• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.35-43
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• 1996

The appearance of the primordial germ cells (PGC's), early gonadogenesis, sex differentiation and sex ratio of the embryo in the viviparous teleost, Ditrema temmincki were investigated by using photomicroscopy. The PGC's were first observed in the fibrous mesenchymal tissue located between the early alimentary tract and the dorsal body wall in the late embryonic development stage. During the period from the hatching to the individual total length (TL) of 4.0 mm the PGC's were evenly distributed in the fibrous mesenchymal tissue between alimentary tract and body wall. But the period of TL 5.0 mm mesenchymal tissue separated from the dorsal body wall, the PGC's moved to the posterior mesenchymal tissue and formed the primitive gonad. During the early gonadogenesis, differentiation of the testis and ovary were distinguished from the arrangement of the germ cells and somatic cells. Gonad of embryo in TL 10.0 mm can be separated into the ovary and testis by external morphology. The testis had a separated form which was consisted with two lobes, and the ovary had a fused form in half-posterior part. In the testicular differentiation of the embryo, histological pattern of the seminiferous tubule appeared when TL of the embryo was to be 25.0 mm, for the seminal vesicle was formed In the individual TL of 30.0mm. The testis of the embryo with TL of 45.0 mm was similar to that of the adult fish in the external and internal structures. In the ovarian differentiation, formation of the ovigerous folds and the ovarian cavity were clearly observed when the TL reached to 30.0 mm. The ovary from the individual with TL of 60.0 mm was differentiated into a similar ovary as seen in the adult fish in the external and internal structure. Right before parturition the total length of the individual was approximately 63.0 mm of which the individual embryo has an ovary containing the oocytes in the chromatin nucleolus stage, or a testis containing the spermatogonia, respectively. And the embryonic sex ratio of female to male was 1.65 : 1. Ditrema temmincki is dioecism and the pattern of sex differentiation is belonged to a differentiation type.

• Journal of Life Science
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• v.25 no.10
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• pp.1184-1195
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• 2015

The zebrafish is an emerging vertebrate model organism in reproductive biology. The oocyte maturation of zebrafish is triggered by maturation inducing hormone (MIH, 17α,20β-Dihydroxy-4-pregnen-3-one). In almost all animals, the oocyte maturation is governed by activation of pre-MPF which consists of cyclinB and inactive Cdk1. In the oocyte of Xenopus and mice, the activity of Cdk1 is regulated in two ways, one is the interaction with cyclinB and the other is phosphorylation/dephosphorylation of T14/Y15 residues on the Cdk1 by Wee1 and Cdc25. Unlike Xenopus and mice that have a sufficient amount of pre-MPF, pre-MPF is absent in GV oocyte of most teleost including zebrafish. Therefore, the activation of MPF during zebrafish oocyte maturation might totally depend on de novo synthesis of cyclinB proteins. It is reported that the translation of maternal mRNA is regulated by combination of several RNA binding proteins such as CPEB, Dazl, Pum1/Pum2, and insulin-like growth factor2 mRNA-binding protein 3 in the zebrafish oocytes. However, the definitive mechanism of these proteins to regulate the translation of stored maternal mRNAs remains to be elucidated. Therefore, the investigation of the maturation process of the zebrafish oocyte will provide new information that can help identify the role of translational control in early vertebrate oocyte maturation.

• Korean Journal of Veterinary Research
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• v.43 no.3
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• pp.339-347
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• 2003

