• The Korean Journal of Malacology
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• v.31 no.1
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• pp.21-26
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• 2015

This study histologically describes the gonadal development and reproductive cycle of the abalone, Haliotis discus discus inhabiting Jeju Island of Korea. Gonads displayed histologically definitive seasonal changes. The gonad index (GI) of both females and males was the highest (3.2 and 3.3) in September and was the lowest (1.7 and 1.4) in January and February. Egg diameter increase from early stage in March and reach about $180{\mu}m$ to ripe stage in August. The condition index (CI) was highest in July and lowest in May. The pattern of changes in the GI, egg diameter and CI were similar to the pattern of seasonal changes in gonadal tissues. The female ratio (F/F + M) was 59% (n = 182:127). The reproductive cycle was divided into an inactive stage (January-February), early active stage (March-April), late active stage (May-July), ripe stage (August-October) and spent and degenerative stage (November-January). The main spawning period of H. discus discus was August to October at Jeju Island in 2014.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.6
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• pp.702-708
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• 2002

Although Umboniunm thomasi is one of marine mollusc (Archaeogastropoda: Trochidae) inhabiting the sands in the intertidal zone of the west coast of Korea, aspects of its reproductive biology are still not too well known. Reproductive cycle, gametogenesis, and first sexual maturity of U. thomasi collected at the west coast of Buan-gun, Jeollabuk-do, Korea were investigated monthly from January to December 1999. U. thomasi was dioecious, and an oviparous. The gonad was placed in the rear of the flesh part in the spiral shell. The external colors of the ripe ovary and testis appeared to be green and milk-white or yellowish white, respectively. Meat weigh rate peaked in July ($37.5\%$). And then the value sharply decreased in September ($28.3\%$), thereafter, gradually increased in November ($31.7\%$). Fully ripe oocytes were approximately 100$\~$110 $/mu$m in diameter, and their cytoplasm contained a great number of yolk Branules. Based on the monthly changes of the Bonadal development, gametogenesis, and meat weight rate, the reproductive cycle of U. thomasi could be devided into five successive stages: early active (November to April), late active (February to May), ripe (April to August), spawning (July to October), and recovery (September to February). Gonadal development and spawning were closely related to the seawater temperature, the main spawning occurred in September when the temperature reached above 24.2$^{\circ}C$. Individuals of 4.4 mm and less in shell height could not take part in reproduction in both sexes. Percentages of first sexual maturity of female and male shells ranging from 5.5 to 6.4 mm were $55.0\%$ and $61.9\%$, respectively, and $100\%$ of those over 7.5 mm in shell heights in both sexes participated in the reproduction.

• The Korean Journal of Malacology
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• v.13 no.1
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• pp.55-64
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• 1997

꼬막, Tegillarca granosa은 우리나라 남해 및 서해안 일대에서 서식하는 중요한 수산자원 중의 하나이지만, 이에 대한 생물학적 기초연구는 거의 없는 실정이다. 따라서 1995년 2월부터 1996년 1월까지 전남 벌교연안에서 채집한 꼬막의 생식소발달, 생식세포형성과정 및 생식주기를 조사하였다. 1. 꼬막은 자웅이체이면서 난생이고, 생식소는 내장낭의 간중장선을 싸고 있는 결합조직으로부터 족부의 근육층까지 분포한다.2. 미분화간층직과 호산성 과립세포들이 초기 활성기의 소낭에 풍부하게 나타나기 시작하여 완숙기에는 거의 없어지는 것으로 보아, 이들은 생식소 및 생식세포형성과 발달에 영향을 공급하는 영향세포로 생각된다.3. 생식소발달, 생식세포형성과정, 조직분화과정 및 세포학적 특성에 따라, 이들의 생식주기를 초기 활성기, 완숙기, 부분 방출기, 방출 및 비활성기 등으로 구분할 수 있다. 4. 방란 및 방정은 수온 2$0^{\circ}C$정도되는 6월하순부터 시작되고, 주산란시기는 수온이 23-24$^{\circ}C$정도 되는 7-8월이며, 완숙란의 크기는 50-60$\mu\textrm{m}$이다.5. 비활성기는 9월에서 이듬해 4월까지 지속되는 비교적 긴 기간이며, 초기 활성기도 비교적 길어 1월에서 5월까지 지속되는 반면, 후기활성, 완숙 및 방출기는 비교적 짧아, 5월에서 8월까지 모두 완료된다.6. 비만도의 월별 변화는 생식소의 발달, 생식주기 및 수온과 밀접한 관계가 있다.7. 사용된 재료 433개체 중 1개체가 자웅동체현상을 나타내었다.

