• Korean Journal of Environment and Ecology
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• v.36 no.4
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• pp.368-380
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• 2022

Biomonitoring of an invasive alien crayfish species, Procambarus clarkii (Girard, 1852), was performed from February to October 2021, along with environmental DNA analysis, at five locations including Wanju-gun, Hampyeong-gun, Naju-si, Gurye-gun, and Cheongju-si. For the investigation, an umbrella-shaped trap for adults and a hand net for young crayfish were used, and 8 to 10L of freshwater was collected for eDNA analysis. The current status and past distributional records of crayfish in Korea were analyzed along with benthic macroinvertebrates at each survey site. As a result of the investigation, a total of 122 individuals were identified, and Hampyeong-gun recorded the largest number of populations with 59 individuals (48.36%) and the highest environmental DNA (eDNA). The frequency of appearance of P. clarkii was highest in May. The ratio of females to males was 21:5, and the body size was 72.2±21.1mm for female, 80.5±15.6mm for male, and 25.3±9.8mm for young crayfish. P. clarkii introduced into Korea is mainly spreading in the southwest region and it has not been observed in Seoul where there had been a record of appearance in the past. No external symbiosis (Branchiobdellida) of P. clarkii has been identified, and P. clarkii that has appeared in Korea was presumed to be imported from Japan. There are more than eight kinds of exotic crayfish distributed in Korea, and among them, the marbled crayfish (P. virginalis) was identified as a harmful species to the ecosystem of Korea by the Ministry of Environment in 2021. The identified species of benthic macroinvertebrates inhabiting the survey area where P. clarkii has appeared were 69 belonging to 39 families, 15 orders, five classes, and three phyla. Among them, Odonata were the most abundant (16 spp.; 24.62%), followed by Coleoptera (11 spp.; 16.92%) and Hemiptera (11 spp.; 16.92%). In the survey area, one Korean endemic species (Rhoenanthus coreanus), one species (Helophorus auriculatus) classified as Near Threatened (NT) on the Korean Red List, and six species of Crustaceans appeared. In the functional feeding group, the predators appeared predominantly while in habitat oriented group, the climbers appeared to be abundant. It was confirmed that P. clarkii in the survey area prefers an area rich in aquatic vegetation with waterside vegetation, and has high resistance to turbid water quality. The omnivore invader P. clarkii is expected to maintain a competitive relationship with carnivorous benthic macroinvertebrates that are predominant in the same species, and is expected to continue to generate ecosystem disturbance along the food chains.

• Journal of Environmental Impact Assessment
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• v.33 no.1
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• pp.1-8
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• 2024

Amphibians are a taxonomic group that ecologically connects terrestrial ecosystems and aquatic ecosystems. They play a very important role in the food chain of the ecosystem. It is known that there are about 5,948 species distributed all over the world, but after the Industrial Revolution, due to industrialization and urbanization, there has been a decrease in species and populations. In particular, it is becoming a factor in exacerbating habitat fragmentation or fragmentation due to artificial canals. In orderto improve the survivalrate of wild animals in artificial canals, escape facilities are installed to reduce it. This study analyzed the slope, height of the escape facility, escape rate, and travel distance in the operating facility for Bombina orientalis, which mainly inhabits near forests. The slope of the escape facility showed a relatively similar escape success rate regardless of height at 50° and 60°, while at 70°, it showed a relatively high escape success rate at only 40cm in height. The success rate of escape from the waterway escape facility in operation was 14.71%, showing a very low utilization rate, and the recognition rate of the artificial canal escape facility was found to be very low as it moved along the side wall of the artificial canal. Therefore, in the case of a waterway escape facility for Bombina orientalis, it is possible to construct it at an angle of 60°, and if the side walls of the artificial canals are built within 60°, Bombina orientalis can move freely in both directions, overcoming the low utilization rate of existing waterway escape facilities. It is expected to minimize the impact of movement and death of artificial canals. In addition, if the spacing between escape facilities is narrowed from the installation standard of 30m and ramps are constructed in both directions upstream and downstream, the escape success rate of amphibians,reptiles, and small mammals otherthan lady frogs is expected to improve.

• Journal of Life Science
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• v.34 no.2
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• pp.86-93
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• 2024

Since replication of plasmids must be strictly controlled, plasmids that generally perform rolling circle replication generally maintain a constant copy number by strictly controlling the replication initiator Rep at the transcriptional and translational levels. Plasmid pJB01 contains three orfs (copA, repB, repC or repABC) consisting of a single operon. From analysis of amino acid sequence, pJB01 CopA was homologous to the Cops, as a copy number control protein, of other plasmids. When compared with a CopG of pMV158, CopA seems to form the RHH (ribbon-helix-helix) known as a motif of generalized repressor of plasmids. The result of gel mobility shift assay (EMSA) revealed that the purified fusion CopA protein binds to the operator region of the repABC operon. To examine the functional role of CopA on transcriptional level, 3 point mutants were constructed in coding frame of copA such as CopA R16M, K26R and E50V. The repABC mRNA levels of CopA R16M, K26R and E50V mutants increased 1.84, 1.78 and 2.86 folds more than that of CopA wt, respectively. Furthermore, copy numbers owing to mutations in three copA genes also increased 1.86, 1.68 and 2.89 folds more than that of copA wt, respectively. These results suggest that CopA is the transcriptional repressor, and lowers the copy number of pJB01 by reducing repABC mRNA and then RepB, as a replication initiator.

