• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.2
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• pp.129-136
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• 2000

Differentiation and development of the digestive organ of the black sea bream, AcanHepagus schlegeli were studied by means of histological methods. The hatched lawn if TL(total length) $2.0 mm (n=10)$ had a yolk sac of $1,000{\times}590 {\mu}m$ and simple straight digestive tract, which was composed of cuboidal epithelium. In the pre-larval stage of TL $3.5 mm$, digestive tract could be distinguished into esophagus, stomach and intestine, and the exocrine glands were appeared in the pancreas. In this stage mucosal folds, eosinophilic granule cells and brush border were observed in the posterior intestine. Yolky materials were completely absorbed and the brush border was recognized in the free surface of anterior intestine in TL $3.7 mm$. In the stomach mucosal folds began to appear from TL $4.0 mm$. In this time the zymogen granules were recognized in the cytoplasm of pancreatic exocrine cells. In the post-larval stage ranged from $4.5 to 5.0 mm$ in TL, hepatic cords started to develop, and the mucous secretory cells of PAS positivewere observed at esophagus and intestine. In the post-larval stage ranged from $6.3 to 7.0 mm$ in TL, histological layer of esophagus and intestine could be distinguished into serous membrane, muscular layer, submucosal layer and mucosal layer. From over TL $9.0 mm$, stomach could be distinguished into cardiac, fundic and pyloric portion, and the gastric gland began to appear at mucosal fold of fundic stomach. In the juvenile stage ranged from $10.0 to 11.0 mm$ in TL, histological structures of esophagus and intestine were similar to those of adult. From over TL $15.0 mm$, histological structures of stomach were similar to those of adult. Structural and functional digestive organ of black sea bream was present from the juvenile stage ranged from $15.0 to 17.0 mm$ in TL.

• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.177-183
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• 1999

This study was conducted to observe the spawning behavior and early life history of chinese minnow, Rhynchocypris oxycephalus reared in the laboratory. The spawning period of Rhynchocypris oxycephalus is from May to June in nature. The eggs of Rhynchocypris oxycephalus were spawned on the sand and surface of the gravel. The fertilization eggs were demersal in shape and adhesive, released as a clump forming a thin layer and their diameter were 1.70~1.90mm (mean 1.80 mm, n=20). Hatching of eggs was started in 88 hour 45 minute after fertilization at water temperature $19{\pm}0.5^{\circ}C$ and finished in 90 hour. Newly-hatched larvae were measured 4.87~5.02 mm in total length (TL, mean 4.94 mm), mouth and anus were not opened. 6 days old larvae were 6.32~6.56 mm in TL (mean 6.44 mm). Yolk sac was almost absorbed, mouth and anus was began to open. 13 days old larvae were 6.74~6.91 mm in TL (mean 6.82 mm). Part of Dorsal fin was began to rising and myomere number was 15+23=38. 25 days after hatching, total length of larvae was 8.45~8.60 mm (mean 8.52 mm). Dorsal and anal fin rays became differentiated, and also caudal part of the notocord flexion was achieved at $45^{\circ}C$. In the time, growth rate was higher than the other stage. Aggregate numbers of all fin rays were completed at 16.39~16.57 mm in TL (60 days after hatching), at which time the larvae reached the juvenile stage, but fin-fold on ventral was remained yet. External features of adult specimens were almost completed at 80 day old juveniles (18.69~18.87 mm in TL).

• Korean Journal of Ichthyology
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• v.12 no.4
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• pp.236-243
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• 2000

The purpose of present the study was to describe the spawning behavior and early life history of the grass puffer, Takifugu niphobles. The grass puffer was caught at the spawning ground on the coast Dolsan, Korea from May to the 1998. Artificial fertilization was carried out to get fertilied eggs. Spawning season was from the end of May to the beginning of July on the coast of the Dolsan, Korea. Form 2~6 days before the spring tide the aduct males and females began to aggregate in the shore water, and they spawned in the upper part of intertidal zone exposed to air among pebble stone. The fertilized eggs were demersal, transparent and spherical in shape, and its diameter were 0.87~0.95 mm with several oil globules of 0.0014~0.0540 mm. Hatching began about 146 hours after fertilization under water temperature $21.2{\sim}22.3^{\circ}C$. The newly-hatched larva was 2.02~2.24 mm in total length (TL, mean: 2.14 mm), with 22~24(8~9+14~15) myotomes, and mouth and anus was not yet open. In 3 days after hatching it was measured 2.64~2.93 mm in TL (mean: 2.76 mm), and yolk sac was completely absorbed and transformed to postlarval stage. In 15 days after hatching it was measured 4.43~4.82mm in TL (mean: 4.59mm), and the caudal notochord flexion started. The larvae reached the juvenile stage in 28 days after hatching and attained 7.55~7.65mm in TL (mean: 7.60mm), and all fin-rays were formed.

