• Korean Journal of Ichthyology
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• v.22 no.1
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• pp.9-16
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• 2010

Osmoregulatory capabilities of a euryhaline medaka, Oryzias dancena (Beloniformes; Teleostei), was examined with a particular emphasis on adult and larval viability during direct salinity changes. O. dancena adults were highly capable for hyper-osmoregulation as well as hypo-osmoregulation, as evidenced by no adverse effect on their viability during the direct transfer either from complete freshwater ($0^{\circ}/_{\circ\circ}$) to $40^{\circ}/_{\circ\circ}$ salinity, or from $70^{\circ}/_{\circ\circ}$ to $0^{\circ}/_{\circ\circ}$. Furthermore, the phased increase of external salinity with acclimation periods allowed them to survive at a salinity as high as $75^{\circ}/_{\circ\circ}$. However, tolerant capability to acute salinity increase in early larval stage was much less than in adult stage, based on the finding that the tolerance range of salinity increase was only $15^{\circ}/_{\circ\circ}$ from freshwater, indicating that the hyper-osmoregulation system might not be fully developed in the early larval stage. On the contrary, the hypoosmoregulation system could be more solidified in O. dancena larvae, as evidenced by their good survival even after direct transfer from $45^{\circ}/_{\circ\circ}$ to $0^{\circ}/_{\circ\circ}$. Knowledge achieved in this study could form the basis for a wide scope of researches including ecotoxicogenomics and geneexpression assay using this model species.

• Journal of fish pathology
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• v.26 no.3
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• pp.283-287
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• 2013

The susceptibility of marine medaka, Oryzias dancena to fish pathogenic viruses (infectious pancreatic necrosis virus (IPNV), viral hemorrhagic septicemia virus (VHSV), hirame rhabdovirus (HIRRV), infectious hematopoietic necrosis virus (IHNV), and lymphocystis disease virus (LCDV)) was investigated. The cumulative mortalities of fish immersed with IPNV (experimental condition: $15^{\circ}C$ sea water (SW)), VHSV ($15^{\circ}C$ SW), HIRRV ($15^{\circ}C$ fresh water (FW)) were 30%, 40% and 60%, respectively. In the fish immersed with IPNV ($15^{\circ}C$ FW, $18^{\circ}C$ FW and SW), VHSV ($15^{\circ}C$ FW, $18^{\circ}C$ FW and SW), HIRRV ($15^{\circ}C$ SW), IHNV ($15^{\circ}C$ FW and SW), LCDV ($15^{\circ}C$ FW and SW, $18^{\circ}C$ FW and SW), and mock-challenged group, mortality rate was less than 10%. IPNV, VHSV and HIRRV were re-isolated from the dead fish. These results suggest that marine medaka is susceptible to IPNV, VHSV and HIRRV, although their susceptibility depends on the environmental conditions.

• Journal of Embryo Transfer
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• v.33 no.4
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• pp.343-348
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• 2018

Although the efforts to establish fish embryonic stem cells (ESCs) have been made for a long time, derivation of authentic ESCs that possess pluripotency is still difficult suggesting a need for the stepwise optimization of the methods to establish fish ESCs. Primary culture of the blastomeres from the embryos at blastula stage is a critical step for establishing continuous ESC lines. Here, we evaluated the effects of temperatures and basal media on primary culture of blastula embryo-derived blastomeres in marine medaka (Oryzias dancena). The blastomeres were isolated from the blastula embryos and cultured in various conditions designed by the combination of 4 temperatures including $28^{\circ}C$, $31^{\circ}C$, $34^{\circ}C$, and $37^{\circ}C$ and 2 basal media including Dulbecco's modified eagle's medium (DMEM) and Leibovitz's L-15 medium (L15). With the exception of a case cultured in L15 at $31^{\circ}C$, the rate of primary cell adherence reached 100% when the blastomeres were cultured over $31^{\circ}C$. The period for primary adherence was significantly shorter in the groups cultured in $34^{\circ}C$ and $37^{\circ}C$ than in the ones in $28^{\circ}C$ and $31^{\circ}C$. The proportion of subculture was significantly high in the group cultured in DMEM at $31^{\circ}C$ compared to the other groups. Collectively, we demonstrated that the culture in DMEM at $31^{\circ}C$ was effective to primary culture of the blastomeres derived from blastula embryos.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.39-51
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• 2011