• Journal of Aquaculture
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• v.5 no.1
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• pp.29-67
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• 1992

Life cycle and seed production of the freshwater prawn, Macrobrachium nipponense, were studied and the results are as follows : 1. Larval development : Embryos hatched out as zoea larvae of 2.06 mm in mean body length. The larvae passed through 9 zoea stages in $15{\~}20$ days and then metamorphosed into postlarvae measuring 5.68 mm in mean body length. Each zoea stage can be identified based on the shapes of the first and second antennae, exo- and endopodites of the first and second pereiopods, telson and maxillae. 2. Environmental requirements of zoea larvae : Zoea larvae grew healthy when fed with Artemia nauplii. Metamorphosing rate was $65{\~}72{\%}$ at $26{\~}28\%$ and $7.85{\~}8.28\%_{\circ}Cl.$. The relationship between the zoeal period (Y in days) and water temperature (X in $^{\circ}C$) is expressed as Y=46.0900-0.9673X. Zoeas showed best survival in a water temperature range of $26{\~}32^{\circ}C$ (optimum temperature $28^{\circ}C$), at which the metamorphosing rate into postlarvae was $54{\~}72\%$ The zoeas survived more successfully in chlorinity range of $4.12{\~}14.08{\%_{\circ}}Cl.$, (optimum chlorinity $7.6{\~}11.6\;{\%_{\circ}}Cl.$.), at which the metamorphosing rate was $42{\~}76{\%}$. The whole zoeal stages tended to be longer in proportion as the chlorinity deviated from the optimum range and particularly toward high chlorinity. Zoeas at all stages could not tolerate in the freshwater. 3. Environmental requirements of postlarvae and juveniles : Postlarvae showed normal growth at water temperatures between $24{\~}32^{\circ}C$ (optimun temperature $26{\~}28^{\circ}$. The survival rate up to the juvenile stage was $41{\~}63{\%}$. Water temperatures below $24^{\circ}C$ and above $32^{\circ}$ resulted in lower growth, and postlarvae scarcely grew at below $17^{\circ}C$. Cannibalism tended to occur more frequently under optimum range of temperatures. The range of chlorinity for normal growth of postlarvae and juveniles was from 0.00 (freshwater) to $11.24{\%_{\circ}}Cl.$, at which the survival rate was $32{\~}35\%$. The postlarvae grew more successfully in low chlorinities, and the best growth was found at $0.00\~2.21{\%_{\circ}}Cl.$. The postlarvae and juveniles showed better growth in freshwater but did not survive in normal sea water. 4. Feeding effect of diet on zoea Ilarvae : Zoea larvae were successfully survived and metamorposed into postlarvae when fed commercial artificial plankton, rotifers, and Artemia nauplii in the aquaria. However, the zoea larvae that were fed Artemia nauplii and reared in Chlorella mixed green water showed better results. The rate of metamorphosis was $68\~{\%}75$. The larvae fed cow live powder, egg powder, and Chlorella alone did not survive. 5. Diets of postlarvae, juveniles and adults : Artemia nauplii and/or copepods were good food for postlarvae. Juveniles and adults were successfully fed fish or shellfish flesh, annelids, corn grain, pelleted feed along with viscera of domestic animals or fruits. 6. Growth of postlarvae, juveniles and adults : Under favorable conditions, postlarvae molted every five or six days and attained to the juvenile stage within two months and they reached 1.78 cm in body length and 0.17 g in body weight. The juveniles grew to 3.52 cm in body length and 1.07 g in body weight in about four months. Their sexes became determinable based on the appearance of male's rudimental processes (a secondary sex character) on the endopodites of second pereiopods of males. The males commonly reached sexual maturity in seven months after attaining the postlarvae stage and they grew to 5.65 cm in body length and 3.41 g in body weight. Whereas the females attained sexual maturity within six to seven months, when they measured 4.93 cm in body length and 2.43 g in body weight. Nine or ten months after hatching, the males grew $6.62{\~}7.14$ cm in body length and $6.68{\~}8.36$ g in body weight, while females became $5.58{\~}6.08$ cm and $4.04{\~}5.54$ g. 7. Stocking density : The maximum stocking density in aquaria for successful survival and growth was $60{\~}100$ individuals/$\ell$ for zoeas in 30-days rearing (survival rate to postlarvae, $73{\~}80{\%}$) ; $100{\~}300$ individuals/$m^2$ for postlarvae of 0.57 cm in body length (survival rate for 120 days, $78{\~}85{\%}$) ; $40{\~}60$ individuals/$m^2$ for juveniles of 2.72 cm in body length (survival rate for 120 days, $63{\~}90{\%}$) : $20{\~}40$ individuals/$m^2$ for young prawns of 5.2 cm in body length (survival rate for 120 days, $62\~90{\%}$) ; and $10\~30$ individuals/$m^2$ for adults of 6.1 cm in body length (survival rate for 60 days, $73\~100{\%}$). The stocking density of juveniles, youngs and adults could be increased up to twice by providing shelters.