• Korean Journal of Environmental Biology
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• v.38 no.2
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• pp.323-331
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• 2020

The method of natural spawning is very passive and inconvenient for the study of developmental engineering in marine medaka, Oryzias dancena. The optimum concentration of human chorionic gonadotropin (HCG) and carp pituitary extract (CPE) for ovulation and spawning, and the injection time for the artificial spawning of marine medaka were analyzed in this study. The success rate, survival rate, and hatching rate were highest with 100IU HCG kg^-1 BW and 5mg CPE L^-1 in both male and female marine medaka (p<0.05). After obtaining unfertilized eggs and sperm by the injection of HCG and CPE into the broodstock of marine medaka, artificial fertilization could be successfully achieved any time fertilized eggs are needed in this species. This result should be useful for developing a study program for marine medaka as an experimental animal.

• Korean Journal of Ichthyology
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• v.18 no.1
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• pp.12-19
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• 2006

To examine the relationship of geological distribution and phylogenetic tree of O. latipes in the Far East, we analyzed cytochrome b (cyt b) gene in the mitochondrial genome. In this study we employed the entire sequence of cyt b of 53 samples collected from nine Korean locations and 117 cyt b data retrieved from the GenBank. From 170 Oryzias latipes cyt b sequence data, 142 different haplotypes were identified and phylogenetic relationship was reconstructed based on the dataset. According to the phylogeny, haplotypes were divided into three major haplogroups A, B and C, and their relationships were well correlated to their distributional patterns. Haplogroup A which is widely distribute in the southern part of Korea is separated in the geographical distribution from the haplogroup B which is found from China to the western part of Korea. Haplogroup C is only found in Japan.

• Korean Journal of Ichthyology
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• v.18 no.3
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• pp.163-169
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• 2006

The Korean ricefish, Oryzias, consisted of 2 species, O. latipes and O. sinensis. Through investigation on their distributions, it was confirmed that O. sinensis was restricted to western areas, and O. latipes was distributed throughout Korea. Interestingly, Daecheon region near the West Sea was sympatric, existing O. latipes and O. sinensis. In addition to their distributions, O. latipes was well distinguished from O. sinensis as the following morphological characteristics: mean 31 vertebrae (vs. 30), mean 15 gill rakers (vs. 12), lots of dots in both sides of body (vs. absent), and yellowish ventral and anal fins (vs. blackish).

• Korean Journal of Ichthyology
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• v.25 no.1
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• pp.33-37
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• 2013

A study on the structures of the pharyngeal bones and teeth in two Korean ricefishes, Oryzias latipes and O. sinensis, was carried out to find out interspecfic differences. In the pharyngeal bones, both two species have a pair of upper pharyngeal bone (stilliform shape) and lower pharyngeal bone (rectangular shape). In the lower pharyngeal bones, in particular, the number of the row was 6 to 7 in O. latipes and 5 to 6 in O. sinensis. The pharyngeal teeth also showed different types in two species: O. latipes of a top-hooked type and O. sinensis of a conical type. Through this study, we confirmed that the two Korean ricefishes show distinctive characteristics in the structure of the pharyngeal teeth.

• Korean Journal of Ichthyology
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• v.28 no.4
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• pp.223-228
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• 2016

The anatomy and histology of the olfactory organ in Oryzias sinensis was researched using a stereo microscope and light microscope. In the gross structure, the paired olfactory organs on the dorsal part of the head consist of two nostrils (a circular anterior nostril and a slit posterior nostril in a distance), a single olfactory chamber and a single accessory nasal sac. In the histological study, the epithelium of the olfactory chamber is classified into both sensory and non-sensory regions. The sensory epithelium consists of olfactory receptor neurons, supporting cells, basal cells and vesicles, and is islet in distributional pattern. The non-sensory epithelium is composed of stratified epithelial cells and two types of mucous cells (acidic and neutral cells). The epithelium of the accessory nasal sac has swollen stratified epithelial cells, mucous cells with a rich glycoprotein. Such an olfactory anatomy and histology of O. sinensis may reflect its habitat surrounding stagnant and polluted water.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.25-31
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• 2000

In order to assess the accumulation levels of cadmium and other metals(Zn, Cu, Ca and Fe) in fish bodies, an experimental study was performed by raising fry of "Oryzias latipes" in the water containing cadmium 0.03 ppm, cadmium 0.03 ppm + zinc 0.03 ppm and in the tap water(control group) were made. In the results the concentration of Cd in fish bodies were increased with advancing exposure time in Cd 0.03 ppm treated group and 0.03 ppm + Zn 0.03 ppm treated group, but there was no significantly different between both groups with Cd concentration in each week. The concentration of Zn in fish bodies was no changed with advancing exposure time in control group and Cd 0.03 ppm + Zn 0.03 ppm treated group were significantly different from control and Cd 0.03 ppm treated group. The concentration of Cu, Ca and Fe in fish bodies were increased with advancing exposure time, and control group was higher than any other groups. Simple correlation analysis showed that the positive correlation between Cd and Zn, Cu and Ca, Fe, Ca and Fe, but Cd was negative correlation with Cu, Ca and Fe. In conclusion, we investigated a tendency that the concentration of Cd and Zn in fish bodies tended to increase with the lapse of time, but Cu was unchanged and those of Ca and Fe were decreased in administrating the trace dose of Cd and Zn in water. in water.

