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Kim M.-J.,South Korean National Fisheries Research and Development Institute | An H.S.,South Korean National Fisheries Research and Development Institute | Choi K.-H.,West Sea Fisheries Research Institute
Fisheries Science

Pacific cod (Gadus macrocephalus) is a commercially important species in Korea. However, overfishing in the 1990s caused a strong decline in catch, and in response, artificially cultured juveniles have been released annually to enhance the stocks. Cod fishing has recently increased in Korea, and the variation within the cod population necessitates the study of their genetic characteristics. In this study, we utilized two newly developed and eight previously reported microsatellite markers to examine the genetic characteristics of Pacific cod populations. We compared the genetic diversity and genetic structure of three cod populations from the Korean coasts with three populations from the North Pacific Ocean. Genetic differences were identified in the eastern sea cod population from Korea. These genetic differences included a large number of alleles per locus, a large number of unique alleles, higher frequencies of the most common alleles, and lower gene diversity compared to the other Korean populations. Additionally, the eastern sea cod population was genetically significantly differentiated from the southern and western sea populations in Korea, in which no significant genetic differentiation was detected (FST = 0.033 and 0.031, respectively, P < 0.005). © 2010 The Japanese Society of Fisheries Science. Source

Kang J.-H.,Biotechnology Research Division | Park J.-Y.,Biotechnology Research Division | Jo H.-S.,West Sea Fisheries Research Institute
International Journal of Molecular Sciences

The mottled skate, Raja pulchra, is an economically valuable fish. However, due to a severe population decline, it is listed as a vulnerable species by the International Union for Conservation of Nature. To analyze its genetic structure and diversity, microsatellite markers were developed using 454 pyrosequencing. A total of 17,033 reads containing dinucleotide microsatellite repeat units (mean, 487 base pairs) were identified from 453,549 reads. Among 32 loci containing more than nine repeat units, 20 primer sets (62%) produced strong PCR products, of which 14 were polymorphic. In an analysis of 60 individuals from two R. pulchra populations, the number of alleles per locus ranged from 1-10, and the mean allelic richness was 4.7. No linkage disequilibrium was found between any pair of loci, indicating that the markers were independent. The Hardy-Weinberg equilibrium test showed significant deviation in two of the 28 single-loci after sequential Bonferroni's correction. Using 11 primer sets, cross-species amplification was demonstrated in nine related species from four families within two classes. Among the 11 loci amplified from three other Rajidae family species; three loci were polymorphic. A monomorphic locus was amplified in all three Rajidae family species and the Dasyatidae family. Two Rajidae polymorphic loci amplified monomorphic target DNAs in four species belonging to the Carcharhiniformes class, and another was polymorphic in two Carcharhiniformes species. © 2012 by the authors; licensee MDPI, Basel, Switzerland. Source

Kang D.-Y.,West Sea Fisheries Research Institute | Kim H.-C.,West Sea Fisheries Research Institute
Comparative Biochemistry and Physiology Part - B: Biochemistry and Molecular Biology

To determine whether proopiomelanocortin (POMC) genes are involved in darkening color camouflage, blind-side hypermelanosis, and appetite in flatfish, we isolated and cloned three POMC genes from the pituitary of the olive flounder (. Paralichthys olivaceus) and compared their amino acid (aa) structures to those of POMC genes from other animals. Next, we examined the relationship of these pituitary POMC genes to camouflage color change, blind-side hypermelanosis, and appetite by quantifying mRNA expression. Olive flounder (. of)-POMC1, 2, and 3 cDNAs consisted of 648-bp, 582-bp, and 693-bp open reading frames (ORF) encoding 216 aa, 194 aa, and 231 aa residues, respectively. Structurally, the three of-POMC cDNAs consisted of seven peptides (signal peptide, N-POMC, α-MSH, CLIP, N-β-LPH, β-MSH and β-END [or END-like peptide]) that are similar to those of other fish POMC cDNAs. α-MSH encoded a protein composed of 13 aa and β-MSH encoded a protein composed of 17 aa. The three POMC genes were predominantly expressed in the pituitary gland, but they were also expressed in a variety of tissues, including brain, eye, kidney, heart, testis, and skin. of-POMC2 exhibited the highest expression, while of-POMC3 displayed the lowest expression. The relative levels of of-POMC1 and 3 mRNAs were not influenced by background color and feeding (or fasting), but the relative level of of-POMC2 mRNA significantly increased in response to a dark background and fasting. The relative levels of of-POMC1 and 2 mRNAs were significantly higher in hypermelanic fish; however, we did not determine a direct anorexigenic or orexigenic relationship for the three POMC genes. These results indicate that pituitary POMC genes are related to darkening color change and the differentiation of pigment cells, but they are not directly related to appetite. © 2014 Elsevier Inc. Source

