• Korean Journal of Ichthyology
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• v.29 no.4
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• pp.252-257
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• 2017

The oogenesis of the Microphysogobio yaluensis was investigated using light microscopy. Various developmental oocytes appeared in the ovary of the M. yaluensis. The oogenesis is largely divided into four stages: nuclear-chromatin stage, peri-nucleoli stage, vitellogenesis (yolk vesicle and yolk granule stages), and mature stage. The nuclear-chromatin is distributed in a large germinal vesicle as threads. The peri-nucleoli stage has many acidic nucleoli lining at the inner side of the nuclear membrane and an egg envelope just weakly starts. As the oogenesis gradually proceeds, they change to the vitellogenesis stage. The oocyte become to drastically increase and the marginal area of the ooplasm is covered with many vacuoles showing no negative reactions with hematoxylin and eosin staining, called the yolk vesicle stage. Many yolk vesicles-owned oocyte largely increase and as the development continues, its ooplasm is changed from the yolk vesicles to the yolk granules of eosinophilic. At the mature stage, lots of granules merged into a big yolk mass, acidophilic. Even at the mature stage, the egg envelope was still thin between the ooplasm and the follicular layer of the oocyte.

• 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.

• Development and Reproduction
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• v.22 no.3
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• pp.213-223
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• 2018

Ultrastructural studies on oocyte differentiation and vitellogenesis in the oocytes of female Kareius bicoloratus were investigated by transmission electron microscopy. The Golgi complex in the cytoplasm is involved in the formation of yolk vesicles that contain yolk carbohydrates in the yolk vesicle of oocytes in the early vitellogenic phase. In this phase, many pinocytotic vesicles (PVs), which are formed by pinocytosis, contain yolk precursors (exogenous substances). These substances are associated with exogenous heterosynthetic vitellogenesis. In yolked oocytes in the late vitellogenic phase, two morphologically different bodies, which formed by modified mitochondria, appear in oocytes. One is a multivesicular body (synthesized by autosynthetic vitellogenesis), and the other is a yolk precursor (an exogenous substance formed by heterosynthetic vitellogenesis). The multivesicular bodies (MVB) are taken into the yolk precursors (YP) and are transformed into primary yolk globules. However, after the YP mix with exogenous PVs near the zona pellucida, they are transformed into primary yolk globules. Vitellogenesis of this species occurs via endogenous autosynthesis and exogenous heterogenesis. Vitellogenesis occurs through endogenous autosynthesis, which involves the combined activity of the Golgi complex, mitochondria and MVB formed by modified mitochondria. However, heterosynthesis involves pinocytotic incorporation of extraovarian precursors (such as vitellogenin in the liver) into the zona pellucida (via granulosa cells and thecal cells) of the yolked oocyte.

• Journal of Fisheries and Marine Sciences Education
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• v.28 no.5
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• pp.1231-1243
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• 2016

The ultrastructural study on oocyt development and the process of vitellogensis in the oocytes during oogenesis in female Pampus echinogaster were investigated by electron microscope observations. In the previtellogenic phase, in particular, several intermitochondrial cements appear in the cytoplasms of the chromatin nucleleolus oocyte and perinuclear oocyte. The number of intermitochondrial cements are associated with the multiplication of the number of mitochondria in the early developmental stage. In the early vitellogenic phase, the Golgi complex in the cytoplasm of the yolk vesicle oocyte is involved in the formation of yolk vesicles containing carbohydrate yolks. At this time, many pinocytotic vesicles containing yolk precursors (exogenous substances) by pinocytosis are observed in the cytoplasm near the region of initial formation of the zona pellucida. In the late vitellogenic phase, two morphological different bodies, which formed by the modified mitochondria, appeared remarkably in the yolked oocytes. The one is the multivesicular bodies and another is yolk precursors. The multivesicular bodies were transformed into the primary yolk globules, while yolk precursors were connected with exogeneous pinocytotic vesicles near the zona pellucida. After the pinocytotic vesicles were taken into yolk precursors, the yolk precursors were transformed into the primary yolk globules. Thereafter, primary yolk globules mixed with each other, eventually, they developed into secondary and tertiary yolk globules. In this study, vitellogenesis of this species occurred by way of endogenous autosynthesis and exogenous heteogenesis. Vitellogenesis occurred through the processes of endogeneous autosynthesis, involving the combined activity of the Golgi complex, mitochondria and multivesicular bodies formed by modified mitochondria. However, the process of heterosynthesis involved pinocytotic incorporation of extraovarian precursors (such as vitellogenin in the liver) into the zona pellucida (by way of granulosa cells and thecal cells) of vitellogenic oocytes.

• Korean Journal of Ichthyology
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• v.19 no.1
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• pp.16-23
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• 2007

Oocyte surface in two Korean minnows, Rhynchocypris oxycephalus and R. kumgangensis was examined by light and electron microscope. In two species, the development of the oocyte was similar, but the follicular layer surrounding full-grown oocyte showed an evident difference. In R. oxycephalus, the follicular layer at the yolk vesicle stage became bilaminar with the retention of its outer squamous cell layer and the acquisition of an inner cuboidal or round cell layer just over the zona radiata. As the oocyte grows, the cuboidal cells of the inner follicular layer began to be replaced by columnar cells. At the yolk granule stage, the columnar cells secreted mucin to their cytoplasm (adhesive materials) and then surround the entire oocyte, as bundles of fence-shaped structures. Whereas, although the follicular layer of R. kumgangensis had an outer squamous layer and an inner cuboidal or round cell layer at the yolk vesicles as in R. oxycephalus, no inner cells were more changed with the retention of its cuboidal or round cells. Finally, in R. kumgangensis, the adhesive materials did not occur. In Korean two minnows, the structural difference in the oocyte surface seems to be related to their habitats and spawning characteristics as well as taxonomic characters.

