• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.245-255
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• 2002

In order to obtain the basic information for seedling production of venus clam, Protothaca jedoensis, the annual reproductive cycle was investigated mainly by histological observation from September 1998 to August 1999. P. jedoensis was dioecious. The gonads are located between the digestive diverticula and muscle tissue of the foot. The ovary was composed of a number of ovarian sacs, and the testis was composed of several testicular tubules. The condition index was reached its maximum (20.0) in February, and then decreased to 11.5 in June. In August, the value was the lowest (9.0) and then increased slowly. Minimum size for the sexual maturation of individuals were 38.4 mm in shell length. One the other hand, the size of mature oocytes was ranged to $50-60\mu{m}$ in diameter and testis-ova was observed in testis of the mature stage. The reproductive cycle of P. jedoensis could be classified into five successive stages: early active (December to February), late active (January to April), ripe (March to July), partially spawned (June to August) and spent/inactive (July to January) stages.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.5
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• pp.659-663
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• 1999

Gametogenesis, reproductive cycle, condition factor, and meat weight rate of the surf clam, Tresus Keenae were studied by histological observations and morphometric data based on the samples which have been collected from the south coast of Korea, from January 1995 to February 1996. The annual ranges of the mean seawater temperature and specific gravity in habitat of the surf clam were $4.9\~24.9^{\circ}C$ and 1.0210$\~$1.0266, respectively. Monthly changes in the condition factor showed in a wide range from 0.2381 to 0.2827, began to increase in January and reached the first maximum (0.2827) in April. And then the value rapidly decreased in June, thereafter, reached the second peak (0.2812) in August. The condition factor of this species showed the two peaks, and gonadal development reached sexually mature and ripe conditions during the period of these two peaks. The meat weight rate ranged from $38.0\%$ to $46.4\%$, and its change showed a similar tendency with the condition factor. The reproductive cycle of this species can be divided into five successive stages: in both sex, multiplicative (December to January, July to August), growing (January to February, September to October), mature (February to April, September to November), spawning (April to June, September to November), and degenerative and resting stage (May to July, November to January).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.2
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• pp.180-187
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• 2021

This study was conducted to investigate the reproductive characteristics of the Neon damselfish Pomacentrus coelestis in Chuuk lagoon (7°27' N, 151°53' E), Micronesia, Equatorial Pacific Ocean. The specimens used in this study were collected from August 2009 to September 2010 from around the coral reef area at a depth of 3-10 m in the northwest coast of Weno Island. Overall, 228 individuals were collected over 14 months from this area, of which 115 were females and 108 were males. Among 108 males, 30 were found to be hermaphrodites and the sex of 5 individuals could not be determined. The overall sex ratio was approximately 1.06:1 (female:male), and the ratio of sexually active individuals was 0.79:1. The gonadosomatic index (GSI) fluctuated and showed the highest value of 8.43±1.21 in December 2009 and the lowest value of 3.36±0.71 in September 2009 in sexually active females. Males showed the highest GSI value of 2.64±0.93 in June 2010 and the lowest value of 0.35±0.06 in July 2010. Based on the fluctuation of GSI, the trends in the appearance of monthly sexually active individuals, and biopsy of the gonads, P. coelestis was found to be a hermaphrodite species of protogynous type and is considered to be reproductively active throughout the year.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.6
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• pp.529-535
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• 1984

This study aims at obtaining the basic data for the development of pen shell culture at Yoja Bay, the southwest coast of Korea. The authors dealt with the annual gonadal changes of the pen shell, Atrina pectinata japonica, to find out the gametogenesis, reproductive cycle and spawning season, and to investigate the fluctuation in the larval occurence in Yoja Bay. From July 1983 to June 1984, an average of 20 individuals as specimens were monthly collected by commercial fishing dredge near Manwol island located at the mouth of Yoja Bay. The degree of gonadal development was determined by the histological observations as resting spent stage, early developmental stage, after developmental stage, early spawning stage, after spawning stage and degenerative stage. According to these degrees of gonadal development, annual reproductive cycle of the pen shell population was determined. From July to August, the gonads were changed through degenerative into resting stage and, in September and October, they became entirely empty gonads. From November they showed the first sign of gametogenesis developing very slowly. Nevertheless, the developing gametes did not increase in number probably owing to a phagocytic phenomenon by phagocytes which appeared in the gonad during this stage. Some individuals started spawning in April and in May majarity of individuals were in spawning stage. In June, majority of the individuals showed signs of degenerative stage. Therefore, the authors came to a conclusion that the pen shells in Yoja Bay spawn chiefly in May. And this is also supported by the result of the survey on the planktonic occurrences of the pen shell larvae. Namely, there were no larvae at all in April, only a few in May and many in June by vertical water sampling.

