• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.10a
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• pp.23-24
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• 2003

The goal of this study is to develop a biomarker used in monitoring abnormal behaviors of Japanese medaka (Oryzias latipes) as a model organism caused by hazardous chemicals. Japanese medaka was treated by copper and fluoranthene of appropriate sublethal concentrations after starvation for 48 hr. In this study we investigated neural toxicity of copper and fluoranthene in Japanese medaka (Oryzias latipes) along with comparative analysis of corresponding behavioral responses. The untreated individuals showed common behavioral characteristics (i.e., smooth and linear movements). Locomotive activity of the fish was monitored using an image processing and automatic data acquisition system. When treated with copper (100 ppb), the fish showed shaking patterns more frequently. As the concentration of copper increased to 1,000 ppb, activity decreased, and the fish showed an erratic movement. The treated with fluoranthene, however, showed stopping and abrupt change of orientation (100 ppb), and severely reduced locomotive activity and enhanced surfacing activity (1,000 ppb).

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.1
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• pp.58-65
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• 2007

Behavioral sequences of the medaka (Oryzias latipes) were continuously investigated through an automatic image recognition system in response to medaka treated with the insecticide and medaka not treated with the insecticide, diazinon (0.1 mg/l) during a 1 hour period. The observation of behavior through the movement tracking program showed many patterns of the medaka. After much observation, behavioral patterns were divided into four basic patterns: active-smooth, active-shaking, inactive-smooth, and inactive-shaking. The "smooth" and "shaking" patterns were shown as normal movement behavior. However, the "shaking" pattern was more frequently observed than the "smooth" pattern in medaka specimens that were treated with insecticide. Each pattern was classified using classification methods after the feature choice. It provides a natural way to incorporate prior knowledge from human experts in fish behavior and contains the information in a logical expression tree. The main focus of this study was. to determine whether the decision tree could be useful for interpreting and classifying behavior patterns of the medaka.

• Development and Reproduction
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• v.20 no.4
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• pp.305-314
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• 2016

The marine medaka, Oryzias dancena is a suitable sample as a laboratory animal because it has a small size and clearly distinguishes between female and male. Data on the growth and maturity of the diploid and triploid sea cucurbit species suitable for laboratory animals are very useful for studying other species. Triploidy was induced in the marine medaka by cold shock treatment ($0^{\circ}C$) of fertilized eggs for 45 min, applied two minutes after fertilization. The diploid and triploid male fish were larger than their female counterparts (P<0.05), and the concentrations of thyroid stimulating hormone (TSH) and thyroxine (T4) were higher in the induced triploids over 1 year (P<0.05). In both the diploid and tri-ploid groups the concentrations of TSH and T4 were higher in the male fish than in the females (P<0.05), while the testo-sterone and estradiol-$17{\beta}$ concentrations in the induced triploids were lower than in the diploids (P<0.05). The gonadosomatic index (GSI) of the triploid fish was lower than that for the diploids, and the GSI for females in each ploidy group were higher than that for the males. For both groups the GSI was highest at 4 months of age, and decreased thereafter to 12 months. Analysis of the gonads of one-year-old triploid fish suggested that the induction of triploidy probably causes sterility in this species; this effect was more apparent in females than in males.

• Fisheries and Aquatic Sciences
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• v.20 no.9
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• pp.21.1-21.10
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• 2017

The aim of this study was to assess visible implant fluorescent elastomer (VIE) tagging and stress response in marine medaka, Oryzias dancena. The experimental fish were anesthetized individually and marked with red, yellow, or green elastomer at each of the following three body locations: (1) the abdomen, (2) the back, and (3) the caudal vasculature. During 12 months, the accumulated survival rates of fish in the experimental treatments were not different among red, yellow, and green elastomers. The experimental fish retained > 85% of the tags injected in the back, > 70% of the tags injected in the caudal vasculature, and > 60% of the tags injected in the abdomen (P < 0.05). An important observation was that the abdomen site was associated with poor tag retention. For all injected sites, the red and green tags were able to be detected more easily than the yellow tags when observed under both visible and UV lights. Tag readability was lower for the abdomen site than for the other sites (back and caudal vasculature). Thus, VIE tags were easy to apply to marine medaka (< 1 min per fish) and were readily visible when viewed under UV light.

