• Korean journal of applied entomology
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• v.41 no.4
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• pp.269-277
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• 2002

Ecological studies on entomopathogenic nematodes are required to increase control efficacy against target insect pests and to obtain basic information for mass production. Thus, effect of temperature and nematode concentration on infectivity and reproduction of Steinernema carpocapsae Pocheon and that of exposure time and soil depth on infectivity were examined using Galleria mellonella larvae. Infectivity and reproduction were examined at five temperatures, 13, 18, 24, 30 and 35$^{\circ}C$ with seven concentrations, 0, 5, 10, 20, 40, 80 and 160 infective juveniles (IJs)/larva. Temperature and nematode concentration influenced infectivity and reproduction of S. carpocapsae Pocheon. Although G. mellonella larvae were killed by S. carpocapsae Pocheon at all given temperatures and nematode concentrations, mortality was higher at 24$^{\circ}C$ than other temperatures. Lethal time of G. mellonella by S. carpocapsae Pocheon was shorter with increasing temperature and nematode concentrations. S. carpocapsae Pocheon was not established in G. mellonella at 13 and $35^{\circ}C$. Time for the first emergence from G. mellonella cadaver was longer $18^{\circ}C$ (about 20 days) than 24 and $30^{\circ}C$ (about 5 days). The highest number of progenies was obtained at $24^{\circ}C$ with 80IJs/1arva, i.e., $18.8$\times$10^4$IJs were produced from a larva. In the exposure time assay, G. mellonella death was recorded in 10 minutes when 300 IJs were inoculated per larva. When S. carpocapsae Pocheon was inoculated at the rate of $10^{9}$ IJs/ha to G. mellonella at the depth of 0, 2, 5 and 10 cm of sand columns, 100% mortality and similar sex ratio were observed but number of established IJs in cadaver was decreased with deepening the soil depth. The results indicated that optimum temperature for infectivity and reproduction of S. carpocapsae Pocheon was $24^{\circ}C$ In addition, S. carpocapsae Pocheon was effective to target insects within 5 cm from the soil surface.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.21 no.1
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• pp.36-43
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• 2016

Wild glass eels found in the Korean peninsula are thought to migrate along the North Equatorial Current and undergo the processes of spawning and incubation in the Mariana Trench. Juveniles of the wild glass eels are collected from the southern and western coasts of the Korean peninsula and used as seeds for aquaculture. To investigate the feeding behavior of wild glass eels, we collected glass eels from the Nakdong River estuary during March and April 2014 and analyzed the total length, wet weight, dry weight, carbon and nitrogen contents, and stable isotope ratio of eels as well as water temperature and salinity. Water temperature in the Nakdong River estuary was $13.2{\pm}1.0$ (mean ${\pm}$ 1SE; range, $10.1{\sim}15.7)^{\circ}C$ and salinity was $24.8{\pm}2.4$ (13.2~34.0), showed a lower range from 13.2 to 30.0 (a mean of 21.2) when the floodgates were opened. The total length of glass eels was $56.5{\pm}0.2$ (51.0~63.6) mm, wet weight was $70.9{\pm}1.4$ (33.6~133.2) mg, and dry weight was $16.5{\pm}0.3$ (10.1~29.1) mg. Carbon and nitrogen contents of glass eels were $51.0{\pm}0.8%$ and $13.9{\pm}0.1%$, respectively. Mean ${\delta}^{13}C$ and ${\delta}^{15}N$ values of glass eels collected from the Nakdong River estuary were -20.9±0.2‰ and 6.1±0.1‰, displaying similar values to those of leptocephalus, glass eel larvae collected from the North Equatorial Current. Therefore, this result suggest that the glass eels collected from the Nakdong River estuary do not feed on prey after metamorphosis from eel larvae to glass eels their migration.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.263-269
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• 2023

