• Animal cells and systems
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• v.6 no.1
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• pp.75-80
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• 2002

A study on the effects of bisphenol A (BPA) on sex differentiation and gonadal development in medaka, Oryzias latipes, was investigated by histological examination. The fish were exposed to aqueous solutions of BPA at nominal concentrations of 50, 100, and 200 $\mu\textrm{g}$/L from newly-hatched larvae stage to 70 d. The ovaries of female fish were composed of oocytes at the chromatin nucleolus and peri-nucleolus stages at 20 d after the exposure. The testes contained a number of spermatogonia and spermatocytes at 30 d. In the process of sex differentiation. gonadal development was not different in all experimental groups until 30 d after the exposure. At 70 d after the exposure, however, advanced development of oocytes in the ovary and inhibition of spermatogenesis in the testis were observed in the BPA-treated groups compared to the non-treated controls. More females than males were identified in the 50 and 100 $\mu\textrm{g}$/L BPA-treated groups, in comparison to the 200 $\mu\textrm{g}$/L BPA-treated group and non-treated controls. Medaka exposed to 200 $\mu\textrm{g}$/L BPA were bigger compared to other experimental groups. The present study suggests that BPA may lead to problems in either mating or sexual behavior due to the difference in growth and disparity of sexual maturation between male and female fish.

• Development and Reproduction
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• v.10 no.3
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• pp.193-196
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• 2006

The process in the formation of primordial germ cells, primitive and early gonadogenesis were investigated by histological examination for the reproductive physiological study in the scorpion fish, Sebastiscus marmoratus. The primordial germ cells about $10\;{\mu}m$ in diameter were observed in the fibrous mesenchymal tissue located between gut and mesonephric duct of the larvae within the maternal body. As the fibrous epithelium extends to the direction of peritoneum, the primordial germ cells moved. From 31 days post parturition, the fibrous epithelium gets thicker, and the primitive gonad starts to form. From 49 days post parturition, as the primitive gonad of the primitive gonad extend, it starts to form cavity, and about 60 days post parturition, the formation of the ovarian cavity is completed. From 79 days post parturition, germ cells proliferated along the inner edge of the ovarian cavity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.654-658
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• 2014

We report the first identification of a spawning ground of the blackfin flounder Glyptocephlaus stelleri near the Wangdol-cho sea mountains, located in the southern East Sea. Eggs and larval fish of G. stelleri were collected during April and June, 2014, when an abundance of eggs was found in the southern area of Wangdol-cho. Our findings suggest that G. stelleri prefers to spawn in the vicinity of the off-shore sea mountains, where the temperature is between 10 and $12^{\circ}C$ and the water depth is 100 m, rather than inshore.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.4
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• pp.389-399
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• 2019

This study is designed to observe the development of skeleton of Sakhalin sole Limanda sakhalinensis in order to use the findings as the basic data for the taxonomic research. As for the development of skeleton, on 20 days of the hatch when its average total length was 5.86 mm, the clavicle and the paraspenoid in the cranium were ossified. As for the jaw bone, the premaxillary and the dentary were ossified. On 28 days of hatch when its total length was 7.05 mm, 25 neural spines and 22 hemal spines were ossified and 5 fin rays appeared. On 34 days of hatch when its average total length was 8.40 mm, the end of tail was twisted by $45^{\circ}$ and 3 hypural bones were ossified. On 48 days of hatch when its average total length was 10.1 mm, 2 actinosts below the postcleithrum were ossified. On 54 days of hatch, when the average total length was 10.4 mm, the ethmoid, prootic and exoccipital were ossified, thus completing the ossification of skeleton.

• Journal of fish pathology
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• v.22 no.1
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• pp.15-21
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• 2009

White spot syndrome virus (WSSV) is a strong causative agent for high mortality in cultured and wild shrimps. From this study, the WSSV prevalence in marine organisms around shrimp farm as well as live feed-mediated transmission of WSSV to farmed shrimps were investigated. Based on nested-PCR method, WSSV was detected in wide array of marine organisms including Perinereis aibuhitensis (81.3% of prevalence rate, 13/16), Enedrias fangi (100%, 16/16), Ruditapes philippinarum (20%, 2/10), crab larvae (100%, 10/10), copepoda (30%, 3/10), Periophthalmus modestus (50%, 5/10), Pachygrapsus crassipes (10%, 1/10), Helice tridens (20%, 2/10) and Neomysis sp. (70%, 7/10). On the other hand, WSSV was not detected in Bullacta exarata, Uca arcuata, and Reishia clavigera. The percent prevalence of WSSV in wild shrimps, Fenneropenaeus chinensis was only 6%, but markedly increased up to 56% after a feeding trial using polychaete worms for one month, indicating that the live feed is one of significant carriers of WSSV to shrimps under practical farming conditions.

