• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.2
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• pp.140-146
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• 2008

Marine ecotoxicological standard method using fish larvae was established with the standard test species of Oryzias latipes(Japanese Medaka) and Paralichthys olivaceus(flounder) and with the 7 day $LC_{50}$ as endpoint. Test method referred to the USEPA(1994) with the replacement of test species found in the Korean water. Standard test species were selected in terms of the species supply and ecological importance in Korean waters. Japanese medaka can be reared with small tanks in the lab and has wide tolerance on salinity, and flounder eggs can be easily obtained from commercial fish hatcheries. General conditions for larval fish toxicity test are as follows. The possible salinity ranges for toxicity test were $0{\sim}35\;psu$ for medaka and >20 psu for flounder. Test type was designated as static non-renewal test if the dissolved oxygen in the test chamber does not fall below 4.0 mg/L. Ages of test species were selected as 7 days after hatched for medaka(about 5 mm TL) and 25 days for flounder(about 10 mm TL) because of the low natural mortality after these periods. Test can be accepted when the survival rates are over 80% in control. Also, species sensitivity on standard reference materials(copper, cadmium or zinc) must be provided with the toxicity test results.

• Journal of Aquaculture
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• v.21 no.4
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• pp.339-345
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• 2008

Farming of the fleshy shrimp Fenneropenaeus chinensis which is a major cultured species in the west coast of South Korea, has been suffered :trom mass mortality due to disease epizootics including viruses. Since the Pacific white shrimp Litopenaeus vannamei was introduced to Korea in 2003, farming of this species has rapidly increased for years, occupying 62.5% of total cultured shrimp production in 2007. However the studies on L. vannamei culture methods for shrimp farming situations in Korea are very limited. Nursery culture of shrimp larvae has some advantages including increased survival, improved feed efficiencies, enhanced growth performance and reduced grow-out period. In this study, L. vannamei postlarvae (${PL_3}-{PL_{10}}$) with a density of $3,750-9,090/m^3$ were cultured in four raceways under limited water exchange condition for 35 days. Survival was the highest (93.6%) in tank stocked with $4,090/m^3$ and was the lowest in tank with $9,090/m^3$ (58.1 %). Mean body weight at harvest ranged from 0.071 to 0.108 g, and FCR was 0.59-0.70 in all tanks. Concentration of total ammonia nitrogen was increased up to 20 ppm on day 10 in all tanks and thereafter gradually decreased by the third week of culture. Nitrite-nitrogen was rapidly increased from the third week, representing bio-floc condition by developed nitrifying bacterial community. Of the present nursery system some modification of structure and consideration for commercial scale are needed in order to be implemented to shrimp farmers.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.6 no.4
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• pp.265-273
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• 2001

The sea urchin has been used as sea food in many countries. This species has also been an important organism of embryological studies for more than a century. In recent years, sea urchin embryos are being used as testing materials for toxicity of pollutants and toxins. Usefulness of sea urchin embryos as experimental models comes from the easiness in obtaining sea urchin samples and a lot of gametes, in rearing embryos in the laboratory, in observing the cellular movement and organ formation during the embryogenesis and in manipulating blastomeres and genetic maferials. The sea urchin in itself is a key organism for the understanding of deuterostome evolution from the protostomes and of indirect development of marine invertebrates which undergo the planktotrophic larval stage. A fertilized sea urchin egg goes through rapid cleavage and becomes a 60 cell embryo 7hr after fertilization. It then develops into a morula, a blastula, a gastrula and finally a pluteus larva approximately 70 hr after fertilization. At the 60 cell stage, the embryo comprises of five territories that express territory-speciflc genes and later form different organs. Micromeres at the vegetal pole ingress into the blastoceol and become the primary mesenchyme cells(PMCs). PMCs express genes involved in skeletogenesis such as SM30, SM37, SM50, PM27, msp130. Among the genes, SM37 and SM50 are considered to be members of a gene family which is characterized by early blastula expression, Glycine-Proline-Glutamine rich repeat structures and spicule matrix forming basic proteins. Genetic studies on the sea urchin embryos help understand the molecular basis of indirect development of marine invertebrates and also of the biomineralization common to the animal kingdom.

