• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.184-191
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• 2000

Gametogenesis and the reproductive cycle of the marsh clam, Corbicula leana(Prime} were investigated monthly Hyongsan estuary, Korea from January to December 1998 by histological observation. C. leana had separate sexes, and oviparous. The gonads were located between the sub-region of mid-intestinal gland in visceral cavity and reticular cennective tissue. The ovary and testis were composed of a number of ovarian and testicular tubules, respectively, Mature oocytes were characterized by germinal vesicles with nucleoli and their sizes ranged $70\;to\;80{\mu}m$ in diameter. A number of mesenchymal tissues and pigment granular cells were distributed in the growing oocytes and spermatocytes during early developmental stages. With the further development of gonad, these tissuse and cells gradually disappeared. The monthly changes in the fatness index were closely related to reproductive cycle. Minimun size for sexual maturity was reached over 10.0 mm in shell length. The reproductive cycle could be classified into 6 stages : multiplicative (March to April): early growing and growing (May to June), mature (July to August), spent (September), degenerative (October) and recovery (November to February).

• Korean journal of applied entomology
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• v.60 no.2
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• pp.175-183
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• 2021

As a baseline study of (common name) Locusta migratoria (Orthoptera: Acrididae) to utilize as a food source, we investigated the developmental characteristics of ovaries and eggs. Locusta migratoria had a pair of ovaries and more than 90-104 panoistic ovarioles. The ovary length in the adult stage was longer than it is in the 5th nymph stage. The length on the first day of the adult stage was 2.5-fold longer than the first day of 5^th instar. The ovary length showed a tendency to increase until the 30th day of the adult phase, but decreased from the 35^th day. Ovarioles length was about half of the ovary length, showing a similar tendency to the variation of ovary length. The lengths of the ovaries and the ovarioles increased proportionally to body weight. The matured eggs were identifiable from the 15^th day of the adult stage, and the number was the highest on the 30^th day at 50.6 individuals. Spermatheca size was also affected by the ovary development. The ovaries of L. migratoria were highly matured until the 30th day of adult stage. Weight and size of eggs increased sharply from the 4th day after egg oviposition and remained from the 7th day after spawning. Based on the above results, we found that the ovary of L. migratoria was most developed on the 30th day of adult phase, and 1st nymph is being hatched on the 10th day of the oviposition.

• Journal of Aquaculture
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• v.13 no.3
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• pp.215-222
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• 2000

The primordial germ cell of the sweet fish was recognized from the 2-day old fry (tl : 0.66 cm), when it began to protrude into peritoneal cavity between meaonephric duct and gut. The primordial gonad, with the formation of genital ridge, developed on the 30-day old fry. Ovarian differentiation was identified by the presence of ovarian cavity and meiotic oocytes from the 90-day old fry (tl : 3.42 cm). Testicular differentiation was identified by the presence of spermatogonial cells with efferent duct from the 100-day old fry (11 : 4.50 cm). Hence the sweet fish belongs to the differentiated type of gonochoristic teleost.

• Journal of Sericultural and Entomological Science
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• v.36 no.1
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• pp.69-75
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• 1994

Through the histological and anatomical investigation of silkworm gonad, N. bombycis infection was found to begin from the peripheral region of ovarial sheath or testicular sheath, then, the pathogens spread to the inner portion. Peroral inoculation with purified spores of N. bombycis to 2nd instar larvae at dosages around 106-8/㎤ of artificial diet resulted in the extremely extended larval survival as long as 15 to 22 days of 4th instar. The growth of ovarioles was confirmed in the 10 to 14 day old larvae, oogonia developed into oocytes and nurse cell against heavy infection of the ovary. Gonads rarely obstructed oogenesis and spermatogenesis in the pupae failed in adult eclosion. Light infection of female hosts effected insignificantly on the ovarial development, however, recorded 100% transmission of the pathogens to the progeny populations. Conclusively, ovarial inflection of silkworm induce transovarial transmission begins around 2~3 day old pupae when ovarioles extruded out to hemocoel, and the infection period thought to be continued until the stage of eggs complete shell formation in the ovariole.

• Journal of Aquaculture
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• v.18 no.2
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• pp.76-80
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• 2005

The early gonadal development and sex differentiation of the mandarin fish, Siniperca scherzeri was described from hatch to the 130th day post-hatch (DPH). Primordial germ cells were observed on the just hatched fry (5.10 mm in total length (TL)) and began to protrude into the peritoneal cavity between mesonephric duct and gut. The primordial gonad, with the formation of genital ridge, developed on the 8-10th DPH (10.77-12.47 mm TL). Ovarian differentiation was identified by the presence of ovarian cavity and meiotic oocytes from the 40th DPH (29.75 mm TL). Testicular differentiation was identified by the presence of spermatogonial cells with efferent duct also from the 40th DPH. Sex differentiation of the mandarin fish was identified as gonochoristic type.

• Korean Journal of Ichthyology
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• v.21 no.3
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• pp.141-148
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• 2009

Sex differentiation and gonad development were investigated in a marine medaka species, Oryzias dancena (Beloniformes; Teleostei). The average time to hatch was 11 days post-fertilization (dpf) at $25^{\circ}C$. Primordial germ cell (PGC) was first observed at 5 dpf and migrated to presumptive gonadal area between the gut and pronephric duct at 9 dpf. Male and female gonads were morphologically differentiated at 12 days post-hatching (dph). Early oocytes at perinucleolus stage as well as the formation of spermatid and efferent duct were observed at 28 dph. At 6 weeks of age, the ovary exhibited yolk granulation in many oocytes, while testis possessed a considerable number of spermatogonia and spermatids. The first ovulation was observed in 9-week-old females, and at the same age, males contained fully-matured spermatozoa. Data obtained in this study indicate that the gonad differentiation of O. dancena is the typical type of differentiated gonochorism.

