Jeong-In Myeong

Wild and Hatchery Populations of Korean Starry Flounder (Platichthys stellatus) Compared Using Microsatellite DNA Markers

Starry flounder (Platichthys stellatus) is an important sport and food fish found around the margins of the North Pacific. Aquaculture production of this species in Korea has increased because of its commercial value. Microsatellite DNA markers are a useful DNA-based tool for monitoring the genetic variation of starry flounder populations. In this study, 12 polymorphic microsatellite DNA markers were identified from a partial genomic starry flounder DNA library enriched in CA repeats, and used to compare allelic variation between wild and hatchery starry flounder populations in Korea. All loci were readily amplified and demonstrated high allelic diversity, with the number of alleles ranging from 6 to 18 in the wild population and from 2 to 12 in the farmed population. A total of 136 alleles were detected at the 12 microsatellite loci in the two populations. The mean observed and expected heterozygosities were 0.62 and 0.68, respectively, in the hatchery samples and 0.67 and 0.75, respectively, in the wild samples. These results indicate lower genetic variability in the hatchery population as compared to the wild population. Significant shifts in allelic frequencies were detected at eight loci, which resulted in a small but significant genetic differences between the wild and hatchery populations (FST = 0.043, P < 0.05). Further studies with additional starry flounder sample collections are needed for comprehensive determinations of the genetic varieties between the wild and hatchery populations. These microsatellite loci may be valuable for future population genetic studies, monitoring the genetic variation for successful aquaculture management and the preservation of aquatic biodiversity.

Genetic Characterization of Five Hatchery Populations of the Pacific Abalone (Haliotis discus hannai) Using Microsatellite Markers

The Pacific abalone, Haliotis discus hannai, is a popular food in Eastern Asia. Aquacultural production of this species has increased because of recent resource declines, the growing consumption, and ongoing government-operated stock release programs. Therefore, the genetic characterization of hatchery populations is necessary to maintain the genetic diversity of this species and to develop more effective aquaculture practices. We analyzed the genetic structures of five cultured populations in Korea using six microsatellite markers. The number of alleles per locus ranged from 15 to 64, with an average of 23.5. The mean observed and expected heterozygosities were 0.797 and 0.904, respectively. The inbreeding coefficient FIS ranged from 0.054 to 0.184 (mean FIS = 0.121 ± 0.056). The genetic differentiation across all populations was low but significant (overall FST = 0.009, P < 0.01). Pairwise multilocus FST tests, estimates of genetic distance, and phylogenetic and principal component analyses did not show a consistent relationship between geographic and genetic distances. These results could reflect extensive aquaculture, the exchange of breeds and eggs between hatcheries and/or genetic drift due to intensive breeding practices. Thus, for optimal resource management, the genetic variation of hatchery stocks should be monitored and inbreeding controlled within the abalone stocks that are being released every year. This genetic information will be useful for the management of both H. discus hannai fisheries and the aquaculture industry.

Ten new microsatellite markers in cutlassfish Trichiurus lepturus derived from an enriched genomic library

Abstract Cutlassfish (Trichiurus lepturus Linnaeus 1758) is a commercially important fish in Korea. In recent years, the catch of cutlassfish in the coastal waters of Korea has significantly declined. Its genetic characterization has been little studied. To assist conservation and management efforts, we isolated and characterized 10 microsatellite loci using an enrichment method based on magnetic/biotin capture of microsatellite sequences from a size-selected genomic library. To characterize each locus, 30 individuals from a natural T. lepturus population in the coastal waters of Jeju Island, Korea, were genotyped. All loci except two, KTh9B and KTh22A, were polymorphic, with an average of 14.3 alleles per locus (range, 10–22). The mean observed and expected heterozygosities were 0.80 (range, 0.50–0.97) and 0.82 (range, 0.68–0.95), respectively. A significant deviation from Hardy-Weinberg equilibrium was observed at three loci (KTh6B, KTh10, and KTh16). This high variability indicates that these microsatellites may be useful for high-resolution studies of population genetics.

New polymorphic microsatellite markers in Pacific abalone Haliotis discus hannai and their application to genetic characterization of wild and aquaculture populations

Seven new microsatellite markers were developed for the Pacific abalone (Haliotis discus hannai, Haliotidae), and allelic variability was compared between a wild population and a hatchery population in Yeosu, Korea. All loci amplified readily and demonstrated allelic variability, with the number of alleles ranging from 6 to 15 in the wild population and from 3 to 12 in farmed populations. Average observed and expected heterozygosities were estimated at 0.65 and 0.77 in the hatchery samples, and 0.79 and 0.87 in the wild samples. These results indicated lower genetic variability in the hatchery population, as compared with the wild population and significant genetic differentiation between the wild population and the hatchery samples (FST=0.055, p<0.001). These microsatellite loci may be valuable for future population genetic studies and for tracking hatchery samples used in stock enhancement programs.