• Korean Journal of Ichthyology
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• v.32 no.3
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• pp.130-135
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• 2020

Male gonadal development of the yellow catfish, Pseudobagrus fulvidraco, one of the most popular fish species in Korean aquaculture performance, was investigated by histological observation of monthly collected specimens to make comparisons between wild and cultured individuals. Their reproductive cycle was classified into the successive developmental stages as follows: a growing stage (April), a spawning stage (May), a degeneration stage (June to July), and a resting stage (August to October) in the wild and outdoor-cage individuals; a growing stage (April to June), a spawning stage (July to August), a degeneration stage (September), and a resting stage (October) in the indoor-cage ones. Values of gonadosomatic index (GSI) of wild and outdoor cages peaked in May, followed by a sudden decline in August~September and June~August, respectively. In contrast, GSI values of the indoor-cage individuals peaked in September and were followed by a sudden drop. Remarkable seasonal variation in condition factor (CF) was undetectable, peaking in June in the wild-cage individuals and November in the wild ones. Overall, our results suggest that it is suitable to use the male of the outdoor-cage individuals for artificial fertilization and that it is efficient to perform artificial fertilization in May, such as reproductive cycle of wild.

• The Korean Journal of Malacology
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• v.20 no.1
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• pp.85-92
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• 2004

We investigated the reproductive cycle with gonadal development of the female Cyclina sinensis by histological observations and seasonal changes in biochemical components of the adductor muscle and visceral mass tissues were studied by biochemical analysis, from January to December, 2001. The reproductive cycle of this species can be classified into five successive stages: early active stage (February to April), late active stage (March to June), ripe stage (May to August), partially spawned stage (July to October) and spent/inactive stage (September to February). Total protein contents in the adductor muscle tissues reached the maximum in February (early active stage) and appeared the minimum in June (ripe stage), while their contents in the visceral mass tissues reached the maximum in the late active and ripe stages (June) and gradually decreased from July (partially spawned stage) to November (spent/inactive stage). Changes in total protein contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.499, p = 0.099). Total lipid contents in the adductor muscle tissues reached the maximum in January (the inactive stages) and their contents gradually decreased from February. Their contents in the visceral mass tissues, however, reached the maximum in June (late active and ripe stage) and gradually decreased from July (the partially spawned stage). On the whole, total lipid contents showed a negative correlationship between the adductor muscle and visceral mass tissues (r = -0.631, p < 0.05). Therefore, These results indicate that the nutrient contents of the adductor muscle and visceral muscle tissues change in response to gonadal energy needs. Glycogen contents in the adductor muscle tissue reached the maximum in March (early and late active stages) and decreased from July to September (partially spawned stage). while their contents in the visceral mass tissues reached the maximum in June (late active and ripe stages) and gradually decreased from July (partially spawned stage). Thereafter, their levels gradually increased in November (spent/inactive stage). On the whole, changes in glycogen contents appeared negative correlationship between the adductor muscle and visceral mass tissues. However, they showed no significant different (r = -0.307, p = 0.331).

• 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).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.489-499
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• 1998

Gonadal development, reproductive cycle and embryonic development of the marbled rockfish, Sebastiscus marmoratus were investigated histologically. A total of 1,035 specimens were collected from the Cheju Island from July of 1992 to May of 1996. Gonadosomatic index (GSI) in female reached the maximum during October to March, thereafter, the values decreased from Norvember to April. GSI in male reached the maximum in September (before one to three months of the female's maximum), thereafter, the values rapidly decreased from October to December. The annual reproductive cycle can be divided into five stages in female and four stages in male: females, Growing(June to September), Mature(September to February), Ripe and copulation(October to March), Gestation and parturition(November to April), Degenerative and resting(December to May); in males, Growing(April to July), Mature(August to November), Ripe and copulation(September to December), and Degenerstive and resting(November to March). Size frequency distribution of eggs and larvae showed non-synchrony. Maternal larvae parturition occurred one or two time during November to April. Mean length of the larvae parturition was 3.5 mm. Mean number of eggs and maternal larvae for the 15 cm minimum class of female was 58,377, and fecundity increased with the increase of total length and body weight.

