• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.61-70
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• 1997

The spawning season, growth and feeding habit of tubesnout, Aulichthys japonicus were examined from the samples collected by a small beam trawl in the Zostera marina belt at the coastal water off Hamduck, Cheju Island, from May 1993 to May 1994. Tubesnout was the dominant species of overall 58 species collected in the study area throughout the year. The larvae and juvenile of tubesnout in the frequency distributions of body length began to appear in the Z. marina belt in March, and adults disappeared after May in the following year. The gonad weight index (GWI) and the condition factor (K) were high from November 1993 to January 1994 for males, while females were high from February to May 1994. Although tubesnout is an oviparous fish, males have the urogenital papilla. These results suggest that they were fertilized between November and January, and then males seemed to be died or move into other places. Females were examined to spawn from February to May. The stomach contents of tubesnout were dominated by copepoda smaller than ca. 1mm, Paracalanus, Oithona, Acartia, Oncaea and Harpacticoidae, accounting for 97% of total food items. The feeding habit of tubesnout did not vary by size. The fishes fed on Calanus, Euchaeta and decapoda larvae larger than ca. 3mm in March and April during the spawning season.

• Journal of the Korean Data and Information Science Society
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• v.26 no.6
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• pp.1249-1258
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• 2015

DGAT1(diacylglycerol O-acyltransferase1) gene is well known as a major gene of milk production in dairy cattle. This study was conducted to investigate how the DGAT1 gene effect on milk yield was appeared from the genome wide association (GWA) using high density whole genome SNP chip. The data set used in this study consisted of 353 Korean Holstein sires with 50k SNP genotypes and deregressed estimated breeding values of milk yield. After quality control 41,051 SNPs were selected and locations on chromosome were mapped using UMD 3.1. Bayesian regression of BayesB method (pi=0.99) was used to estimate the SNP effects and genomic breeding values. Percentages of variance explained by 1 Mb non-overlapping windows were calculated to detect the QTL region. As the result of this study, top 1 and 3 of 2,516 windows were seen around DGAT1 gene region and 0.51% and 0.48% of genetic variance were explained by these two windows. Although SNPs on the DGAT1 gene region are excluded in commercial 50k SNP chip, the effect of DGAT1 gene seem to be reflected on GWA by the SNPs which are in linkage disequilibrium with DGAT1 gene.

• The Korean Journal of Malacology
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• v.20 no.2
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• pp.121-124
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• 2004

Water temperature tolerance of spats of the Manila clam, Ruditapes philippinarum was investigated in the different temperature groups, 15, 20, 25, 30 and 35$^{\circ}C$. The survival rates of the groups were 99.7%, 91.0%, 88.7%, 73.3% and 0%, respectively (p < 0.05). When the temperature of the water decreased from 15$^{\circ}C$ to 5$^{\circ}C$, the survival of spats was higher than when the temperature increased. The growth and survival of spats were investigated in different types of bottom substrates in the tanks. The spats grew the best in the polyvinyl plates, the average shell length was 3.9 ${\pm}$ 0.4 mm. In the FRP tank bottom and sand bottom, the average shell lengths of spats were 3.6 ${\pm}$ 0.3 mm and 3.2 ${\pm}$ 0.3 mm, respectively. The best survival of spats cultured in the FRP tank bottom (22.9 g) and in the polyvinyl plates (20.6 g) (p < 0.05).