Kang D.-Y.,West Sea Fisheries Research Institute | Kim H.-C.,West Sea Fisheries Research Institute
Fish Physiology and Biochemistry

To study the relevance of density and background color to stress response, appetite, and growth in olive flounder, Paralichthys olivaceus, we reared two duplicate groups of juveniles (total length 4. 46 ± 0. 06 cm, body weight 0. 77 ± 0. 03 g) in flat-bottom aquaria with dark-green (control) and white backgrounds for 120 days. We measured cortisol and glucose levels in blood and calculated the daily food intake, food conversion efficiency, survival rate, and growth rate. To study the relevance of density and background color to malpigmentation (hypermelanosis) on the blind side, we also compared malpigmented ratios and prepro-melanin-concentrating hormone mRNA activities in the brain between the dark-green and white background groups, as well as between a relatively lower density (60 days) and higher density (120 days). Although we measured relatively higher levels of cortisol and glucose in the white background group and over 200 % of coverage area [PCA]), the bright background failed to induce an acute stress response of more than 20 ng/ml cortisol and 40 mg/dl glucose both in 60 days and 120 days, but did enhance appetite and growth. Also, a bright background color delayed hyperpigmentation only at a low density below 200 % PCA, but did not inhibit malpigmentation at a high density of more than 200 % PCA. In addition, below 200 % PCA, expression of MCH mRNA was significantly higher in the white group, but the level was reversed and was lower in the white group at more than 200 % PCA. In conclusion, although did not induce a high stress response over 200 % PCA, the bright background color resulted in a moderate increasing of cortisol level in blood below 20 ng/ml and enhanced appetite and growth. Moreover, at a density below 200 % PCA, the bright color inhibited hypermelanosis with high MCH mRNA activity, but at more than 200 % PCA did not inhibit malpigmentation, and the fish showed low MCH mRNA activity, indicating that the inhibitory effect of a bright background color on hypermelanosis is density dependent. © 2012 Springer Science+Business Media B.V. Source

Kang D.-Y.,West Sea Fisheries Research Institute | Kim H.-C.,West Sea Fisheries Research Institute
General and Comparative Endocrinology

To investigate the involvement of two melanin-concentrating hormones (MCHs) in skin color change and appetite in flatfish, we isolated two forms of prepro-melanin concentrating hormone (pMCHs) mRNA in the starry flounder Platichthys stellatus and compared their amino acid structures to those of other animals. Then, we examined the relationship of the two starry flounder pMCH (sf-pMCH) with physiological color change, blind-side malpigmentation, and feeding by quantifying mRNA expression level. Sf-pMCH1 cDNA had a 387-bp open reading frame (ORF) that encoded a protein consisting of 129 amino acid residues. The sf-pMCH1 protein included a signal peptide composed of 24 amino acid residues; MCH1 encoded a protein consisting of 17 amino acids. The sf-pMCH2 cDNA had a 450-bp ORF that encoded a protein consisting of 150 amino acid residues, which included a signal peptide comprising 23 amino acid residues; MCH2 encoded a protein consisting of 23 amino acids that was structurally similar to mammalian MCH. Reverse transcription-polymerase chain reaction (RT-PCR) revealed that the strongest sf-pMCHs gene expression was observed in the brain and pituitary, but weak or no amplification was detected in other tissues. The expression of sf-pMCH1 was relatively high compared to that of sf-pMCH2 in the brain. The relative levels of mRNA were significantly lower in dark background-reared and hypermelanic fish, indicating that the two pMCHs and background color are related to the physiological and morphological color changes of skin. In term of feeding regulation, we found an obvious functional role of pMCH1 in appetite, whereas the pMCH2 gene was not found to play a role in feeding. © 2013 Elsevier Inc. Source

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