• Journal of Aquaculture
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• v.7 no.4
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• pp.189-205
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• 1994

Formerly, adult-tiger puffer, Takifugu rubripes with ova caught in the sea, were used for seedling production. But it was difficult to secure naturally-ripened adults. For the purpose of adult tiger puffer in captivity, this study was carried out. To determine the growth 220 tiger puffers hatched in 1990 (3-year-old) and 1991 (2-year-old) were used. For spawning and egg incubation leading to fry development, eggs were stripped from tiger puffers hatched in 1988 (5-year-old) and 1990 (3-year-old) through human chorionic gonadotropin (BCG) treatments. In May, 1993, mean body length and mean body weight of 2-year-old tiger puffer were $30.72\pm1.35cm\;and\;1,048\pm228 g,$ and that of 3-year-old tiger puffers were $36.02\pm1.17cm$ and $1,402\pm66g$ respectively. The relationship between body length (L) and body weight (W) of 2-year-old the tiger puffers during the experiment period was represented as $W\;=\;1.7892L^{31524}\times10^5$ (r= 0.9436) and that of 3-year-old, $W=\;3.2840L^{36099}\times10^6$ (r= 0.9070) respectively. The GSI in female 2-year-old-fish changed from $0.23\times0.l2\;to\;0.74\pm0.08$, during the experiment period, and in male it didn't change remarkably until November, but thereafter it increased and showed a peak of $8.69\pm5.09$. The GSI of 3-year-old-fish showed a peak of $8.05\pm5.58$ in April in female and $12.65\pm4.60$ in May in male. The change of HSI in 3-year-old-fish was correlative to the change of GSI, but in 2-year-old-fish it was little correlative. In female gonad of 2-year-old tiger puffer, the mature oocytes reached $350{\mu}m$ in April, but thereafter they didn't spawn and became atrophied. But in male gonad, a great number of spermatozoa were crowded in the testicular lobuli in April. Female gonad of 3-year-old tiger puffer had the mature oocytes of 650 pm in March and the ripe oocytes, $900{\mu}m$ in April. Male testis development was similar to that of 2-year-old-fish. Egg-stripping after hormone treatments was possible past 139 hours and 142 hours from each of two 5-year-old-fish (500IU/kg, BW), and after 114 hour from a 3-year-old-fish (1,000 IU/kg, BW) under water temperature $16.3\~17.8^{\circ}C$. Eggs stripped amounted was 650 g and 400 g from two 5-year-old-fish and 610 g from the 3-year-old-fish, and fertilization rates were $98.0\%,\;97.4\%\;and\;96.5\%$ respectively. All the hatched larvae devloped into normal fry.

• Korean journal of applied entomology
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• v.52 no.2
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• pp.115-123
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• 2013

A microbial insecticide "Bt-Plus" has been developed to enhance an insecticidal efficacy of an entomopathogenic bacterium, Bacillus thuringiensis (Bt). However, its wettable powder formulation is not preferred by farmers and industry producers due to relatively high cost. This study aimed to develop a soluble concentrate formulation of Bt-Plus. To this end, an optimal mixture ratio of two bacterial culture broths was determined to be 5:4 (v/v) of Bt and Xenorhabdus nematophila (Xn) along with 10% ethanol preservative. In addition, Bt broth was concentrated by 10 times to apply the mixture at 1,000 times fold dilution. The resulting liquid formulation was sprayed on cabbage crop field infested by late instar larvae of the diamondback moth, Plutella xylostella. The field assay showed about 77% control efficacy at 7 days after treatment, which was comparable to those of current commercial biopesticides targeting P. xylostella. For storage test in both low and room temperatures, the liquid formation showed a relatively stable control efficacy at least for a month. To develop a quality control technique to exhibit a stable control efficacy of Bt-Plus, Bt spore density ($5{\times}10^{11}$ spores/mL) and eight active component concentrations of Xn bacterial metabolites in the formulation products have been proposed in this study.