This study aims to contribute to the research on resource recovery for the rapidly declining population of Liparis tanakae by observing the larval development process and the morphology of juveniles based on their growth. Natural spawning eggs collected in Yeosu were used for observing the process of egg development and larval morphology. The water temperature during the rearing process was maintained at 12.3~13.5℃ (average 12.7℃). The fertilized eggs had an egg diameter ranging from 1.57 to 1.79 mm (average 1.71 mm) and were spherical and adhesive. Within 4 hours 35 minutes after fertilization, they reached the two-cell stage, and after 74 hours 10 minutes, the formation of the yolk sac began. At 106 hours post-fertilization, a caudal fin appeared at the tail tip. Hatching began at 526 hours, and the larvae developed with the yolk sac positioned just behind the eyes. The newly hatched larvae had both the mouth and anus open. Melanophores appeared inside the lower jaw and around the tail on the third day after hatching. By the 16th day after hatching, most of the yolk was absorbed, and melanophores were visible in the head region. Finally, on the 63rd day after hatching, the head region significantly developed, and the body shape and mouth were similar to those of an adult fish, signifying the transition to the juvenile stage. This study will serve as valuable data for aquaculture techniques related to the conservation and restoration of fish species based on the hatching and juvenile morphology of Liparis tanakae.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.2
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• pp.131-136
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• 2001

Relative growth and composition of larval development stages in brood pouch of the melania snail, Semisulcospira libertina libertina were investigated based on monthly field samples for a year. Total number of specimens examined was 1,200. Size values (mean$\pm$S. D.) of shell height (SH), shell diameter (SD), total weight (TW), meat weight (MW) and shell weight (SW) were $15.96\pm3.41\;mm$, $7.82\pm1.38\;mm$, $0.55\pm0.31\;g$, $0.24\pm0.15\;g$ and $0.39\pm0.23\;g$, respectively, Water temperature (WT) of the sampling site varied from $1.3^{\circ}C\;to\;22.5^{\circ}C$. Relative growth equations among SH, SD, TW, MW and SW of S. libertina libertina specimens pooled were as follows: SD=0,3583SH+2.1648 $(R^2=0.8391)$, $TW=0.0005SH^{2.4853}\;(R^2=0.8391)$,$MW:\;0.0005SH^{2.849}\;(R^2= 0.8391)$ and $SW=0.0004SH^{2.3798}\;(R^2=0.7057)$. Female S. libertina libertina had larvae in its brood pouch throughout the year, Average number of larvae in the brood pouch varied from $91\pm33(July)$ to $396\pm174\;(November)$, decreasing in spring and increasing in autumn. In the monthly composition of larval stage in the brood pouch, trochophore, pre-veliger, veliger and juvenile showed maximum as $66.7\%$ in May, $70.7\%$ in November, $60.9\%$ in February and $13.9\%$ in January, respectively. Percent composition of the juveniles decreased in spring and autumn. In conclusion, S. libertina libertina is likely to have two main parturition periods, March to May and September and October.

• Journal of Aquaculture
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• v.11 no.4
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• pp.529-546
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• 1998

