• Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.125-129
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• 2013

Vibrio ichthyoenteri is a facultatively anaerobic gram-negative bacterium with straight or slightly curved rod morphology. The bacterium is an etiological agent of bacterial enteritis of Olive flounder Paralichthys olivaceus. Only a handful of studies, using a limited number of isolates, have investigated the phenotypic and genetic characteristics of V. ichthyoenteri. We isolated 40 V. ichthyoenteri strains, identified based on the 16S rRNA gene sequence, from the diseased flounder larvae and investigated the API 20E and ZYM profiles. The isolates exhibited highly divergent phenotypic characteristics regardless of sampling time point and location, and fish age. Essential enzymes produced by V. ichthyoenteri seemed to be alkaline phosphatase, leucine arylamidase, and N-acetyl-${\beta}$-glucosaminidase. This study reveals a much greater enzymatic and biochemical phenotype diversity than has been evident to date. These results suggest that a given population of V. ichthyoenteri could be heterogeneous in terms of its phenotypic characteristics.

• Development and Reproduction
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• v.11 no.2
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• pp.121-125
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• 2007

Morphological changes on digestive tract were observed using Flounder, Paralichthys olivaceus to elucidate the early developmental processes. Hatched larvae, ($2.50{\pm}0.14\;mm$ in total length: TL) has not opened its mouth and anus. The digestive tract showed linear tubular form from mouth to anus extending along with yolk. On $7{\sim}8$ days from hatching, the post-larvae, ($5.05{\pm}0.40\;mm$ TL) has developed digestive tract and activated for feeding. The digestive tract expanded into dorsal side, joined to intestine, and the stomach began to develop. The digestive tract was divided into an anterior and posterior region, and began to differentiate. In the post-larvae($6.50{\pm}0.25\;mm$ TL) on $13{\sim}14$ days from hatching, the digestive tract twisted one cycle in the anterior region, the area was expanded. The digestive tract was completely differentiated into oesophagus, anterior intestine, middle intestine, posterior intestine and arranges fundamental structure. In the embryo($12.40{\pm}0.55\;mm$ TL) after 30 days from hatching, stomach became large and could be distinguished from cardia and pyloric parts apparently. The digestive tract developed similar with that of adult flounder showing clear division of stomach, anterior intestine, middle intestine, posterior intestine and rectum. In the embryo($16.15{\pm}0.85\;mm$ TL) after 40 days from hatching, esophagus, pyloric part, anterior intestine, middle intestine, and rectum have largely expanded, and thus the morphological features are somewhot different with those of post-larvae flounder.

• Development and Reproduction
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• v.24 no.1
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• pp.19-30
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• 2020

The pH of water is one of the main environmental factors exerting selective pressure on marine and freshwater organisms. Here, we focus on the influence of pH on an organism's ability to maintain homeostasis and investigate the effects of acidification on immunity-related genes and osmotic pressure during early development of the olive flounder, Paralichthys olivaceus. The aim of our study was to determine the influence of various pH levels on the fertilized eggs and larvae of P. olivaceus. Gametes of P. olivaceus were artificially introduced and the resulting fertilized eggs were incubated at pH 4.0 (low), 6.0, and 8.0 (equivalent to natural sea water; control). We found that all eggs sank from the water column at pH 4.0. After 38 h, these eggs showed slow development. Hatching occurred more slowly at pH 4.0 and 6.0 and did not occur at all at pH 4.0. Result of gene expression, caspase and galectin-1 were expressed from the blastula to pre-hatch stages, with the exception of the two-cell stage. HSP 70 was also steadily expressed at all pH levels over the five days. The osmolality of fertilized eggs differed marginally at each stage and across pH levels. So, this results demonstrates that low pH level is detrimental to P. olivaceus fertilized eggs.

• Journal of fish pathology
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• v.20 no.3
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• pp.257-267
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• 2007

The hypo-salinity effects on fertilized eggs, embryos and larvae were investigated in olive flounder (Paralichthys olivaceus) obtained from hatcheries in Cheju-Island, Yeosu and Chungnam. Those were treated to eight concentration; 0, 3.4, 6.7, 10.1, 13.4, 20.2, 27.4 and 33.6 ‰. It was not discrepancy in the survival rate and hatching success rate of fertilized embryos obtained from different regions. Also, in the larvae, the regional difference was not appeared. The survival rate and hatching ability of embryos significantly diminished in the lower groups than 13.4 ‰ compared to 33.6 ‰. After fertilization, namely embryos are tolerant of a wide range of salinity (13.4 - 33.6 ‰). Reduced salinity induced an increase of the malformed embryo and larvae including various deformities; irregular embryos membrane (or yolk sac depression), fin erosion and swim bladder inflation in the flounder embryo. The hatching success of embryos was significantly reduced in lower salinity than 13.4 ‰. Notably, the reduction of larval survival rate significantly was observed in ≤10.1 ‰ treated groups with the same manner of survival rates of the embryos. Additionally, olive flounder was found to be adequate model for measuring external impulses because there are no the regional differences.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.6
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• pp.1828-1833
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• 2016

The purpose of this research was to investigate the bacterial flora of healthy olive flounder larvae (Paralichthys olivaceus) and live feeds (Rotifer spp. and Artemia spp.). The total bacteria counts were $9.2{\times}10^7$ and $1.2{\times}10^{10}cfu/g$ and Vibrio sp.(82.8%) was dominant in rotifers. The total bacteria counts were $3.8{\times}10^6$ and $9.2{\times}10^6cfu/g$ and Vibrio sp.(73.3%) was dominant in artemia. In olive flounder larvae, the total bacteria counts were $1.4{\times}10^6{\sim}8.3{\times}10^7cfu/g$ and V. harveyi (38.5%) was dominant. It might be potential marker of disease outbreak in olive flounder larvae.

