• Korean Journal of Poultry Science
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• v.40 no.1
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• pp.17-23
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• 2013

This work was carried out to investigate the performance of early laying period of large-type Korean native ducks. One hundred sixty eight ducks were used in this work and divided into A and B strains (6 replications/strain, 14 birds/replication). The days at first egg of A and B strains were the age of 154.5 and 154.7 days, egg weights were 69.1 g and 65.5 g, and body weights were 3,187 g and 3,105 g at the period of laying the first egg, respectively. The days at sexual maturity of A and B strains were the age of 175.8 and 171.5 days, egg weights were 75.2 g and 74.9 g, and body weights were 3,245 g and 3,225 g at the period of laying the first egg, respectively. There were no significant differences on the day of first egg, the day of sexual maturity, egg weight and body weight at first egg and the sexual maturity, average body weight, and daily feed intake between A and B strains (P>0.05). The day of the sexual maturity of B strain was earlier than that of A strain (P<0.05). However, weekly body weight was the highest at the age of 28 weeks (P<0.05), and weekly feed intake increased after 26 weeks old (P<0.05). Egg production (%) of B strain was higher than that of A strain at the age of 22~24 weeks (P<0.05), but there was no significant difference on egg production (%) the other weeks. A number of egg laid of B strain was higher than A strain at 22~24 weeks old (P<0.05). Feed conversion ratio of A and B strains were 10.7 and 6.53 at 24~24 weeks old, respectively, so feed conversion ratio of A strain was higher than that of B strain (P<0.05). Weekly feed conversion ratio wes the highest at 20~22 weeks old, and significantly decreased until 24~24 weeks old, but were lowly maintained from the age of 24 weeks to the age of 30 weeks. These results provided the basic data on the record of early laying period of large-type Korean native ducks.

• The Korean Journal of Malacology
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• v.30 no.2
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• pp.139-153
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• 2014

We investigated fecundities in egg capsules and sizes at 50% of group sexual maturities in female Rapana venosa in three different salinity concentration regions (S-1, S-2, and S-3). In three different salinities, egg capsule heights, the number of egg capsules and the number of eggs and embryos were remarkably increased with the increase of female shell heights (or ages) and also increased with the increase of salinity concentrations. Heights of egg capsules, the number of egg capsules and fecundities (the number of eggs and embryos) were the maximum at S-1 (Gwangyang Bay (average 31.5 psu)) and the minimum at S-3 (the upper reaches of Seomjin River (average 15.5 psu)). Total numbers of fecundities of R. venosa $individual^{-1}year^{-1}$ were about $1{\times}10^6$ at S-1 region, about $8{\times}10^5$ at S-2 region, and about $2{\times}10^5$ at S-3 region. Rates (50%) of individuals reaching first sexual maturities in three different salinity regions (S-1, S-2 and S-3) were over 50% in females measuring 7.1-8.0 cm in shell height (considered to be two years old), and 100% in those > 10.1 cm (considered to be five years old). Biological minimum sizes ($RM_{50}$) in females in three different regions are 72.0 mm SH at S-1 region, 70.9 mm SH at S-2 region, and 74.6 mm SH at S-3 region, respectively. Exceptionally, smaller individuals (considered to be one year old) were participated in reproduction.

• The korean journal of orthodontics
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• v.27 no.5 s.64
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• pp.853-864
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• 1997

