• Korean Journal of Environment and Ecology
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• v.35 no.3
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• pp.285-293
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• 2021

This study was conducted to elucidate spawning period characteristics and early life development of eight barbel loach, Lefua costata (Balitoridae) at the Jusucheon stream, Okgye-myeon, Gangneung-si, Gangwon-do, Korea between January and December in 2018. The spawning period was estimated to be from May to August, considering the change in the gonad-somatic index, the appearance of young fry, and frequency distribution in egg diameter. It was a multi-spawning type. The gender ratio was 1:0.79 with 1,117 females and 879 males collected. The egg size was 0.24-0.93 mm, with mature and immature eggs found during the spawning period. The size of mature eggs was 0.71±0.02 mm, and the average number of fecundity was 1,786±818 (n=31). Observation of the egg development showed that the fertilized eggs were the sticky, gray, segregated, and demersal type with 0.76±0.03 mm in diameter. The hatching of the embryos began at about 34 hours (hatching rate 50%) after fertilization underwater temperature of 25℃. The average length of the newly hatched pre-larvae was 2.7±0.11 mm. The average length of pre-larvae at 4 days after hatching was 4.5±0.16 mm, and the yolk sac was completely absorbed and entered the post-larvae stage. At 20 days after hatching, the average length of post-larvae was 11.5±0.67 mm, and their fin rays were formed before they transitioned to the juvenile stage. At 100 days after hatching, the average length reached 49.8±2.60 mm, and the appearance and the lateral sideband patterns were similar to those of the adult fish.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.141-148
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• 2009

Sex differentiation and gonad development were investigated in a marine medaka species, Oryzias dancena (Beloniformes; Teleostei). The average time to hatch was 11 days post-fertilization (dpf) at $25^{\circ}C$. Primordial germ cell (PGC) was first observed at 5 dpf and migrated to presumptive gonadal area between the gut and pronephric duct at 9 dpf. Male and female gonads were morphologically differentiated at 12 days post-hatching (dph). Early oocytes at perinucleolus stage as well as the formation of spermatid and efferent duct were observed at 28 dph. At 6 weeks of age, the ovary exhibited yolk granulation in many oocytes, while testis possessed a considerable number of spermatogonia and spermatids. The first ovulation was observed in 9-week-old females, and at the same age, males contained fully-matured spermatozoa. Data obtained in this study indicate that the gonad differentiation of O. dancena is the typical type of differentiated gonochorism.

• Korean Journal of Ichthyology
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• v.24 no.2
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• pp.94-100
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• 2012

The spine loach, Cobitis hankugensis endemic to Korea were collected at the Nokdong River, Unbong-eup, Namwon-si, Jeollabuk-do during June 2007 for study its eggs development and early life history. The eggs were obtained by injecting gonadotropin (LHRH-1) to female and were fertilized by dry method in the laboratory condition. The matured eggs were separative, demersal and light yellowish with $1.29{\pm}0.07mm$ in diameter average. Under $23{\sim}25^{\circ}C$, the eggs were hatched in 45~52 hours after fertilization, and just hatching larvae were $4.5{\pm}0.24mm$ in total length. On 5 days after hatching, they were $6.6{\pm}0.13mm$ in total length and their yolk sacs were completely absorbed. From 25 days after hatching, they became the juvenile stage with $9.0{\pm}0.49mm$ in total length. On the 100 days after hatching, their external forms and band patterns were similar to those of adults with average $27.3{\pm}2.82mm$ in total length.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.21-21
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• 2003

경골어류의 뇌하수체에서는 두 종류의 생식선자극호르몬 (FSH, LH)이 생산되며, 이 호르몬들은 공통적인 α 쇄와 특이적인 β 쇄를 가진다. 연어과 어종들에서, FSH는 난황형성과 정자형성의 역할을 하며, LH는 배우자의 최종성숙을 조절한다. 냉수성 고유어종인 열목어 (Brachymystax lenok)의 멸종을 방지하고 종묘생산을 원활히 하기 위하여 먼저 열목어의 GTHα, FSHβ 및 LHβ 쇄를 cloning하여 염기서열을 결정하였다. 열목어 GTHα, FSHβ 및 LHβ의 cDNA는 산천어의 해당 cDNA와 높은 상동성 (각각 84, 95, 98%)을 보였다. 다음으로 기능적인 생식선자극호르몬을 제작하기 위해서 2개의 쇄를 single-strand로 연결하여 진핵세포를 숙주로하는 시스템에서 생식선자극호르몬을 생산할 수 있는 구조체인 FSHβ-GTHα (235 amino acids) 와 LHβ-GTHα (240 amino acids)를 각각 재조합하였다. 또한 각각의 융합단백질 생산용 구조체의 3'-말단에는 단백질추출이 용이하도록 histidine×6 구조를 첨가하였다. 이상의 단일쇄 FSH와 LH 유전자재조합 산물을 포유동물 유래의 세포 (CHO-K1)에 liposome chemical을 사용하여 유전자도입 후 세포에서 분비되는 단백질을 모니터링하였다. 배지를 부분정제한 후 SDS-PACE로 조사한 결과, LH 재조합 유전자를 도입한 후 48-60 시간째에 약 25 kDa의 단백질로서 관찰되었다. 현재 FSH 재조합 유전자에 대해서도 조사중이며, 향후 이를 재료로 하여 기능형 생식선자극호르몬을 생산하고 추출하기 위한 연구가 계속적으로 수행 될 것이다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.554-558
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• 2000