• Journal of Life Science
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• v.23 no.3
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• pp.333-340
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• 2013

This study was performed to determine whether stem bark extract containing saponin of Albizzia julibrissin in the diet influences gonadal maturation and spawning in medaka (Oryzias latipes). The crude extraction containing saponin (HaBC) was partially purified from n-BuOH extraction of A. julibrissin stem bark by Diaion HP-20, Silica gel and Sephadex LH-20 chromatographies. We fed diets supplemented with HaBC to medaka. We then studied the effects of the HaBC supplement on the suppression of gonadal maturation and spawning in female medaka that were reared in aquaria with recirculation systems. In the experiment with immature female medaka, the periods of initiation of gonadal maturation and spawning were delayed in the fish that were fed diets supplemented with at least HaBC 20 mg/g-feed. In the experiment with mature female medaka, the fish that were fed diets supplemented with at least HaBC 20 mg/g-feed had lower GSIs than the control diet group did. The results showed that the growth of the immature medaka was not correlated with the amount of supplementation of HaBC in the diet. However, the condition factors (CF) in the medaka that were fed diets supplemented with at least HaBC 20 mg/g-feed were higher than in the medaka fed on the control diet. We concluded that extracts containing saponin from the stem bark of A. julibrissin have the potential to inhibit gonadal maturation in female medaka, but they did not act as growth stimulation. Further studies are required to determine the mechanism of the action.

• Fisheries and Aquatic Sciences
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• v.17 no.4
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• pp.479-486
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• 2014

To evaluate their potential utility as an ornamental organism, novel transgenic marine medaka Oryzias dancena strains with a highly vivid fluorescent phenotype were established through transgenesis of a cyan fluorescent protein gene (cfp) driven by the endogenous fast skeletal myosin light chain 2 gene (mlc2f) promoter. The transgenic marine medaka strains possessed multiple copies of transgene integrants and passed their fluorescent transgenes successfully to subsequent generations. Transgenic expression in skeletal muscles at both the mRNA and phenotypic levels was, overall, dependent upon transgene copy numbers. In the external phenotype, an authentic fluorescent color was dominant in the skeletal muscles of the transgenic fish and clearly visible to the unaided eye. The phenotypic fluorescent color presented differentially in response to different light-irradiation sources; the transgenics displayed a yellow-green color under normal daylight or white room light conditions, a strong green-glowing fluorescence under ultraviolet light, and a cyan-like fluorescence under blue light from a light-emitting diode.

• Environmental Analysis Health and Toxicology
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• v.18 no.2
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• pp.145-153
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• 2003

The goal of this study is to develop a biomarker used in monitoring abnormal behaviors of Japanese medaka (Oryzias latipes) as a model organism caused by hazardous chemicals. Japanese medaka was treated by copper of appropriate sublethal concentrations after starvation for 48 hr. The untreated individuals showed common behavioral characteristics (i.e. , smooth and linear movements). Locomotive activity of the fish was monitored using an image processing and automatic data acquisition system. When treated with copper (100 ppb), the fish showed shaking patterns more frequently. As the concentration of copper increased to 1,000 ppb, activity decreated, and the fish showed an erratic movement. Fish were exposed to copper at various concentrations (0,100 and 1,000 ppb) for 24 hrs, and acetylcholine esterase (AChE) activity was observed. When fish were exposed to 1,000 ppb of copper, the body AChE activities appeared to decrease but the head AChE activities showed little change. Expressions of tyrosine hydroxylase (TH) protein in the different organs from both head (brain) and body (kidney) portions affected by the copper treatment were analyzed using immunohistochemical technique compared with control. Five organs of the fish (olfactory bulb, hyothalamus, optic lobe, pons and myelencephalon regions) showed a relatively strong TH protein expression in the control experiment. A differential expression of TH, however, was observed in the treatment (100 ppb and 1,000 ppb). The treatment (1,000 ppb) significantly suppressed TH protein production in the brain regions. In kidney, however, the same treatment caused little suppression compared with the control. Copper appeared to be less effective in suppression of TH than diazinon, a known TH suppressor. It was concluded that TH could be used at a potential biomarker to monitor the acute copper toxicity in Japanese medaka.