Comparative genetic diversity of wild and released populations of Pacific abalone Haliotis discus discus in Jeju, Korea, based on cross-species microsatellite markers including two novel loci

Abstract Pacific abalone Haliotis discus discus is an important fisheries resource in Jeju, Korea. For basic information about its current genetic status in relation to stock enhancement, the level and distribution of genetic variation between wild and released stocks of Pacific abalone in Jeju were examined at nine cross-species microsatellite markers including the use of two novel primers. High levels of polymorphism were observed between the two populations. A total of 146 different alleles were found at all loci, with some alleles being unique. The allelic variability ranged from five to 27 in the wild population and from four to 16 in the released sample. The average observed and expected heterozygosities were estimated to be 0.74 and 0.84 in the wild sample and 0.70 and 0.78 in the released sample, respectively. Although a considerable loss of rare alleles was observed in the released sample, no statistically significant reductions were found in heterozygosity or allelic diversity in the released sample compared to the wild population. Low but significant genetic differentiation was found between the wild and released populations. These results suggest that the intensive breeding practices for stock enhancement may have resulted in a further decrease in genetic diversity, and that the cross-species microsatellite markers used in this study represent a potentially efficient means for further genetic studies, providing beneficial information for the protection and management of H. discus discus.

Morphological Analysis of Blind-Side Hypermelanosis of the Starry Flounder, Platichthys stellatus during Early Development

In Pleuronectiformes, blind-side malpigmentation (hypermelanosis) is common in cultured flatfishes, and is economically important. To understand the mechanism of blind-side hypermelanosis in flatfishes, we examined when the malpigmentation initially occurred, and studied how the symptoms proceeded during early development of the starry flounder, Platichthys stellatus. To assess quantitative pattern changes of blind-side skin, we observed morphological development of the whole body from 22 (total length [TL] 10.0±0.2 mm and body weight [BW] 8.8±0.57 mg) to 110 days (TL 23.4±0.7 mm, BW 193.6±23.3 mg) after hatching (DAH), and also examined the malpigmented area rate of blind-side skin and the malpigmented fish ratios. The experimental animals were reared in fiberglass-reinforced plastic (FRP) tanks in water at a temperature of 18.9±1.9°C and salinity of 32.6±0.6 psu and were fed with rotifer and Artemia nauplii from 22 to 48 DAH, and with A. nauplii and commercial feed from 49 to 110 DAH. As results, the first staining patch seen by the naked eye was observed around the area between the anus and pelvic fin or caudal edge of the trunk at 80 DAH (TL 20.6±0.5 mm, BW 112.5±8.8 mg). The pigmented area and the pigmented fish ratios were significantly increased from 80 to 110 DAH. These results indicated that malpigmentation on the blind side of starry flounder was initially observed at about 2 cm in length and 100 mg in weight, and the pigmented domain on the blind-side skin was continually broadened by the differentiation of pigmented cells (melanophores and xanthophores) with growth.

Early Life History of the Sevenband Grouper, Epinephelus septemfasciatus from Korea

This study is conducted to monitor the morphological developmental features of the egg development, larvae and juvenile of Epinephelus septemfasciatus, the fertilized eggs were gotton using artificial insemination. Matured parents are collected from marine caged fish farms in Geomun-ri, Samsan-myeon, Yeosu-si, Jeollanamdo Korea in June 2012. The fertilized eggs were pelagic eggs containing one oil globule, and measured 0.81~0.89 mm (0.85±0.04 mm, n=50) in diameter. In regard to rearing environment, the water temperature is 21.0~23.0°C and the salinity is 32.0~33.2‰. Hatching was observed from 48 hours after fertilization, the mouth and anus of prelarvae was not opened but had egg yolk at newly hatched. 4 days after hatching, the mouth and anus of postlarvae was opened and began to eat Rotifer and was measured 2.40~2.49 mm (2.45±0.03 mm n=10) in total length. 12 days after hatching, postlarvae was measured 3.77~4.67 mm (4.27±0.33 mm) in total length, its the second pole tide of dorsal fin and the first pole tide of pelvic fin was extended longitudinally. 71 days after hatching, juvenile was measured 40.5~45.4 mm (42.6±2.04 mm) in total length. Seven bands were observed in body, and pole tides of dorsal and pelvic fins were shortened.

