• Journal of Aquaculture
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• v.17 no.3
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• pp.221-227
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• 2004

In the present study, we investigated the effects of food and salinity on growth and survival of river puffer, Takifugu obscurus offsprings in indoor land-based tank during the early development. In the food experiment, the river puffer larvae (TL 8.7$\pm$0.1 mm, BW 20.0$\pm$3.2 mg) were fed with tubificid, Limnodrilus gotoi, water flea, Daphnia carinata, mysid, Neomysis awatschensis, Manila clam, Ruditapes philippinarum and artificial food together Artemia nauplii for 30 days, and the growth and the survival of larvae were investigated. In the salinity experiment, the river puffer larvae and juvenile at three stages (Stage I: TL 5.8$\pm$0.4 mm; Stage II: TL 12.0$\pm$0.2 mm, Stage III： TL 44.5$\pm$0.7 mm) were supplied with Artemia nauplii, water flea and/or artificial food and were reared in 0, 10, 20 and 30 psu at respective stages. The results shows that the growth rates of larvae feeding with artificial food and tubificid together Artemia nauplii were higher than those of larvae in other groups, but the survival rates of larvae feeding with water flea and mysid together Artemia nauplii were higher than those of larvae in other groups. In salinity, the results shows that the growth and survival rates of offsprings were significantly higher in 10∼20 psu than those in 0 and 30 psu at Stage I and n. At Stage III, the growth and the survival rates were the highest in 20 psu, but the lowest in 0 psu. However, it should be noted that the rates in 0 and 30 psu were significantly enhanced at Stage III in comparison with those at Stage I and II. Therefore, it is concluded that river puffer, T. obscurus is euryhaline marine species, which can normally grow and live at salinities from 0 to 30 psu, and that a combinative supplement with Artemia nauplii and water flea, D. carinata may confer an advantage on growth and survival of the river puffer offsprings in indoor land-based tank.

• Journal of Marine Life Science
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• v.6 no.2
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• pp.73-79
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• 2021

Bisphenol A is a representative endocrine disruptor and continuously detected in aquatic environment due to wide use, resulting in adverse effects on growth, development, and reproduction in diverse organisms as well as human. Structural analogs have been developed to substitute BPA are also suspected to have endocrine disrupting effects. In the present study, the time-dependent expression patterns of ecdysteroid synthesis (nvd, cyp314a1), receptors (EcRA, EcRB, USP, ERR), and downstream signaling pathway - related genes (HR3, E75, Vtg, VtgR) were investigated using quantitative real time reverse transcription polymerase chain reaction (qRT-PCR) in the brackish water flea Diaphanosoma celebensis exposed to Bisphenol analogs (BPs; BPA, BPF, and BPS) for 6, 12, and 24 h. As results, the expression of nvd, cyp314a1, EcRs, USP, ERR and E75 mRNA was upregulated at 6 h exposure to BPF, which is earlier than BPA and BPS (12 h). On the other hand, HR3, E75 and VtgR mRNA levels were elevated at 6 h earlier at BPS and BPF than at BPA (12 h), but Vtg mRNA level was slightly changed within 24 h. These findings suggest that like BPA, BPF and BPS can also modulate the transcription of ecdysteroid pathway - related genes with different mechanisms, and have a potential as endocrine disruptors. This study will provide a better understanding the molecular mode of action of bisphenols on ecdysteroid pathway in the brackish water flea.

• Korean Journal of Environmental Biology
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• v.41 no.1
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• pp.41-53
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• 2023

E171, a mixture of titanium dioxide, has been widely used as a food additive due to its whitening effect and low toxicity. However, it has been proven that E171 is no longer safe for public health. So far, there are insufficient studies on the toxic effects of E171 on organisms especially using standardized test methods. In this study, toxicity assessments of E171 to two aquatic species, water flea (Daphnia magna) and zebrafish (Danio rerio), were performed using modified standardized test methods based on the physicochemical properties of E171. The hydrodynamic diameter, polydispersity index, and turbiscan stability index (TSI) were measured to ensure the dispersion stability of E171 in exposure media during the test period. The EC₅₀ for immobilization of water flea was 141.7 mg L^-1 while zebrafish was not affected until 100 mg L^-1 of E171. Measurements of reactive oxygen species (ROS) and antioxidant enzyme activities confirmed that E171 induced oxidative stress, leading to the activation of superoxide dismutase and catalase in both water flea and zebrafish, although the expression of antioxidant enzyme genes differed between species. These results suggested the potential risk of E171 to aquatic organisms and provided toxicological insights into the impacts of E171 on the environment.