Acute toxicity test and behavioral change analysis of seawater acclimated Japanese medaka were conducted to identify the brine effects on fish by seawater desalination. 7 day acute toxicity test of brine revealed linear concentration-response relationship from 40.0~80.0 psu treatment groups. There was no significant brine effect for 30-40 psu groups and mass mortality was observed from >50 psu exposure (7-day $LC_{50}$=51.4 psu). Images from the real time camera system were analyzed to observe the changes in behavioral patterns of medaka exposed to various salinity. 40.0 and 50.0 psu exposed groups were stabilized in behavioral patterns after 3.1 and 4.6 hours, respectively and 60.0 psu group showed sharp increase in activity during first 12 hours and 50% mortality thereafter. Similar patterns were observed to 70 and 80 psu groups and both experimental groups showed 100% mortality within 12 hours. Acute toxicity test and behavioral patterns showed very similar toxicity results which revealed the increases in mortality and behavioral activities from 50.0 psu. This critical salinity for fish impacts must be implemented to brine discharge strategy by seawater desalination into the coastal area. Also, we recommend that real time camera monitoring system must be a useful tool for early warning of fish toxicity for other applications. This research was funded by Ministry of Land, Transport and Maritime Affairs, Korea.

• Korean Journal of Ichthyology
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• v.22 no.1
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• pp.25-33
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• 2010

Effects of different salinity levels on spawning performance, embryonic development and early viability of a euryhaline medaka species, Oryzias dancena, were examined. O. dancena were able to spawn eggs in a wide range of salinity from 0 to 70$^{\circ}/_{\circ\circ}$, however, the spawning frequency was lowered in complete freshwater (0$^{\circ}/_{\circ\circ}$) and in highly salted water (70$^{\circ}/_{\circ\circ}$). Fertilization success was negatively affected when the environmental salinity was higher than the salt concentration found in normal seawater. Embryonic viability and hatching success were also inversely related with the salinity levels. Typical abnormality was observed in developing embryos incubated at high salinities (30, 45 and 60$^{\circ}/_{\circ\circ}$). In addition, the time to hatch was significantly delayed with increasing salinities: peak hatching occurred at 12~14 days post fertilization (dpf) in freshwater and at least at 17 to 18 dpf in 60$^{\circ}/_{\circ\circ}$. Mean survival rates of the hatched larvae up to 7 days post hatching (dph) were at least 97% in salinity levels ranging from 0 to 30$^{\circ}/_{\circ\circ}$. However, larvae reared in 45 and 60$^{\circ}/_{\circ\circ}$ experienced significant mortality, especially in the early phase, resulting in only 75% and 64% survival rates up to 7 dph, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.2
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• pp.160-168
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• 2017

Optimizing the conditions for stem cell culture is an essential prerequisite for the efficient utilization of stem cells. In the culture of fish embryonic stem cells (ESCs) or ESC-like cells, embryo extracts are important for stable growth, but there is no rule for determining the developmental stage of the embryos used to obtain extracts. Therefore, this study investigated the effects of the developmental stage of extract donor embryos on the culture of Oryzias dancena ESC-like cells. O. dancena ESC-like cells were cultured in different media containing each of four types of embryo extract depending on the developmental stage of the extract donor embryos. Growth, morphology, colony-forming ability, alkaline phosphatase (AP) activity, and embryoid body (EB) formation of the cells were investigated. While the developmental stage of the extract donor embryos did not influence the growth, morphology, AP activity, or EB formation of ESC-like cells, colony-forming ability was affected and the pattern of the effects differed completely between the two ESC-like cells investigated. These results suggest that the developmental stage of extract donor embryos should be selected carefully for the culture of ESC-like cells, according to the research purpose and type of cell line.

