• Research in Community and Public Health Nursing
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• v.23 no.4
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• pp.405-414
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• 2012

Purpose: The purpose of this study was to examine the sexual maturation, body image, and self-esteem of Korean elementary school girls with symptoms of precocious puberty compared to those with no symptoms of precocious puberty. Methods: The subjects were 309 girls of lower grades in elementary school. Tanner's Sexual Maturation Rating (SMR), Self Image Scale, and Self-esteem Scale were utilized to determine the presence of symptoms of precocious puberty, body image, and self esteem. Collected data were analyzed by Chi-square test, independent t-test, and one-way ANOVA using the SPSS/WIN 17.0 program. Results: The percentage of the girls with breast development was 14.9%. Breast development usually began in the third grade (56.5%). Of the subjects, 0.3% were experiencing menstruation. Breast development was related to grade, age, height, weight, and a cause of worry. There was a significant difference of body image between girls with breast development in the first grade and in the second grade. Conclusion: An effective intervention that can improve the self-image of children with symptoms of precocious puberty should be developed to prevent and treat physical and mental problems related to sexual maturation.

• Animal cells and systems
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• v.11 no.2
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• pp.227-234
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• 2007

Spermatogenesis, the reproductive cycle, and the size at first sexual maturity in male Mactra chinensis were investigated by cytological and histological observations. The spermatozoon exhibits a primitive type morphology and is similar to those of other bivalves in that it contains a short midpiece with four mitochondria surrounding the centrioles. The morphologies of the sperm nucleus type and the acrosome shape of this species are cylindrical and modified cap-like, respectively. The spermatozoon is approximately $40-45\;{\mu}m$ in length including the sperm nucleus (about $1.46\;{\mu}m$), acrosome (about $1.20\;{\mu}m$) and tail flagellum. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure. The spawning period of this species lasts from June to September, and the main spawning occurs in July and August, when the seawater temperature is greater than $20^{\circ}C$. The percentage of individual male clams at first sexual maturity was 56.5% for those whose shell lengths were 35.1-40.0 mm, and 100% for over 45.1 mm. Accordingly, harvesting clams <35.1 mm in shell length could potentially cause a drastic reduction in recruitment, and a measure indicating a prohibitory fishing size should be taken for adequate fisheries management.

• Animal cells and systems
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• v.11 no.2
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• pp.191-198
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• 2007

The ultrastructure of germ cells and follicle cells during oogenesis, oocyte degeneration, reproductive cycle, and first sexual maturity in female Cyclina sinensis were investigated for clams collected from Simpo, Jeollabuk-do, Korea, by cytological and histological observations. Vitellogenesis occured by way of endogeous autosynthesis and exogenous heterosynthesis: vitellogensis occurred through a process of autosynthesis, which involves a combined activities of the Golgi complex, mitochondria, and rough endoplasmic reticulum. The process of heterosynthesis involved endocytotic incorporation of extraovarian precursors into the basal region of the early vitellogenic oocytes prior to the formation of vitelline envelope. The follicle cells appear to play an integral role in vitellogenesis and oocyte degeneration, functioning in phagocytosis and digestion of products originating from the degenerated oocytes: these functions can permit the transfer of yolk precursors needed for vitellogenesis. Follicle cells might have a lysosomal system for breakdown and might also resorb phagosomes in the cytoplasm for nutrient storage during oocyte degeneration.

• Fisheries and Aquatic Sciences
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• v.4 no.4
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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.

• 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.

• The Korean Journal of Malacology
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• v.4 no.1
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• pp.30-41
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• 1988

The gonadal development, the annual reproductive cycle and the first sexual maturity of surf clam, Mactra veneriformis Reeve were studied histologically. Speciemens were monthly collected at the intertidal zone of Naechodo, Chollabuk-do, Korea, for one year from March 1986 to February 1987. Sexuality of the clam is dioecious. The gonads were located between the subregion of mid-intestinal gland in the visceral cavity and the reticular connetive tissues of the foot, The ovary is composed of a number of ovarian sacs, and the testis comprise several testiculat lobules. The undifferentiated mesenchymal tissues and eosinophilic granular cells function as nutritive cells in the early stage. The ripe eggs were about 50-60${\mu}{\textrm}{m}$ in diameter, and they were wurroundedby the gelatinous membranes. The spawing period was from early June to September the main spawning occurred beetween July and August when the water temperature reached above 24$^{\circ}C$. The annual reproductive cycle of this species could be classified into five successive stages: multiplicative(January to March), growing(March to May), mature(April to August), spent(June to September), degenerative and resting(September to February). The monthly changes of fatness coefficient closely correlated with the annual reproductive cycle. Percentages of the first sexual maturity of female and male clams were over 50% among those individals ranging from 2.1 To 2.5cm, and 100% in those over 2.6cm in shell length.