• Korean Journal of Ichthyology
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• v.4 no.1
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• pp.1-13
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• 1992

The gobiid fish, Luciogobius guttalus Gill has an anguilliform with some blackish and reddish brown color in life. It grows up to 90mm in total length. The specimens have been collected from several localities in the southern parts of Korea and Hokkaido, Japan. During the ebb tide, the fish was found in high level of intertidal zone exposed to the air among pebbles in the hollows and slopes of rocks. There are also some other small gobiid fishes comprising 3 species of relative gobies and 1 species of blennioid fish. A total of 5 egg masses were collected from the coast of Haeundae in April to May 1990. Each egg mass was deposited in one layer on the underside of a stone embedded in pebbles and guarded by the male parent. The eggs are club-shaped ranging from 2.71 to 2.80mm in long axis and from 0.65 to 0.74mm in short axis. The eggs were hatched in 98 hours after incubatied at the temperature varying from 19.5 to $25.5^{\circ}C$The newly hatched larvae were from 3.85 to 4.00mm in total length with 35~36 myomeres. In eleven days after hatching, total length reached 5.50mm. The part of the fin-fold of the future dorsal and anal fins became high. In sixteen days after hatching, the lavae averaged 6.20mm in total length and the caudal notochord flex at $45^{\circ}$. The larvae reached the juvenile stage in 48~50 days after hatching and attained 12.80~14.00mm in total length, and all fin-rays was formed. Ossification of the cranium took place at 5.50mm of mean total length in parasphenoid and basioccipital. Ossification of the visceral skeleton occurred in areas where active movements of bones are required, notalbly in the parts of feeding and respiration. Vertebrae began to develop from the anterior end to ossify posteriorly. Neural and haemal spines of vertebrae ossified always prior to the corresponding centra. When larvae reached to about 6.60mm in mean total length (17~18 days after hatching), jaw bones were more repidly ossified than vertebrae and cranium. Ossification of all bones nearly completed when the larvae reached to 13.40mm in mean total length (47~50 days after hatching).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.1
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• pp.16-23
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• 1987

The cyprinid loach, Misgurnus mizolepis $G\ddot{u}nther$, a freshwater teleost, is a member of the family Cobitidae and is known to distribute in Korea and China. This fish is considered to be an excellent food fish in Korea. This report is a description of the gross morphology of the embryos and larvae up to the development of juvenile period of life. The eggs were obtained by injecting gonadotropin and fertilized by wet method in the laboratory on July 10 in 1986. The inseminated eggs were rinsed with tap water and incubated at $25^{\circ}C$. Live, freshly laid eggs were separative, demersal, adhesive, light yellow and average 1.1mm in diameter. The hatching took place in about yellow and average 1.1mm in diameter. The hatching took place in about 24 hours after fertilization. The newly hatched larvae were average 2.7 mm in total length possessing yolk sac and 35-36 myotomes. Ten hours after hatching, the prelarvae attained 3.5 mm in total length. The first heart pulse and melanophores at the side of the body were observed at this stage. Yolk sac was completely reserved at four days after hatching. The larvae that was cultured 24 days after hatching, 15.4-16.4 mm in total length, entered the juvenile period of life. All the un rays were already peresent; D. III 6, A. III, 5, P.10, V. 4-5, C.14.

• Journal of fish pathology
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• v.33 no.2
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• pp.127-138
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• 2020

We attempted to isolate and identify potentially pathogenic bacteria from geoduck clam (Panopea japonica) larvae, juvenile and adult, focusing on Vibrios. The isolates were identified by molecular approach and biochemical characterization. In particular, we applied MLSA (multilocus sequence analysis) to the isolated Vibrios for clear identification and phylogenetic relationships, by combining 16s rDNA and several houskeeping genes (pyrH, recA, rpoA). We obtained 141 isolates; 10 from healthy adults, 52 from moribund adults with blisters and 79 from larvae. 46 from the moribund adults and 39 from the larvae were identified as Vibrio species, while the rest of these samples and all the isolates from healthy adult were identified as marine general bacteria. Among Vibrio species, Vibrio splendidus was the most frequently identified from the moribund adults and clustered with the known V. splendidus in GenBank by MLSA. However, it was still unclear that V. splendidus was the cause of blisters because the artificial infection experiment was not conducted and V. splendidus was isolated also from the larvae. Further studies are necessary to clarify the etiological agent of the blisters found in geoduck clam in this study.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.1
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• pp.81-88
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• 2018

A study for species composition and abundance of the fish assemblages in the eastern Jinhae Bay, Korea was conducted using monthly larval collection by a RN80 net from October, 2010 to September, 2011. Of all the 45 species collected, the dominant species were Clupea pallasii, Hexagrammos otakii, Pholis fangi and Engraulis japonicus. Clupea pallasii, Hexagrammos otakii, Pholis fangi in winter and examined Engraulis japonicus, Acanthogobius sp., Parablennius yatabei, and Tridentiger trigonocephalus in summer appeared seasonally. Popoulation characteristic by stations was not clear seasonally and spatially, and appearance aspects of dominant species were similar by stations. Compared our results with other studies in the South Sea, dominant species and their appearance period were similar to their spawning period. Finally, the appearance period of the larvae in the South Sea was closely resulted to spawning period rather than the regional characteristic.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.3
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• pp.252-258
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• 2013

The quality and quantity of food organisms in fish seed production are important. The marine microalgae Nannochloropsis oculata are used as initial food organisms in the field. We investigated the effects of salinity (0, 10, 20, 30, 40 and 50 psu) on the lipid and fatty acid composition of N. oculata. Cultivation of N. oculata at varying salinities showed the highest growth rate at 20 psu. Total lipid content ranged from 17.26 to 18.63% at salinities from 0 to 50 psu). The nonpolar lipid content increased markedly at 30 psu and was highest at 15.55%. The polar lipid content was lowest at 30 psu, by 84.45%. It was also found that the omega-3 and EPA contents were inversely proportional to salt concentration. For the polar and nonpolar lipid compositions, there was no significant effect of salinity. Omega-3 polyunsaturated fatty acid content especially the content of EPA in the seawater larvae is the essential fatty acid in this food organism. It is thus advantageous to culture N. oculata at 20 psu.