• Korean Journal of Ichthyology
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• v.25 no.4
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• pp.189-199
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• 2013

The distribution status and habitat characteristics of the endangered species, Lethenteron reissneri were investigated in 2011~2012 in Korea. During the study period, L. reissneri were collected 60 stations among 755 sampling stations investigated. The total numbers of ammocoetes and adults were 208 and 435, respectively from eight stations of the Han River drainage system, four stations of Geum River drainage system, 32 stations of Seomjin and Yeongsan River drainage systems, and 16 stations of Nakdong River drainage system. The Han and Geum river drainage systems, the Sapkyo Stream and independent streams running toward the East Sea were estimated to have suffered sudden reductions of population density, whereas the Seomjin River drainage system showed increased population density compared with historic occurrence records. L. reissneri inhabited the middle-upper stream of clean water with well-developed rapids and lots of aquatic organisms. According to IUCN Red List categories and criteria L. reissneri was assessed to be vulnerable (VU) [B2ab (ii,iii,iv,v);D1] because of the rapid reduction of the occupying areas and the small number of mature individuals. Besides the distribution status and habitat characteristics we discussed the conservation strategies of L. reissneri.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.2
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• pp.422-435
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• 2017

Intermolt periods, growth rates, survival (%) and relative growth of the megalopa larvae of Portunus trituberculatus (Miers, 1876) were studied up to the crab 7th stage for 160 days in the 3 different temperature groups in which each has 60 larvae. The higher the water temperature was the shorter the intermolt period was in each crab stage. In addition, a deviation of intermolt periods was shown as few as the water temperature gets higher. The intermolt period in the 7th crab stage was $29.8{\pm}3.26$ days in the experimental group at the room temperature, $45.2{\pm}3.89$ days at the temperature of $17^{\circ}C$, and $25.6{\pm}2.23$ days at the temperature of $27^{\circ}C$, respectively. The survival (%) of larvae of P. trituberculatus (the crab 7th stage) is the highest in the group at the room temperature: However, they showed 15% at the temperature of $27^{\circ}C$ and 10% at the temperature of $17^{\circ}C$. All the groups were shown the similar relative growth, but significant differences appeared in some comparison. The sizes (mean growth of carapace width) of the crabs in the group at the temperature of $27^{\circ}C$ reached 5.01~25.45 mm length (it is the longest among the groups) from the crab 1th to the crab 7th stage. However, the sizes (mean growth of carapace width) of room temperature were 4.99~22.26 mm and the size of crab in the group at the temperature of $17^{\circ}C$ reached 4.8~17.26 mm, The sizes (mean growth of carapace length) of the crabs in the group at temperature of $27^{\circ}C$ reached 2.88~13.56 mm, However, the size of the crab in the group at the room temperature showed 2.88~12.34 mm, while in the group at temperature of $17^{\circ}C$, their average growth of carapace length were 2.51~8.03 mm. The growth rates of larvae of P. trituberculatus (from the crab 1th to the crab 7th stage) were changed with the increase of the instar stage, however their changes showed irregular.

• Korean Journal of Ecology and Environment
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• v.49 no.4
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• pp.334-342
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• 2016

In this study, we explain the environmental variables that mainly influence the spatial and seasonal pattern of Galerucella nipponensis in 38 wetland and stream located at mid-low Nakdong River. G. nipponensis were found at total of 32 wetland, was strongly positively correlated with the biomass of Trapa japonica (t=2.173, $r^2=0.013$, p<0.05). In result of seasonal distribution during 3 years, the largest density of G. nipponensis adult were observed in summer (7~8 months), egg and larva was recorded in only early spring (4~5 months). Rainfall were negatively related with the seasonal distribution of G. nipponensis. They were more abundant in dry season (2015 year) than rainy seasons(2013~2014 year). Stable isotope analysis showed that the G. nipponensis consumed as food source no submerged leaf of T. japonica than other plant. However, utilization of T. japonica on Galerucella nipponensis were not influence to plant biomass and/or species composition in vegetated bed. Those considered as adaptive strategies for sustainable habitat maintenance that because T. japonica use as not only food source but also their lives for G. nipponensis.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.566-572
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• 2017

