• Journal of Aquaculture
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• v.9 no.4
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• pp.429-435
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• 1996

We investigated the effects of rearing water temperatures during sex differentiation period on sex ratios in olive flounder, Paralichthys olivaceus. Control and gynogenetic diploid juvenile flounder reared at water temperature of 18, 21, 24 and $27^{\circ}C$ for 65 days from 35 to 100 days after hatching. Fish were sampled to examine sex ratios at 195 or 260 days after hatching. Female ratios of control and gynogenetic diploid flounder declined rapidly as water temperature increased. Sex ratio of gynogenetic diploid reared at $27^{\circ}C$ was very close to 1 : 1 ratio (P<0.01), The survival rates of control and gynogenetic diploid reared at $27^{\circ}C$ were different from other water temperature groups. The growth of body weight of control and gynogenetic diploid reared at $18^{\circ}C$ were different from other water temperature groups.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.143-149
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• 2015

This experiment was conducted to evaluate the synergistic effects of vitamin C and E on methylmercury (MeHg) toxicity in juvenile olive flounder Paralichthys olivaceus. In a $3{\times}3$ factorial design, 9 experimental diets containing three different vitamin C (0, 200 or 400 mg/kg diet in the form of l-ascorbyl-2-monophosphate) and vitamin E (0, 100 or 200 mg/kg diet in the form of dl-${\alpha}$-tocopheryl acetate) levels with the Hg toxicity level (20 mg/kg diet in the form of MeHg) were formulated. Triplicate groups of fish averaging $2.3{\pm}0.05g(mean{\pm}SD)$ were fed one of the 9 diets in a flow through system for 8 weeks. Fish fed 400 mg vitamin C/kg diet with 100 or 200 mg vitamin E/kg diet showed significantly (P < 0.05) higher weight gain (WG) than did fish fed the other diets. Fish fed 400 mg vitamin C/kg diet at all vitamin E levels and those which fed vitamin C and E equally at a rate of 200 mg/kg diet showed significantly (P < 0.05) higher feed efficiency (FE), specific growth rate (SGR) and protein efficiency ratio (PER) than did fish fed the other diets. Fish fed 200 and 400 mg vitamin C/kg diet exhibited significantly (P < 0.05) lower Hg concentration in their muscle as well as kidney than did fish fed the other diets. Therefore, these results clearly indicated that the synergistic effects of these two vitamins on MeHg toxicity by supplementing dietary vitamin C (200 and 400 mg/kg diet) with vitamin E (100 and 200 mg/kg diet) in juvenile olive flounder.

• Journal of Aquaculture
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• v.11 no.3
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• pp.319-325
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• 1998

Quality evaluation of fish muscle was conducted in olive flounder, Paralichthys olivaceus fed with control or experimental diet containing 0.3% of Obosan (Sungam Co., Korea). Sensory panel members preferred the experimental fish were more preferable than those of control (P<0.01 or 0.05). The difference test was shown that the experimental fish muscle is more firm elastic and palatable than the control ones (P<0.01 or 0.05). The physical properties of meats from fish fed a diet containing Obosan improved qualities with compared to those of control meats. The total amount of free amino acids in muscles from control fish (31.7 mg/100mg), especially with the significant increase of glutamic acid, proline, glycine, alanine and methionine. In all nucleotides and their related compounds, ATP was the most abundant in muscles from fish fed a diet containing Obosan (about 1.9 fold compared to mean of control), however, IMP was more abundant in control muscles.

• Environmental Analysis Health and Toxicology
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• v.24 no.2
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• pp.119-125
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• 2009

This study was carried out to investigate the toxic effect of WSF (water soluble fraction) in crude oil on the hatch, survival rate, abnormality and physiological activity of fertilized eggs and early larvae in Paralicthys olivaceus. The time required in hatching the fertilized eggs exposure to crude oil was 50.8${\sim}$53.2 hours both in control group and experimental group, showing no significant difference(p>0.05). The hatching rate in the control group was more than 80% in 1.9 ${\mu}g/mL$ WSF concentration, but hatching rate was less than 55.7% in below of 3.9 ${\mu}g/mL$ WSF concentration, showing significant difference (p<0.05). The survival rate on the 3rd day of early larval stage was 61.96% with 1.9 ${\mu}g/mL$ WSF, 11.1% with 3.9 ${\mu}g/mL$ WSF, and they all died with other concentration levels. The oxygen consumption rate in experimental groups was lower than control group. The heart rate (no./min) was 47.4${\sim}$52.8 before hatching and there was no significant difference between control group and experimental group, but heart rate reduced with the decrease of WSF concentration after hatching. The abnormality was 1.1% in the control group whereas 36.7% with 3.9${\mu}g/mL$ WSF, and abnormality was mostly comprised of incomplete spinal formation and spinal curvature. The results of this study suggest that even low concentration to WSF affects the early development of the flounder, Paralicthys olivaceus.

