• Korean Journal of Ecology and Environment
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• v.45 no.2
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• pp.190-199
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• 2012

The reproductive ecology of an endangered species, Gobiobotia macrocephala (Pisces: Cyprinidae), was investigated in the Seom River, a tributary of the Han River drainage system, from March 2010 to February 2011. During the non-spawning season, no difference in the external morphology was observed between males and females; however, during the spawning season, clear differences merged for the depth and width of the body, preventral length and preanal length in the standard length. The sex ratio of females to males was 1 : 1.01. The spawning season was estimated to last from late April to middle of June, at water temperatures of $15{\sim}25^{\circ}C$. The number of mature eggs in the ovary averaged about $2,134{\pm}930$ (mean${\pm}$SD), and the mean diameter was approximately $0.88{\pm}0.04$ mm. The spawning area was composed of pebble and cobble bottoms (3~10 cm), with current velocities of 13~24 cm $s^{-1}$ and water depths of 12~18 cm. Spawning behavior between males and females was observed in a water tank 14~15 h after injecting females with Ovaprim to promote reproduction. Fish spawned near the water surface with monogamous pairing.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.126-136
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• 2017

We describe characteristics of diversity and distribution of oak forests on the Daegok-cheon gorge of the Southeastern Korean Peninsula, the oldest prehistoric site, in view of a sort of food resources of acorns. The $Z{\ddot{u}}rich$-Montpellier School's method was adopted for field investigation on the oak dominant stands. A total of 20 phytosociological $relev\acute{e}s$ composed of 193 taxa were analyzed by syntaxonomy and ecological flora. The Daegok-cheon's oak forests occupied 36.9% ($513,374m^2$) of the surveyed area, and its 99% ($507,677m^2$) was Quercus variabilis and Q. serrata stands. Oak forests of the Daegok-cheon gorge are a kind of regional vegetation type characterizing by the high relative net contribution degree (r-NCD) of Platycarya strobilacea and Sapium japonicum, which are an edaphic type of the xerophilous and thermophilic oak forests. The region of the Daegok-cheon petroglyphs is defined as an ecoregion with rich acorn supply and abundant water resources, and the warmer environment, which attracts prehistoric man.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.3
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• pp.216-222
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• 2010

The structural methods used to protect coastal erosion are usually very expensive in construction as well as in spending on maintaining the structures from damage. Those structures like embankments, breakwaters, jetties etc. are commonly constructed with concretes (rigid methods) to protect coastal erosion. But those rigid methods are not effective always, because the wave energy and impact force on the structures could not be effectively reduced by those methods. For avoiding sediment erosion on coastal areas by the way of reducing wave energy, a flexible breakwater is introduced which will reduce energy and protect coastline economically and environmentally. The flexible device is a combination of flexible wire nets and stack of rings made of used vehicle tires and soft blades on surfaces. This flexible wire net is placed in between two stacks of rings. The stack of rings is mainly used to hold the flexible wire nets and the flexible wire net is mainly used to reduce wave energy and helps to deposit sediments in coastal area. For a field experiment study, the above-mentioned flexible breakwater of coastal protection has been set up at the Shuang-Chun coastal area in Tainan County since June 10, 2009. The length of the flexible device is 50.0 meters and the height is 2.0 meters. The function of the device has been examined by Typhoon Linfa during June 19~22, 2009 and by Typhoon Morakot during August 6~10, 2009. The result shows that the flexible breakwater has effectively trapped sediments and let them deposit on coastal. The depth of sediment deposition around the device was about 0.5 to 0.8 meters.