Reproductive biology of the female red tongue sole, Cynoglossus joyneri was investigated by means of histological methods. Gonadosomatic index (GSI) was the highest in June. Developmental pattern of oocytes was group-synchronous. Egg stalk and yolk nucleus were observed in the early growing oocytes. Reproductive cycle could be classified into the growing ($February{\~}May$), maturation ($May{\~}June$), ripe and spent ($June{\~}August$), and recovery and resting ($August{\~}February$). The absolute fecundity per individual ($TL 28.1{\~}30.8 cm$) was 2,197 and relative fecundity per g body weight was 18.0.

• Korean Journal of Animal Reproduction
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• v.16 no.3
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• pp.247-260
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• 1992

This study was carried out to investigate the histomorphological changes of ovaries obtained from 100 of 1-year-old female Korean loach(misgurnus anguillicaudatus). The light microscopic and ultrastructural changes ofooplasm and follicular membranes of oocytes, were observed by lightand transmission electron microscope during the reproductive cycle. All data were collected from November in 1991 to May in 1992. The results obtained in this study were as follows: The size of the nucleoli and number of the yolk granules increased as the oocytes grown. Yolk granules were loosely deposited in the oocytes as crystalline granules. Due to the presence of large early and late maturing oocytes, their ovaries were enlarged, transparent, granular and yellowish in color. The lattice was broken down at hydration, leaving the egg transparent. As the percentages of fish in LMO and RO stage increased from March to April, mean gonadosomatic index(GSI) values(18.49%) increased. Zona radiata change a squamous into cuboid shape in EMO stage. Processes from the granulosa cells and from the oocyte, microvilli grow and make contact with other in the pore canals of the zona radiata during vitellogenesis, but are withdrawn as the zona radiata becomes more compact and devoid of pore canals during oocyte maturation. Seasonal changes in the microscopic appearance of the ovaries were well correlated with those in both GSI and macroscopic appearance.

• Korean Journal of Ichthyology
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• v.18 no.3
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• pp.266-272
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• 2006

The egg development and early life history of Korean endemic bitterling Rhodeus pseudosericeus were observed under the controlled water temperature, $17.0{\pm}0.5^{\circ}C$. Fertilized eggs are opaque yellow in color, measuring 2.9~3.1 mm in length and 1.6~1.9 mm in breadth. The eggs of this species began to hatch about seventy hours after insemination and the range of total length of larvae were 3.2~3.4 mm. The larvae reached at the heterotrophic stage about twenty-five days after hatching. R. pseudosericeus had a pair of wing-shaped yolk projection during the prelarval stage that is a common character of the genus Rhodeus.

• The Korean Journal of Zoology
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• v.13 no.3
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• pp.68-74
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• 1970