The regional distribution and relative frequency of some endocrine cells in the pancreas of the Korean aucha perch, Coreoperca herzi Herzenstein belonging to the family Serranidae in order Perciformis, were observed using specific mammalian antisera against serotonin, insulin, glucagon, somatostatin and human pancreatic polypeptide (hPP) by peroxidase antiperoxidase (PAP) method. The pancreas was divided into four portions (principal and secondary islets, exocrine and pancreatic duct regions). In addition, the pancreatic islet regions were further subdivided into three regions (central, mantle and peripheral regions). Spherical to spindle or occasionally round to oval immunoreactive (IR) cells were demonstrated in the pancreatic islets and exoccrine portions, but no cells were detected in the pancreatic duct portions. In the principal islets, serotonin-IR cells were not detected but most of insulin-IR cells were located in the central regions and they were also demonstrated in the mantle and peripheral regions in moderate and rare frequencies, respectively. Glucagon- and hPP-IR cells were mainly situated in the mantle regions but the cells were also demonstrated in the peripheral regions in relatively lower frequency. Somatostatin-IR cells were evenly distributed in the central and mantle regions in a few frequency and cells were also demonstrated in the peripheral regions in rare frequency. Cell clusters were consisted of hPP-IR cells that were situated in the peripheral to mantle regions. In the secondary islet portions, serotonin-IR cells were randomly distributed throughout the whole pancreatic islet regions but lower frequency was detected in the peripheral regions compared to that in central and mantle regions where cells were detected in a few frequency, respectively. Insulin-IR cells were restricted to the central regions in numerous frequency and glucagon-IR cells were evenly distributed in the mantle and peripheral regions in moderate frequencies, respectively. Somatostatin-IR cells were observed in the central and mantle regions in moderate and a few frequencies, respectively. In addition, hPP-IR cells showed similar distributional patterns to those of glucagon-IR cells except cells were also located in the central regions in rare frequency. In the exocrine portions, only glucagon- and hPP-IR cells were demonstrated in rare and a few frequencies, respectively. In conclusion, the regional distribution and relative frequency of pancreatic endocrine cells of the Korean aucha perch showed general patterns, which were observed in other teleost. However, some species-dependent different distributional patterns and/or relative frequencies were also demonstrated especially to serotonin-IR cells. In pancreas of the Korean aucha perch, insulin-IR cells were the most predominant cell type followed by glucagon-, somatostatin-, hPP- and serotonin-IR cells.

• Korean Journal of Ichthyology
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• v.7 no.2
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• pp.150-159
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• 1995

First sexual maturity, monthly changes in gonadosomatic index and reproductive cycle of viviparous teleost surfperch, Ditrema temmincki were investigated under photomicroscopy. Samples were collected from May 1992 to August 1993 in the vicinity of Suyoung Bay, Pusan, Korea. Body length at the first sexual maturity in female and male were 12.5cm and 13.5cm, respectively. Gonadosomatic index(GSI) in female reached the maximum in June(just before parturition) and male GSI reached the maximum in October(just before copulation). The testis is composed of a number of seminiferous tubules, and spermatogonia are originated from the germinal epithelium on the seminiferous tubule. The ovary consists of several ovigerous folds, and oogonia are originated from the inner surface of the germinal epithelium within the ovigerous fold. Annual reproductive cycle was classified into the following successive periods : in male, growing period from May to August, maturation period from September to October, copulation period from November to December, and degeneration and resting period from January to April, and in female, growing period from September to October, copulation and maturation period from November to December, gestation period from January to June, and resting period from July to August. Hepatosomatic index(HSI) in male appeared to be negatively correlated with gonadosomatic index, but that in female showed to be positively correlated.

• Development and Reproduction
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• v.2 no.1
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• pp.75-80
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• 1998

