• The Korean Journal of Malacology
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• v.22 no.1 s.35
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• pp.13-22
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• 2006

Gonadosomatic index (GSI), oogenesis and reproductive cycle of Glossaulax didyma were investigated by the cytological histological obserbations and morphometric data. Samples were collected monthly from the intertidal zone of Biin Bay, Seocheon, Korea, for one year. Monthly variations in the GSI showed similar patterns with gonadal development. In the early vitellogenic oocyte, the Golgi complex and mitochondria were invovled in the formation of lipid droplet and yolk precursor. In the late vitellogenic oocytes, the rough endoplasmic reticulum and multivesicular bodies were involved in the formation of profeid yolk granules in the cytoplasm. A mature yolk granule was composed of three components: main body (central core), superficial layer, and the limiting membrane. The spawning season was from early June to late August, and the main spawning occurred between July and August when the seawater temperature was above $19^{\circ}C$. The female reproductive cycle can be classified into five successive stages: early active stage (December to February), late active stage (February to March), ripe stage (April to July), spawning stage (June to August), recovery stage (August to November). Fully mature oocytes were approximately $250-270{\mu}m$ in diameter.

• Applied Microscopy
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• v.31 no.1
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• pp.19-35
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• 2001

Outlines for plasma $estradiol-17\beta$, components, electrophoretic patterns, and ultrastructural changes were obtained in female rainbow trout (Oncorhynchus mykiss) during the seasonal reproductive cycles. Plasma $estradiol-17\beta$ under the natural conditions, exhibited distinct seasonal variation, peaking very late in vitellogenic season during September, decreasing gradually the halt of spawning in December, and ultimately falling during the early stages of seasonal ovarian recrudescence in February and March. This change in $estradiol-17\beta$ appeared to stimulate vitellogenin production as evidenced by increases in plasma calcium, phosphorus, glucose, albumin and total protein levels. The electrophoretic patterns of late maturing or spawning oocytes were stained more intensively than those of late perinucleolus oocytes (molecular weights of approximately 70,000 and 200,000). Two protein bands were found in the SDS-PAGE separation, coincident with the $estradiol-17\beta$ hormone peak. Gonadosomatic indices (GSI) significantly increased from October to January, and showed the highest peak in January, coinciding with the numerically abrupt increase of ripe ova in female. A positive correlation (r=0.701, p<0.01) was established between plasma $estradiol-17\beta$ levels and the gonadosomatic index during the prespawning. The highest level of hepatosomatic index (HSI) observed in December. During the breeding season (December), the gonadotropes were large and filled with GTH-containing inclusions such as granules and globules. The vitellogenic phase began as late perinurleolus oocytes became transformed into early maturing oocytes through the accumulation of yolk, and oocytes reached the late maturing stages as the ooplasm was completely packed with yolk. Marked ultrastructural changed in the granulosa cells during nuclear migration involve the dilation of the rough endoplasmic reticulum and the appearance of the rod-shaped mitochondria with tubular cristae. Microvilli (finger-like projections), from the zona radiata and from the oocyte grew, and made contact with each other in the pore canals of the zona radials during vitellogenesis, but were withdrawn as the zona radiata became more compact and devoid of pore canals during oocyte maturation. The zona radiata grew to a tripartite structure such as an outer thin homogeneous layer, and two inner thick helicoidal layers (zona radials interna and zona radiata externa). Under the normal conditions, the ovarian follicle influenced the histological development and periodical secretion of the hormones , sufficient for a oogenesis and gonadal steroid production.

• Development and Reproduction
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• v.12 no.3
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• pp.231-241
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• 2008

The present study was designed to clarify aspects of the annual reproductive cycle of the fresh water mitten crab, Eriocheir japonicus inhabiting Sumjin river, and to determine the adequate conditions of temperature, photoperiod and salinity on the gonadal maturation and breeding of adult female crabs. Based on the seasonal changes of GSIs and gonadal histology of adult crabs, the annual reproductive cycle could be divided into 4 periods as follows: previtellogenesis period (from September to October) when GSIs were low value and ovaries had oocytes in previtellogenesis stage and meiotic prophase stage; maturing period (from November to March of the next year) when GSIs increased gradually and ovarian oocytes accumulated yolk globules; spawning period (from April to June) when high value of GSI of female was kept and ovigerous female appeared; resting period (from July to August) when GSIs decreased rapidly, and vitellogenic oocytes degenerated. Gonadal maturation was influenced by water temperature, but not photoperiod and salinity. GSI more increased in experimental regime of $18^{\circ}C$ than that of $10^{\circ}C$ regardless of photoperiod conditions (12L12D and 15L9D). However, in $26^{\circ}C$ regime of both photoperiod conditions, the value of GSI was not changed, and vitellogenic oocytes were not observed. Spawning was considerably influenced by water temperatures and salinities regardless of photoperiods. Vitellogenic female crabs did not spawn at $10^{\circ}C$ in any salinity conditions. However, at $18^{\circ}C$ and $26^{\circ}C$, over a half of rearing female crabs spawned in condition of 30% sea water (salinity 9.6%o) and 60% sea water (salinity 19.2%o), while no female spawned in freshwater condition (salinity 0.0%o).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.423-435
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• 1984