• Proceedings of the Korean Environmental Health Society Conference
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• 2005.06a
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• pp.279-285
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• 2005

Endocrine disrupting effects of four pharmaceutical products were evaluated with fish. The test pharmaceuticals, i.e., sulfamethoxazole, sulfamethazine, oxytetracycline and tetracycline have been often detected in aquatic environment, but their ecological hazard on receptors of various trophic levels has seldom been evaluated. In the present study, we conducted acute toxicity assays with a fish, Japanese medake (Oryziα lαtipes). The vitellogenin induced in female fish normally, but a endocrine disrupting chemical could give effects even male fish. We have tried 4 pharmaceutic chemicals to find out the endocrine disrupting effects. Sulfamethoxazole 1, 0.5 ppm induced vitellogenin even at male Japanese medaka. Sulfamethazine 10, 5, 1 ppm could induced vitellogenin at male fish. Oxytetracycline 10, 5, 1ppm could induced vitellogenin With the fish. Tetracycline 10, 5 ppm could induced vitellogenin at male fish. Some pharmaceuticals such as sulfamethoxazole, sulfamethazine, oxytetracycline and tetracycline could give effects to male Oryzias latipes. They could induced vitellogenin under exposure range 0.5 ${\sim}$ 10 ppm of chemicals at male Oryzias latipes.

• Development and Reproduction
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• v.22 no.3
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• pp.275-281
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• 2018

The purpose of this study is to examine fluctuating asymmetry of eye diameter, maxilla length, operculum length, and the number of pectoral fin ray and pelvic fin ray between ploidy and sex in diploid and triploid marine medaka, Oryzias dancena. In all experimental groups, eye diameter and maxilla length showed no significant difference between left side and right side (p>0.05). Results of operculum length in triploid male group and pectoral fin ray's number in diploid male group showed similarity ones with results of operculum length in triploid female group and pectoral fin ray's number in diploid female group (p<0.05). However, the operculum length in diploid male group and pectoral fin ray's number in triploid male group showed consinderable difference with those of operculum length in diploid female group and pectoral fin in triploid female group. Findings of pelvic fin ray's number in all groups were similar to those of pectoral fin ray's number in all groups (p<0.01).

• Environmental Analysis Health and Toxicology
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• v.15 no.3
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• pp.61-67
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• 2000

Toxic lesions of styrene in the Japanese Medaka (Oryzias latipes) were compared with those of styrene oxide, the active metabolite of styrene, using embryo-larval assays. The developmental stages of Japanese Medaka (Oryzias latipes) treated with both chemicals were not altered and progressed normally. However, styrene oxide was more toxic than styrene in terms of causing death and lesions . High concentrations of styrene (higher than 4.9 ppm) and styrene oxide (higher than 2.4 ppm), resulting in more than 50% mortality, caused similar lesions of cardiovascular system, craniofacial bone formation and spinal deformities, although a number of lesions were not observed by both chemicals . In the group treated with styrene, eyeball sizes and intereye distances were reduced, while, in the group treated with styrene oxide , the eyes and eye cups were not developed and two eyes were sometimes fused. In addition, styrene oxide caused the lesion which involved the posterior brain and brain stem were herniated through the spinal cord . The noticeable difference of toxic symptoms between these two chemicals was the time of onset. Toxicities of cardiovascular system and craniofacial bone formation appeared on day 3 of development in styrene oxide treated group, but, styrene treated group staned to show hemorrhages on day 3 and the craniofacial malformation were appeared on day 5, These differences between two chemicals may be due to the metabolism of styrene to styrene oxide, the reactive intermediate.

• Environmental Engineering Research
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• v.22 no.4
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• pp.426-431
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• 2017

Some phototoxicity of titanium dioxide nanoparticles ($TiO_2$ NPs) has been reported in recent years in studies with fish embryos or larvae. However, it is necessary to focus on the potential effects of embryonic exposure due to irreversible abnormalities and mortalities observed in sac-fry, and to expand various fish embryos to generate multiple test species. The aim of this study was to evaluate the effects of $TiO_2$ NPs under different irradiation conditions in exposed Oryzias latipes (O. latipes) at the embryonic and sac-fry stages. The effects of different irradiation conditions were observed using ultra-violet (UV) and visible light, and the corresponding effects were monitored by determining cumulative mortality and abnormality. O. latipes were exposed for 8 d to 0, 1, 5, 10, or 50 mg/L $TiO_2$ NPs under UV ($4,818.86mW/m^2$ at the bottom of clear vials) or visible light, after which the embryos were transferred to NP-free embryo-rearing solution until 16 days post fertilization (dpf). Abnormalities of embryos and sac-fry increased at high $TiO_2$ NP concentrations under UV irradiation, compared to control samples treated with visible light or UV irradiation alone. This work provides information regarding the phototoxicity of $TiO_2$ NPs using O. latipes at the embryonic and sac-fry stages.