For four times, zooplankton collection were conducted seasonally in October 2015-July 2016 at five sites located in the wet lands of the lower Han River, ie., Si-am, Sung-dong, Gong-reung stream, San-nam and Jang-hang. A total of 46 species of zooplankton were collected, which comprise 25 species of rotifers, seven cladocerans, ten copepods, and one species of nematod, ostracod and decapod, respectively. No brackish and marine species were distributed except for two species of brackish water copepods. Prosperity in the species number of 15 species was observed in October at Sung-dong and Jang-hang. The maximum abundance was recorded in March at Si-am with $8,000indiv.\;L^{-1}$ with the explosion of Brachionus calyciflorus. Other sites also showed high abundances in March with the abundance higher than $5,000indiv.\;L^{-1}$. Except in March, the abundance levels were recorded as less than some hundred $indiv.\;L^{-1}$ throughout the study. Species diversity varied between 0.4-1.8. The gut contents of the copepodite showed that various diatoms might be their major food items, and lots of unidentified materials were also observed. The environmental conditions of water temperature, pH and dissolved oxygen content showed to vary $10.1-28.2^{\circ}C$, 7.1-8.6 and $4.5-11.0mg\;L^{-1}$, respectively.

• The Korean Journal of Malacology
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• v.9 no.1
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• pp.1-16
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• 1993

한국의 담수에 광범위하게 서식하고 있으면서 역학적으로 중요한 역할을 하고 있는 두 종의 복족류 즉 쇠우렁이(Parafossarulus manchouricus)와 물달팽이(Radix auricularia coreana)의 소화기관 중에서 식도, 소화선 및 장에 대한 미세구조 관찰을 시도하였다. 이 부위들은 간흡충(간디스토마)과간질(소간디스토마)의 유생들이 그들의 생활사 중 거쳐가는 곳으로 알려진 소화관들이어서 이후 흡충류의 유충들이 위의 소화관에 주는 영향을 연구하는데 필요한 기초자료를 얻고자 수행된 것이었다. 관찰해 본 결과 다음과 같은 결론을 얻을 수 있었다. 식도의 상피조직은 두 종류에서 공히 원주세포와 원주섬모세포 및 점액분비 세포로 이루어져 있었다. 식도강상피 내에서도 어느 정도의 흡수와 소화가 이루어 지고 있음은 특이한 현상이라 하겠다. 소화선은 두 종에서 공히 복분지 관상선으로서 그 상피는 micovilli를 선강 또는 도관에 연한 유리표면에 가지고 있어 brush boredr을 이루고 있는 원주세포과 원주섬모세포로 구성되어 있었다. 이들 세포들의 내부 구조로 보아 소화세포와 배석세포로 구분할 수 있었다. 장의 상피는 원주세포와 원주섬모세포로 구성되어 있었으며 이들도 장강에 연한 유리표면에는 brush border를 이루고 있었다. 흡수와 분비기능이 활발한 것으로 사료된다. 전반적으로 보아 본 연구에서 관찰한 두 복족류의 소화관은 모든 부위에서 세포의 유리표면에 microvilli를 가지고 있어 물질의 흡수기능을 가지고 있음을 시사해주고 있었고, 이들 세포 중에는 때로 밀집한 cilia를 가지고 있어 소화관 내의 액체물질이나 이에 내포된 미세입자들의 유동을 도와주고 있음을 추측할 수 있었다.)은 결합조직으로 이루어진 근육질의 두꺼운 벽을 가지고 있었으며 내강은 돌출부위에 의해 4부분으로 갈라져 있었다. 내강에 연한 상피는 원주세포로 되어 있었다. 상음경(epiphallus)의 벽은 근섬유 다발은 벽의 외곽으로 갈수록 밀도가 높아졌다. 상부에 내강과 연결되는 함입구조(groove)를 가지며, 내강에 연한 상피는 섬모가 없는 원주세포로 이루어져 있었다. 음경(penis)은 근섬유가 산재된 두꺼운 벽을 가졌으며 상음경보다 굵은 원통형이었다. 내강은 많은 돌출부에 의해 복잡하게 나뉘어 있으며 상피세포는 원주 세포로 이루어져 있었고 섬모는 관찰되지 않았다. 내강 내의 분비물과 세포의 형태로 보아 내강상피세포는 분비기능을 가진 것으로 사료된다.술적 문제가 적절히 해결되는 경우 비활성 가스 제너레이터는 민수용으로는 대형 빌딩, 산림, 유조선 등의 화재에 매우 적절히 사용되어 질 수 있을 뿐 아니라 군사적으로도 군사작전 중 및 공군 기지의 화재 그리고 지하벙커에 설치되어 있는 고급 첨단 군사 장비 등의 화재 뿐 아니라 대간첩작전 등에 효과적으로 활용될 수 있을 것으로 판단된다.가 작으며, 본 연소관에 충전된 RDX/AP계 추진제의 경우 추진제의 습기투과에 의한 추진제 물성 변화는 미미한 것으로 나타났다.의 향상으로, 음성개선에 효과적이라고 사료되었으며, 이 방법이 편측 성대마비 환자의 효과적인 음성개선의 치료방법의 하나로 응용될 수 있으리라 생각된다..7%), 혈액투석, 식도부분절제술 및 위루술·위회장문합술을 시행한 경우가 각 1례(2.9%)씩이었다. 13) 심각한 합병증은 9례(26.5%)에서 보였는데 그중 식도협착증이 6례(17.6%), 급성신부전증 1례(2.9%), 종격동기흉과 폐염이 병발한 경우와 폐염이 각