The reproductive cycle of the small filefish, Rudarius ercodes was investigated based on the annual variations of gonadosomatic index(GSI) and hepatosomatic index(HSI) by electronic and photic microscophy. The specimens used were collected at the coastal area of Benden island, Sizuokagen, Japan, from September 1982 to August 1983. GSI began to increase from March, starting season of longer daylength 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 November and February without any evident variation. The annual variations of HSI were not distinct in male filefish and were negatively related to GSI in female : HSI decreased in the summer season when the ovary was getting mature and reached the maximum in the winter season when the ovary was getting retrogressive. The ovary consisted of a pair of saccular structure with numerous ovarian sacs branched toward the median cavity. Oogonia divided and proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophile cytoplasm showed several scattering nucleoli along the nuclear membrane. when the oocytes growing to about 300 ${\mu}m$, nuclear membrane to disappear with nucleus migrating toward the animal pole. The regions of protoplasm were extremely confined within the animal hemisphere in which most of cytoplasms were filled with yolk materials and oil drops. After ovulation, residual follicles and growing oocytes remaining in the ovarian sacs degenerated. But perinucleatic young oocytes without follicles formed were not degenerated, and growing continuously still in the next year. Mitochondria and endoplasmic reticula in the cytoplasm remarkably increased with oocytes maturing and yolk accumulating. Those were considered to be functionally related to the yolk accumulation. Five or six layers of possible vitellogenin, oval-shaped disc structures with high electron density, appeared in the apex of follicular processes stretching to the microvilli pits of mature oocytes. Testis consisting of a pair of lobular structures in the right and left were united in the posterior seminal vesicle, Cortex of testis was composed of several seminiferous tubules, and medulla consisting of many sperm ducts connected with tubules. Steroid hormone-secreting cells with numerous endoplasmic reticula and large mitochondria of well developed cristae were recognized in the interstitial cells of the growing testis. Axial filament of spermatozoon invaginated deeply in the central cavity of the nucleus and the head formed U-shape with acrosome severely lacking, mitochondria formed large globular paranuclei at the posterior head, and microtubular axoneme of the tail represented 9+9+2 type. The annual reproductive cycles could be divided into five successive stages : growth(March to July), maturation(May to September), Spawning(mid May to early October) and resting stages(October to February). The spawning peak occurred from June to August.

• Korean Journal of Environmental Biology
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• v.18 no.3
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• pp.323-330
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• 2000

Early life history and spawning for Odontobutis interrupta were observed in the laboratory during May-August 1999 with a condition of natural habitats in the field. Optimal water temperature for spawning was between 17.5 and 22.$0^{\circ}C$ and appropriate water depth and current velocity in the natural habitat ranged 0.3-0.6 m and 0.1-0.3 m/sec, respectively. Ovary maturation index peaked at about 100mm in the total length and their values gradually decreased after the size. Male fishes showed a territory and courtship behavior to adult females and the males frequently pushed upper-ventral part of females for egg releases. After females spawned, the males guarded the egg masses and supplied dissolved oxygen using pectoral fins. According to observation of egg development in the laboratory, blastodisc formed in 1hr 17 min after the fertilization, cleavaging at 36-minute interval regularly. Blastulation occurred in 7 hr 12 min after the fertilization, with gastrulation after 11 hr 11 mins and formation of york plug after 32 hr 48 min. Embryo was formed in 33 hr 45 min after fertilization and optic vesicles appeared in 47 hr 27 mins when 30-31 somites were formed. Cardiac primordium was formed in 65 hr 15mins and its beat averaged 44- 48 time/min. Pectoral fins were formed in 138 hr 40 min, air-bladder and black vesicles were observed in lower portion of young fish. Embryo hatched from she-11 membrane after about 10 days and juvenile was 5.8$\pm$0.2mm in total length 3.0$\pm$0.5mg in weight.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.121-129
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• 1997

The five species of genus Cobitis from Korea were investigated by electron microscopes to clarify the adhesive membranes on zona radiata. In the late vitellogenic stage the adhesive membranes could be classified into two form as follows: 1) granular form of Cobitis lutheri, C. striata, C. sinensis, and C. sinensis-longicorpus, 2) villous form of C. melanoleuca. Although C. lutheri, C. striata, C. sinensis, and C. sinensis-longicorpus possessed the same granular form, it was evident that fine structure of the zona radiata varied according to species. The adhesive membranes and fine structures of zona radiata in Cobitis showed a species specificity closely related to their habitats and spawning properties.