• The Korean Journal of Malacology
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• v.30 no.2
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• pp.107-116
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• 2014

Gonadal development and maturation mechanism were studied on the freshwater marsh clam Corbicula papyracea (Heude), which is the endangered species in Korea. The specimens were collected in the rearing ponds and waterway of NFRDI in Gapyeong-gun, Gyeonggi-do from January to December 2004, and then investigated by condition factor, relative growth, gonadal development phases and gonad histological characters based on 30-50 individuals every month. Comparing with the freshwater marsh clam, C. papyracea is small, light olive brown shell and violet interior. The hermaphrodite individuals of C. papyracea take an internal fertilization and fertilized eggs are stored in the foster-sack in the gills, then the hatched juveniles are released outside after an ovoviviparous process. The average water temperature of inhabit area was in range of $1.8-27.0^{\circ}C$ and usually took great effects on the gonad maturation of C. papyracea. The condition factor ranged from 0.14 to 0.21 throughout the year, which was the lowest during winter season (December-February), and gradually increased to the highest value of 0.21 in May. The ratio of meat weight to total weight was 25.9-38.7%, indicating the similar trend with condition factor. The highest values of condition factor and the ratio of meat weight appeared 1-2 months later than gonadosomatic index reached the peak value, it was probably because that the ovoviviparous eggs would spend a long period before hatching from the foster-sack in the gills. To synthesize the characters of meat weight, condition factor and gonad development by histological study, reproductive cycle of C. papyracea could be divided into five successive stages: multiplicative stage (December to February), growing stage (February to May), mature stage (June to August), spawning stage (August to November), recovery stage (November to December). The smallest shell length of matured C. papyracea was 12.6 mm, and individuals, larger than 16 mm, was formed the nursery in the gills.

• The Korean Journal of Malacology
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• v.22 no.1 s.35
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• pp.13-22
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• 2006

Gonadosomatic index (GSI), oogenesis and reproductive cycle of Glossaulax didyma were investigated by the cytological histological obserbations and morphometric data. Samples were collected monthly from the intertidal zone of Biin Bay, Seocheon, Korea, for one year. Monthly variations in the GSI showed similar patterns with gonadal development. In the early vitellogenic oocyte, the Golgi complex and mitochondria were invovled in the formation of lipid droplet and yolk precursor. In the late vitellogenic oocytes, the rough endoplasmic reticulum and multivesicular bodies were involved in the formation of profeid yolk granules in the cytoplasm. A mature yolk granule was composed of three components: main body (central core), superficial layer, and the limiting membrane. The spawning season was from early June to late August, and the main spawning occurred between July and August when the seawater temperature was above $19^{\circ}C$. The female reproductive cycle can be classified into five successive stages: early active stage (December to February), late active stage (February to March), ripe stage (April to July), spawning stage (June to August), recovery stage (August to November). Fully mature oocytes were approximately $250-270{\mu}m$ in diameter.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.1-11
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• 2005

Reproductive cycle, first sexual maturity, spawning amount related with the size and spawning interval in female Ruditapes philippinarum were investigated by histological observation and the analysis of morphometric data during artificial spawning induction. Ruditapes philippinarum is dioecious and oviparous. The reproductive cycle of this species can be subdivided 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). The spawning period was once a year between May and early October, and the main spawning occurred between July and August when seawater temperature was approximately $20^{\circ}C$. Percentages of first sexual maturity of female clam of 15.1-20.0 mm in shell length were 56.3%, and 100% for the clams > 25.1 mm. The mean number of the spawned eggs increased with the increase of size classes (shell length). In case of spawning induction by the same size class, the number of spawned eggs were gradually decreased with the increase of 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 15-17 days (average 16.5 days).