• Korean Journal of Ecology and Environment
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• v.54 no.3
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• pp.156-169
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• 2021

Traditional morphological identification difficulties, such as phenotypic plasticity, misidentification of cryptic species, and larval stage species, can be compensated for by using DNA analysis techniques, such as DNA barcoding, in surveying zooplankton populations, including species identification. Recently, the rapid development of DNA sequencing techniques has allowed DNA-based community analysis not only for zooplankton assemblages in various aquatic ecosystems but also for the gut contents of zooplankton that are limited by conventional methods such as visual and microscopic identification. Therefore, the application of DNA sequencing can help understand biological interactions through the analysis of zooplankton food sources. The present paper introduces the major DNA-based approaches in zooplankton research topics, including taxonomic approaches by DNA barcoding, community-level approaches by metabarcoding, and gut content analyses, summarizes the analysis methods, and finally suggests the methodological topics that need to be considered for future applications.

• Korean Journal of Environmental Biology
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• v.39 no.3
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• pp.311-318
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• 2021

In this experiment, we investigated the toxicity of tebuconazole (fungicide) using domestic frog embryos, along the FETAX (Frog Embryo Teratogenesis Assay-Xenopus) protocol. Bufo gargarizans, Hyla japonica, and Pelophylax nigromaculatus embryos were incubated, and investigation of the tebuconazole effect was performed by the probit analysis. As a result, depending on the concentrations of tebuconazole, the mortality and malformation rates were increased and larval body length was decreased. The teratogenic concentrations (EC₅₀) of tebuconazole were 34.4mg L^-1, 10.6mg L^-1, and 14.9mg L^-1, respectively, and the embryo lethal concentrations(LC₅₀) of tebuconazole were 74.7 mg L^-1, 38.5 mg L^-1, and 39.1 mg L^-1, respectively. The teratogenic index (TI) valuesof tebuconazole were 2.19, 3.58, and 2.65; thus, it showed teratogenicity in embryonic development of these three frogs. These results revealed that in this experiment, tebuconazole suppressed the development of embryos at a relatively low concentration. In addition, mortality, malformation ratios, malformation patterns, and growth rates were similar to the results from the other assay systems. Therefore, tebuconazole was thought to have an effect on the embryo development of domestic frogs. In future, it will be necessary to identify species specificity in order to the clarify the causes of differences in mortality, malformation rate, and malformation patterns depending on the species.