• The Korean Journal of Zoology
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• v.39 no.4
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• pp.419-425
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• 1996

The five spedes of genus Iksookimia from Korea were investigated by electron microscopes to clarify the adhesive membranes on zona radiata. In the late vitellogenic stage the adhesive membranes could be classified into three form as follows: 1) villous form of Iksookimia koreensis, I pumila, and I. hugowolfeldi, 2) cotton-shaped form of I. longicorpus, and 3) vine-shaped form of I. choii. And although I. koreensis, I pumila, and I. hugowolfeldi possessed the same villous form, It was evident that fine structure of the zona radiata varied according to spedes. The adhesive membranes and fine structures of zona radiata in Iksookimla showed a species specificity related to closely their habitats and spawning properties.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.323-328
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• 1982

Kareius bicoloratus (Basilewsky) is one of the commonly found right-eye flounders and widely distributed in the coastal waters of Korea and Japan. On December 11,1980, the ailthors carried out an experiment to obtain a large number of fertilized eggs from wild adult fish caught by a trawler. The fish were obtained from Maisaka fish market, Shizuoka Prefecture, Japan. The egg is pelagic, spherical in shape and measuring 1.014-1.04 mm in diameter. The yolk as well as the egg capsule is colorless and transparent, and contain no oil globules. The hatching took place in 73 hr 45 min after fertilization at the water temperature $8.0-9.5^{\circ}C$. Newly hatched larvae are 3.09-3.146 mm in total length, with the anus situated in the middle of the body. The marginal fin does not have Pigment cells and myotome number is 17+20=37. Within one day after hatching, the larvae attained 3.77 mm in total length, and there appeared three or four melanophore on yolk sac. When the larvae attained 3.96 mm in total length, melanophores began to appear on the eye ball. Two days after hatching, the larvae attained 4.05 mm in total length, most of yolk material was absorbed, and the caudal fin began to grow at the terminal part of the notochord. When the larvae attained 4.21 mm in total length, mouth and eyes began to move. After 3 days, the larvae attained 4.342-4.394 mm in total length, alimentary canal differentiated, melanophores appeared on the lower jaw and posterior part of the fin membrane. When the larvae attaind 4.576 mm in total length, marginal line of dorsal fin membrane became concave.

• Korean Journal of Ichthyology
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• v.13 no.3
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• pp.181-189
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• 2001

Spawning behavior of the Takifugu pardarlis (Temminck et Schlegel) was observed on the Jook-do coast in Tongyong from March 1997 to June 1999. The spawning ground was locted in the intertidal zone between Tongyong and Koje-do. Its bottom was mainly gravels and stones, and its depth was 0.5~1.0 m. Spawning season was from the end of the March to the middle of May. During the spawning season, the mature fishes formed school a of 10~30 individuals, then moved to the spawning ground together. When a mature female spawned eggs, the attendant males fertilized them at the same time. The fertilized eggs obtained from the parent fishes caught at the spawning ground were adhesive, opaque and spherical, measuring 1.14~1.24 mm (mean 1.19 mm, n = 50) in diameter with numerous tiny oil globules. Hatching period was about 205 hours after fertilization at water temperature of $18.0{\pm}0.5^{\circ}C$. The newly hatched larvae were 2.92~3.10 mm (mean 3.01 mm, n = 20) in total length (TL), had a large yolk, and 11~13+14~15 = 25~28 myomeres. At 5 days, the larvae had attained 3.79~3.85 mm (mean 3.82 mm, n = 20) in TL and had transformed into the postlarval stage. At 15 days, the postlarvae had attained 7.78~7.90 mm (mean 7.84 mm, n = 20) in TL. At 21 days, had larvae attained 10.15~10.27 mm (mean 10.21 mm, n = 20) in TL and had reached the juvenile stage. All fins were formed with a complete set of fin rays having the following counts: dorsal fin rays 11~12; anal fin rays 9; pectoral fin rays 14~15; caudal fin rays 11~12.

• Journal of Aquaculture
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• v.9 no.1
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• pp.83-92
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• 1996

This study was conducted to compare the immunochemical properties of female-specific serum proteins (vitellogenin, VTG) and egg yolk proteins in female fusilier, Caesio diagramma. VTG of fusilier was identified and characterized by using immunochemical analysis. Two types of VTG (VTG1 and VTG2) reacted clearly with antiserum against egg proteins, were confirmed in the serum of mature female. The results of sephacryl S-300 showed that the molecular weights of VTG1 and VTG2 were 560,000 and 410,000, respectively. Yolk proteins, E2 and E3, were isolated from egg extracts, and molecular weights of them were estimated 410,000 and 170,000, respectively. The treatment of $17\beta$-estradiol ($E_2$) to males has induced the synthesis of VTG of which immunological characteristics seems to be similar to the yolk proteins. The results suggest that VTG can be synthesized in the liver by the action of $E_2$ stimulation, and incorporated into the oocytes through the blood circulation. The level of serum $E_2$ was moderately high throughout the spawning period of June. The level of serum VTG was also sustained at high in May and June. The concentration changes of serum $E_2$ and VTG were corelated to the ovarian development in female fusilier. The results indicated that $E_2$ may have some important roles for the vitellogenesis in female fusilier. Also) the VTG can be a precursor protein of yolk not only because it could be synthesized in the liver then incorporated into the oocytes but also because an egg yolk protein had the similiar molecular weights and antigenecity with VTG.