• Applied Microscopy
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• v.40 no.2
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• pp.65-71
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• 2010

Kribensis, Pelvicachromis pulcher is a teleost belonging to Cichlidae. The oogenesis was investigated by light microscope. The ovary was located between intestine and air bladder, a yellowish and ellipsoidal shape with the major axis 20mm and the minor axis 5 mm. Cytoplasm of oogonia in early stage was basophilic and many nucleoli were located at inside of nuclear membrane. In primary oocytes, yolk vesicles were distributed only in the marginal area and egg envelope was not formed on the outside of an egg. In secondary oocytes, the egg envelope was formed and yolk vesicles in the cytoplasm were increased than the earlier stage. The basophilic substance of cytoplasm was changed to acidic. Some yolk vesicles started forming small yolk mass except the surrounding nucleus. In case of matured egg, size of egg were increased. The yolk vesicles were changed to yolk mass in accordance with development. The yolk mass contained crystal-like structures. In conclusion, the oogenesis of Pelvicachromis pulcher was summarized by the increase in cell size, the formation and the accumulation of yolk, and the decrease of basophilic substance in the cytoplasm. The oogenesis of Coreoleuciscus splendidus is similar with other teleost. But there were differences in distribution of yolk vesicle and yolk mass containing cristal-like structures.

• The Korean Journal of Zoology
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• v.34 no.2
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• pp.217-227
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• 1991

Ultrastmctura changes of multivesicular bodies and mitochondria of oocytes of PseudopotamU- Ia occelata Moore were examined with transmission electron microscope in order to follow the process of yolk formation. Yolk granules begin to form at the previtellogenic stages of 50 $\mu$m diameter from multivesicular bodies. Small vesicles and membranous structures within the multivesicular bodies are fused to form the precursors of core bodies of yolk granules. Some vesicles from cytoplasm are also coalesced into the multivesicular bodies. Mature yolk granules are composed of electron-dense core bodies which are seperated from each other by electronopaque small vesicle-like structures. Structural changes of cristae into vesicular shapes and increase in electron density of matrix in mitochondria strongly suggested that mitochondria are in the process of transformation. The transformed mitochondria appear to be basic structures which later become multivesicular bodies.

• Journal of Marine Life Science
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• v.7 no.1
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• pp.55-59
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• 2022

This study was conducted to provide basic information on the sexual mature and reproductive biology of Trichiurus lepturus. During the oogenesis, size of oocyte and nucleus showed the increase tendency but size ratio of nucleolus to nucleus was decreased. In the result of H-E stain, the stainability of the cytoplasm was changed from basophilic to eosinophilic. The egg diameter of initial vitellogenic oocyte was about 63.2 (±12.7) ㎛. In the cytoplasmic cortex, eosinophilic yolk nucleus was observed. The size of mature oocyte was 216.6 (±24.7) ㎛ and GVBD (germinal vesicle breakdown) was observed. The size of ripe oocyte was 317.9 (±80.9) ㎛ and the thickness of zona radiata was 4.2 (±1.7) ㎛. The oocyte developmental type is considered to belong to the group synchronous type. The accumulation of yolk in the oocyte, like most teleost, is thought to be of two types: exogenous and endogenous accumulation.

• Korean Journal of Ichthyology
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• v.26 no.3
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• pp.179-184
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• 2014

A histological study on the egg envelope and oogenesis of Gobiobotia brevibarba (Pisces, Cyprinidae) was carried out by a light microscope and a scanning electron microscope. Various developmental cells appeared in the ovary caught during May 2014, spawning season. For the relative area of oocyte, the ovary consisted of mature stage (74.5%), a vitellogenic stage (yolk granule stage, 16.6% and yolk vesicle stage, 6.6%) and previtellogenic stage (perinucleolus stage 2.2%), which means its spawning season. The cytoplasm of the perinucleolus oocyte is acidic and many nucleoli are located at the inner side of the nuclear membrane. The yolk vesicles, an early vitellogenic stage, has a follicular layer and a zona radiata clearly. Numerous villi, called an egg envelope, begin to form on the zona radiata. The yolk granules, an another vitellogenic stage, proceeds and they show a strong eosinophilic nature. Such yolk granules appeared between the yolk vesicles occupying most cytoplasm, and as the stage proceeds, there are some yolk masses fused with each other. Egg envelope is covered with plenty of villi ($2{\sim}3{\mu}m$ in the length) over the entire egg surface.

• Applied Microscopy
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• v.40 no.1
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• pp.9-14
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• 2010

Coreoleuciscus splendidus is a teleost belonging to Gobioninae, Cyprinidae. The oogenesis was investigated by light microscope. The ovary was located between intestine and air bladder, a grayish and ellipsoidal shape with the major axis 20 mm and the minor axis 5 mm. Cytoplasm of oogonia was basophilic and many nucleoli were located at inside of nuclear membrane. In primary oocytes, yolk vesicles were distributed only in the marginal area and egg envelope was not formed on the outside of an egg. In secondary oocytes, the egg envelope was formed and yolk vesicles in the cytoplasm were increased than the earlier stage. The basophilic substance of cytoplasm was changed to acidic. In case of matured egg, thickness of egg envelope and size of egg were increased. The yolk vesicles were changed to yolk mass in accordance with development. In conclusion, the oogenesis of C. splendidus was characterized by the increase in cell size, the formation and accumulation of yolk, and the decrease of basophilic substance in the cytoplasm. The oogenesis of C. splendidus is similar with other Cyprinidae fishes. But further study on ultrastructural study of fertilized egg envelope will be necessary to get the species specificity.