• Fisheries and Aquatic Sciences
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• 제4권4호
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• pp.208-218
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• 2001

We have investigated the gonad index (GI), gonadal development, reproductive cycle, first sexual maturity, sex ratio, the number of spawned eggs and spawning frequency of the Manila clam, Ruditapes philippinarum. Samples were collected from the intertidal zone of Komso Bay, Korea from January to December in 1999. Monthly changes in the gonad index (GI) and condition index showed a similar pattern in the reproductive cycle. The spawning period was once a year between early June and early October, there was a spawning peak between July and August when seawater temperature was over $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (June to October), and spent/inactive stage (August to March). Percentages of first sexual maturity of female and male clams of l5.1-20.0mm in shell length were $56.3\%$ and $60.0\%$, respectively, and $100\%$ for the clams >25. mm. The sex ratio of individuals >15.1 mm in shell length was about 1:1 $(\chi^2= 0.02,\;p>0.05)$. Number of the eggs released from each clam by the induction increased as the size of clam in terms of shell length increased. Mean number of the eggs from the second induction of the spawning was $75.35-84.30\%$ $(average\;79.81\%)$ of the number of the eggs released in the first spawning. Our data indicated that R. philippinarum in Komso Bay has one major spawning peak with over two minor spawning, and the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• 한국발생생물학회지:발생과생식
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• 제27권3호
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• pp.127-135
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• 2023

Effects of changes in photoperiod on the reproductive events in fish are suggested to be mediated mainly via the action of melatonin (MEL). Changing levels of plasma MEL throughout the day and year are suggested to influence the hypothalamus-pituitary-gonadal axis in fish. Therefore, in this study, we aimed to investigate the effects of MEL on oocyte maturation and germinal vesicle breakdown (GVBD) in the marine fish, Chaenogobius annularis, in vitro. Oocytes at three different stages (pre-, mid-, and late-vitellogenesis) were incubated with (a) only MEL (5, 10, 50, 100, 500, and 1,000 pg/mL) and (b) 50 pg/mL of 17α,20β-dihydroxy-4-pregnen-3-one (17α20βP), maturation-inducing hormone (MIH) of this species, and MEL (4-h incubation before addition of MIH). Any single MEL treatment did not significantly induce GVBD. However, treatment with 50 pg/mL MEL or MIH significantly induced GVBD. These results suggest that preincubation with MEL accelerates the effect of MIH on longchin goby oocyte maturation.

• 한국수산과학회지
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• 제43권5호
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• pp.474-481
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• 2010

The sperm collection time, sex steroid hormones, and gonadal development of protandrous black porgy, Acanthopagrus schlegeli, acclimated in freshwater for more than 2 years were investigated to evaluate its reproductive capability. The gonadal development of black porgy reared in seawater and freshwater could each be classified into four successive stages. For black porgy reared in seawater (BSW) as the control, these were the growing (December to February), mature (February to March), spent (March to June), and degeneration and resting (July to December) stages; for black porgy reared in freshwater (BFW), these were the growing (November to January), mature (January to February), spent (February to May), degeneration and resting (June to November) stages. In both BSW and BFW, the plasma cortisol levels were the highest in March. The plasma testosterone (T) levels of BSW and BFW were the highest in March and February, respectively. The plasma estradiol-$17{\beta}$ ($E_2$) levels did not differ significantly between BSW and BFW. The 11-ketotestosterone (11-KT) levels in the plasma of BSW and BFW were the highest in April. Sperm was collectible from March to June in BSW and from February to May in BFW. The results indicated that the gonadal maturation of BFW was about 1 month faster than that of BSW.