• Development and Reproduction
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• v.3 no.1
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• pp.53-58
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• 1999

The androgenic gland secretes a hormone, androgenic gland hormone, which is believed to act on the differentiation of the primary, secondary, and behavioral sex characteristics in most malacostracan crustaceans. This report presents the ultrastructural morphology of the androgenic gland in the freshwater prawn Macrobrachium nipponense. This gland, located in the coxopodite of the last pair of walking legs, was attached to the subterminal region of the sperm duct. The gland was composed of simple cellular strands, encased by a fibrous sheath. Microvilli were situated in the fibrous sheath, especially at the edge of each cellular strand. The androgenic gland cells had the large and round nucleus and rough endoplasmic reticulum arranged either in spirals or in concentric circles throughout the cytoplasm of the cell. They also had the well-developed Golgi complex and long mitochondria with flat and transverse cristae. The Golgi complex was similar to microvesicular cluster, but usually in the shape of typical dictyosomes, These features of androgenic gland cells coincides well with the protein/peptide secretion in their function. However, despite the apparent ultastructual equipment for protein/peptide secretion, no accumulation of materials secreted were noticed in the cytoplasm. Therefore it is strongly suggested that the transient transportation of the materials into the hemocoel has occurred just after synthesis.

• Korean Journal of Environmental Biology
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• v.17 no.2
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• pp.129-138
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• 1999

Chlorinated aromatic compounds are one of the largest groups of environmental pollutants as a result of world-wide distribution by using them as herbicides, insecticides, fungicides, solvents, hydraulic and heat transfer fluids, plasticizers, and intermediates for chemical synthesis. Because of their toxicity, persistence, and bioaccumulation, the compounds contaminated ubiquitously in the biosphere has attracted public concerns in terms of serious influences to wild lives and a human being, such as carcinogenicity, mutagenicity, and disturbance in endocrine systems. The biological recalcitrance of the compounds is caused by the number, type, and position of the chlorine substituents as well as by their aromatic structures. In general, the carbon-halogen bonds increase the recalcitrance by increasing electronegativity of the substituent, so that the dechlorination of the compounds is focused as an important mechanism for biodegradation of chlorinated aromatics, along with the cleavage of aromatic rings. The removal of the chlorine substituents has been known as a key step for degradation of chlorinated aromatic compounds under aerobic condition. This can occur as an initial step via oxygenolytic, reductive, and hydrolytic mechanisms. The studies on the biochemistry and genetics about microbial dechlorination give us the potential informations for microbial degradation of xenobiotics contaminated in natural microcosms. Such investigations might provide biotechnological approaches to solve the environmental contamination, such as designing effective bioremediation systems using genetically engineered microorganisms.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.192-199
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• 2015

Under the economic banner of "self-reliance," North Korea has focused on hydro and thermal power as its main energy supply sources. However, in the face of extreme energy penury caused by machinery and material supply instability in the wake of the collapse of the former communist block as well as equipment aging and deterioration due to floods and other disasters, North Korea and international aid organizations are increasingly turning their attention toward energy source diversification. In particular, renewable energy is recognized as the best strategic energy source for North Korea and it is a decentralized energy option that is suitable in light of North Korea's power distribution networks and its pursuit of self-reliance. Biogas can contribute to improving the human rights situation of North Koreans in conjunction with an increase in food production. For this reason, renewable energy is the most promising option for an energy source that is likely to secure humanitarian aid from international organizations such as the Food and Agricultural Organization (FAO) and the World Food Programme (WFP). However, the implementation of such humanitarian aid has been hampered by rising concerns about the diversion of provided energy materials for military purposes and the disguised introduction of dual use items strategic materials as well as UN Security Council resolutions and sanctions of the international community against North Korea's military provocation, including nuclear tests and missile launches. This paper explores the possibility of solving this dilemma and proceeding with the humanitarian aid to North Korea by evaluating the potential for sanction and the risk of diversion of the possible products for biogas-related aid on the basis of the list of UN-sanctioned items.

• Applied Microscopy
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• v.29 no.3
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• pp.343-351
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• 1999

The structures of the fertilized egg envelope from three species, three-spot gourami (Trichogaster trichopterus), pearl gourami (Trichogaster leeri) and marble gourami (Trichogaster trichopterus trichopterus) belong to Belontiidae were observed, utilizing light, scanning and transmission electron microscopes. In all three species, the fertilized eggs were the colorless, transparent, spherical, adhesive and pelagic type. A large oil droplet was located in vitelline membrane of the fertilized egg. The egg envelopes have a single micropyle, which is thought to the pathway of sperm in the area of the animal pole. Specially, the micropyle of three-spot gourami was similar to that of marble gourami which is subspecies of three-spot gourami. An outer surface of the fertilized egg envelope was arranged by grooves in all three species. The fertilized egg envelopes consists of two distinct layers; an adhesive outer layer and an inner layer with high electron density. In conclusion, the morphological similarity of the fertilized egg, micropyle, outer surface and transverse section of the fertilized e9g envelope seems to be an indication of the Belontiidae.

