• 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.

• Environmental Analysis Health and Toxicology
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• v.14 no.1_2
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• pp.55-63
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• 1999

Endocrine disrupting chemicals probably cause the cytological or/and morphological changes of germinal cells in gonad. Accordingly, this study was aimed to make sure that the effect of hormone-mimicking chemicals on gonad morphology such as decrease of germinal cells, inhibition of cellular maturation and change in the ratio of germinal cells in the different developmental phase can be observed by histopathological procedures and can be a useful bio-indicator for the evaluation of endocrine disruption by environmental chemicals. In this experiment, female Japanese medaka were exposured to quercetin, a phytoestrogen, at the concentration of 100 $\mu\textrm{g}$/L. quercetin showed the significant decrease in the number and rate of vitellogenic follicular oocytes in the treated group for 4 and 6 weeks. The weak development of yolk could be also observed. We could conclude that quercetin has anti-estrogenic or androgen-like potency by exerting the inhibition effect on oogenesis in fish female- gonad. From the result of this study, the applied methods and techniques can be evaluated to be a useful biomonitoring means for water pollution, expecting a good result of the subsequent study on apoptosis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.1
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• pp.17-22
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• 2022

Successful reproduction in vertebrates necessitates complex interactions along the brain-pituitary-gonad axis, it is determined by gonadotropin releasing hormone produced in the hypothalamus of the brain, gonadotropin synthesized in the pituitary gland, and sex hormone secreted by the gonads. The goal of this study was to secure and test technology for controlling (inhibiting) sexual maturation hormones such as maturation hormones through hormone regulation. We studied the effect on sexual maturation of zebrafish Danio rerio by tamoxifen, anastrozole, exemestane and dopamine 4 kinds of sexual maturation inhibitors to feed and after administration. As a result, 4 kinds of sexual maturation inducing substances were mixed with zebrafish feed, it could be concluded that all of them were effective in inhibiting sexual maturation by reducing mRNA levels of genetic materials related to sexual maturation.

• The Korean Journal of Malacology
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• v.26 no.3
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• pp.201-209
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• 2010

The investigated of survival rate, sex ratio, condition index, gonad development frequency, gonad index, fertilization rate, hatching rate and time required development of D shape larvae of the ark shell, Scapharca subcrenata. Survival rate was lower in heating group compared with control group (P < 0.05). Sex ratio (female:male) observed 1:0.97 in control group, 1:0.62 in heating group. Condition index was significantly higher in heating group than control group (P < 0.05) and higher increased more than water temperature $17^{\circ}C$ of heating group. Gonad development observed slow in control group but more than ripe stage 80% in heating group (21-28 day, $20^{\circ}C$). Gonad index was higher in heating group compared with control group (P < 0.05). Fertilization rate and hatching rate of the ark shell was observed $82.17{\pm}3.55%$ and $63.57{\pm}2.36%$, respectively. The time required development of D shape larvae of the ark shell was observed 15 hour after fertilization. The suggested that results of the ark shell by heating were effective sex maturation and normal egg development.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.41-47
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• 2009

The seasonal reproductive cycle of Gomphina melanaegis collected in the coastal area of Jumunjin, between April 2006 and March 2007, was analyzed. Maturation cycle parameters such as the gonad index (GI), ovarian egg diameter, frequency of developmental stages, protein content, and RNA/DNA variation in the gonads were analyzed monthly for the 40 samples. According to the indices from histological sections, the frequency of gonad developmental stages, and the oocyte diameter, this clam has a long-term partial spawning pattern from March to October. However, GI and nucleic acid values showed that the mature stage is from March to July and that the main spawning season is August. The peak RNA and DNA contents were good indicators of sexual maturation in females and males, respectively. The variation in protein content corresponded with the RNA/DNA ratios.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.4
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• pp.410-412
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• 1983

On maturation of abalone KIKUCHI'S concept of accumulative temperature expressed ${\Sigma}(t_i-{\theta})$ have been apply importantly for an anniversary spawning of the animals. In case of Haliotis discus hannai he was formulated ${\Sigma}(t_i-7.6)>1300$. This expression is able to modify by UKI'S the relationship between the daily feeding rate ($\%$) (Y) ana temperature ($^{\circ}C$) (t) expressed Y= 0.4291 t-0.1501. The modified expression is as the formula ${\Sigma}(Y-3.05)>570$. And the concept its meaning involves is replaced with accumulative ingestion instead of accumulative temperature. This modified concept is understood that on maturation of abalone temperature decide on satiation level, food ingestion decide on gonad maturity rate.