• Journal of Wetlands Research
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• v.17 no.3
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• pp.320-324
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• 2015

This study was executed to know the effect of three differently controlled temperature conditions on Huanren brown frog (Rana huanrensis )'s growth in 2013. We've collected nine Huanren brown frog egg's sacs on Mt. Surak ($37^{\circ}40^{\prime}55.86^{{\prime}{\prime}}N$, $127^{\circ}05^{\prime}19.99^{{\prime}{\prime}}E$) in Seoul. We put those nine egg sacs in the controlled growth chambers under low temperature (LT, $5{\pm}2^{\circ}C$), medium temperature (MT, $10{\pm}2^{\circ}C$), and high temperature (HT, $13{\pm}2^{\circ}C$) conditions with three egg sacs, respectively. We measured the eggs' hatching rate, their hatching periods, and the size of the hatched individuals. The hatching rate was higher in MT (95.6%) and the rates of the other treatments were relatively lower but very similar such as LT (82.2%) and HT (82.6%). The three hatching periods were 10 days at HT, 14 days at MT and 23 days at LT. The body sizes of the hatched individuals were biggest at MT ($7.62{\pm}0.11mm$), smallest at LT ($6.82{\pm}0.10mm$) and medium at HT ($7.19{\pm}0.15mm$) (P-value ${\leq}0.0001$). From our results, we found that the various water temperatures could be very effective to Huanren brown frog eggs' hatch and growth including their body sizes. We suggest if we study more about the growth of Huanren brown adult frogs under similar temperature conditions for a long term period, it must be very helpful for conservation study about metamorphosis rate and size of adult frog as well as we could understand about the amphibians who are adapting to the climate change.

• The Korean Journal of Pesticide Science
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• v.17 no.4
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• pp.363-370
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• 2013

Susceptibility of each developmental stage of Phthorimaea operculella (Lepidoptera: Gelechiidae) were investigated using 16 insecticides which are available in the market in Korea. For the eggs and pupae, only spinosad showed a 71.1% inhibition rate for egg hatchability and a 66.7% inhibition rate for emergence. For the 3rd instar larvae, the feeding toxicities were over 90% for fenitrothion ($LC_{50}$ 336.6 ppm), esfenvalerate ($LC_{50}$ 8.6 ppm), ethofenprox ($LC_{50}$ 35.7 ppm), and emamectin benzoate ($LC_{50}$ 0.05 ppm). Furthermore, the contact toxicities were over 90% for esfenvalerate ($LC_{50}$ 0.87 ppm), ethofenprox ($LC_{50}$ 16.5 ppm), emamectin benzoate ($LC_{50}$ 0.53 ppm), and spinosad ($LC_{50}$ 2.48 ppm) at the recommended concentrations. Deltamethrin and spinosad yielded 100% mortality for adult P. operculella 48 h after treatment. The adult female fecundity was inhibited by deltamethrin, esfenvalerate, emamectin benzoate, spinosad and dinotefuran, which were significantly different from the control. The adult longevities (7.3-8.3 days) were reduced by approximately 1-2 days compared with the control (9.3 day). The emamectin benzoate maintained 100% insecticidal activity 14 days after treatment and ethofenprox maintained over 90% activity 7 days after treatment.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.337-343
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• 2008

This study was conducted to investigate the distribution pattern, ecological characteristics and life cycle of the Black Soldier Fly (Hermetia illucens, BSF). The BSF was widely distributed throughout Korea. The insect was mainly found in the vicinity of and in cattle sheds, manure sheds, living waste dump grounds, and food waste dump grounds. Developmental characteristics of the BSF are as follows: the egg was long oval shaped of 887 ${\mu}m$ in the major axis and 190 ${\mu}m$ in the minor axis; it weighed 24 ${\mu}g$. Female oviposited ca. 1,000 eggs on average; eggs hatched in 81 hours under laboratory condition ($27^{\circ}C$, 60% R.H.). The duration of the larval stage was approximately $15{\sim}20$ days. The size of the last instar larvae was 21 mm. The cuticle of the pupae gradually acquired red-brown color and the size of them was 19 mm. The pupal stage was shorter for females (16 days) than males (15 days). Adults were sized about $13{\sim}20$ mm long and black-colored. The life span of adult insects was $5{\sim}8$ days for the first generation (June${\sim}$July), $7{\sim}10$ days for the second generation (Aug.${\sim}$Sept.), and $13{\sim}18$ days for the third generation (Sept.${\sim}$Oct.). Mating started on the next day of emergence and actively occurred at the third day after emergence. Mating mostly occurred between 10:00 and 16:00 during which light intensity is highest. Egg-laying started on the third day and was most frequent from the fourth to the sixth day after emergence. Similar to mating time, females oviposited mostly between 10:00 and 16:00.