In the previous studies, the present author found that high proportion of the follicular oocytes from mouse and rabbit ovaries are able to resume their maturation division in the anterior chamber of the eye in which they have been incubated by auto- or homoplastic transplantation. Especially in the case of the homoplastic transplantation, it was known that no trouble has been detected in the process of resumption of the oval maturation in particular connection with the antigen-antibody reaction between donor and recipient. These findings provide a possibility that the follicular oocytes from various animals would be matured in the eye even after the xenoplastic transplantation. Under such an assumption, the present studies were performed to examine the behavior of the follicular oocytes in the eye chamber of the animals of different species. For the donor of the follicular oocytes, domestic rabbits, albino rats of Sprague-Dowley strain, and albino mice of A-strain bred in our laboratory were used. The oocytes obtained from the ovarian follicules were introduced to the anterior chamber of the eye of different species of animals, with an exception of rabbit in which only the female animals were used as a recipient. The procedures of collection of ova, introduction to the eye, harvest from the eye ball, fixation, and staining were the same as mentioned in the previous reports (Cho, 1967b; Cho and Kim, 1968). The conclusions obtained are summarized as below. 1. The rabbit follicular oocytes are able to mature in the eye chambers of both male mouse and rat, although the proportion of the maturation is lower than when they are incubated autoplastically in the eye. When the ova were incubated in the male mouse eye for 24 hours, 21 per cent of them showed chromosomes at metaphase I and II, whereas the rate was 32 per cent when they were incubated in the eye of the male rat. These are apparently low comparing to the rate of 52 per cent of autoplastic transplantation. 2. When rat follicular oocytes were transferred into the mouse eye chamber and recovered after 24 hours, 43 per cent of them produced the mataphase I and II chromosomes. This proportion was higher than the result of the homoplastic transplantation which yielded 23 per cent of the ova on maturation. 3. The most striking result was found in the experiment with mouse follicular oocytes. Seventy-six per cent of the oocytes resumed their maturation division within 24 hours after they were transferred into the male rat eye chamber, and this figure was significantly high compared to the result o 55 per cent obtained by the homoplastic transplantation. In the rat eye, the induction of the degenerative ova also was low (19%). On the other hand, the proportion of the oval maturation decreased to 45 per cent, while that of degeneration increased 33 per cent when they were incubated in the eye of the female rabbit. 4. It was apparent from the present experiments that the follicular oocytes can reveal their activation to maturation in the eye chamber which contains aqueous humor which is known to be composed of low protein content and of very little gamma-globulin which acts as an antibody(Oser, 1965), and that it shows higher osmolarity than blood serum(Levene, 1958). Taking these properities into consideration the humor may provide unfavourable environment to the cells and tissues incubated in. However, it could be noteworthy finding that only the follicular oocytes in the eye of the different species can grow in healthy condition although the maturation rates are varied with the animal species. The fact that the rabbit follicular oocytes show the lower proportion in maturation may be due to the greater amount of the yolk granules in the egg cytoplasm than those in the mouse and rat oocytes. That the mouse oocytes incubated in the eye of the rat mouse and rat oocytes. That the mouse oocytes incubated in the eye of the rat resumed their maturation process in greater proportion would e explained by the fact that the rat eye chamber particularly provides the better environment to the mouse oocytes than the eye chamber of mouse does.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.243-252
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• 1985

The mechanism of reproductive cycle of longchin goby Chasmichthys dolichognathus was investigated for the annual variations of gonadosomatic index(GSI), histological changes of gonad, reproductive cycle, and initiating and terminating factors of the breeding season. The experimental fish were captured in the tide pool of Tongbaeksom, Pusan, Korea from February 1983 to September 1984. Experimental fish for the study of initiating and terminating factors of the breeding season were maintained in filtered recirculating aquariums and exposed to various temperature and photoperiod regimes. The ovary is a pair of sac-shaped organ, and the testicular structure is tubular and it is connected to the seminal vesicle which is located at the posterior end of the testis. GSI began to increase from February when the water temperature began to increase and reached peak in April. It began to decrease from August, the top water temperature season, and maintained relatively low values until January. The annual reproductive cycle includes successive six developmental stages : early growing from December to February, late growing from January to March, early mature from February to May, late mature and ripe from March to August, spawning from April to July, degeneration and resting stage from May to December. An experimental study based on the reproductive cycle of this species indicated that rising temperature under long photoperiod during spring stimulated gonadal maturation, whereas terminating factor of the breeding season with recrudescence of the gonads was demonstrated as high water temperature during summer regardless of photoperiod.

• Korean Journal of Ichthyology
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• v.23 no.3
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• pp.198-205
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• 2011

Early life history of the endangered species, Gobiobotia macrocephala was investigated to provide baseline data for biological characteristics and recovery. Adult fish were sampled by spoon net at Hongcheon-gun, Gangwon-do, Korea in April to June 2010. The female's eggs were obtained by injecting Ovaprim and fertilized by dry method in the laboratory. The mature eggs were slightly adhesive and transparent with greyish and average 0.89${\pm}$0.04mm in diameter. The hatching of the embryo took place in about 107 hours after fertilization under water temperature of 23$^{\circ}C$ and newly hatched larvae were average 4.6${\pm}$0.16mm in total length. At 4 days after hatching, they were average 6.1${\pm}$0.20mm in total length and their yolk sacs were completely absorbed. From 15 days after hatching, they entered the juvenile stage and reached at 8.6${\pm}$0.67mm in total length. At the 100 days after hatching, their band patterns and external form were similar to those of adults, and they averaged 31.5${\pm}$3.32mm in total length.