• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.1-8
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• 1996

The effects of temperature and salinity on hatching rate of fertilized egg were examined to develop the method for the efficient seed production in fleshy shrimp, Penaeus chinensis. At the temperature ranging from $20^{\circ}C\;to\;24^{\circ}C$, the hatching rate increased with temperature and the highest hatching rate $(95.5\%)$ occurred at $24^{\circ}C$. But, with the temperature above $26^{\circ}C$, the hatching rate decreased suddenly, and at $30^{\circ}C$, the egg did not hatch at all. The hatching rate increased with salinity within the range of $20\%_{\circ}\;to\;31\%_{\circ}$ and the highest hatching rate $(95.5\%)$ occurred at $31\%_{\circ}$. However, with the salinity above $31\%_{\circ}$, the rate decreased abruptly, and it was only $25.5\%\;at\;40\%_{\circ}$. The hatching speed of egg was the fastest at $24^{\circ}C$. The hatching rate at $24^{\circ}C$ with the salinity of $31\%_{\circ}\;was\;30.5\%$ within 18hrs of the hatching experiment and it attained to $95.5\%$ within 48hrs of the hatching experiment. At $24^{\circ}C$, the hatching rate with the salinity of $30\~31\%_{\circ}$ is 1,2 times higher than that of egg with the salinity of $33\~35\%_{\circ}$.

• The Korean Journal of Malacology
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• v.19 no.2
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• pp.117-124
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• 2003

Reproductive cycle and sex ratio of the marsh clam Corbicula japonica, a oviparous clam, were investigated monthly by histological observation. Samples were collected in brackish water of Namdae stream on the east coast of Korea from November 2000 to October 2001. It was able to devide the reproductive cycle of this species into five successive stages; early active (April to June), late active (May to June), ripe (June to August), partially spawned (June to September), spent (September to January) and resting stage (February to April). The spawning period was from July to September, and the main spawning occurred between August and September when seawater temperatures reached above 26$^{\circ}C$. Mature eggs of Corbicula japonica were 60-70 ${\mu}m$ in diameter. The sex ratio of individuals over 10.1 mm in shell length was about 1:1 (x$^2$ = 1.22, p > 0.05).

• Development and Reproduction
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• v.13 no.4
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• pp.341-351
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• 2009

The effects of serotonin (5-hydroxytryptamine, 5-HT), ecdysone (20-hydroxyecdysone, 20-E) and HCG (human chorionic gonadotropin) on the ovarian maturation of the fleshy shrimp, Fenneropenaeus chinensis were investigated. Adult female fleshy shrimps were injected with 5-HT ($5{\mu}g$/g body weight (BW) or $20{\mu}g$/g BW), 20-E ($5{\mu}g$/g BW, $10{\mu}g$/g BW or $20{\mu}g$/g BW) or HCG (5 IU/g BW or 10 IU/g BW) three times at 5-day intervals and were sacrificed 10 days after the last injection. The effects were compared against an intact control group and sham control group which received the injection of sterile saline solution as a vehicle. 20-E and HCG showed no effectiveness on ovarian maturation in fleshy shrimps. However flesh shrimp given 5-HT of $20{\mu}g$/g BW showed significant increase in gonadosomatic index (GSI) in early spring. The results suggest that treatment of 5-HT of $20{\mu}g$/g BW or more is useful approach for the nursery production of the fleshy shrimp, Fenneropenaeus chinensis aquaculture.

• Horticultural Science & Technology
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• v.32 no.6
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• pp.906-911
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• 2014

A new coreopsis cultivar, 'Uridream Pink', was developed by mutation breeding using gamma-ray irradiation. Rooted cuttings of 'Uridream 01', developed at Uriseed Company, were exposed to various gray ranges of gamma-rays from a $^{60}CO$ source for 24 h in 2009 at the Korea Atomic Energy Research Institute. Using gamma-rays with the range of 10-100 Gy, a chimeric mutant with pastel pink flowers was induced at 30 Gy from 'Uridream 01', which blooms red-purple flowers (Red-purple group, 59A). Clones that produced flowers with modified pink color were separated from the chimeric mutant and fixed by more than three rounds of cutting back from 2009 to 2010. The separated mutant clones with modified pink color were found to bloom flowers with marketable color and be free of any abnormal plant characteristics. The typical color of the flowers was pastel pink (Red-purple group, 67B), and the clones were registered as 'Uridream Pink' at the Korea Seed and Variety Service (plant variety protection number: 4410). Although the size of flowers and leaves of 'Uridream Pink' are smaller than those of 'Uridream 01', the number of flowers per plant is greater. 'Uridream Pink' can be used as both a pot and a garden plant because of its long blooming period from late spring to late autumn.

• Journal of fish pathology
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• v.8 no.2
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• pp.157-164
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• 1995

In order to examine the effects of $O_2$ saturation and pH on gas-bubble disease of blue crab, portunus trituberculatus, zoeal larvae were reared under 5 different concentrations (6.0, 4.0, 3.1, 2.2, and 0.7million cell/cc) of Chlamydomones sp. under natural light for 4days. Observed pH and $O_2$ saturation in the rearing chamber increased drastically from 12 to 18 o'clock with the increasing of Chlamydomones sp. concentrations, but rapidly decreased from 2 to 6 o'clock in the rearing chamber. Gas-bubble disease of zoeal larvae was observed 4hours after starting of experiment at the pH 8.5 and 118% $O_2$ saturated conditions in rearing chamber during the day, and recovered rapidly with the decreasing of pH and $O_2$ saturation at night. Thus, gas-bubble disease of zoeal larvae was repeated with the increased pH($\geq$8.5) and $O_2$ saturation ($\geq$118%) almost every days. Mortality of zoeal larvae was observed when pH and $O_2$ saturations were reached 8.5 and 118% levels respectively, and deteriorated with the increasing of water temperature, pH and $O_2$ saturation.

