• The Korean Journal of Malacology
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• v.23 no.2
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• pp.199-208
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• 2007

The gonad index, gonadosomatic index, the condition index, reproductive cycle, first sexual maturity, and sex ratio of the hard shelled mussel, Mytilus coruscus were investigated by using histological analysis and morphometric data. Specimens were collected monthly in Kyeokpo, western Korea from January to December, 2006. The gonad index reached a maximum in February, and minimum in September. Both the monthly variations of the gonad index (GI) and the gonadosomatic index (GSI) reached a maximum in February. After that, their values continually decreased between March and April because of spawning. The monthly variation of the condition index coincides with the GI and the GSI. The spawning period was from February to April, with the main spawning occurring between February and March. The reproductive cycle of this species could be classified into six stages: early active stage (November to January), late active stage (November to February), ripe stage (December to April), partially spawned stage (February to April), degenerative stage (April to October), and resting stage (June to December ). Percentages of sexual maturity was over 50% for the female and male hard shelled mussels that ranges from 40.1 to 50.0 mm in shell length. The percentage was 100% for those that are over 50.1 mm. The sex ratios of females to males over 40.1 mm in shell length were not significantly different from a 1:1 sex ratio $(x^2\;=\;0.63,\;p\;>\;0.05)$. No evidence of hermaphroditism was found in histological sections of any hard shelled mussel examined.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.1
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• pp.103-106
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• 2020

We investigated the biological maturation of blackthroat seaperch Doederleinia berycoides in southern Korea waters, based on samples collected from March 2018 to February 2019. We analyzed monthly changes in maturity stage, gonadosomatic index (GSI) and total length (TL) at 50%, 75% and 97.5% group maturity. The spawning period was May to October in 2018. We estimated the TL at 50% group maturity as 27.0 cm for females in 2018. We estimated the TL of females at 75% and 97.5% group maturity as 28.7 cm and 32.7 cm, respectively, in 2018.

• 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 Ecology and Environment
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• v.33 no.4 s.92
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• pp.395-404
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• 2000

The gonadosomatic index (GSI), hepatosomatic Index (HSI), egg size distribution, gonad development and reproductive characteristics of venus fish, Aphyocypris chinensis, were examined during March 1997- March 1998 in agricultural waterways of the Sedo-myun, Puyo county, Chungnam Province, Korea. Annual reproductive cycle was classified into the following five successive phases by monthly changes in GSI and the characteristics of ovary: quiescent phase (January- February), secondary growing and mature phase (March-May), ripe and spawning phase (June-July), degenerating and resting phase (August-September) and primary growing phase (October-December). The hepatosomatic index (HSI) showed clear seasonal pattern with two separate peaks. However, it exhibited a negative correlation to changes of GSI values. The regression analysis suggested that fecundity showed a strong positive linear relationship ($r^2\;=\;0.91$, n = 34) with body weight. The sex ratio of female to male was 1.4 : 1 in the natural population during the study. The minimum reproductive size of female and male venus fish was 38 mm and 33 mm in fork length, respectively.

• The Korean Journal of Zoology
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• v.36 no.4
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• pp.580-587
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• 1993

북방산개구리의 성체 수컷들 년중 채집하여 gonadosomatic index(GSI)와 정자형성과 정 및 정소내 testosterone양의 변화를 조사하였다 정자형성은 8월에 시작되어 9월에 가장 활발하게 진행되었으며 이때 GSI도 가장 높았고 세정관의 단면적도 가장 넓었다 번식기(2월) 이후 일정기간 동안에는(3월-7월) 정자형성이 정지되었으며, GSI나 세정관의 단면적도 최저치를 나타내었다. 정소내 testosterone양은 11월부터 급격히 증가하여 2월에 가장 높았으며 3월부터 급격히 감소되어 10월 까지 매우 낮은 농도를 유지하였다. Interstitial cell의 수도 동면기간이 찰동기 보다 훨씬 많았으며 핵의 크기도 동면기간이 훨씬 컷다. 따라서 testosterone의 생성 증가와 interstitial cell의 활성화가 일치함을 알 수 있었다. 본 결과들은 북방산개구리의 정 소에서는 정자형성과정이 불연속적으로 일어난다는 것과 2월 이후에는 testosterone의 양이 급격히 줄어드는 것으로 보아 이 개구리의 번식기가 2월임을 확인해 주고 있다.

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.95-105
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• 2005

Gonadosomatic index, reproductive cycle, spermatogenesis and first sexual maturity of Chlamys farreri were investigated by cytological and histological observations, from January 1998 to December 1999. The gonadosomatic index (GSI) rapidly increased in April and reached a maximum in May when seawater temperature rapidly increase. Then the GSI gradually decreased from June to August when spawning occur. Accordingly, monthly changes in the GSI in males coincide with the reproductive cycle. The spermatozoon of Chlamys farreri is the primitive type found in external fertilization species. The head of the spermatozoon is approximately $2.75{\mu}m$ in length including the acrosome measuring about $0.50{\mu}m$ in length, and its tail was approximately $20{\mu}m$, the axoneme of the tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. Five spherical mitochondria around the centriole (the satellite body) appear in the middle piece of the sperm. The spawning period was from June to August and the main spawning occurs from July to August when seawater temperatures are greater than $20^{\circ}C$ The reproductive cycle of this species can be categorized into five successive stages; early active stage (January to March), late active stage (March to April), ripe stage (April to August), partially spawned stage (June to August), and spent/inactive stage (August to January). Over 50% of male scallops attained first sexual maturity between 50.0 and 60.0 mm in shell height, and 100% of those over 60.0 mm in shell height achieved maturity. Accordingly, we assume that male individuals begin reproduction at three years of age.