The evaluation of growth potency can be done with many physiologic indicators. It has been well known that skeletal maturity has a close relation with both sexual maturity and somatic maturity, but the correlation between skeletal maturity and dental maturity was believed to be less certain. But, recent studies show that specific teeth, including lower canines, present close correlations with skeletal maturity. So, in this study, we studied hand-wrist X-ray films and orthopantomograms of 387 Korean boys and girls aged from 7 to 15; the purpose was to determine skeletal and dental maturity, and to find out a new method to estimate individual skeletal maturity using multiple-regression model, without the help of hand-wrist X-ray film. As a result of this study, followings were observed. 1. The following multiple-regression model can estimate skeletal maturity index (SMI) with 84% of accuracy, and regression coefficient of chronologic age, sex and lower canine show statistical significance. SMI = 0.60 x chronologic age - 1.67 x sex$^{**}$ + 0.88 x lower canine$^{*}$ - 0.05 x lower 2nd molar$^{*}$ - 10.3 $^{*}$ : mean age corresponding each developing stage, $^{**}$ : male=1, femal=0 2. The following multiple-regression model can estimate skeletal age with 87% of accuracy, and regression coefficient of chronologic age, sex and lower canine show statistical significance. Skeletal age = 0.75 x chronologic age - 0.55 x sex$^{**}$ + 0.71 x lower canine$^{*}$ - 0.09 x lower 2nd molar* -5.77 $^{*}$ : mean age corresponding each developing stage, $^{**}$ : male=1, femal=0

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.1
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• pp.16-23
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• 2007

Nonylphenol (NP) is an estrogen-mimicking compound or xenoestrogen. This study investigated the effects of nonylphenol on the reproductive status of the equilateral venus Gomphina veneriformis. The experiment lasted 24 weeks, Experimental groups consisted of a control and three nonylphenol exposures ($1.0,\;2.5,\;and\;5.0\;{\mu}g\;NP/L$). Mortality did not differ significantly between the control and the exposure groups. The sex ratio (F:M) was 1:1 in nature and 1:1.03 in the control group. However, it changed to 1:3.5 with $5.0\;{\mu}g\;NP/L$ exposure. Gonad maturity in females was higher in the nonylphenol exposure groups than in the control group. By contrast, in males, it was lower in the nonylphenol exposure groups. Intersex individuals constituted 0% in nature, 3.08% in the control group, and 23.6% in the group exposed to nonylphenol, with female characteristics more prevalent than male. As the concentration of nonylphenol increased, the accumulation of lipofuscin increased in the mid-gut gland.

• The Korean Journal of Malacology
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• v.22 no.1 s.35
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• pp.51-61
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• 2006

Oogenesis and the reproductive cycle in female Ruditapes philippinarum were investigated by cytological and histological observations. R. philippinarum is dioecious and oviparous. During vitellogenesis, the Golgi complex, glycogen particles and mitochondria were involved in the formation of lipid droplets and lipid granules in the cytoplasm of the early vitellogenic oocyte. In the late vitellogenic oocyte, cortical granules, the endoplasmic reticulum, and mitochondria were involved in the formation of proteid yolk granules in the cytoplasm. At this time, exogenous lipid granular substance and glycogen particles in the germinal epithelium passed into the oocyte through the microvilli of the vitelline envelope. The spawning period was once a year between early June and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages: early active stage (January to March), late active stage (February to May), ripe stage (April to August), partially spawned stage (May to October), and spent/inactive stage (August to February). Percentages of female clams at frst sexual maturity of 15.1-20.0 mm in shell length were 52.6% (50% of the rate of group maturity was 17.83 mm in length), and 100% for the clams > 25.1 mm.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.3
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• pp.231-238
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• 2010

The Induction of regeneration and maturation in the free-living gametophytes of Ecklonia stolonifera Okamura was studied at four temperatures (5, 10, 15, and $20^{\circ}C$), four levels of irradiance (5, 10, 20, and 40 ${\mu}mol\;m^{-2}s^{-1}$) and three photoperiods (14:10, 12:12, and 10:14 h L:D). Female gametophyte fragments were maintained in active regeneration without reaching sexual maturity under $5{\sim}10^{\circ}C$, 10 ${\mu}mol\;m^{-2}s^{-1}$, 10:14 h (L:D), whereas the conditions for male gametophytes were slightly different at $20^{\circ}C$, 40 ${\mu}mol\;m^{-2}s^{-1}$, 10:14 h (L:D). The sexual maturation of female and male gametophytes was facilitated at $15^{\circ}C$, 20 ${\mu}mol\;m^{-2}s^{-1}$, 14:10 h (L:D). These results provide basic information for controlling the regeneration and maturation of the free-living gametophytes for artificial seed production of E. stolonifera.