• Journal of Life Science
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• v.19 no.12
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• pp.1851-1854
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• 2009

This study correlated changes in the plasma levels of estradiol-$17{\beta}$ (E2) with changes in the gonadosomatic index (GSI) and ovarian development during the annual reproductive cycle of the pike eel Muraenesox cinereus, collected at the Tongyung coast region. Ovarian maturity was classified based on histological observations; the perinucleolus stage (November to February), the oil droplet stage (March to April), the early vitellogenic stage (April to May) and the late vitellogenic stage (June to October). Seasonal changes in the GSI were correlated with water temperature and reflected the degree of ovarian maturity. Plasma E2 levels were correlated with changes in the GSI, which increased from April to a peak in July, and the levels remained comparatively high until October. These data indicated that changes in the GSI and plasma E2 levels are correlated with the annual ovarian activity of the pike eel. In this study, however, female pike eels were not collected during the spawning stage. Therefore, spawning of this species seemed to be closely related to its migration toward the deep sea of offshore.

• Development and Reproduction
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• v.25 no.3
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• pp.157-171
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• 2021

To determine whether the reproductive processes of sea bass, Lateolabrax japonicus, proceed normally after transportation from an outdoor net-cage into indoor tanks, we examined changes in the gonadosomatic index (GSI), histological gonadal tissue, and plasma levels of sex hormones (testosterone and estradiol-17ß) during their annual reproductive cycle. We also measured maturation and spawning across two sea water salinity levels (full and low salinity). Fecundity was estimated by the relationship between egg number and body size in female sea bass. Monthly changes in the GSI, histological gonadal tissues, and oocyte size showed both male and female sea bass reach final maturation in January and February, respectively, indicating that the spermiation of males occurs earlier than the spawning of females. The histological results indicated that the sea bass is a multiple spawner, similar to many marine teleosts, exhibiting group-synchronous oocyte development. Female maturation and spawning were enhanced in lower salinity seawater (29.6-31.0 psu) compared to that of normal salinity (34.5-35.1 psu). These results confirm that sea bass reproduction can occur successfully in captivity and imply that fertilized eggs can be collected from February to March. Additionally, our results show that lower salinity enhances oocyte maturation and spawning of female sea bass.

• The Korean Journal of Zoology
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• v.36 no.1
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• pp.36-50
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• 1993

한국산 관박쥐(Rhinolophusfewmequinum Jroma의 웅성생식 pattern을 알아보기 위하여 정소의 형태변화와 세정관 정상피의 1년주기를 조사하여 다음과 같은 결론을 얻었다. 정자형성은 5월에 시작되어 10월말에 완료되었다. 7월초부터 10월중순까지는 정자변태과정이며, 정자형성과정의 활성도가 가장 높은 달은 8월 중순경이었다. 또한 교미가 끝난 11월경부터 세정관내에는 미성숙한 정자세포가 Sertoli cell의 식작용과정의 일환으로 포식되어졌고, 91년 12월부터 92년 1월, 2월, 3월, 그리고 동면각성기인 4월의 실험군에서도 역시 점진적으로 식작용 과정을 관찰할 수 있었다. 교미가 끝난 후의 세정관 내에는 새로운 정자를 만들기 위한 준비단계로서 미성숙된 정자들이 Sertoli cell의 식작용에 의해 정화(cleaning)되므로 이 기간을 정화기간(cleaning time)이라 볼 수 있다. 따라서 정소내 세정관의 1년 주기를 볼 때 정화기간은 동면 개시기인 11월부터 익년 4월까지 약 6개월에 걸쳐 이루어 진다. 이상의 결과로 볼때, 정자형성은 동면각성 직후부터 시작하여 10월경에 완료되며 교미개시기에는 정지되고, 동면기 동안 정자형성이 일어나지 않는 점으로 보아 한국산 관박쥐는 'Pipistnfluspottem'에 속한다고 할 수 있다.