• Journal of fish pathology
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• v.27 no.2
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• pp.91-97
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• 2014

Since the "Aquatic life disease control act" was established in 2009, we have monitored OIE notifiable and legally designated diseases which are associated with white shrimp Litopenaeus vannamei but are as yet outbreak in South Korea. We had monitored only two viral diseases of YHD and IMN, but further added IHHN, TS and WTD in an attempt to reinforce monitoring as a countermeasure against the increasing possibility of imported diseases led by continuous growth in global fisheries trade. We also increased the number of monitoring areas, and shrimp farms. In 2013, we examined a total of 2,650 white shrimp from 29 hatcheries and farms to check whether they were infected with any of the 5 diseases (YHD, IMN, IHHN, TS, WTD). The result showed that none of the samples contained the viruses. To regulation of the exotic diseases from landing in our country and to strengthen prevention, management and control of the diseases on a national level, we must continue the surveillance monitoring of the diseases.

• Journal of fish pathology
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• v.11 no.1
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• pp.35-41
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• 1998

We investigated the optimal concentration of lidocaine and MS-222 (tricaine methanesulfonate) for the exfoliation and recovery of abalone, Haliotis discus hannai in different shell lengths, for the purpose of preventing the damage of shell and muscle. However, most anaesthetics applied at present have a strong toxic effect on abalone. MS-222 is the only anaesthetic which is approved for use in food fish by FDA, and lidocaine belongs to a group of anaesthetic which are used in human medicine. These chemicals were evaluated as anaesthetic for different shell size of abalone. The response varied for different shell size groups (shell length 1, 2 and 3 cm). In this study, we suggested the result that the exfoliation and recovery time by lidocaine and MS-222 in shell length 1 cm group were more shorter than in 3 cm group. In shell length 1 cm group, the optimal concentrations of lidocaine and MS-222 for anaesthetic were 200 ppm and 100 ppm, respectively. Lidocaine and MS-222 are preferable to other conventional abalone anaesthetics since these are cheap, safe and convenient to use.

• Journal of Life Science
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• v.27 no.10
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• pp.1097-1103
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• 2017

For the artificial induction of the sexual maturation of Anguilla japonica, salmon pituitary extract (SPE) is continuously injected into females, and the eggs obtained from artificial sexual maturation are artificially fertilized with sperms and hatched. However, repeated injection of SPE in the abdominal cavity causes tremendous stress in females, which may prevent their complete sexual maturation and reduce the immune system function, ultimately resulting in death. In addition, the poor quality of the ovulated eggs can reduce the hatching and survival rate of larvae. In the present study, sexual maturation of females was induced by inserting an osmotic (OS) pump containing hormone analogs known to effectively induce sexual maturation into the abdominal cavity of female eels, and the effect of the OS pump on the induced sexual maturation was investigated. Our study results showed that the gonadosomatic index (GSI) was significantly higher in the fish subjected to SPE injection than those subjected to human chorionic gonadotropin (hCG), gonadotropin-releasing hormone analog (GnRHa), and methyl testosterone (MT) injections, either separately or in combination. In addition, a histological analysis showed that the oocytes in the SPE OS pump groups were more mature (entered the nuclear shift stage) than those in the other groups. These results suggest that an osmotic pump containing hormone analogs can be used to induce sexual maturation in female A. japonica artificially.

• Journal of Aquaculture
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• v.20 no.1
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• pp.47-50
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• 2007

The primordial germ cells of the oblong rockfish, Sebastes oblongus were buried under fibrous mesenchymal tissues between gut and mesonephric duct of pre-larva with 4.0 mm total length (TL) at 1 day after the parturition. In the juvenile of 22.0 mm TL at 71 days after the parturition, the gonad composed of a large number of gonial cell and formed of cavity along the lateral side of the gonad, differentiated to the ovary. At this time, the gonad formed seminiferous tubules by somatic cells, was differentiated to the testis. The smallest oblong rockfish that possessed primary oocytes was about 42.1 mm TL at 141 days. Spermatogonia remained quiescent until most fish were over 42.1 mm TL at 141 days. The oblong rockfish the differentiated directly into male or female without an intermediate female phase at the early indifferentiated stage. Therefore, the oblong rockfish belongs to the differentiated type of gonochoristic teleosts.

• Journal of Aquaculture
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• v.6 no.4
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• pp.273-284
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• 1993

Ion concentrations and osmolarities of the body fluid and oxygen consumption of the larvae of the freshwater crab, Eriocheir japonicus under the influence of various salinities and water temperatures were studied. The levels of $Na^+\;and\;Cl^-$ ions in the body fluid of the crab placed in the low salinities (freshwater and $30\%$ seawater) were higher at the low temperature $(16^{\circ}C)$ than high temperature $(30^{\circ}C)$. However, the crab in the high salinity $(90\%\; seawater)$, those ions in the body fluid were higher at the high temperature $(30^{\circ}C)$ than the low temperature $(10^{\circ}C)$ When the zoea larvae were young (first and second stages), the ion concentrations of the body fluid were more affected by salinities and temperatures of the media. The salinity levels of the media more influenced the levels of $K^+$ ions of the body fluid of the larvae than the temperature. The osmolarities of the body fluid of the larvae were almost isotonic when they were placed at $70\%$ seawater $(24.5\%o)$. Oxygen consumption of individual larva was lower in zoea 1 and 2 stages than the other stage larvae. The high oxygen consumption of the larvae was observed at $70\%$ seawater compared to the other salinity levels.