• Korean Journal of Environmental Agriculture
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• v.4 no.2
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• pp.118-125
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• 1985

To establish an evaluation system of aquatic toxicity of chemicals at no-effect level, flow through and early life stage toxicity test were performed on a freshwater fish, the medaka (Oryzias latipes). The characteristics of medaka as a bioassay organism for the chronic toxicity test were discussed. Maximum acceptable toxicant concentration(MATC) of butachlor for the madaka in soft water was estimated using survival, growth, and reproduction as indicators of toxic effects. During a 3-month period, the fry of medaka were exposed to butachor concentrations ranging from 0.16 to 0.0l mg/liter and the DO concentration, temperature, and pH in the exposure chamber were measured to check the test condition. The highest concentration showed slight decrease of growth rate in medaka and reduced hatchability of spawning egg. Survival, growth, and reproductive success of adults in butachlor concentration of 0.04 and 0.01 mg/liter were not different from those of the control. The MATC was estimated to be between 0.04 and 0.16 mg/liter for medaka.

• Environmental Analysis Health and Toxicology
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• v.18 no.1
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• pp.21-25
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• 2003

카바메이트계 농약인 카보푸란은 어류에 대한 독성이 매우 높으며, 낮은 농도에서 어류의 척추기형이나 행동이상을 유발한다. 이러한 카보푸란의 독성기전을 밝히기 위한 일환으로 신경물질대사와 관련이 깊은 acetylcholine esterase(AChE)와 monoamine oxidase(MAO)에 미치는 농약의 효과를 송사리(Oryzias latipes; Medaka fish)를 이용하여 평가하였다. Medaka fish에 대한 카보푸란의 반수치사농도(LC$_{50}$)는 2.5 ppm이었으며, 1 ppb 카보푸란에 24시간 노출된 경우, AChE 효소활성이 머리와 몸통부위에서 각각 30, 20%씩 감소되었다. 한편, MAO 효소활성은 카보푸란의 농도가 증가함에 따라 머리부위에서는 감소한 반면, 몸통부위에서는 증가하는 경향을 보였다. 특히 카보푸란의 농도가 1 ppb에서도 송사리의 MAO 효소활성이 영향을 받는 것으로 나타나, 카보푸란에 의한 송사리의 행동이상은 AChE 활성 뿐 아니라 MAO활성의 변화에 의한 복합적인 효과일 가능성이 높다.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.3 no.1
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• pp.47-53
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• 2022

The escape behavior of prey fish to predator attack is directly linked to the survival of the fish. In this study, I explored the escape behavior of Medaka fish to bird attacks. To simulate the attack, I designed a model triangular-shaped bird to slide along a fishing line connected between rods at both ends of the tank. The triangular shape was set to 10×15 (S=1), 15×20 (S=2), and 20×25 cm (S=3) with base×height. The slope (θ) of the fishing line, which determines the attack speed of the model bird, was set to values of 15° (θ=1), 30° (θ=2), and 45° (θ=3). The escape behavior was characterized using five variables: escape speed (ν), escape acceleration (α), responsiveness (γ), branch length similarity entropy (ε), and alignment (ϕ). The experimental results showed when (S, θ)=(fixed, varied), the change in values of the five variables were not significant. Thus, the fish respond more sensitively to S than to θ In contrast, when (S, θ)=(varied, fixed), ν, α, and γ showed increasing trends but ε and ϕ did not change much. This indicates the nature of fish escape behavior irrespective of the threat is inherent in ε and ϕ. I found that fish escape behavior can be divided into two types for the five physical quantities. In particular, the analysis showed that the type was mainly determined by the size of the model bird.