메기 정자는 그 길이가 약 62.5 \mu m이며 구형의 핵, 짧은 중편 및 꼬리를 ㄱ진 일반적인 메기류 정자의 미세구조적 특징을 나타내었다. 정자는 대부분의 경골어류의 정자에서와 같이 첨체를 가지고 있지 않았으며 염색질은 완전치 농축되어 있었다. 핵와(nuclear fossa)는 약 0.6 \mu m 함입되어 있었고 그 속에 기부 중심립과 말단 중심립의 일부가 포함되어 있었다. 두 중심립은 140 \circ C의 각도로 배열되어 있었으며 말단 중심립에서 9개의 부수체가 언형질막을 향하여 배열되어 있었다. 미토콘드리아는 중편 세포질에서 2층 또는 3층으로 배열되어 있었으며 핵의 후반부와 꼬리의 기부를 둘러싸고 있었다. 꼬리는 축사만으로 구성되어 있었으며 lateral fins는 관찰되지 않았다. 메기 정자의 가장 큰 구조적 특징은 중편 세포질에 구성되어 있는 관구조(tubular structure)이었다. 대부분의 경골어류의 정자는 중편 세포질에 미토콘드리아만을 포함하고 있으나, 메기 정자에서는 중편 세포질의 전반부에 미토콘드리아가 포함되어 있고, 후반부에는 소관이 모여 망상구조를 형성하는 관구조가 잘 발달되어 있었다. 이와 같은 관구조는 현재까지 Characiformes의 정자 이외의 다른 경골어류에서는 보고된 바 없으며 이러한 구조는Characiformes과 메기류의 계통학적 관계를 연구하는데 매우 중요한 형질로 여겨진다. ^u The spermatozoa of Silurus asotus are appoximately 62.5 \mu m in length and relatively simple cells composed of spherical head, a short midpiece and a tail as in most Siluriformes. The ultrastructure of the spermatozoa of S. asotus is characterized by the following features. The nucleus measuring about 1.5 \mu m in length is depressed with a deep nuclear fossa of about 0.6 \mu m in length, two fifth of the nuclear diameter. The fossa contains the proximal centriole and the half of the distal centriole. Two centrioles form an angle of approximately 140 \circ to each other. the nine satellite rays radiate from the outer surface of the distal centriole. the mitochondrea surround the basal nucleus and the axoneme, and are arranged in two or three layers in the postnuclear cytoplasm. The lateral fins are lost in the sperm tail. The most significant feature is manifested in the midpiece. The midpece comprises two parts, the mitochondria and the tubular structure unlike other teleost fishes containing only the mitochondria. The tubular structure was reported only in the spermatozoa of Citharinus belonging to the characiformes of teleost fishes. Thus it is considered to be a good characteristics for the study of phylogenetic link between Siluriformes and Characiformes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.438-449
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• 1996

Development of alimentary tract and nutrient absorption in embryo of the viviparous teleost surfperch, Ditrema temmincki were investigated with histochemical methods. Just after hatching mouth of the embryo was opened, and the end part of alimentary tract was opened in TL 4.0 mm. Mucosal folds in the alimentary tract appeared at posterior region from TL 5.0 mm. In TL 30.0 mm, the alimentary tract of the embryo could be distinguished into pharynx, esophagus, anterior intestine, mid intestine, posterior intestine, rectum and anus. From over TL 50.0 mm, the internal histological patterns of the alimentary tract showed similar structures as seen in the adult. The mucous cells in the pharynx were positively reacted to PAS in TL 7.0 mm. PAS positive goblet cell appeared in the intestine from 25.0 mm, from TL 30.0 mm in the rectum, from TL 40.0 mm in the anus and from 50.0 mm in the esophagus. Yolky materials were absorbed completely in TL 6.0 mm. PAS positive polysaccharide absorptive cells began to appear at the posterior parts of the intestine in TL 7.0 mm and appeared in TL 13.0 mm at the rectum, in TL 15.0 mm at the anterior intestine and in TL 40.0 mm at the anterior part of anus. During the gestation period, nutrient absorptive type of the embryo within the maternal body is a placental analogues type of metrotrophy.

• Applied Microscopy
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• v.41 no.3
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• pp.163-168
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• 2011

Tiger barb (Puntius tetrazona Bleeker, 1855) is a teleost belonging to Cyprinidae. The oogenesis of tiger barb was investigated by light microscope. The ovary was of white and ellipsoidal shape with the major axis 2 cm and the minor axis 1 cm. Cytoplasm of oogonia was basophilic and many nucleoli were located at inside of nuclear membrane. In early stage of primary oocyte, yolk vesicles were distributed only in the marginal area. In secondary oocyte, the egg envelope was formed and yolk vesicles was formed in the cytoplasm. 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. Also, there is not the formation of oil droplets in cytoplasm. In conclusion, the oogenesis of tiger barb was characterized by the increase in cell size, the formation of yolk, the decrease of basophilic substance in the cytoplasm, and formation of yolk mass.