• Ocean and Polar Research
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• v.34 no.1
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• pp.93-99
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• 2012

The effect of water temperature and body weight on oxygen consumption by the fasted olive flounder Paralichthys olivaceus was investigated in order to assess the metabolic rate of this species under different conditions. The oxygen consumption rate (OCR) was measured at three different water temperatures (15, 20 and $25^{\circ}C$) and two different body weights [$9.1{\pm}1.2$ g (mean${\pm}$SD) for the juvenile group and $266.4{\pm}29.3$ g for the immature group] at an interval of 5 minutes for 24 hours using a closed flow-through respirometer. For each treatment condition, three replicates were set up and 135 fish in the juvenile group and 18 fish in the immature group were used. The OCRs exhibited a linear increase described by OCR=-82.06+28.30T ($r^2$=0.96, p<0.001) in the juvenile group and OCR=-52.52+14.73T ($r^2$=0.97, p<0.001) in the immature group. The OCRs decreased with increasing body weights at a given water temperature (p<0.001). The metabolic rate was related to the body weight of the fish as a power function with a weight exponent of between 0.77 and 0.82. $Q_{10}$ values ranged 1.67~2.28 when the temperature was between 15 and $20^{\circ}C$, 1.57~1.93 when the temperature was between 20 and $250^{\circ}C$, and 1.79~1.89 when the temperature was between 15 and $250^{\circ}C$. The energy expenditure by respiration increased with increasing water temperature and decreasing body weight (p<0.001). The mean energy loss rates at 15, 20 and $25^{\circ}C$ were 115.9, 149.8 and 208.2 kJ $kg^{-1}d^{-1}$ in the juvenile groups and 53.8, 81.2 and 101.9 kJ $kg^{-1}d^{-1}$ in the immature groups.

• Journal of Aquaculture
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• v.21 no.3
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• pp.190-195
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• 2008

We investigated the changes in growth, digestive enzymes activities, nucleic acids contents and RNA/DNA ratio of flounder Paralichthys olivaceus larvae (C for Paracyclopina nana, A for Artemia, and M for Mix of C and A) for 14 to 28 DAH. Body length of flounder larvae showed the best in the C trial at 28 DAH. The change of nucleic acids contents showed faster in C and M trials than A trial. And RNA/DNA ratio showed the significantly faster changes in C trial than A trial. High metamorphosis rates were also observed in C and M trial. $\alpha$-amylase activities increased gradually up to 28 DAH in all trials. Total alkaline protease (TAP) activities of A trial showed the highest value to 9 mU/larvae at 26 DAH. But others trials showed lower to $5{\sim}6$ mU/larva than A trial. TAP:$\alpha$-amylase activity ratio did not significantly changed to $0.025{\sim}0.053$ in A trial during the experiments. But, C and M trials tended to gradually decrease from $0.078{\sim}0.083$ (initial) to $0.013{\sim}0.018$ (final). Therefore, it shown the ratio gradually decreased of TAP:$\alpha$-amylase activity, stability of TAP activity, and rapid change of nucleic acids in trials grown positively. Thus, because P. nana could continuously supply the optimal nutrients for flounder larvae, we suggested the supplement of the copepod to an efficient feed of the flounder larvae.

• Fisheries and Aquatic Sciences
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• v.17 no.3
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• pp.325-337
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• 2014