• Journal of Environmental Science International
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• v.16 no.1
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• pp.55-63
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• 2007

There are concerns that chemical residues could harm the consumer on the environment, although 50 to 80% of the crops would be destroyed by pests and others without agrochemicals. Environmental fate and ecotoxicity studies are usually carried out to assess the impact on the human and the environment. A comparision of the Daphnia magnia and Simocephalus mixtus toxicity was performed to study the relative sensitivities and discrimination abilities to agriculture chemicals. The species of Simocephalus mixtus was more sensitive to agriculture chemicals than Daphnia magnia. Simocephalus mixtus was approved to be a water flea in determining insecticide and pesticide toxicity by heart-beat rate in a consistency and repeatability. The order of acute toxicity to water flea Daphnia magnia for ecotoxicity test was carbaryl>benomyl>amtirole with both Daphnia magnia and Simocephalus mixtus. The heartbeat pattern after the exposure to agrochemicals was different from that of exposure to heavy metals. Agrochemical leathal concentration test with heartbeat rate measurement was found to be more appropriate than inhibition concentration test with respect to toxicological endpoint.

• Korean Journal of Ecology and Environment
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• v.40 no.3
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• pp.357-369
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• 2007

Water fleas are very important organisms in aquatic ecosystem because they are key constituents of food webs as either glazers or foods for predators. Daphnia magna is a representative test species and it has been extensively used in ecotoxicity evaluation. However, Daphnia magna has not been found yet in Korean water environment. There are limitations of using the foreign species such as Daphnia magna to reflect domestic situations in Korea. Consequently it is mandatory to find domestic species suitable for bioassay, and to develop corresponding toxicity test methods using the domestic species. In this study, we widely collected the domestic and foreign toxicity test methods performed by using domestic water fleas in Korea. The 58 test methods were collected from the standard methods (OECD, US EPA, ASTM), government reports, SCI papers and domestic papers. Ten domestic water fleas selected were Bosmina longirostris, Ceriodaphnia dubia, Ceriodaphnia reticulata, Daphnia obtusa, Daphnia puex, Moina macrocopa, Moina micrura, Simocephalus mixtus, Simocephalus serrulatus, and Simocephalus vetulus. We suggested the domestic ecotoxicity test methods using domestic water fleas in Korea through providing a range of test conditions, and future directions for toxicity test using water flea. This study could be a useful basis for establishing the aquatic toxicity test methods with domestic organisms in Korea.

• Journal of Korean Society on Water Environment
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• v.24 no.1
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• pp.36-43
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• 2008

To develop the continuous water quality monitoring system using the daphnid Daphnia sp., the growth of test animal, sensitivity, and behaviour response of toxicants were observed. Growth of test animal significantly increased with increasing the food density under the 90~105 mg/L ($CaCO_3$) hardness, except the concentration of food (Chrollela sp.) was exceeded than optimal food supply. Behaviour responses of test animals were continuously analyzed by changes of fractal dimension value (FDV). The FDV sharply decreased after exposure to the concentrations of 0.13 mg/L copper, 0.06 mg/L lead, and 0.38 mg/L cadmium. In these concentrations, mortality and abnormal behaviour of daphnids exhibited within ca. 1.0-h after exposure. Comparison of 24-h $LC_{50}$ values with other zooplankton species indicated that sensitivity of the Daphnia sp. was higher than most zooplankton for lead, and brain shrimp, rotifer, and water flea (Ceriodaphnia dubia, D. magna) for copper, and brain shrimp, water flea (D. lumholzi), and amphipod for cadmium. Based on the above experimental results, significant relationship between toxicity and behaviour response of Daphnia sp. was supported the high potential of water quality monitoring system. Consequently, behavioural monitoring method in this study suggests a good estimation tool for detection of the discharged toxicants in water body and for ecotoxicological assessment aquatic organisms.