• Korean Journal of Ichthyology
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• v.23 no.3
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• pp.179-186
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• 2011

Slime flounder, Microstomus achne is distributed in the coastal waters of Korea, west sea of Japan, BoHai, Yellow sea and East china sea. They are mainly caught by bottom trawl net during winter, from December to March. Sexual maturation of slime flounder were investigated using samples collected from commercial catch in the southern coast of Korea from November, 2006 to March, 2007. The ovary of the slime flounder is a conical bag in shape and is bilateral structure develops lengthily from the posterior of the abdomen to the end of the anal fin. The testis also is bilateral in structure, usually located in small size in the abdomen. In females, the gonadosomatic index (GSI) were peaked in January (12.46), then decreased rapidly thereafter. Female GSI values plummeted to 2.72 in March just after spawning. Male GSI values were peaked in December (2.46) before in the spawning season, then decreased slowly thereafter. The reproductive cycle would be classified into three successive developmental stages : maturation stage (November to January), ripe and spawning stage (December to February), degenerative and resting stage (February to March). Relationships between the fish sizes in total length (TL) and the number of ovarian eggs (F), the body weights (BW) and the number of ovarian eggs were indicated by the exponential equation respectively: F=29.027TL-767.8 (r$^2$=0.7686), F=0.3998BW+24.288 (r$^2$=0.8919).

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.6
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• pp.501-508
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• 1987

Gonadal development, the annual reproductive cycle and the first sexual maturity of hen clam, Mactra chinensis were studied histologically. Sexuality of the species was dioecious. The gonads were irregularly arranged from the subregion of mid-intestinal 91an4 in visceral cavity to the reticular connective tissue of the foot. The ripe eggs were about $50-60\;{\mu}m$ in diameter, and they were surrounded by gelatinous membrane. The spawning period was from May to September when the water temperature ranged $18.5-27.0^{\circ}C$, with the peak in June and July. The annual reproductive cycle of Mactra chinensis could be classified into five successive stages; multiplicative, growing, mature, spent, and degenerative and resting. The monthly changes of the 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 individuals ranging from 3.5 to 3.9cm, and $100\%$ in those over 5.0cm in shell length.

• The Korean Journal of Malacology
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• v.20 no.1
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• pp.75-84
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• 2004

Reproductive cycle, the condition index, sex ratio of the Pacific oysters, Crassostrea gigas were investigated by histological and morphometric data. The specimens were collected in the two oyster farms of Geoje and Namhae, Gyeongsangnam-do, Korea, from November 1995 to October 1996. Growth of shell length in two regions was similar, but growth of total weight of the oyster in Namhae was faster than that in Geoje oyster farm. The spawning periods in female and male clams were from July to October in Geoje and from June to October in Namhae oyster farm. Ripe oocytes were approximately 50 m in diameter. The reproductive cycle of in females and males in Geoje and Namhae oyster farms can be divided into five successive stages: early developing, late developing, ripe, partially spawned and spent/inactive. Monthly changes in gonad developmental phases showed somewhat different patterns between female and male clams except for the spawning period. On the whole, however, monthly changes in the gonad developmental phases showed a similar pattern in the same sex. The sex ratios of females to males in Geoje and Namhae oyster farms were not significantly different from a 1:1 sex ratio ($x^2$ = 0.55 (p > 0.05) in Geoje and $x^2$ = 0.27 ( p > 0.05) in Namhae). Artificial induction of maturation by heating of adult oysters (two-year-old) was investigated from 17 January to 18 March in 1996. Maturity at the fixed water temperature group of $20^{\circ}C$ was 80%, it showed the highest maturity of experimental groups cultured for five weeks. The survival (%) of Crassostrea gigas in the raised water temperature experimental groups (15, 20, $25^{\circ}C$) were over 98.5%, as similar to the control group (100%). But, the survival of C. gigas in the fixed water temperature experimental groups (15, 20, 25, $30^{\circ}C$) were decreased with the increase of the water temperatures. In the fixed water temperature experimental group of $30^{\circ}C$, the survival was 51.1%. Base on these results, the fixed water temperature of $20^{\circ}C$ was the best condition for artificial induction of sexual maturation.