To assess the functional structure of prepro-melanin-concentrating hormone (pMCH), we isolated and cloned pMCH (of-pMCH) mRNA from the brain of the olive flounder, Paralichthys olivaceus, and compared its amino acid sequence with those from other animals. In addition, to examine whether activation of the brain of-pMCH gene is influenced by background color, density, and feeding, we compared pMCH mRNA activities against different background colors (bright and dark) and at different densities (100% PCA and 200% PCA). To examine whether the pMCH gene is related with malpigmentation of blind-side skin and appetite, we compared pMCH gene expression between ordinary and hypermelanic flounders, and between feeding and fasting flounders. The of-pMCH cDNA was 405 bp in the open reading frame [ORF] and encoded a protein of 135 amino acids; MCH was 51 bp in length and encoded a protein of 17 amino acids. An obvious single band of the expected size was obtained from the brain and pituitary by RT-PCR. In addition, of-pMCH gene activity was significantly higher in the bright background only at low density (< 100% PCA) making the ocular skin of fish whitening, and in ordinary fish. However, the gene activity was significantly decreased in dark background, at high density (>200% PCA), and in hypermelano fish. These results suggest that skin whitening camouflage of the flounder is induced by high MCH gene activity, and the density disturbs the function of background color in the physiological color change. Moreover, our data suggest that a low level of MCH gene activity may be related to malpigmentation of the blind-side skin. In feeding, although pMCH gene activity was significantly increased by feeding in the white background, the pMCH gene activity in the dark background was not influenced by feeding, indicating that the MCH gene activity increased by feeding can be offset by dark background color, or is unaffected by appetite. In conclusion, this study showed that MCH gene expression is related to ocular-skin whitening camouflage and blind-skin hypermelanosis, and is influenced by background color and density.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.1
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• pp.1-14
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• 2024

We investigated the functional properties and in vitro bioactivity of protein isolates (RPIs) recovered from olive flounder Paralichthys olivaceus roes by isoelectric solubilization/precipitation process, according to pH-shift treatments. The buffer capacity of RPIs was shown to be stronger in alkaline pH than in acidic pH. Water holding capacity of RPIs was in range of 4.5-5.2 g/g protein with no significant differences (P>0.05). The foaming capacity and emulsifying activity index of RPIs did not show any significant differences between RPI-1 (pH 11/4.5) and 3 (pH 12/4.5), however they were superior to RPI-2 (pH 11/5.5) and 4 (pH 12/5.5). The 2,2'-azino-bis-3-ethylbenzo-thiazoline-6-sulfonic acid radical scavenging activity of RPI-3 (2.5 mg protein/mL) was 102.4 ㎍/mL, and the angiotensin I converting enzyme inhibitory activity was 30.8%. Among the RPIs, RPI-3 was relatively superior in protein functional properties such as buffer capacity, foaming capacity, emulsification, and anti-oxidative activity. Therefore, we suggest that RPI prepared from olive flounder roes could serve as a potential food resource.

• Korean Journal of Ichthyology
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• v.12 no.3
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• pp.173-179
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• 2000

Effects of Estradiol-$17\beta(E_2)$ and 2, 4-dichlorophenoxy acetic acid (2, 4-D) on vitellogenin(VTG) production were investigated in primary hepatocyte culture of olive flounder, Paralichthys olivaceus. Highest survival rate of hepatocyte were observed at $27^{\circ}C$, which markedly declined equal to 50% of those of $15^{\circ}C$. Vitellogenin production peaked at the concentration of $10^{-6}M\;E_2$. No effect was observed on VTG production at various concentrations of 2, 4-D. However, a low concentration of 2, 4-D (ie, $10^{-8}M$) only appeared increased VTG production. $E_2$ or $10^{-8}M$ 2, 4-D-primed VTG production was markedly inhibited by the addition of $10^{-6}M$ tamoxifen to the culture medium(P<0.01). Inhibition was not affected by combinational treatment with $10^{-6}M$ $E_2$ and $10^{-6}M$ 2, 4-D. These results from the current investigation suggest that 2, 4-D mimics $E_2$, but the mechanism of reaction in inducing the $E_2$ receptor are different in VTG production in oliver flounder hepatocytes.

• Korean Journal of Environmental Biology
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• v.36 no.2
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• pp.124-130
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• 2018

Paralichthys olivaceus (mean length, $13.3{\pm}1.6cm$; mean weight, $25.6{\pm}3.7g$) were exposed to waterborne hexavalent chromium at different concentrations (0, 0.5, 1.0, and $2.0mg\;L^{-1}$) for 10 days. Hematological parameters such as hemoglobin and hematocrit of P. olivaceus were significantly decreased after waterborne chromium exposure. There were no significant alterations in inorganic plasma components, calcium, or magnesium after waterborne chromium exposure. Organic plasma components such as glucose and cholesterol levels were significantly increased after exposure to chromium at concentration over $1.0mg\;L^{-1}$. However, significant change in total protein was not observed. Enzymatic plasma components such as aspartate aminotransferase (AST), alanine aminotransaminase (ALT), alkaline phosphatase (ALP) levels were significantly increased after chromium exposure. Results of this study indicate that waterborne chromium exposure can cause significant alterations in hematological parameters and plasma components of P. olivaceus. Such changes in parameters could be used as reliable indicators for toxic effects of waterborne chromium exposure.