• Development and Reproduction
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• v.5 no.1
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• pp.39-45
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• 2001

Black rockfish Sebastes schlegeli is one of scopaenid fish giving birth to yolk-sac larvae and distributed around the coast of Korea and Japan, and is one of main species which is cultured in Korea. The difffrentiation of thyroid gland and the changes of thyroid hormones (THs) concentrations in the whole body during early development of this species were examined and the relationship between thyroid gland and their growth will be presented. Total length (TL) and body weight (BW) of the larva at the parturition were 6.3${\pm}$0.1 mm and 3.6${\pm}$0.1 mg, respectively. The larvae transformed to juvenile after 30th day after parturition. According to Hoshiai(1977), they had gown into stage Fl (TL 13.2${\pm}$0.9 mm, BW 46.5${\pm}$1.5 mg) at 50th day. The thyroid gland of black rockfish was first observed histologically in hatching larvae in mother fish. The larvae just after parturition have 1${\sim}$3 of the thyroid follicles diffrentiated between basibranchial bone and ventral aorta, at the base of the first gill arch. In this time, thyroid follic1e number (TFN),thyroid follicle diameter (TFD) and thyroid cell height (TCH) were 1.6${\pm}$0.8 pieces/inds., 18.1${\pm}$0.6 ${\mu}$m and 4.1${\pm}$0.2 ${\mu}$m, respectively. TFN and TFD at 50th day were increased to 32.5${\pm}$6.9 pieces/inds. and 41.5${\pm}$1.7 ${\mu}$m, respectively. These results indicate that they are related to the growth of black rockfish during early development. However, TCH indicates that the activity of thyroid gland appearedat special day, eg. 5, 20 and 50th day, suggesting that TCH may have some role in the physiological activity. L-thyroxine (T$_4$)concentration decreased sharply to 10 days after parturition, and at 25th day (metamorphosis stage) increased markedly to 3.44${\pm}$0.93ng/g fish. After this time, T$_4$ concentration decreased at 35th day, but then increasedagain to the highest concentration, 5.63${\pm}$0.70ng/g fish. 3,5,3'-triiodo-L-thyronine (T$_3$) concentration declined sharply from just after pafurition (4.96${\pm}$1.90 ng/g fish) to 5th day (0.30${\pm}$0.07 ng/g fish). However T$_3$ concentration increased markedly to 0.95${\pm}$0.11 ng/g fish at 30th day and then did not significantly change until 45th day, increased also sharply to 1.67${\pm}$0.23 ng/g fish at 50th day.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.509-519
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• 1987

Annual reproductive cycle of the Damselfish, Chromis notatus collected monthly at the four coastal areas around Chejudo, Korea are studied on the bases of histological observations of gonadal tissue and various quantitative variables including gonadosomatic index (GSI), fatness, egg diameter composition and the first maturity. The ovary consisted of a pair of saccular structure with many ovarian sacs. Oogonia proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophilic cytoplasm showed several nucleoli along the nuclear membrane. When the oocytes reached about $450{\mu}m$ in diameter, nucleus migrate toward the animal pole, nuclear membrane disappeared and most of cytoplasm were filled with yolk materials and oil drops. After ovulation, residual follicle and growing oocytes remaining in the ovarian sacs degenerated. But early young oocytes without follicle layer were not degenerated, and growing continuously till the next year. The testis consisted of a pair of lobular structures in the right and left were united in the posterior seminal vesicle. Cortex of testis was composed of many sperm ducts connected with lobuli. GSI began to increase from March, starting season of longer day length and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between October and February without any evident variation. The annual reproductive cycle could be devided into five successive stage : growing(April to Many), mature(May to August), ripe and spent (June to August) and recovery and resting stage(September to March). The spawning peak occurred from June to August. According to the frequency distribution of egg diameter, Chromis notatus was a polycyclic species to spawn twice or more in a spawning season. Fatness, correlated with gonadal phases, was remarkably decreased by spawning. Percentage of the first maturity . in femate and male fish ranging from 7.0 to 7.9 cm were $50\%$ and from 9.0 to 9.9 cm in total length $100\%$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.2
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• pp.71-96
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• 1977