Gonadal part that developed by indifferentiation period for 6 months after hatching is made as gonad and fat body. These gonad are thin semi-transparant and undistinguished germ cell. Germinal epithelium is distinguished by development of gonad epithelial tissue from 7 months after hatching. Sex differentiation is begun by oogonia develoment at 8 months after hatching. Primary oocytes grow over germinal epithelium of gonadal cavity, at 9 months after hatching, gonadal cavity become ovarian cavity as they increasing. As soon as oocytes at 13 months after hatching are filled with the whole part of gonad, degeneration of oocyte is begun. And then, gonad has cavity tissue, a small number of oocyte are located in gonadal cavity. At 15 months after hatching, new primary oocyte develop and cavity of ovarian tissue in the central of ovarian cavity. Spermatogonia multiplicate and cavity tissue consist of testicular tissue. These gonad become hermaphrodite and then ditermine the sex of female and male. These results show the red sea bream is juvenile hermaphrodite and undif-ferentiated gonochoristic teleost. Male and female differentiation type of gonad is divided in undifferentiation stage, oogonia-like stage, ovary-like stage, ovary development stage, hermaphroditic testis stage, hermaphroditic ovary stage, and testis development stage. Undifferentiation stage is continued total lenth 18cm at 13 months after hatching. ovary-like stage is continued total length 11~18cm at 13 months after hatching. Ovary-like stage is continued total length 14~26cm at 10~14 months after hatching. Ovary development stage begins from total length 20cm, 14 months after hatching. At 20 months after hatching, 44 percent of total sampled individuals had ovary. Hermaphroditic ovary stage first begins total length 19~20 cm at 15 months after hatching, but it is not observed total length 28~29cm at 20months after hatching. Hermaphroditic testis stage first begins total length 21~22cm at 20months after hatching and is continued for 20months. Testis development stage first begins total length 20~21cm at 20 months after hatching, and is occupied 33 percent total length 28~29cm at 20 months. The beginning of sex differentiation more than 50 percent is from total length 16cm at 11 months after hatching. Sex determination begins total length 20cm, 14months after hatching in female and total length 20cm, 15 months after hatching in male. Sex determination more than 50 percent begins total length 23cm,, 17 months after hatching. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks. This appearence is showed the same tendency in 3-year old red sea bream. 1.9mm larvae after hatching grow about 19mm larvae for 47 days. The relationship between the total length and body weight of larvae and juveniles in $BW=4.45{\times}10^{-6}TL^{3.4718}$ r=0.9820. Fishes in cage culture grow to maximum total length 28.4cm. The relationship between the total length and body weight of these fishes is $BW=2.36{\times}10^{-2}TL^{2.9180}$, r=0.9971. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks.

• Development and Reproduction
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• v.13 no.4
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• pp.239-247
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• 2009

Hatching rate, larval deformation and growth rate of selected olive flounder (Paralichthys olivaceus) for rapid growth were compared to those of the unselected fish. Fish were spawned on the same day and cultured under the similar conditions. The selected fish had a significantly higher eggs hatching rate, and lower larval deformation. The selected fish grew significantly faster, and at the end of the experiment (8 weeks after hatching) averaged 50.49${\pm}$2.67 mm in total length, 16.30${\pm}$0.08 mm in body height, and 1.036${\pm}$0.118 g in weight, compared to 40.55${\pm}$3.13 mm, 13.50${\pm}$0.96 mm, and 0.557${\pm}$0.073 g for unselected fish, respectively. The selected fish had a significantly higher body shape index, however lower condition factor than the unselected fish. The results of the present study demonstrate that the selected fish of the olive flounder for rapid growth had superior growth and improved body shape.

• Development and Reproduction
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• v.13 no.4
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• pp.281-289
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• 2009

The slime flounder Microstomus achne were caught at Geomun Island, Yosu-si, Jeollanamdo from January to March in 2006. The fertilized eggs were observed for morphological development of egg, embryo and larva. Eggs were colorless transparent, separative pelagic, absent of oil globule, and the diameter was 1.64${\pm}$0.03 mm (n=50). The eggs were hatched at 168 hours 40 minutes after fertilization in the range of $9.8\sim13.0^{\circ}C$ (mean $11.4{\pm}1.6^{\circ}C$). Total length of newly hatched larva was 4.05${\pm}$0.18 mm (n=20). The larva had developed membranous fin showing waterdrop-shaped structure, and their mouth and anus were not open. The myotomes were 14~15+33~34=47~49. The egg yolks were 1.64${\pm}$0.12 mm in major axis, and 1.23${\pm}$0.19 mm in minor axis. At 12 days after hatching, the total length was 7.32${\pm}$0.42 mm(n=20). The egg yolk was completely absorbed and transferred to post larval stage. Star-shaped melanophores and branch-shaped xanthophores in the edge of membranous fin were more densed. Chrysanthemum-shaped melanophores in the notochord were densed and formed 4~5 melanophore bands. At 90~93 days after hatching, morphological features of the larva, 19.91${\pm}$1.63 mm TL(n=20), were transferred to juvenile stage showing similar features with those of the adult fish.