Digestive Physiological Characteristics of the Gobiidae

In this study, we investigated the characteristics of CCK-producing cells and mucus-secreting goblet cells with respect to stomach fish and stomachless fish of the Gobiidae in order to provide a basis for understanding the digestive physiology. Hairychin goby (Sagamia geneionema), which is stomachless fish, the numbers of mucus-secreting goblet cells is highest in the posterior intestine portion (P<0.05), while CCK-producing cells are scattered throughout the intestine. Gluttonous goby (Chasmichthys gulosus), which is stomach fish, mucus-secreting goblet cells are most abundant in the mid intestine portion (P<0.05), whereas CCK-producing cells are observed only in the anterior and mid intestine portion. Trident goby (Tridentiger obscurus) which is stomach fish, mucus-secreting goblet cells were most abundant in the mid intestine portion (P<0.05). CCK-producing cells are found in the anterior and mid intestine portion. Giurine goby, Rhinogobius giurinus which is also stomach fish, the largest number of mucus-secreting goblet cells showed in anterior intestine portion except for esophagus (P<0.05). CCK-producing cells are present only in the anterior and mid intestine portion. In S. geneionema, digestive action occurs in the posterior intestine portion to protect and functions to activate digestion. In contrast, in C. gulosus, T. obscurus and R. giurinus, their digestive action occurs in the anterior and mid intestine portion to protect and functions to activate digestion. Further studies of the modes of food ingestion by these fish, the contents of their digestive tracts, and the staining characteristics of the goblet cells need to be carried out.

Gill Na + /K + -ATPase Activity and Expression in Black Sea Bream Acanthopagrus schlegelii Exposed to a Hyposaline Environment

대부분의 경골어류는 어체 내부와 외부 환경 사이의 삼투압 차이가 있거나 동일한 환경에서 서식하는데, 이들은 효과적인 삼투압조절(해산어: 저삼투압조절, 담수어: 고삼투압조절)을 함으로써 이온의 항상성 유지 및 생존이 가능하다(McCormick et al., 1989). 아가미는 이러한 삼투압조절을 담당하는 가장 중 요한 외부 기관으로 해수 및 담수에서 아가미의 염류세포는 염 분을 각각 배출 및 흡수하는 기능을 한다(Payan et al., 1984). 이 세포는 주로 2차새변의 기저에 위치하고 있으며, 특히 미토 콘드리아와 Na+/K+-ATPase (NKA)가 풍부한데, 이것은 능동 적 이온 수송과 관련이 있다(Hirose et al., 2003). 경골어류에서 삼투압조절과 관련하여 해수에서 NKA는 Na+를 염류세포 밖 (혈액)으로 배출시키며, 배출된 Na+는 염류세포와 인접한 부세 포(accessory cell) 사이에 밀착연접을 통해 해수로 나간다. 담 수에서 NKA는 염류세포 선단에 위치한 Na+/H+-교환체 또는 Na+채널을 통해 담수의 Na+를 염류세포로 흡수하는데 에너지 를 공급하며, 또한 흡수된 Na+를 혈액으로 보낸다(McCormick, 2001; Hirose et al., 2003). 따라서 경골어류는 외부 염분변화에 적응하기 위해서는 아가미 NKA 활성의 변조는 반드시 필요하 다(Marshall, 2002). 광염성 경골어류의 아가미 NKA 활성은 외부 염분농도와 관련이 있는데, 연어과 어류의 경우 NKA 활 성은 염분농도와 정상관계로 나타나지만(McCormick, 1995), 숭어류, 농어류, 망둥어류 등의 다른 어류에서는 이 두 요인의 관계가 U 형태의 관계(염분농도가 높거나 낮을 때 NKA가 증 가하며, 이 중간의 염분농도에서 NKA가 감소)보고되고 있다 저염분 노출에 따른 감성돔(Acanthopagrus schlegelii) 아가미의 Na/K-ATPase 활성 및 발현 민병화*·박미선·명정인·서정수·박정준·노경언·강덕영

Oxygen Consumption of Long-term Cultured Male Black porgy Acanthopagrus schlegelii in Freshwater by Water Temperature During the Reproductive Period

Oxygen consumption (OC) of male black porgy Acanthopagrus schlegelii reared in freshwater (BFW) and seawater (BSW) during the reproductive period was 165.4±11.0, 77.6±8.0 mg O2/kg/h at 15 , °C 186.2±13.1, 133.4±6.7 mg O2/kg/h at 20 and 267.9±19.1, 198.6±8.3 mg O °C 2/kg/h at 25 , respectively. °C During the non-reproductive period, it was shown as 174.0±7.0, 85.6±5.5 mg O2/kg/h at 15 , 200.6±11.1, °C 119.2±8.7 mg O2/kg/h at 20 and 271.1±7.5, 194.7±16.7 mg O °C 2/kg/h at 25 , respectively. Thus, OC of °C BFW was higher than BSW both for non-reproductive and reproductive period. Also, OC increased in proportion to the rise in water temperature, and there was no difference of OC between BFW and BSW at each water temperature during the reproductive or non-reproductive period. OC of BFW and BSW showed clear circadian rhythms on photic conditions of reproductive and non-reproductive period, and the fish consumed more oxygen during the dark phase than for the light phase. In particular, OC of BFW during the reproductive period increased more sharply compared to non-reproductive period when the increase of water temperature was accompanied by the shift from dark to light phase. This implies that they react to the light more sensitively for reproductive period than for non-reproductive period.