• Development and Reproduction
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• v.27 no.3
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• pp.101-115
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• 2023

Environmental factors impact oyster growth, condition, and gonadal development, which is linked to gamete characteristics observed through histology. The reproductive cycle of bivalves is related to energy storage and utilization. Therefore, in this study, the year-round growth change and gonadal development of oysters were observed using histological analysis, and the biochemical composition changes were confirmed. The oysters used in this study are being nurtured in Gadeok-do, and 40 oysters were randomly sampled monthly from March 2021 to February 2022. Result of histological analysis of gonads, oysters were showed early development from December to February, late development from March and April, mature and ripe from May to July, spawned from August to October, and spent from November to December. Condition index values of oysters decreased in summer and autumn and increased again when entered the spent after spawning. The protein content of oysters was high in May, the maturity period, and the lipid content decreased during the spawning period. In addition, EPA and DHA, the major fatty acids of oysters, were low during the spawning period and high during the maturation period. As a result, this study suggested a close relationship between changes in oyster growth, biochemical composition, and the reproductive cycle.

• 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.

• International Journal of Industrial Entomology and Biomaterials
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• v.34 no.2
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• pp.23-31
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• 2017

Bumblebees, more efficient than honeybees, provide important services for pollination especially in tomato, pepper, cucumber, strawberries and other crops grown under tunnel farming or glasshouse conditions to yield maximization. These bees require pollen and nectar to meet their dietary needs and maintain their colony structure, development and reproduction. Keeping in view their economic importance, the effect of five concentrations of sugar and honey solutions (1:1, 1:1.5, 1:2, 2:1,1.5:1) each as alternative to nectar were used to observe their effect on life history parameters of Bombus terrestris. The 1:1 ratio of sugar solution was found most effective followed by 1.5:1, 1:1.5, 1:2 and 2:1 and also more effective of all five concentrations of honey solutions on all three stages of colony development i.e., at colony initiation, colony development and colony maturation stages. At colony initiation stage, early pre-oviposition period ($6.40{\pm}0.97$ days), early emergence of first worker in the first batch ($25.40{\pm}1.21$ days) and maximum numbers of workers ($6.20{\pm}0.24$) emergence in the first batch were observed at 1:1 ratio of sugar solution. Colonies reared on 1:1 ratio of sugar solution reached earlier ($52.13{\pm}1.28$ days) at colony foundation stage with minimum mortality ($3.27{\pm}0.54$ workers). At colony maturation stage, maximum numbers of workers, sexual (males, queens) and maximum mother queen longevity was observed at the same 1:1 ratio of sugar solution. It can be suggested from present study that sugar solution as alternative of nectar at 1:1 ratio was better than other sugar concentration levels and also from those of honey solution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.1
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• pp.48-55
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• 2009

The gonad maturation and spawning of blue crab, Portunus trituberculatus (Miers, 1876) using samples caught by trammer net in the western coast of Korea from January to December. The gonadosomatic index (GSI) showed the highest value of 15.0 in June and lowest value of 1.29 in August. Hepatosomatic index (HSI) showed the lowest in the spawning season from June to July. Thereafter, from August the value started to increase to 5.77 in December, showing an adverse trend against GSI. In the histological studies of the female reproductive organ, the gonad filled with primary oocytes from January to February and secondary oocytes in May. The female gonads mature from June, and mature and immature groups could be distinguished from December to February or March. In August, female developed another cycle of gonad development, showing new primary oocytes in the gonads again. Some of female crabs had receptaculum filled with already active sperm cells in it from March to May. In the time of August to September, almost all the females had the sperm sacs in the receptaculum. From the result, the coupling period estimated from August to September. Total RNA and DNA values of the crabs were highest in May (2.51, $0.57{\mu}g/mg$). The DNA value remained unchanged except for the value in May ($0.09-0.13{\mu}g/mg$). while RNA value was lowest in January ($1.08{\mu}g/mg$). The RAN/DNA ratio was the lowest (6.23%) in May and highest (18.05%) in July. The value of correlations coefficient between body weight and fecundity of the crabs was higher that of between carapace width and fecundity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.38 no.2
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• pp.112-117
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• 2005

Sargassum fulvellum (Turner) C. Agardh, an edible brown alga is farmed commercially by sexual reproduction and vegetative regeneration. Investigations were made on the phenology, abundance and maturity of reproductive structures in mature fronds, egg release and young germling development under different light conditions (20, 50, 80 and $100{\mu}mol/m^2/s$) and temperatures (5, 10, 15, 20 and $25^{\circ}C$). Monthly sampling was carried out by SCUBA diving at Chungsando on the southwestern coast of Korea from September 2002 to August 2003. The Maximum length of thalli was $104.6{\pm}20.7{\cal}cm$ in March 2003 when the water temperature was $9.0^{\circ}C$ and minimum was $0.8{\pm}0.5{\cal}cm$ in June when the water temperature was $19.5^{\circ}C$. Receptacle formation was observed from February to April. The peak period of egg release for this alga was in April when the water temperature was about $10^{\circ}C$ in nature. In the culture regimes of temperature and irradiance, the egg release of the excised female receptacle was highly affected by temperature. The maximum rate of egg release was $96.7{\pm}5.8{\%}$ under $20^{\circ}C$ and $80{\mu}mol/m^2/s$. The maximum length of young germlings was $3.9{\pm}0.2{\cal}mm$ after 35 days culture under $15^{\circ}C$ and $80{\mu}mol/m^2/s$.