• 한국발생생물학회지:발생과생식
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• 제19권1호
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• pp.33-41
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• 2015

The gonadosomatic index (GSI), gonadal development and changes in hormones in plasma level of the indoor cultured grunt (Hapalogenys nitens) were investigated by histological study from August 2011 to October 2012. The GSI showed similar trends with gonad developmental stages during the culture periods. Changes in plasma level of estradiol-$17{\beta}$ of female H. nitens reached the highest value before the spawning period, and seasonal changes in plasma level of estradiol-$17{\beta}$ were similar in trends of oocyte developments and GSI changes. Testosterone levels of male H. nitens reached the highest value before and after the spent stage. Ovarian developmental stages of H. nitens could be classified into early growing stage, late growing stage, mature stage, ripe and spawning stage, recovery and resting stage. The testicular developmental stages could be divided into growing stage, mature stage, ripe and spent stage, and recovery and resting stage.

• 한국발생생물학회지:발생과생식
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• 제24권2호
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• pp.79-88
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• 2020

This study was carried out to obtain information on the developmental biology and the management of biological resources of the abalone Haliotis gigantea in Korea. The sex ratio (female:male) in the present study was 1:1.7 and the proportion of females was 36.6% (n=106/290). Their gonadal structures displayed definitive seasonal changes which were similar in pattern to the changes in the gonad index (GI). The GI showed a pattern of definitive seasonal changes in both males and females it was high in the fall and low in the spring. The reproductive cycle could be categorized into the following six stages: inactive, early active, late active, ripe, spent, and degenerative stage. Based on the monthly changes in GI and stages of gonadal development, October to November was determined to be the main spawning period for H. gigantea on Jeju Island, Korea.

• 한국발생생물학회지:발생과생식
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• 제12권3호
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• pp.231-241
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• 2008

본 실험은 동남참게, Eriocheir japonicus의 명확한 생식년주기를 밝히기 위하여, 그들의 자연 서식처인 섬진강에서 채집한 성체 참게의 생식소 조직의 계절적인 변화 그리고, 암 참게 생식소의 성숙과 산란에 미치는 환경요인 즉, 온도, 광주기 그리고, 염분 농도에 대하여 조사하였다. 암 참게의 생식소 발달과 GSI의 계절적 변화를 기초로하여 생식년주기를 다음과 같이 4단계로 구분하였다: 난황형성전기$9{\sim}10$월), GSI는 낮았으며, 난소내에는 난황형성전기와 감수분열전기의 난모세포들을 가지고 있었다; 성숙기(11월$\sim$다음해 3월), GSI는 점차적로 증가하여 난모세포내에는 난황구들이 축적되었다;에는 영향을 받지 않았다. 광주기 조건(12L12D, 9L15D)에 관계없이, $10^{\circ}C$ 실험군의 암 참게보다, $18^{\circ}C$ 실험군의 암 참게의 GSI가 더욱더 증가하였다. 그리고, $26^{\circ}C$ 실험군에서 두 개의 광주기 조건(12L12D, 9L15D)에서 암 참게의 GSI는 변화하지 않았으며, 난소내에는 난황이 축적되고 있는 난모세포들은 없었다. 산란은 수온과 염분 농도에 의하여 많은 영향을 받으며, 난황형성중인 암 참게는 두 달간 사육하여도, $10^{\circ}C$에서는 전혀 산란을 하지 않았으며, $18^{\circ}C$와 $26^{\circ}C$에서 사육한 암 참게의 반 이상은 염분 농도 9.6%o와 19.2%o의 조건하에서 산란하였다. 그러나, 염분 농도 0.0%o의 조건에서는 산란한 암 참게가 한 마리도 없었다.

• Asian-Australasian Journal of Animal Sciences
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• 제14권2호
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• pp.174-183
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• 2001

