesis was 25.1%, and the majority of somatic embryos formed had a abnormal morphology with cupshaped cotyledon (48.3%), one cotyledon (12.6%), three cotyledons (9.4%), four cotyledons (1.9%), whereas was only normal morphology with two cotyledon (27.5%). When the somatic embryos with normal or abnormal cotyledons transfer to MS basal medium or $\frac{1}{2}$ MS medium with/or without plant growth regulators ($GA_3$, IBA) for regeneration, the frequency (%) of two-cotyledon embryos regenerated into plantlets was higher 11.1% than one cotyledon (0.0~8.3 %), three cotyledons (0.0~5.8%), four cotyledons (0.0%), cup-shaped (0.3~4.2%). These results demonstrated that the anomalous cotyledons of somatic embryos could caused to decrease the rate of plant regeneration.

• Journal of Aquaculture
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• v.18 no.1
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• pp.1-6
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• 2005

This study focused on spawning season, induce spawning, spawning and larval development of the Jicon scallop in Daehuksan Island of southwestern waters in Korea. The condition index and gonadosomatic index were used to investigate the reproductive pattern of the Jicon scallop. The major spawning season was from July to August, showing an unimodal gametogenic cycle per year. Several different tests were carried out to induce spawning of the mature male and female C. farreri. For females, the injection of serotonin, temperature induction technique and the combination of the both treatments produced significantly faster gamete release. Unlike females, males spawned only in response to the UV rays irradiation stimulation. Mean size of fertilized eggs was 69.5 $\mu$m in diameter. After fertilization, the zygote could be divided into 2 cells as early as 2 hours. It took about 8 hours to develop the 8-cell stage, about 20 hours to hatch trochophore larvae, and about 40 hours to be D-shaped larvae.

• Journal of Aquaculture
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• v.15 no.1
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• pp.23-29
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• 2002

To develop techniques for the production of artificial seedling of Corbicula japonica, protocols for induction of spawning and larval development were developed. During the assumed spawning period of August to mid-September, attempts were first made to induce spawning by gonadal incision and UV-irradiation but all in vain. At the end of August, elevated thermal induction evoked 90 % positive response in animals maintained at $3\textperthousand$ salinity. Immersion in (1/1000~3/1000 N) ammonium hydroxide ($NH_4$OH) also induced spawning in 15~45%) of the treated animals at $3\textperthousand$ salinity. Fertilized eggs measured 86$\mum. At 23.0~24.5$^{\circ}C$, the fertilized egos developed into 4-cell stage embryos within 2 hours, trochophores 15 hours, D-shaped larvae 2 days, umbo 9 days and fully grown veligers, ready to infiltrate into the sediment, within 16 days.

• Korean Journal of Ichthyology
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• v.24 no.2
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• pp.101-109
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• 2012

The egg development and early life history of Acheilognathus macropterus from Japan which is an exotic bitterling from China were observed under the controlled water temperature, $20.0{\pm}1.0^{\circ}C$. Fertilized eggs are opaque yellow in color and long elliptic globe shaped measuring $2.78{\pm}0.12mm$ in length and $1.44{\pm}0.04mm$ in breadth. The number of egg averaged 151 per an oviposition. The eggs of this species began to hatch about seventy eight hours after insemination and the mean of total length of larvae were 3.8 mm. S form moving of larvae were observed from three days after hatching. The larvae reached at the heterotrophic stage about twenty-five days after hatching. Morphological character and analysis of cytochrome DNA of this species from Japan were relatively similar to Korean but spawned egg shape was different remarkably. Taxonomical research is necessary in the future.

• 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 $(25^{\circ}C\;and\;28^{\circ}C)$.

• Applied Microscopy
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• v.40 no.2
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• pp.81-88
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• 2010

The fine structural characteristics of the apoptotic cells in the cutaneous epithelium of the anuran tadpole of the black-spotted frog, Rana nigromaculata was examined using the TUNEL (Terminal deoxynucleotidyl transferase-mediated biotinylated d-Uridine triphosphate Nick End Labeling) staining technique and TEM (transmission electron microscopy) observations. The cutaneous epithelium of the tadpole was composed of stratified cuboidal cells and the apoptotic cell death was observed continuously during the tail degeneration stages from the Shumway stage number 31 to 33. The early apoptotic cells shown in the epithelium demonstrated condensation and margination of the chromatin material at the nuclear periphery, and nuclear breakdown and cytoplasmic condensation were followed. Subsequent cytoplasmic degeneration of the apoptotic cell were produced by membrane-bounded cell fragments with relatively well preserved organelles. Following the processes of autophagic degradation, the late apoptotic cells being phagocytosed by other surrounding cells. These nearby cells, presumptive intraepithelial macrophages, contain a variety of lysosomal residual bodies which fuses with other cell organelles or other cytoplasmatic material to form secondary lysosomes. They are soon transformed into lamellar shaped vesicles and finally disappeared during the process of degradation.