• Fisheries and Aquatic Sciences
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• v.23 no.2
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• pp.3.1-3.8
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• 2020

Background: The IGF system plays important roles in controlling growth, development, reproduction, and aging of organisms. Methods: To estimate maturation of the Pacific oyster Crassostrea gigas, we investigated the expression of insulin-like growth factor (IGF) system components and sex-specific genes. To determine the role of the IGF system in the growth and spawning period of female and male oysters, we examined mRNA expression levels of the C. gigas insulin receptor-related receptor (CIR), IGF binding protein complex acid labile subunit (IGFBP_ALS), and molluscan insulin-related peptide (MIP), as well as those of vitellogenin (Vg) and receptor-type guanylate cyclase (Gyc76C) in gonads of C. gigas collected between April and October, when sex can be determined visually in this species. Results: We found that MIP, IGFBP_ALS, and CIR mRNA expression levels were dependent on sex and month and were greater in males than in females. CIR and Vg mRNA expression levels were very similar among females, whereas IGF system components and Gyc76C were very similarly expressed among males. The highest expression values were observed in May, when oysters are mature; CIR and Vg mRNA expression levels were highest in females, and those of MIP, IGFBP_ALS, CIR, and Gyc76C were highest in males. Interestingly, we observed a 1:1 proportion of females to males during this period. Conclusion: Our results suggest that IGF system components, as well as Vg and Gyc76C, are associated with sexual maturation in C. gigas.

• Korean Journal of Ichthyology
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• v.12 no.3
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• pp.192-202
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• 2000

Reproductive biology of the slimy, Leiognathus nuchalis was investigated by means of histological methods. Sex ratio was 1.81 : 1 in female to male. Developmental pattern of oocytes was group-synchronous. Testicular structure was restricted spermatogonial testis-type of tubular testis. The size of first group maturity is 7.5 cm in total length. Gonadosomatic index(GSI) of female was the highest in July(12.83) and the lowest in September(1.08). GSI of male was the highest in June(19.0) and the lowest in October(0.24). Hepatosomatic index(HSI) of female showed to be positively correlated with GSI. Thoracic spot index(TSI) showed to be the minimum value from May to July when the maturation and ripe season of gonad. Reproductive cycle of female could be classified into the growing(March~May), maturation(May~June), ripe and spent(June~August), recovery(August~November), and resting stage(November~March). Reproductive cycle of male could be classified into the multiplicative and growing(January~April), maturation(April~May), ripe and spent(June~August), recovery(August~October), and resting stage(October~December).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.2
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• pp.119-124
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• 2008

Reproductive ecology of the snow crab Chionoecetes opilio was investigated in terms of the reproductive organs, abdominal flap, fecundity, and maturity. Specimens were collected with gill nets and trawls from June 2002 to May 2003 in the eastern waters of Korea. The female and male C. opilio are distinguished only by the shape of the abdominal flap, which is triangular in males and circular in females. The gonads of female and male crabs are generally X-shaped. The male gonad is white, while the female gonad appears milk-white after spawning and then turns from light orange to dark orange with maturation. The female gonads matured from June, and mature and immature groups could be distinguished from December to February or March. Brooding eggs changed from bright orange to dark brown with formation of the compound eye immediately before hatching. Accordingly, the main spawning season is February and March. The minimum maturity carapace width of female crabs was 61.1 mm, and the mean fecundity is about 108,300 eggs.

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.142-148
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• 1999

Monthly changes in the gonad index (GI), egg-diameter composition, gonadal development, reproductive cycle of the ark shell, Scapharca subcrenata, were investigated by histological method and morphometric data. This species is dioecious and oviparous. The gonad is located among the subregion of mid-intestinal gland, digestive diverticula and the outer fibromuscular layers compacted by the fibrous connective tissues and muscle fibers. The gonad index sharply increased in May, reached the maximum value in June, and then gradually decreased from July to December. The reproductive cycle of this species can be divided into six successive stages: early active stage (January to May), late active stage (June to July), ripe stage (June to August), partially spawned stage (July to September), degenerative stage (August to December), and resting stage (January to April). S. subcrenata spawns once a year between July and early September, and the main spawning occurred between July and August when the water temperatures were above $20^{\circ}C$. This evidence suggest that timings of maturation and spawning are closely related to water temperatures. Even though the spawning period was once a year, it is assumed that the number of spawning frequencies (broods) may occur more than twice during the spawning season.