• Journal of fish pathology
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• v.19 no.2
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• pp.99-108
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• 2006

Diseased tiger puffer (Takijugu rubripes) showed anorexia and severe anemia in the gills. In wet mount preparations Heterobothrium sp. with 4 sets of clamps on the opisthohaptor attached to the gill filaments of the diseased fish. From the drum-shaped filter for filtration of the culturing water and the sediment of aquarium held the diseased fish in the laboratory, their eggs forming long strings through connection of the bipolar filaments could be easily collected. The parasites with 4 pairs of clamps on the opisthohaptor were 2.38mm in length and 0.71 mm in width, but had no isthmus which was separated the opisthohapor from the body proper. The parasites could be easily distinguished from Heterobothrium tetrodonis and H. okamotoi in the absence of distinct isthmus, and resembled H. yamagutii described from the gills of Takifugu xanthopterus in Japan. Their eggs were yellowish spindle in shape and 180-200 x 5-6 Iffil in size, which were pointed at both ends. The eggs were linked to adjacent egg shells like a string of beads by the filaments. Onchomiracidia, ciliated larvae spawned from the eggs were 133 Iffil (120-146 Iffil) x 751ffil (68-80 Iffil) in size. The length of the ciliates was 12 Iffil in the anterior part of the larvae and 14 Iffil in the posterior part. Round or leaf-shaped young parasites attached on the secondary gill lamellae. There was a tendency that most of round smaller parasites without an opisthohaptor were found in the middle part of the gill lamellae while leaf-shaped larger ones with a opisthohaptor attached on the distal part of the gill filaments. Each clamp of mature parasites grasped one secondary gill filament which resulted in bending of the filaments and hyperplasia of the epithelium and mucous cells. In the branchial cavity around the pseudobranch, mature parasites grasped the adjacent ones by means of the clamps, and the epithelia of the branchial cavity around the parasites showed severe irregular hyperplasia and erosion with strongly PAS-positive mucous cells.

• 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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.3
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• pp.217-226
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• 2012

Reproductive ecology of the sharp toothed eel, Muraenesox cinereus was investigated based on the samples captured in southern Korean waters from January 2010 to December 2011. Gonadosomatic index began to increase in April, and reached maximum between July to August. After spawning it began to decrease from October. Reproductive season was estimated to April-September, with peak in July. Fecundity was proportional to the size of the female, with the clutch size varying from 56,000 eggs in the smallest female (anal length, 27.0cm) to 1,400,000 eggs in the largest (anal length, 49.5cm). Size at 50% sexual maturity ($AL_{50}$), determined from mature females, were 21.9cm. Annual reproductive cycles of this species could be divided into four successive stages; immature stage (October-February), maturing stage (March-May), mature stage (June-August) and spent stage (August-October).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.194-202
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• 2011

Maturation and spawning of the Shotted halibut, Eopsetta grigorjewi was investigated based on the samples captured in South Korean waters from January 2008 to December 2009. Gonadosomatic index began to increase in December, and reached maximum between January to March. After spawning it began to decrease from May. Reproductive season was estimated to January-April, with peak in February. Fecundity was proportional to the size of the female, with the clutch size varying from 170,000 eggs in the smallest female (total length, 28.9cm) to 1,300,000 eggs in the largest (total length, 41.5cm). Size at 50% sexual maturity (TL50), determined from mature females, was 28.8cm. Annual reproductive cycles of this species could be divided into six successive stages; immature stage (May-October), nucleolus stage (November-January), yolk vesicle stage (January-February), vitellogenic and ripe stage (January-April) and spent stage (April-May).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.3
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• pp.226-231
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• 2004

Maturation and spawning of Acentrogobius pflaumi were studied using samples collected from the Gwangyang Bay, Korea, from January to December, 1999. The gonadosomatic index (GSI) of the female was the highest in May. The spawning season lasted from May to June. There was a significant difference in the 1 : 0.59 sex ratio between males and females (p<0.01). The percentage of sexually mature females was over $50\%$ for the size group between 4.5 cm and 4.9 cm, and $100\%$ for the size group over 5.5 cm in body length. The size of eggs spawned was between 0.4 to 0.6 mm, and the spawning occured once a year. Fecundity varied between 3,600 and 9,700 eggs. The relationship between the fecundity and body length of the fish was expressed in the fecundity equation as; $F=0.294{\times}10^3\;BL^{1.899}.$ The first spawning length was 4 cm BL.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.368-375
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• 2010

Maturation and spawning of the Blackthroat seaperch, Doderleinia berycoides were investigated based on the samples captured in Korean waters from January 2008 to December 2009. Gonadosomatic index began to increase in June, and reached maximum between July to September. After spawning it began to decrease from October. Reproductive season was estimated to July-September, with peak in August. Fecundity was proportional to the size of the female, with the clutch size varying from 115,500 eggs in the smallest female (TL〓28.2cm) to 652,000 eggs in the largest (TL〓33.5cm). Size at 50% sexual maturity ($TL_{50}$), determined from mature females, was 29.6cm. Annual reproductive cycles of this species could be divided into six successive stages; immature stage (October-May), nucleolus stage (June-July), yolk vesicle stage (July-August), vitellogenic stage (June-September), ripe and spent stage (August-October).