• Korean Journal of Environment and Ecology
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• v.20 no.3
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• pp.345-351
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• 2006

This study investigates the toxic effects of $Cd^{2+}$on frog (Rana dybowskii) by the determination of oocyte maturation and development of embryo exposure to different concentrations of the toxicant. The results show that $Cd^{2+}$ concentration of 0.1ppm suppressed the maturation of the oocytes. To examine the reversibility of the inhibitory effects, the oocytes were exposed to the $Cd^{2+}$ only for 3 hours, and then transferred to plain medium and cultured further for 17 hours. The oocytes were recovered from the toxic effect of the $Cd^{2+}$ when they were exposed to 1ppm, but not to 2.5ppm of the $Cd^{2+}$. The development of 2 cell embryos to 32 cell was completely suppressed at 0.1ppm and the longer the embryos were exposed to the $Cd^{2+}$, the more damage appeared to the embryos and the cytolysis of the 32 cell was induced by $Cd^{2+}$ at 0.1ppm. On the other hand, the embryos of blastula stage were cultured 96 hours in presence of the $Cd^{2+}$ at various concentrations and were examined. The rates of mortality and malformed larvae were investigated by probit analysis. From the results of LC$_{50}$ of 0.1ppm and EC$_{50}$ of 0.08ppm, Tl of 5.0 was derived, which indicates $Cd^{2+}$ is to be considered a teratogenic compound. Such specific malformations occurred in 14.3% as spine deformations at the 0.05ppm, in 75.0% as tail deformations at the 0.1ppm, in 66.7% as abdominal deformations at the 0.01ppm and in 26.0% as profound deformations at the 0.1ppm of $Cd^{2+}$ concentration which living embryos were exposed to. $Cd^{2+}$ suppressed growth to head-tail length at 0.1ppm. In conclusion, The study results reveal that $Cd^{2+}$ must be considered highly toxic effect to oocyte maturation and embryonic development.

• Korean journal of applied entomology
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• v.42 no.3
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• pp.217-223
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• 2003

Effects of temperature on the development and reproduction of the Luciola lateralis were investigated at various temperatures. The development time of eggs, larvae, and pupae were shorter at higher temperatures than at lower ones. The insect did not develop at 10$^{\circ}C$ and 35$^{\circ}C$. The hatchability was 61.5% at 15$^{\circ}C$, 73.9% at 20$^{\circ}C$, 93.3% at 23$^{\circ}C$, 91.8% at 25$^{\circ}C$, 74.0% at 27$^{\circ}C$, and 46.0% at 30$^{\circ}C$, indicating the best hatchability rate at the temperature condition of 23 DC. Larval periods were 341.5:t 23.2 days at 15$^{\circ}C$, 265.5${\pm}$17.5 days at 20$^{\circ}C$, and 250.9${\pm}$11.7 days at 25$^{\circ}C$. Pupal periods were 94.7${\pm}$11.5 days at 15$^{\circ}C$, 41.7${\pm}$9.1 days at 20$^{\circ}C$, and 18.5${\pm}$7A days at 25$^{\circ}C$. Emergence rate was 23.3, 89.3 and 80.7%, respectively at the above temperatures. Adult longevity of female was 18.0 days at 15$^{\circ}C$, 2004 days at 20$^{\circ}C$, 10.7 days at 25$^{\circ}C$, and 5.8 days at 30$^{\circ}C$. Mean fecundity per female was higher at 20$^{\circ}C$ compared with at other temperatures. The developmental zero point temperatures (1) and the total effect temperatures (I<) of egg, larva, pupa, and complete development were 10.6, 14.0, and l3.1$^{\circ}C$ and 214.8, 1,564.8, and 229.2 degree-days, respectively. Mean generation time in days (T) was shorter at higher temperature. Net reproductive rate per generation (Ra) was the lowest at the highest temperature as well as at the lowest, and it was 177.19 which was the highest at 23$^{\circ}C$. The intrinsic rate of natural increase (r$\sub$m/) was highest at 27$^{\circ}C$ as 0.019. As a result, optimum range of temperature for L. lateralis growth was between 20-25$^{\circ}C$.