• Journal of Life Science
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• v.21 no.3
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• pp.406-411
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• 2011

To investigate the effects of short-term treatment with tri-n-butyltin chloride (TBTCl) and bisphenol A (BPA) on the reproduction of striped field mice, the mice were intramuscularly injected with TBTCl or BPA immediately before the reproductive season and examined in the reproductive season after keeping them for 4 months. As a result, there were no differences between the control and the compound-treated groups regarding body weight in both sexes, the residual levels of the compounds in the adult males, and the gonadosomatic index (GSI) and the histological structures with LM and EM of the testes and epididymides in both the adult and young males. The infant mortality and abortion rate, however, were high in the TBTCl-treated groups and BPA-treated groups respectively, compared to the control group. Conclusively, it was suggested that short-term treatment with TBTCl or BPA in mice in the non-reproductive season might have inhibited the development of the uterine embryos or fetuses, although it did not induce accumulations of these compounds or affect the reproductive organs of adult and young (F1) males.

• Korean Journal of Ichthyology
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• v.31 no.3
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• pp.141-149
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• 2019

This study presents data on spawning season, weight-length relationships (WLRs) and condition factor of Gadus chalcogrammus inhabiting the middle East Sea, Korea. Monthly changes in the gonadosomatic index (GSI) revealed that the spawning period was from December to March. Overall value of the exponent b, estimated by nonlinear least squares from weight and length data was 2.806, ranging from 2.778 for female fishes to 2.985 for immature group. The b values were similar between spawning and non-spawning, and between female and male fishes, but it was significantly higher for immature than mature fishes. The condition factors were significantly higher for immature than mature groups, and during non-spawning than spawning periods, but it was not significant between male and female fishes.

• Korean Journal of Environmental Biology
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• v.38 no.2
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• pp.315-322
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• 2020

A 210-day experiment was conducted to examine the effects of starvation on survival, the gonadosomatic index (GSI), hepatosomatic index (HSI), and the intestinosomatic index (ISI), and histological changes in the renal tubule epithelium, midgut epithelium, and hepatocytes in Far Eastern catfish (Silurus asotus). The survival rate decreased to 92.2±0.47% in the fed group and 74.4±2.59% in the starved group during the 210-day experimental period. GSI, HSI, and ISI were lowest in the starved group (p<0.05). The hepatocyte nuclear area, hepatocyte cell area, the nuclear height of the midgut epithelium, and the nuclear height of the kidney were highest in the fed group (p<0.05). The hepatocyte nuclear area, nuclear height of the midgut epithelium, and nuclear height of the kidney were lowest in the starved group(p<0.05). The numbers of melano-macrophages (MMs) found in the kidney cells increased during starvation in this species. This suggests that thinner body cavity regions, the contraction of hepatocyte nuclear sites, and the spreading of kidney cell MMs in this species could be used as alternative indicators for identifying starvation conditions. Therefore, the results from our study provide accurate indications of the nutritional status of Far Eastern catfish.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.2
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• pp.121-124
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• 2007

Freshwater-adapted maturing chum salmon (Oncorhynchus keta) involuntarily captured by stationary nets in Yang-yang seashore areas were transferred to freshwater in an outdoor raceway tank at Yeongdong Inland Fisheries Research Institute, NFRDI, Yang-yang, Gangwon, Korea and kept over 1 day until the start of the experiments. The freshwater-adapted females were single-injected intraperitoneally with gonadotropin-releasing hormone analogue, (GnRH-a: $70\;{\mu}g/kg$ body weight, BW) alone or combined with a dopamine receptor antagonist, pimozide($700\;{\mu}g/kg$ BW). Although gonadosomatic indices [GSI, (gonad weight/BW)${\times}100$] did not show significant changes in both 2004 and 2005, GSI of GnRH-a-injected fish during the 2005 trial slightly increased on the 5th and 7th days post-injection compared to those of vehicle treated fish. Hepatosomatic indices [HSI, (liver weight/BW)${\times}100$] of fish injected with GnRH-a alone and combined with pimozide decreased significantly on the 7th day post-injection in 2004(P<0.05). In 2005 trials, HSI was significantly reduced in GnRH-a treated fish on the 7th day post-injection (P<0.05). Pimozide-injected fish showed a pattern with increase of GSI and decrease of HSI, without significant differences. Taken together, these results suggest that at least in part hypothalamic hormones and dopamine receptor antagonist may induce sexual maturation in freshwater-adapted maturing chum salmon. It remains to evaluate these preliminary results by further researches.