Early development Linuparus trigonus(von Siebold) has been studied based on the samples collected monthly in Je-ju Island, Korea from February, 1975 to January, 1977. Gametogenesis, reproductive cycle, embryonic development were investigated by histological mettled, and morphological description was made on the first phyllosoma larva which reared in the laboratory. Testis is composed of two tubular duct which are symmetrical with H-shaped appearance. Outer layer of testis is of fibrous connective tissue capsule. In the lumen there is a convoluted seminiferous tubule with interstitial tissue. Ovary is a pair of symmetrical blind tubular lobes, and the midportions are connected each other. The ovary consists of a couple of ovarian sacs partitioned by two-layered connective tissue fibers. Proliferation of spermatogonia are observed all the year around on the germinal epithelium of seminiferous tubule. Partial spermatogenesis is always in progress, and the spermatozoa appear all the year around in the tubules. Nutrition of early oogonia is supplied by fibrous mesenchyme which is abundantly distributed in ovarian sacs. Oocytes grow and couplete maturation divisions in the follicle layers. They finally develop into mature ova before spawning. Reproductive cycle is classified into four successive stages; multiplication stage from September to December, growing stage from January to March, maturation division stage from April to May and mature stage from June to August. Spawning takes place from May to August with peak spawning from Into July to early August. Cleavage type is superficial. Blastopore is formed in blasto-disc region which is proliferation of blastoderm cells. Germinal layers are also derived from tile region. Mesoderm formation is originated from endodermal cells which are formed front the blasto-disc region. The endodermal cells are separated by the process of delamination from yolk sac and take part in the formation of the mid-gut. Morphological characteristics of first phyllosoma larva are different from the larvae of other Palinurid and Scyllarid species.

• Korean Journal of Poultry Science
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• v.16 no.3
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• pp.175-192
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• 1989

A total of 9, 012 cases was submitted for diagnosis of chicken diseases to Veterinary Research Institute, Rural Development Administration from domestic chicken farms during 18 years from 1971 to 1988. Of them, 6, 181 cases diagnosed as the infectious disease were investigated for the detection rate of infections on basis of you, season , and chicken age. The results obtained were summarized as followings：1. Detection rate or the infections was lowest as 49.3% in the year 1973, and highest as 78.6% in 1985 (average 68.6%). 2. Of infections detected, bacterial diseases were most frequent (32.6%), and followed in order by viral (26.3%), parasitic (7.7%), and fungal diseases (2.1%) in geneal. 3. The most frequently detected bacterial diseases in order of prevalence were mycoplasmosis (8.8%), colibacillosis (8.5%), and staphylococcosis (5.8%), and followed by salmonellosis pullorum disease , yolk sac disease, and salpingitis (0.8-1.5%). 4. In viral diseases, 7.5% of infections detected was lymphoid leukosis and 7.2%-Marek's disease, 4.4%-Newcastle disease, 2.0%-infectious laryngotracheitis, 1.7%-infectious bursal disease, and 1.0%-avian encephalomyelitis, while detection rate of infectious bronchitis, egg drop syndrome '76, and inclusion body hepatitis was less than 1.0%, respectively. 5. The most prevalent parasitic disease was coccidiosis (4.5%), followed by ascariasis (1.4%). The detection rate of other parasitic diseases including leucocytozoonosis, black head , heterakiasis, and ectoparasitosis was very as 0.2-0.7%, respectively： In fungal diseases, 2.0% of infections was detected as aspergillosis, and followed by candidiasis (0.1%). 6. Detection rate of the infections on basis of season was somewhat higher in summer. (27.7%), and autumn (27.7%) than in winter (23.5%), and spring (21.5%) in general. In bacterial, viral, and fungal diseases, there were the similar tendencies of detection rate as in infections, while parasitic diseases were much highly detected in summer (34.3%), and autumn (39.5%) than in any other season. 7. Among bacterial diseases colibacillosis was most frequently detected in summer, and staphylococcosis in autumn. In detection rate of viral diseases, Marek's disease, infectious laryngotracheitis, and infectious bursal disease was highest in summer, lymphold leukosis, fowl pox and egg drop syndrome '76 in autumn, and infectious trachitis in winter, repectively. The majority of important parasitic diseases including coccidiosis were highly detected in summer and autumn. 8. On basis of chicken age, detection rate of infections were highest in chicken of growing period between 30 and 150 days of age (41.4%), and followed by 35.3% in laying chicken over 150 days of age, and 17.3% in chicken of brooding age under 30 days of age. Bacterial, and parasitic diseases were most frequently detected in chicken of growing period, viral diseases in chicken of growing, and laying period as nearly equal rate of detection, and fungal diseases in chicken of brooding age.