• The Korean Journal of Malacology
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• v.29 no.2
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• pp.97-103
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• 2013

In the present study, we monitored the early development of Saccostrea kegakia subtropical oyster species distributing on rocky intertidal off the northern Jeju Island using scanning electron microscope (SEM). The female oyster collected in early August, 2012 were fully mature exhibiting relatively small eggs ($46.5{\pm}1.4{\mu}m$ in diameter) in the gonad, while testis of the mature male oysters were filled with fully developed sperms of 36.9 ${\mu}m$ in length. The fertilized eggs developed into 2-cell stage with polar body after 1 hr 20 min of fertilization, then followed by Morula stage (3 hr 20 min), Blastula stage (4 hr 50 min), Gastrula stage (7 hr), and trochophore larvae stage (9 hr 30 min). The observed early development of S. kegaki in this study was similar the early development of other oysters, although size of the fertilized eggs were somewhat smaller.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.1
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• pp.89-95
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• 2018

The maturation and spawning of black scraper, Thamnaconus modestus were studied using samples collected monthly from March, 2015 to February, 2016 in the coastal waters off Middle East Sea, Korea. The gonadosomatic index (GSI) of female was the highest in June. The spawning periods lasted from March to September based on histological observation of female gonad development. The percentage of sexually mature females estimated from a logistic function was over 50% for the size group 18.02 cm (total length, TL). The size of eggs spawned was between 0.40 to 0.58 mm. Fecundity varied between 185,648 and 9,747,250 eggs. The relationship between the fecundity and TL of the fish was expressed in the fecundity equation as $F=0.0297TL^{5.4835}$.

• Korean Journal of Ichthyology
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• v.29 no.3
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• pp.197-204
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• 2017

Life history of the Siberian stone loach, Orthrias toni, were investigated using samples collected from Buk Stream, Goseong-gun, Gangwon-do, Korea. Growth was rapid between April and October when water temperature exceeded $10^{\circ}C$, but growth almost stopped from November-March when water temperature was below $10^{\circ}C$. Age groups for O. toni estimated by frequency distribution of total length in spawning season (May) indicated the 60~81 mm is 1-year old, the 82~99 mm group is 2-years old, the 100~119 mm is 3-years old, and the 120~140 mm is more than 4-years old. Total length range by sex was similar, and sex ratio (♂/♀) was 0.73. Spawning season according to the gonadosomatic index (GSI) was May with water temperature $14{\sim}17^{\circ}C$, and almost all fish were mature after one year old. Fecundity increased rapidly with age with an average of $4,460{\pm}3,302$ ($mean{\pm}SD$). Size of mature eggs was $0.87{\pm}0.03mm$ in diameter irrespective of age.

• Applied Microscopy
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• v.25 no.3
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• pp.63-74
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• 1995

The development of pale chub oocyte from the immature oogonium to mature oocyte was investigated by light and electron microscope. The cytoplasm of pale chub oogonia was acidic and many vesicles were located at inner side of nuclear membrane. In primary oocytes, yolk vesicles were distributed in cytoplasm. Also, fibrous materials and protuberances were distributed on the surface of zona radiata. The nucleus of secondary oocyte was enlarged and yolk vesicles in cytoplasm migrated to zona radiata. In early egg, yolk mass are formed and yolk vesicles were located at inner side of zona radiata. Three-layered zona radiata was about $3{\mu}m$ in thickness. The three layers were an outer fibrous material layer, a middle nurse cell layer in which microvilli of early egg cytoplasm contact with processes of nurse cells, and an inner layer with high electron density. In mature egg, euchromatin and a germinal vesicle were developed, mitochondria, free ribosomes, and yolk mass were distributed in cytoplasm. But, yolk vesicles were disappeared. Specially, zona radiata of matured eggs were better thin than the one of immature eggs In conclusion, it is summerized that the oogenesis of pale chub were the increase of cell size, the formation and accumulation of yolk, the decrease in nucleat electron density, changes of zona radiata, and the development of microvilli.