• Journal of Fisheries and Marine Sciences Education
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• v.26 no.2
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• pp.270-283
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• 2014

본 연구는 온도 변화에 따른 해산송사리, Oryzias dancena의 마취 효과 및 생리적 스트레스 반응을 평가하고, 고온 및 저온에서 최적의 마취 수온을 구명하였다. 해산송사리에서 고온 실험($36{\sim}42^{\circ}C$)과 저온 실험($4{\sim}10^{\circ}C$)을 통해 마취 효과를 조사하였으며, 각 마취수온에서 전어체의 cortisol과 glucose를 측정하였다. 각 수온 마취 실험 후, 전개체는 모두 생존하였으며, 해산송사리의 마취시간은 고온 실험에서 고온 일수록, 저온 실험에서는 저온 일수록 유의적으로 빨랐다(P<0.05). 회복 시간은 유의하게 고온 실험에서 수온이 감소할수록, 저온 실험에서는 수온이 증가할수록 유의적으로 느렸다(P<0.05). 아가미 운동수는, 고온 실험에서 수온이 증가함에 따라 빨랐으며, 저온 실험에서는 수온이 감소할때 빨랐다(P<0.05). 수온이 $38^{\circ}C$ 나 $8^{\circ}C$ 일때의 마취 조건에서 실험직후 전어체 cortisol이 최대치로, 실험후 6시간까지 점진적으로 감소한 반면, 전어체 glucose는 실험후 1시간에 최고치를 보이고 실험후 2시간까지는 감소하였다. 기존의 마취제를 쓰지 않은 본 연구로 인해, 해산송사리의 여타 연구에서 샘플 및 사용자가 보다 더 안전하고 용이한 샘플 취급이 가능할 것으로 사료된다.

• Korean Journal of Environmental Biology
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• v.27 no.4
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• pp.391-396
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• 2009

The biological effects of carcinogenic polycyclic aromatic hydrocarbons (cPAHs) including benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DBA), benzo[a]anthracene (BaA), benzo[b] fluoranthene (BbF), benzo[k]fluoranthene (BkF), and indeno[1,2,3-c, d]pyrene (InP) on transcriptomic changes were determined in the liver of Oryzias latipes. Differentially expressed genes (DEGs) by binary exposure to cPAHs (BaP+BaA, BaP+BbF, BaP+BkF, BaP+DbA, BaP+InP) were screened by annealing control primers-based polymerase chain reaction followed by sequence analysis and BLAST searching. The results showed that four DEGs were commonly expressed by cPAHs and they were identified as ribosomal protein S4, coagulation factor II, elongation factor 1 beta, and a predicted protein similar to human immunodeficiency virus type I enhancer binding protein 3. This finding suggests that binary exposure to cPAHs interferes protein synthesis required for fundamental liver functions in fish.

• Journal of fish pathology
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• v.24 no.2
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• pp.131-139
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• 2011

Bisphenol A (BPA) is mainly used in the production of epoxy resins and polycarbonate plastics, which is a known endocrine disruptor and acutely toxic to aquatic organisms. In this study, estrogenic effect of BPA was investigated on hybrid between Oryzias dancena and O. javanicus (ODJ). ODJ were exposed to BPA of various concentrations (eg. 2.5 mg/L, 5.0 mg/L and 10.0 mg/L) for 56 days. The growth rate, abnormality and the ratio of female and male were observed in test group and control group. As a result, the growth was $14.7{\pm}2.0$ mm in total length (TL) in 2.5 mg/L, $13.7{\pm}2.5$ mm in 5.0 mg/L, $12.8{\pm}2.5$ mm in 10.0 mg/L in test group while it was $18.0{\pm}1.2$ mm in TL in control group which was not treated with bisphenol A. The result showed that the growth decreased as the concentration of BPA increased. The abnormality rate was 13.6% in control group, 65.4% in 2.5 mg/L, 81.3% in 5.0 mg/L and 98.1 % in 10.0 mg/L which showed increase in abnormality as an increase of BPA concentration. As a result of analyzing ratio of sex in the test group and control group, 6.0% was examined to be interspecific in controls, 76.9% in 2.5 mg/L and 100.0% in 5.0 mg/L and 10.0 mg/L. In conclusion, these results suggest that BPA has estrogenic effect on ODJ.