• The Korean Journal of Physiology and Pharmacology
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• v.14 no.6
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• pp.399-405
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• 2010

Gamma-aminobutyric acid (GABA)-ergic inhibition is important in the function of the visual cortex. In a previous study, we reported a developmental increase in $GABA_A$ receptor-mediated inhibition in the rat visual cortex from 3 to 5 weeks of age. Because this developmental increase is crucial to the regulation of the induction of long-term synaptic plasticity, in the present study we investigated in detail the postnatal development of phasic and tonic inhibition. The amplitude of phasic inhibition evoked by electrical stimulation increased during development from 3 to 8 weeks of age, and the peak time and decay kinetics of inhibitory postsynaptic potential (IPSP) and current (IPSC) slowed progressively. Since the membrane time constant decreased during this period, passive membrane properties might not be involved in the kinetic changes of IPSP and IPSC. Tonic inhibition, another mode of $GABA_A$ receptor-mediated inhibition, also increased developmentally and reached a plateau at 5 weeks of age. These results indicate that the time course of the postnatal development of GABAergic inhibition matched well that of the functional maturation of the visual cortex. Thus, the present study provides significant insight into the roles of inhibitory development in the functional maturation of the visual cortical circuits.

• 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.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.5
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• pp.391-397
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• 2006

This study correlated changes in estradiol-l7$\beta$ ($E_2$), testosterone (T), 17$\alpha$,20-dihydroxy-4-pregnen-3-one (DHP), and vitellogenin (VTG) levels with changes in the gonadosomatic index (GSI) and ovarian histology during the annual reproductive cycle of the wild marbled sole, Limanda yokohamae. Synchronous oocyte development occurs in this fish. Ovary maturity was classified into four periods, based on histological observations: the spawning (December to February), post-spawning (February to April), recovery (May to August), and vitellogenic (September to November) periods. Seasonal changes in the GSI were inversely correlated with water temperatures and reflected the degree of ovarian maturity. Plasma VTG levels were correlated with changes in the GSI, which increased from September to a peak in January, and levels remained comparatively high until February. Estradiol-17$\beta$ was at baseline levels (<0.11 ng/mL) during the spring and summer, and peaked rapidly (1.55$\pm$0.445 ng/mL) from October to January. Plasma T and DHP levels had a similar profile; they rose markedly during the spawning period and remained low (or were not detectable) from spring through autumn. These data indicate that changes in plsama steroid hormones and VTG levels are correlated with the annual ovarian activity of the marbled sole. Based on these results and published reports, it appears that in this species DHP is the most important maturation-inducing steroid and that T is also related to final maturation.

• Journal of Aquaculture
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• v.11 no.4
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• pp.513-519
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• 1998

Ovulation of maturing femal mandarin fish, Siniperca scherzeri was induced using single injection of human chorionic gonadotropin (HCG) or gonadotropin releasing hormone-analogue (GnRH-a), GnRH-a plus prostaglandin F2 (PG$F_2$) or GnRH-a plus pimozide. The response was evaluated by fertilization, embryo-formation and hatching rate after insemination. Those rates were generally higher in GnRH-a group than in HCG group. The higher hatching rat of above 89% was achived using a dosage of 5,000 IU/kg HCG plus 10 ${\mu}$g/kg GnRH-a, 10${\mu}$g/kg GnRH-a plus 500 ng/kg PGF2, and 10 ug/kg GnRH-a plus 1-5 mg/kg pimozide. Ovulation was induced in all female injected with sex-maturation hormones and stimulator, but blocked in female injected with HCG plus GnRH-a plus dopamine combination, and GnRH-a plus PGF2 plus indometacin combination. These results show that the mandarin fish in spawning period secrete a sex-mutruation assosiated hormones and gonadotropin-releasing -inhibiting factor(GRIF).

• The korean journal of orthodontics
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• v.15 no.2
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• pp.197-209
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• 1985

To investigate the relationship between the pubertal spurt in body height and bone maturity of the hand-and-wrist in normal occlusion, the author X-rayed the hand-and-wrists of 1,141 students (male 614, female 527) and assessed their bone maturity. In this study, eleven skeletal stages were selected. The bones used to determine skeletal maturity were the ulnar sesamoid of the metacarpophalangeal joint of the first finger, the epiphyses of the proximal, middle, distal phalanges of the third finger, and middle phalanx of the fifth finger, and distal epiphysis of the radius. From the longitudinal data for height, an assessment was made of the change in growth velocity. The pubertal growth stage was divided into onset and peak height velocity phases. The results were as follows; 1. The onset of the pubertal growth was between the $PP_3=\;and\;MP_3=$ stage for boys, and between the $MP_3=\;and\;MP_5=$ stage for girls; the mean age of onset was 10.6 years for boys and 9.0 years for girls. 2. The peak height velocity was between the S and $MP_{3_{cap}}$ stage for boys, and between the $MP_{3_{cap}}$ and $MP_{5_{cap}}$ stage for girls; the mom age of peak height velocity was 12.5 years for boys and 10.9 years for girls. 3. As the stages of bone maturity progressed from $DP_{3u},\;to\;PP_{3u},\;MP_{3u}$, Ru, the peak height velocity had been reached, and the growth rate retarded, therefore the approach to full physical maturity was attained. 4. The evidence for the period of onset, peak height velocity and bone maturation suggested that girls were in advance of boys. During the latter part of pubertal growth, the rate of boys' bone maturation was faster than that of girls'.