• Applied Microscopy
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• v.38 no.4
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• pp.315-319
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• 2008

Glow-light tetra, Hemigrammus erythrozonus is a teleost belonging to Characidae. The natural habitate of this fish is the wild in the Essequibo river, Guyana and South America. The oogenesis of glow-light tetra was investigated by light microscopy to compare with those of other families. A pair of ovary was located between swim bladder and intestines. The ovary was of white color and ellipsoidal shape with the major axis 11 mm and the minor axis 4 mm. Cytoplasm of oogonia was basophilic and many nucleoli were located at inside of nuclear membrane. In primary oocytes, yolk vesicles were distributed only in the marginal area and egg envelope was not formed on the outside of an egg. In secondary oocytes, the egg envelope was formed and yolk vesicles in the cytoplasm were increased than the earlier stage. The amount of basophilic substance was decreased. In case of matured egg, thickness of egg envelope and size of egg were increased, basophilic substance was distributed in only around the egg envelope. The yolk vesicles were changed to yolk mass in accordance with development. In conclusion, the oogenesis of glow-light tetra, Hemigrammus erythrozonus was characterized by the increase in cell size, the formation and accumulation of yolk, and the decrease of basophilia a in the cytoplasm. The oogenesis of glow-light tetra seems to share common patterns in Characidae, teleost and have a similar pattern with other teleost.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.136-143
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• 2011

Early life history of the endangered species Gobiobotia brevibarba was investigated to provide baseline data for biological characteristics and restoration. Adult fish were sampled by spoon net capture at Hongcheon-gun, Gangwon-do, Korea, in April 2010. Eggs were obtained after injection of Ovarprim and were artificially fertilized by the dry method in the laboratory. The mature eggs were slightly adhesive and transparent with greyish and average $1.24{\pm}0.07$ mm in diameter. The hatching of the embryos took place about 120 h after fertilization at a water temperature of $23^{\circ}C$. The newly-hatched larva averaged $5.5{\pm}0.29$ mm in total length. Four days after hatching, they averaged $7.4{\pm}0.26$ mm in total length and their yolk sacs were completely absorbed. From 15 days after hatching, they entered the juvenile stage and reached $9.9{\pm}0.72$ mm in total length. One hundred days after hatching, their band patterns and external form were similar to those of adults, and they averaged $36.0{\pm}3.11$ mm in total length.

• Journal of Life Science
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• v.27 no.7
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• pp.746-753
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• 2017

In order to rapidly identify four drums species, Larimichthys polyactis, L. crocea, Atrobucca nibe, and Pseudotolithus elongates, a highly efficient and quick method has been developed using multiplex polymerase chain reaction (PCR) with species-specific primers. Around 1.4 kbp of the mitochondrial COI gene sequences from the four drums species were aligned, and species-specific forward primers were designed, based on the single nucleotide polymorphism (SNP). The optimal conditions for PCR amplification were selected through cross-reactivity, using a gradient PCR method. The PCR results demonstrated species-specific amplification for each species at annealing temperatures between 50 and $62^{\circ}C$. Multiplex species-specific PCR (MSS-PCR) amplification reactions with four pairs of primers were performed for sixteen specimens of each species. MSS-PCR lead to a species-specific amplification of a 1,540 bp fragment in L. polyactis, 1,013 bp in A. nibe, 474 bp in L. crocea, and 182 bp in P. elongates, respectively. The four different sizes of each PCR product can be quickly and easily detected by single gel electrophoresis. The sensitivity of the MSS-PCR of the DNA was up to $0.1ng/{\mu}l$ as a starting concentration for the four different species tested. These results suggest that MSS-PCR, with species-specific primers based on SNP, can be a powerful tool in the rapid identification of the four drums species, L. polyactis, L. crocea, A. nibe, and P. elongates.