During the rapid phase of gonadal development of the freshwater teleost, the catfish (Silurus asotus), the influence of hCG upon the inducement of final oocyte maturation and spawning was investigated electrophoretically and ultrastructurally. The electrophoretic patterns obtained were different in the presence and absence of some of the major or minor zones, because of the hormone level in catfish. The vitellogenin of hormone-treated fish was stained more intensively than that of sham-treated fish. These proteins showed some minor or main bands of egg extracts which migrated at positions corresponding to molecular weights of approximately 90,000. However, the thickness of electrophoretic band in molecular weight for hCG-treated fish was slightly lower than that for saline control. It seemed the plasma protein with molecular weight of approximately 45,000 in hCG-treated fish disappeared. In contrast to the control fish, the ovaries in the catfish treated with hCG shows a marked ultrastructural change under the electron microscope. No dilated profiles were seen in the granulosa cells of the mature oocyte before ovulation. After germinal vesicle breakdown (GVBD), the zona radiata interna (ZRI) becomes more compact, and there is a loss of all the processes from the pore canals. There is a wide space between the vitelline membrane and zona radiata. Also, during final maturation, the microvillar processes from the oocyte are seen no longer to penetrate deeply into the extracellular spaces of the overlying granulosa cells, and the reticulate patterns of the zona radiata interna becomes occluded, giving the zona radiata a more solid appearance. It has been possible to initiate 100% oocyte maturation in yolk granules and follicles in vivo by treatment with hCG and a high water temperature ($27^{\circ}C$). In hCG-treated fish, the percentages of successful artificial fertilization and hatching were maximal at 15 h after a single injection. It seems clear that a long acting preparation containing hCG can be successfully used in prespawning fish to advance the final events of gonadal maturation and initiate spawning. Further studies are necessary to evaluate the potential of hCG to either stimulate or inhibit the reproductive development of fish at other stages of the seasonal reproductive cycle.

• 한국발생생물학회지:발생과생식
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• 제17권3호
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• pp.241-246
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• 2013

To effects of sex maturation in olive flounder by regulating long photoperiod, gonadal development and GTH mRNA expression in the pituitary were investigated. Photoperiod was treated natural photoperiod and long photoperiod (15L:9D) conditions from September 2011 to March 2012. The results showed that natural photoperiodic group showed a higher gonadosomatic index (GSI) than long photoperiodic group during the spawning season (March 2012). The histological analysis of ovarian tissue showed that natural photoperiod group of ovaries contained vitellogenic oocytes, but long photoperiod group of ovaries mainly contained perinucleolus staged oocyte and oil-drop staged oocytes. The FSH mRNA of olive flounder, under natural photoperiod group, showed a significantly higher expression but no significant difference under long photoperiod group. The $LH{\beta}$ mRNA showed a significantly higher expression only under natural photoperiod group. These results may suggest that long photoperiodic information regulates secretion of pituitary FSH and LH and maintain early growing stage of gonadal development in this species.

• Animal cells and systems
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• 제6권1호
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• pp.75-80
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• 2002

A study on the effects of bisphenol A (BPA) on sex differentiation and gonadal development in medaka, Oryzias latipes, was investigated by histological examination. The fish were exposed to aqueous solutions of BPA at nominal concentrations of 50, 100, and 200 $\mu\textrm{g}$/L from newly-hatched larvae stage to 70 d. The ovaries of female fish were composed of oocytes at the chromatin nucleolus and peri-nucleolus stages at 20 d after the exposure. The testes contained a number of spermatogonia and spermatocytes at 30 d. In the process of sex differentiation. gonadal development was not different in all experimental groups until 30 d after the exposure. At 70 d after the exposure, however, advanced development of oocytes in the ovary and inhibition of spermatogenesis in the testis were observed in the BPA-treated groups compared to the non-treated controls. More females than males were identified in the 50 and 100 $\mu\textrm{g}$/L BPA-treated groups, in comparison to the 200 $\mu\textrm{g}$/L BPA-treated group and non-treated controls. Medaka exposed to 200 $\mu\textrm{g}$/L BPA were bigger compared to other experimental groups. The present study suggests that BPA may lead to problems in either mating or sexual behavior due to the difference in growth and disparity of sexual maturation between male and female fish.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2000년도 춘계수산관련학회 공동학술대회발표요지집
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• pp.282-283
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• 2000

The egg development of various fishes is studied by various methods including electron microscopy(Matsuyama et al, 1991) and hormone treatment(Schoonbee et al. 1980). In addition to attempt to induce final maturation and spawning, the present experiments were conducted to investigate the influence of hCG upon reproductive cycles in catfish(Silurus asotus) with developing gonads and to stimulate the reproductive system during the rapid phase of gonadal development. (omitted)