• The Korean Journal of Pesticide Science
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• v.11 no.1
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• pp.32-37
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• 2007

The study was carried out to establish buffer zone for the protection of the non-target organisms by aerial pesticide application. The two pesticide combination of 3-way tank-mixing of three pesticides for aerial application, ferimzone tricyclazole SC + BPMC EC + validamycin-A SL and hexaconzole EC + isoprothiolane EC+phenthoate EC were selected for the simultaneous control of key pests on paddy rice as blast, sheath blight, brown planthopper and moth. Aquatic organisms including killifish and loach in the paddy field and nearby water reservoirs were not affected by aerial application of the pesticides. However, all the water flea were killed, when they were exposed 10 m from the aerially sprayed site, while the water flea exposed in 30 m away from the site were not affected. Honeybees within 50 m in the wind direction and 20 m in the opposite wind direction showed a mortality of $7{\sim}100%$. Residues concentration of the pesticides in paddy water were not detectable level after six days from aerial application. Drifting distance of aerially sprayed droplet from the target area was within 30 m in the wind direction and 20 m in the opposite direction. Consequently, it was the buffer zones in the aerial pesticides application for the protection of the non-target organisms should be at least 50 m for aquatic organisms and 100 m for honeybees.

• Korean Journal of Environmental Biology
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• v.37 no.1
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• pp.72-81
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• 2019

Bisphenol A (BPA), a representative endocrine disrupting chemicals, has adverse effects on growth, development and reproduction in aquatic organisms. The object of this study was to investigate the modulation of antioxidant enzyme-coding genes using quantitative real time RT-PCR (qRT-PCR), enzyme activity and total protein content, to understand oxidative stress responses after exposure to BPA for 48 h in brackish water flea Diaphanosoma celebensis. The BPA ($3mg\;L^{-1}$) significantly upregulated the expression of Cu/Zn-SOD, Mn-SOD, and catalase (CAT) mRNA. Three GST isoforms (GST-kappa, GST-mu, and GST-theta) mRNA levels significantly increased at the rate of $0.12mg\;L^{-1}$ of BPA. In particular, GST-mu showed the highest expression level, indicating its key role in antioxidant response to BPA. SOD activity was induced with a concentration-dependent manner, and total protein contents was reduced. These findings indicate that BPA can induce oxidative stress in this species, and these antioxidants may be involved in cellular protection against BPA exposure. This study will provide a better understanding of molecular mode of action of BPA toxicity in aquatic organisms.

• Journal of Marine Life Science
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• v.7 no.2
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• pp.145-153
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• 2022

Mercury (Hg) is a major concern in marine environment because of their bioaccumulation and biomagnification properties, and adverse effects to aquatic organisms at even a trace amount. However, little information on the effects of Hg, compared to other heavy metals, is available in marine small crustaceans. Here, we investigated the transcriptional modulation of metabolism-related genes in the brackish water flea, Diaphanosoma celebensis after exposure to sublethal concentration (0.2, 0.4, 0.8 ㎍/l) of HgCl₂ for 48 h. Relative mRNA expression levels of five detoxification enzyme-coding genes (cytochrome P450; cyp360A1, cyp361A1, cyp4AP3, cyp4C122, and cyp370C5) and six digestive enzyme-coding genes [alpha amylase (AMY), alpha amylase related protein (AMY-like), trypsin (TRYP), chymotrypsin-like protein (CHY), lipase (LIP), pancreatic lipase-related protein (PLRP)] were analyzed using quantitative real time reverse transcription polymerase chain reaction (qRT-PCR). As results, Hg increased the mRNA level of cyp370C5 (clan2) and cyp4AP3 (clan4) in a concentration dependent manner. A significant increase in TRYP mRNA was also concentration-dependently observed after exposure to Hg. These findings suggest that cyp370C5 and cyp4AP3 play a key role in Hg detoxification in D. celebensis, and Hg can affect energy metabolism by modulating the transcription of digestive enzyme. This study will provide better understanding the molecular effects of Hg in marine small crustacean.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.255-266
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• 2022

In crustaceans, molting is regulated by interactions between ecdysteroid and juvenile hormone (JH) signaling pathway-related genes. Unlike the ecdysteroid signaling pathway, little information on the role of JH signaling pathway-related genes in molting is available in zooplanktonic crustaceans. In this study, three genes (juvenile hormone acid O-methyltransferase (JHAMT), methoprene-tolerant (Met), and juvenile hormone epoxide hydrolase (JHEH)) which are involved in the synthesis, receptor-binding, and degradation of JH were identified using sequence and phylogenetic analysis in the brackish water flea, Diaphanosoma celebensis. Transcriptional changes in these genes during the molting cycle in D. celebensis were analyzed. Sequence and phylogenetic analysis revealed that these putative proteins may be functionally conserved along with those of insects and other crustaceans. In addition, the expression of the three genes was correlated with the molting cycle of D. celebensis, indicating that these genes may be involved in the synthesis and degradation of JH, resulting in normal molting. This study will provide information for a better understanding of the role of JH signaling pathway-related genes during the molting process in Cladocera.