• Korean Journal of Ichthyology
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• v.4 no.1
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• pp.20-28
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• 1992

The influence of starvation on morphological change and survival rate of the left eye flounder larvae was examined at the KORDI laboratories in March, 1990. 1. The larvae of left eye flounder began of feed on rotifers in 5 days after hatching. In case of non-feeding, all of the larvae died in 11 days after hatching. The larvae which fed 1 day after the normal first feeding schedule grew normally but 100 of the larvae died in 14 days when the feeding was delayed for 2 days after hatching. 2. With the exhaustion of the yolk, the total length, body length, myotome height and gut height of unfed larvae decreased. Gut height is the most decreased demensions while starving. 3. The ratio of gut height to myotome height in unfed larvae has declined most rapidly compare to other demensions during the starvation. At 13 days after hatching, the ratios of these between fed and unfed larvae were 0.797 and 0.467, respectively. 4. The morphology of starving larvae were characterized as sharpened jaw, projected edge of lawer part of clavicle and slender gut.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.76-77
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• 2003

Olive flounder Paralichthys olivaceus larvae and early juveniles were reared for 43 days after hatching in order to observe the effects of starvation during development and metamorphosis. Morphological, histological and biochemical measurements were made to assess the nutritional condition during growth and starvation from pre-matamorphic through post-metamorphic phases. Two groups of fish were compared ; one with sufficient food supply and one under continuous starvation until death. Among morphometric analyses, both ratios of body height at anus/head height and pre-/post-anal lengths appeared to be sensitive to starvation during which substantial reduction was observed within a day of food deprivation. Histological variables as intestinal and rectal epithelial heights and gall bladder volume changed significantly with onset of starvation. The gut epithelial heights of starving fish decreased with advances in starvation, although they fluctuated during mid-metamorphic phase. In contrast, gall bladder volume increased remarkably soon after starvation. Ontogenetic changes in both gut epithelial height and gall bladder volume were evident, those associated with settlement and/or completion of metamorphosis. Abrupt decrease in the RNA/DNA ratios of starving fish were found right after onset of starvation. Even in the fed fish marked fluctuations in its ratios during metamorphosis were observed, evident by decreasing from late-metamorphic to post-metamorphic stages. These findings suggest that a combination of morphologically and histologically sensitive characteristics, and biochemical measurement could be utilized as a measure to evaluate nutritional condition related to starvation in wild olive flounder larvae and juveniles.

• Journal of Aquaculture
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• v.7 no.1
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• pp.55-61
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• 1994

Triploid fish were induced successfully in olive flounder (Paralichthys olivaceus) by cold shocking fertilized eggs 3 minutes post fertilization at $2^{\circ}C$ for 45 minutes. Percent incidence of triploid was $92.6\%$ in this treatment. Floating rate and fertilization rate of eggs were not significanlty different from that of diploid controls (P> 0.05). However, hatchability and abnormal larvae of triploids were significantly different from that of diploid controls (P< 0.05). Incidence of triploidy was confirmed by erythrocyte measurements and chromosome counts. The surface area of triploid erythrocytes and nucleus was 1.6 times larger than that of diploids. Diploids had 48 acrocentric chromosomes, while triploids had 72.

• Journal of Aquaculture
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• v.8 no.2
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• pp.133-140
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• 1995

Olive flounder (Paralichthys olivaceus) larvae of pre-metamorphic and early metamorphic stage were treated with different concentrations of triiodothyroxine $(T_3)\;and\; thyroxine\;(T_4)$ by immersion (0.02, 0.04, 0.08 and 0.16 ppm) for 11 days. Although $T_3$ was more potent than $T_4,\;both\;T_3\;and\;T_4$ accelerated the settlement time of fish larvae. Duration upto complete settlement in hormone-treated groups was significantly shorter than that in controls. Survival of hormone-treated groups at the pre-metamorphic stage decreased as hormone concentrations increased, however groups treated at the early metamorphic stage were not differ from control. Growth rates of groups treated with high concentration of hormone were slightly lower than that of control except 0.02ppm $T_4$ treated group.

• Journal of Aquaculture
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• v.21 no.3
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• pp.125-132
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• 2008

Seed production of olive flounder Paralichthys olivaceus was performed in a pilot RAS. The growth of juvenile olive flounder and changes in water quality were monitored for the entire production period. The pilot RAS consisted of 8 circular culture tanks($4.0mD{\times}1.0mH$), 2 trickling biofilters($1.7mD{\times}2.0mH$), 2 protein skimmers ($0.8mD{\times}2.5mH$), and 4 sedimentation chambers($0.7mD{\times}1.5mH$). The culture surface area was about $100.5m^2$ and the actual working volume was about $106.9m^3$. As many as 300,000 fertilized olive flounder eggs were initially distributed into 2 culture tanks with the water temperature at $19.0^{\circ}C$. Live feeds such as rotifers and Artemia nauplii were fed until the 32nd day after hatching, and a commercial diet was fed from the 19th day to the end of the experiment. After 70 days, 150,256 juveniles with a body length of $65.8{\pm}3.9mm$ were produced in the RAS, with a daily growth rate for body length of 4.7%/day. At this time, the final culture density was 1,495 individuals $m^{-2}$, and 13.6 L of makeup water, 0.071 kW of electricity and 0.025 L of diesel fuel were used to produce a juvenile olive flounder. During metamorphosis of the larvae, the TAN concentration increased to 0.99 mg/L, which made the larvae sensitive to result in some mortality. However no more massive mortality occurred at the juvenile stage after metamorphosis even at a TAN concentration of 4.25 mg/L and a ${NO_2}^{-}-N$ concentration of 2.45 mg/L.