• Journal of Aquaculture
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• v.16 no.4
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• pp.240-244
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• 2003

The primitive gonad development in Paralichthys olivaceus was classified into (ⅰ) primordial germ cell (PGC), (ⅱ) genital ridge type (GRT), (ⅲ) primitive gonad type I (PGT I) and (ⅳ) primitive gonad type II stages. In the control group, PGC was recognizable on the 3rd days after hatching, and the primodial gonad after 24th days, while it was around the 22nd day after hatching in the group exposed to PCBs 3.0 $\mu\textrm{g}$/L for 30 days. Likewise, the progress of kidney development was recognized in four stages; unitubular type of mesonephric duct (UTMD), the branched mesonephric duct (BMD), convoluted tubule formation (CTF) and glomerulus appearing (GA) stage. It was structurally completed between the 25th and 30th day after hatching in two groups. There was no significant difference (p>0.05) in the time scale of development of gonad, and kidney between control and the PCBs - exposed group.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.5
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• pp.398-403
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• 2006

Gonad development and the gametogenic cycle of pen shells, Atrina pectinata, collected from November 2004 to October 2005 in the coastal waters of Jangheung, Jeollanam-do, Korea were investigated histologically. The clams are dioecious. The gonads consist of a number of gametogenic follicles. The sex ratio (Female:male) was 1:1.2. The gonad index (GI) reached a maximum in May and a minimum in July. The condition index (CI) reached a maximum in April and a minimum in June. The gonadosomatic index (GSI), GI and CI all increased with gonad development. The gametogenic cycle of the clam could be divided into five stages: the degenerative/inactive (August to October), early active (November to March), late active (December to April), ripe (May to June) and spent (June to July) stage.

• Development and Reproduction
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• v.25 no.4
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• pp.299-303
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• 2021

The ascidian Halocynthia aurantium (sea peach), a marine invertebrate, belongs to the same genus of the phylum Chordata along with the ascidian Halocynthia roretzi (sea pineapple), which is one of the model animals in the field of developmental biology. The characteristics of development and reproduction of H. aurantium are not yet known in detail. In order to find out the spawning period of H. aurantium, we investigated development of the gonads during the annual reproductive cycle. Testis and ovary were both in the bisexual gonads (ovotestes) of H. aurantium, which is a hermaphrodite like H. roretzi. In H. aurantium, the right gonad was longer and slightly larger than the left gonad throughout the year. In each gonad, the number of the testis gonoducts was slightly higher than that of the ovary gonoducts. These features were similarly observed in H. roretzi. However, the number of the testis gonoducts and the ovary gonoducts in each gonad of H. aurantium was about half that of H. roretzi. The gonads of H. aurantium contracted during the winter and summer seasons. The gonads decreased to the smallest size around February, and then started to increase again in March. The gonads were most developed in September of the year. Therefore, it is estimated that the spawning of H. aurantium begins around this period.

• Animal cells and systems
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• v.5 no.1
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• pp.37-44
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• 2001

Gonadal development, reproductive cycle, gonad index, meat weight rate, and first sexual maturity of the top shell, Omphalius rusticus were Investigated monthly by histological observations. Specimens were collected from the west coast of Korea during the period from January to December in 1999. O. rusticus is dioecious and oviparous. The gonad is widely situated on the surface of the digestive g1and located in the posterior spiral meat part in the shell. The ovary and the testis were composed of a number of oogenic follicles and several spermatogenic follicles, respectively. Ripe oocytes were approximately 120-130 $\mu$m in diameter. The meat weight rate peaked in June (27.7%), and then rapidly decreased in September (19.5%). Monthly changes in the gonad index in both sexes reached the maximum in June, and then sharply decreased in September. Percentages of first sexual maturity of female and male snails ranging from 9.0 to 9.9 mm in shell heights were 58.3% and 54.5%, respectively, and 100% in those over 11.0 mm in both sexes participated in reproduction. Reproductive cycle of this species can be categorized into five successive stages: in females, early active (October to April), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to January): in males, early active (November to March), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to December). Gonadal development, gametogenesis, reproductive cycle, and spawning were closely related to the seawater temperature.

• Development and Reproduction
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• v.27 no.4
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• pp.221-226
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• 2023

A stem cell niche provides an environment that governs stem cell maintenance and division. Thus, the development of a proper niche is of prime importance to stem cell behaviors. Mechanisms of niche development are beginning to be revealed in the Drosophila male gonad. Niche cells are initially dispersed throughout the gonad, then assemble at its apical tip through the anterior migration of posteriorly located niche cells. The molecular mechanisms of this migration and assembly are still poorly understood. Here we show evidence suggesting that Lin28, an RNA-binding protein and regulator of let7 genesis, might be an intrinsic factor for the anterior migration of niche cells. We found that a dispersed, ectopic niche, a phenotype observed with anterior migration defects, occurs in lin28 mutant gonads. This phenotype is rescued by expression of lin28 in the niche cells. These findings suggest that Lin28 might be required for the anterior migration of niche cells.