• Journal of Veterinary Clinics
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• v.33 no.2
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• pp.138-141
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• 2016

The aim of this study was to diagnose the fertility of a female western lowland gorilla kept in Seoul Zoo, in accordance with age by analyzing the fecal sex hormone metabolites. The study was conducted in two period of times, when the animal was from 35 to 37 years old and when the animal was from 40 to 42 years old. Non-invasive method by using fecal samples was used for safe and efficient fertility diagnosis. We collected the feces from the enclosure at least three times a week. Then $17{\beta}$-estradiol and progesterone, which are fecal sex hormone metabolites, were measured by time-resolved fluoro-immunoassay to compare the menstruation cycle and the annual reproductive cycle. For the duration of the primary study (when the animal was 35~37 years old), irregular menstruation and high concentrations of estradiol and progesterone were observed. However, menstruation was hardly observed and the concentrations of both hormones were statistically very low in the period of secondary study (when the animal was 40~42 years old). This observed phenomenon in our study was very comparable to menopause in adult women; therefore, it was confirmed that our female gorilla has reached menopause because of the natural aging, as they become older.

• Development and Reproduction
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• v.12 no.3
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• pp.231-241
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• 2008

The present study was designed to clarify aspects of the annual reproductive cycle of the fresh water mitten crab, Eriocheir japonicus inhabiting Sumjin river, and to determine the adequate conditions of temperature, photoperiod and salinity on the gonadal maturation and breeding of adult female crabs. Based on the seasonal changes of GSIs and gonadal histology of adult crabs, the annual reproductive cycle could be divided into 4 periods as follows: previtellogenesis period (from September to October) when GSIs were low value and ovaries had oocytes in previtellogenesis stage and meiotic prophase stage; maturing period (from November to March of the next year) when GSIs increased gradually and ovarian oocytes accumulated yolk globules; spawning period (from April to June) when high value of GSI of female was kept and ovigerous female appeared; resting period (from July to August) when GSIs decreased rapidly, and vitellogenic oocytes degenerated. Gonadal maturation was influenced by water temperature, but not photoperiod and salinity. GSI more increased in experimental regime of $18^{\circ}C$ than that of $10^{\circ}C$ regardless of photoperiod conditions (12L12D and 15L9D). However, in $26^{\circ}C$ regime of both photoperiod conditions, the value of GSI was not changed, and vitellogenic oocytes were not observed. Spawning was considerably influenced by water temperatures and salinities regardless of photoperiods. Vitellogenic female crabs did not spawn at $10^{\circ}C$ in any salinity conditions. However, at $18^{\circ}C$ and $26^{\circ}C$, over a half of rearing female crabs spawned in condition of 30% sea water (salinity 9.6%o) and 60% sea water (salinity 19.2%o), while no female spawned in freshwater condition (salinity 0.0%o).

• Journal of Aquaculture
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• v.10 no.2
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• pp.133-141
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• 1997

Gonadal maturation and annual reproductive cycle of the cultured scallop, Patinopecten yessoensis from eastern waters near of Kangwon-do province, Korea were studied on the basis of monthly variation of gonadosomatic indices (GSI) and histological observations of gonadal tissue. During the experimental period, water temperature at the depth of 20m and sunshine duration per day were ranged from $5.3^{\circ}C\;to\;18.0^{\circ}C$ and 9.4 to 14.6 hours, respectively. GSI values of femal were in a wide range from $2.8\pm0.37(August)\;to\;22.66\pm4.38(April)$. GSI values began to increase in March and reached the maxium in April, then decreased repidly. GSI values of male were in a range from $2.04\pm0.80(August)\;to\;20.46\pm1.49(April)$ and were same tendency with female's. Digestive diverticula indices (DDI) of both sex reached the maximum values in December, then deceased gradually until September. Contrary to GSI, adductor muscle indices (AMI) of both sex were the minium values in April, but began to increase rapidly until July and reached $47.71\pm3.17(female)\;and\;48.70\pm3.55(male)$. In the scallp collected hermaphroditic gonads were found. Monthly changes of oocyte diameter were in a range from 11.3 um(October) to 73.3um (April) and nuclear diameters were in a range from 8.3um (September) to 35.3um (April), similar tendency with each other. The changes in number of ovarian tubules were reciprocal tendency with those of oocyte diameter and monthly number of ovarian tubules per $\textrm{mm}^2$ in the tissue perpatation was in a range from 51 (April) to 175 (August). As the results, the annual reproductive cycle of the cultured scallolp from eastern waters of Korea could be classified into five successive stages : multiplicative (October), growing (November to February), mature (March and April), spawning (April to June) and recovery (July to September) in female ; multiplicative (October and November), growing (December and January), mature (February to April), spawning (April to June) and recovery (July to September) in male.