• Development and Reproduction
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• v.13 no.2
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• pp.123-132
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• 2009

The gonadosomatic index (GSI), fatness, ovarian development, first sexual maturity, and fecundity of the Korean anchovy Coilia nasus were investigated by histological observations and morphometric analysis from January to December, 2007. The GSI and fatness began to increase in February, and reached the maximum in June when the ovary was getting mature and spawning occurred. Thereafter these parametes rapidly decreased in July when spawning occurred. Therefore, monthly changes in the GSI and fatness were closely related to ovarian maturation and spawning. The duration of ovarian development in females can be classified into five successive stages: early growing stage (February to March), late growing stage (March to April), mature stage (May to June), ripe and spent stage (June to July), and recovery and resting stage (December to January). Maturation and spawning of this species occurred between June and July during the period of high seawater temperature-long day length. Percentages of first sexual maturity in female individuals were over 50% for fish ranging 24.1 to 27.0 cm in total length, and 100% for fish over 30.1 cm in total length. The number of total eggs and mature eggs in the absolute fecundity were increased with the increase of total length and body weight, respectively. The number of total eggs and mature eggs in relative fecundity were also proportional to total length, but rather these numbers decreased in the maximum body weight (126.0${\sim}$150.0 g).

• The Korean Journal of Malacology
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• v.21 no.2 s.34
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• pp.81-93
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• 2005

Reproductive cycle with the gonadal phases, first sexual maturity, artificial spawning amount by the size and spawning interval of the hard clam, Meretrix lusoria were investigated by histological observations and morphometric data by artificial spawning induction. Meretrix lusoria is dioecious and oviparous. The reproductive cycle of this species can be classified into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (June to September), and spent/inactive stage (September to February). The spawning period was from June to September, and the main spawning occurred between July and August when the seawater temperature exceeds over $20^{\circ}C$. Percentage of first sexual maturity of female and male clams ranging from 40.0 to 45.0 mm in shell length was over 50%, and all clams over 50.0 mm in shell length sexually matured. Female and male clams ranging from 40.0 to 45.0 mm in shell length are considered to be two years old. Therefore, we assume that the hard clams of both sexes begin reproduction from two years of age. The mean number of the spawned eggs increased with the increase of size (shell length) classes. In case of artificial spawning induction, the number of spawned eggs from the clams of a sized class was gradually decreased with the increase of the number of the spawning frequencies (the first, second, and third spawnings). In the experiments of artificial spawning induction during the spawning season, the interval of each spawning was estimated to be 15-18 days (average 17 days).

• Development and Reproduction
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• v.20 no.2
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• pp.119-125
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• 2016

This study describes results on sexual maturation and characteristics of natural spawned eggs to develop a method for the production of stable, healthy fertilized eggs from captive-reared yellowtail kingfish, Seriola lalandi. A total of 59 yellowtail kingfish were captured off the coast of Jeju Island, after which the broodstock was cultured in indoor culture tank ($100m^3$) until they were 6.1-14.9 kg in body weight. As part of the rearing management for induced sex maturation, the intensity of illumination was maintained at 130 lux. The photoperiod (light/dark; L/D) was set to a 12 L/12 D from October 2013 to January 2014, and 15 L/9 D from February 2014 to June 2014. Feeds comprised mainly EP (Extruded Pellets), with squid cuttlefish added for improvement of egg quality, and was given from April to June 2014. The first spawning of yellowtail kingfish occurred in May 3, 2014, at a water temperature of $17.0^{\circ}C$. Spawning continued until June 12, 2014, with the water temperature set at $20.5^{\circ}C$. Time of spawning was 26 times at this period. The total number of eggs that spawned during the spawning period was $4,449{\times}10^3$. The buoyant rate of spawning eggs and fertilization rate of buoyant eggs during the spawned period were 76.1% and 100%, respectively. The diameters of the egg and oil globule were $1.388{\pm}0.041mm$ and $0.378{\pm}0.029mm$, respectively, which was higher in early eggs than in those from late during the spawned period.

• Korean Journal of Ichthyology
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• v.7 no.2
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• pp.150-159
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• 1995

First sexual maturity, monthly changes in gonadosomatic index and reproductive cycle of viviparous teleost surfperch, Ditrema temmincki were investigated under photomicroscopy. Samples were collected from May 1992 to August 1993 in the vicinity of Suyoung Bay, Pusan, Korea. Body length at the first sexual maturity in female and male were 12.5cm and 13.5cm, respectively. Gonadosomatic index(GSI) in female reached the maximum in June(just before parturition) and male GSI reached the maximum in October(just before copulation). The testis is composed of a number of seminiferous tubules, and spermatogonia are originated from the germinal epithelium on the seminiferous tubule. The ovary consists of several ovigerous folds, and oogonia are originated from the inner surface of the germinal epithelium within the ovigerous fold. Annual reproductive cycle was classified into the following successive periods : in male, growing period from May to August, maturation period from September to October, copulation period from November to December, and degeneration and resting period from January to April, and in female, growing period from September to October, copulation and maturation period from November to December, gestation period from January to June, and resting period from July to August. Hepatosomatic index(HSI) in male appeared to be negatively correlated with gonadosomatic index, but that in female showed to be positively correlated.