• Applied Microscopy
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• v.39 no.1
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• pp.9-15
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• 2009

The ultrastructure of the fertilized egg envelope in Cichlasoma managuensis belonging to Cichlidae were investigated by routine light and electron microscopes. The fertilized eggs of Cichlasoma managuensis was of the light yellow, non-transparent, ellipsoidal, adhesive and nonfloted type. The size of fertilized egg was the major axis $1.92{\pm}0.08\;mm$, the minor axis $1.43{\pm}0.04\;mm$. The egg envelopes have a single micropyle, which is thought to the pathway of sperm in the area of the animal pole. An outer surface of fertilized egg envelope was covered by a adhesive reticular structures and the fertilized egg envelopes consisted of two distinct layers; an outer adhesive layer and an inner layer of $13{\sim}15$ horizontal lower electron density lamellae alternating with interlamellae of higher electron density. The external shape of fertilized egg is common trait of fishes belonging to Cichlidae and these ultrastructural characters of fertilized egg envelope can be utilized in taxonomy of teleost.

• Applied Microscopy
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• v.35 no.2
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• pp.89-96
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• 2005

The ultrastructures of the fertilized egg envelope from Hyphessobrycon serpae belonging to Characidae was studied using scanning and transmission electron microscopes to get systematic fundamental data for classification of species and to confirm whether micropyle is a common trait of Characidae or not. The fertilized egg was of colorless, transparent, spherical, adhesive and demersal type. There were not oil droplets in vitelline membrane and attached structures in the outside of fertilize egg envelope. The egg envelope had a single micropyle resembling the pathway of sperm in the area of the animal pole. The micropyle was surrounded by 13 to 15 protruded lines of the egg envelope in a radiated form. The outer surface of fertilized egg envelope was covered by reticular adhesive fibrous structures and irregularly arranged by pore canals. The fertilized egg envelope consisted of three distinct layers an outer adhesive fibrous layer with high electron density, a middle layer with pore canals, and an inner layer consisting of 6 to 7 lamellae alternating layers with interlamellae of lower electron density. These ultrastructural characters of fertilized egg envelope form Hyphessobrycon serpae can be utilized in taxonomy of teleost, and as fundamental data for study on early development of fertilized egg. It seems that the morphology of micropyle is a common trait of Characidae

• Fisheries and Aquatic Sciences
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• v.8 no.3
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• pp.142-150
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• 2005

The effects of photoperiod, temperature, and fish size on oxygen consumption (OC) in the black porgy Acanthopagrus schlegeli, a euryhaline marine teleost, were studied using a closed recirculating seawater system with a respiratory chamber. Fish reared in indoor recirculating seawater tanks were divided into two groups: small (15.7-55.8 g, mean 38.1$\pm$15.9 g) and large (108.7-238.8 g, mean 181.8$\pm$54.9 g) fish. The OC of the fish showed a clear diel rhythm, with higher values in the daytime and lower values at night, in accordance with light (09:00-20:59 h) and dark (21:00-08:59 h) cycles. The OC of the fish increased linearly with the water temperature. The OC was the highest at 10:00 h, one hour after the onset of daylight and was the lowest at 03:00 h, six hours after dusk. The average OC at $20^{\circ}C$ during the light period was as high as 219.8 mg $O_2$/kg/h in the small fish and 156.3 mg $O_2$/kg/h in the large fish, while during the dark period it was as low as 130.5 and 110.4 mg $O_2$/kg/h, respectively. The OC during the dark period, which showed limited variation, could be regarded as the resting OC, and was 107.6, 130.5, and 219.8 mg $O_2$/kg/h at 15, 20, and $25^{\circ}C$, respectively, in small fish, and 52.3, 110.4, and 171.0 mg $O_2$/kg/h in large fish. As the body weight of black porgy increased, the OC decreased exponentially and the relationship was expressed as OC=1,222.8$BW^{-0.567}$, OC=1,113.2$BW^{-0.448}$, and OC=1,495.3$BW^{-0.468}$ at 15, 20, and $25^{\circ}C$, respectively. At a fish density of 14.5 g/L at $20^{\circ}C$, black porgy had the highest OC per breath compared to fish at the same density at 15 or $25^{\circ}C$. This suggests that the black porgy responds to the stocking density (15 kg/$m^3$) and water temperature ($20^{\circ}C$) conditions commonly observed in intensive aquaculture with the deepest breath and the highest metabolic activity.