• Korean journal of applied entomology
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• v.30 no.4
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• pp.258-264
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• 1991

Studies were carried out to investigate effects of temperature and photoperiod on diapause induction and of juvenile hormone III and 20-hydroxyecdysone treatment on diapausing adults of the alder leaf beetle, Agelastica coerulea Baly(Chrγsomelidae: Coleoptera). Its life cycle and ovarian development in adults were also observed. The beetle had one year life cycle with egg, larval, pupal and adult periods being 7-10, 19-21, 14-15 days and about 10 months, r respectively. All adults showed a diapause syndrome when the larvae were reared at $20^{\circ}C$ or $25^{\circ}C$ in combination of photoperiods of 16L/8D, 12L/12D, or 8L/16D. Their ovarioles did not s show any development of vitellogenesis before or during diapause and even when exposed at $15^{\circ}C$ after overwintering. When diapausing adults were treated with JH III they resumed feeding and laid several eggs and broke diapause condition temporally. But diapausing adults treated with 20-hydroxyecdysone did not show any response.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.5
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• pp.423-435
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• 1984

The reproductive cycle of the small filefish, Rudarius ercodes was investigated based on the annual variations of gonadosomatic index(GSI) and hepatosomatic index(HSI) by electronic and photic microscophy. The specimens used were collected at the coastal area of Benden island, Sizuokagen, Japan, from September 1982 to August 1983. GSI began to increase from March, starting season of longer daylength and higher water temperature, and reached the maximum value between June and August. It began to decrease from September with the lowest value appearing between November and February without any evident variation. The annual variations of HSI were not distinct in male filefish and were negatively related to GSI in female : HSI decreased in the summer season when the ovary was getting mature and reached the maximum in the winter season when the ovary was getting retrogressive. The ovary consisted of a pair of saccular structure with numerous ovarian sacs branched toward the median cavity. Oogonia divided and proliferated along the germinal epithelium of the ovarian sac. Young oocytes with basophile cytoplasm showed several scattering nucleoli along the nuclear membrane. when the oocytes growing to about 300 ${\mu}m$, nuclear membrane to disappear with nucleus migrating toward the animal pole. The regions of protoplasm were extremely confined within the animal hemisphere in which most of cytoplasms were filled with yolk materials and oil drops. After ovulation, residual follicles and growing oocytes remaining in the ovarian sacs degenerated. But perinucleatic young oocytes without follicles formed were not degenerated, and growing continuously still in the next year. Mitochondria and endoplasmic reticula in the cytoplasm remarkably increased with oocytes maturing and yolk accumulating. Those were considered to be functionally related to the yolk accumulation. Five or six layers of possible vitellogenin, oval-shaped disc structures with high electron density, appeared in the apex of follicular processes stretching to the microvilli pits of mature oocytes. Testis consisting of a pair of lobular structures in the right and left were united in the posterior seminal vesicle, Cortex of testis was composed of several seminiferous tubules, and medulla consisting of many sperm ducts connected with tubules. Steroid hormone-secreting cells with numerous endoplasmic reticula and large mitochondria of well developed cristae were recognized in the interstitial cells of the growing testis. Axial filament of spermatozoon invaginated deeply in the central cavity of the nucleus and the head formed U-shape with acrosome severely lacking, mitochondria formed large globular paranuclei at the posterior head, and microtubular axoneme of the tail represented 9+9+2 type. The annual reproductive cycles could be divided into five successive stages : growth(March to July), maturation(May to September), Spawning(mid May to early October) and resting stages(October to February). The spawning peak occurred from June to August.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.6
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• pp.656-660
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• 2001

Gametogenesis, the reproductive cycle, and the condition index of the soft clam, Mya arenaria were investigated monthly based on histological observation at Sachon Bay, south coast of Korea from May 1998 to September 1999 . M. arenaria is dioceious. The ovary and testis were composed of a number of ovarian sacs and testicular tubules, respectively. Ripe oocytes were characterized by germinal vesicles with nucleoli, and their sizes about $60{\mu}m$ in diameter. Monthly changes in condition index and water temperature were closely related to the annual reproductive cycle. The reproductive cycle can be classified into 5 stages: early active stage (february to March), late active stage (April to August), ripe stage (September), partially spawned and spent stage (September to October), inactive stage (November and January).

• Korean journal of applied entomology
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• v.43 no.3 s.136
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• pp.225-231
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• 2004

An endoparasitoid wasp, Cotesia plutellae, has been used for a biological control agent against the diamondback moth, Plutellae xylostella. It has a symbiotic polydnavirus in their reproductive tract, which is required for its successful parasitization. Here, we measured a specific replication time of the polydnavirus during female development of C. plutellae. We, also, analyzed the reproductive potentials of female C. plutellae under mating or different host conditions. At $25^{\circ}C$, pupal C. plutellae began to develop adult tissues such as compound eyes and wings since day 2. At day 5, all adult tissues including antennae were developed and were ready to emerge. With polyclonal antibody raised against C. plutellae polydnavirus, an immunobloting could confirm virus replication at day 4 during pupal stage. Virus particles could be visualized by transmission electron microscope in the oviduct lumen of day 5 pupae. After adult eclosion, venom gland and ovarian calyx increased in size, though ovarioles did not. Mated females layed large number of eggs (over $60\%$) at first 4 days during their mean longevity of ca. 8 days at $25^{\circ}C$. Unmated females showed less active ovipositional behavior, where all the eggs developed into males. C. Plutellae parasitized both P. xylostella and fall webworm, Hyphantria cunea. However, C. Plutellae developed faster and showed higher successful paarasitization in P. xylostella than in H. cunea.