• Development and Reproduction
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• v.25 no.3
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• pp.173-183
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• 2021

The incidence of infertility among individuals of reproductive age has been growing due to genetic and environmental factors, and considerable research efforts are focused on solving this issue. Ovarian development is an overly complex process in the body, involving the interaction between primordial germ cells and gonad somatic cells. However, follicles located in the center of the in vitro ovary are poorly formed owing to ovarian complexity, nutrient deficiency, and signaling deficiency. In the present study, we optimized methods for dissociating gonads and culture conditions for the in vitro generation of miniaturized ovaries. The gonads from embryos were dissociated into cell masses and cultured on a Transwell-COL membrane for 3-5 weeks. Approximately 12 follicles were present per in vitro ovary. We observed that miniaturized ovaries successfully matured to MII oocytes in vitro from 150 to 100 ㎛ gonad masses. This method will be useful for investigating follicle development and oocyte production.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.4
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• pp.234-241
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• 1975

Reproductive cycle of Haliotis discus hannai Ino was studied based on the samples which were collected in Yeosu area from January, 1973 to December, 1974. Particular emphasis was paid on the seasonal variation of gonad maturity factor, coefficieot of gonad maturity, fatnesss, and relationship of gonad weight to growth of the abalone. seasonal fluctuation of water temperature and induction of artificial spawnings were also checked. The abalone of this area spawns twice a year: spring spawning(early May-late July) and Autumn spawning(early September-late November). peak spawning occurs from late May to middle of June for spring spawning: it occurs from late September to early November for Autumn spawning. Gonad maturity factor was closely related to the spawning seasons. For the spring spawning Gonad maturity factor reached to its maximum value as 18.84 in April; for the Autumn spawning it reached to its maximum value as 22.65 in September. Annual minimum value was 12.65 in January. Annual maximum values of coefficient of gonad maturity were 44.10 in May and 49.05 in September and the annual minimum was 10.09 in January. Fatnesswas highest in July as 0.221 and it was lowest in October as 0.1058. Ratios of shell length to gonad weight were formulated as follows : $$In\;September\;GW=0.000003710SL^{3.7860}$$ $$In\;January\;GW=0.000021198SL^{2.8564}$$ $$Annual\;mean\;GW=0.00000005013SL^{4.2273}$$ Relations of total weight to gonad weight were formulated as follows : In September GW=0.1918TW-4.9231 In January GW=0.0992TW-0.1759 Annual maan GW=0.1568UW-3.5256.

• Development and Reproduction
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• v.24 no.3
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• pp.225-230
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• 2020

This study reports the presence of mature and bi-sexual phase gonads in red spotted grouper, Epinephelus akaara after less than a year of cultivation in a commercial indoor tank and a net cage. In December 2018, juveniles were placed in an indoor tank and cultured for five months. In June 2019, the fish were transferred to a net cage and cultured until September. The rearing temperatures ranged from 19.86℃-24.65℃ in the indoor tank and 21.86℃-27.65℃ in the net cage. During the net cage culture period, specimens were randomly selected for histological gonad examination. The highest gonadosomatic index (GSI) value was measured in July (3.38±2.53), and dramatically decreased in August (0.44±0.21) and September (0.42±0.30). In July, some mature fish showed signs of vitellogenic stage oocyte development (vitellogenic and oil droplet stage oocytes), but immature fish were in an early developmental stage containing peri-nucleolus stage (PNS) oocytes. Bi-sexual phase gonads containing spermatocytes and spermatids were observed in the lumen and several PNS oocytes. By August and September, most specimens showed early-stage ovary development. However, mature testis (in August) and bi-sexual phase gonads (in September) were also observed. These results provide evidence for early puberty and hermaphroditism in the red spotted grouper.

• Fisheries and Aquatic Sciences
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• v.19 no.1
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• pp.5.1-5.7
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• 2016

The study was conducted to know the cyclic changes in gonadal maturation and to investigate the developmental stages of oocytes and testicular germ cells of an air-breathing fish, Channa striata. Fish were sampled monthly from lentic and lotic environments of three geographical locations of Bangladesh from December to November and the histological analysis of their gonad was done to evaluate the objectives. The highest mean GSI was $5.95{\pm}0.20$ for female in July and $0.14{\pm}0.01$ for male also in July showing that the gonadal development reached its peak during this month. The highest mean oocyte diameter was $1257.50{\pm}24.17{\mu}m$ observed in July implying that the oocyte reached maturity in this month. Histological study of ovary revealed the evidence of early yolk granule stage and late yolk granule stage from April to July. In case of male four stages of spermatogenesis were distinguished and spermatozoa were highly abundant in June and July. So the monthly pooled values of GSI and the analysis of gonadal histology indicated that the peak breeding season of C. striata occurred in July in the lentic and lotic environments. Samples collected from lentic and lotic habitats are suggestive of no difference in the development of the gonad. The results of the present study will be useful for selective breeding programme, conservation and sustainable fishery management of C. striata in its natural habitat.

• Development and Reproduction
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• v.16 no.3
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• pp.185-193
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• 2012

For the gonadal sex management of younger longtooth grouper (Epinephelus bruneus), this work investigated the timing and histological process of ovary differentiation and oocyte development of longtooth grouper larvae and juvenile. Specimens (from 1 to 365 DAH) were collected for gonadal histological study from June 2008 to August 2009. Rearing water temperature was ranged from 20 to $24^{\circ}C$. The primordial germ cells could be observed from 10 to 15 DAH, while undifferentiated gonad occurs from 20 to 50 DAH in longtooth grouper. The initial ovarian phase was 60 to 110 DAH with the formation of ovarian cavity and the increased in size of gonad. The ovarian phase started at 140 DAH with appearance of oogonia. The gonad at 365 DAH appeared to have full of oogonia and primary growth stage oocyte. Formation of ovarian cavity indicates that the ovarian differentiation beginning at 60 DAH in longtooth grouper. The gonads in longtooth grouper differentiated directly into ovaries in all fish examined.