• Korean Journal of Ichthyology
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• v.34 no.3
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• pp.208-217
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• 2022

We wanted to develop a real-time PCR assay capable of detecting Liobagrus obesus in environmental DNA (eDNA) extracted from freshwater samples using a pair of species-specific primers and probe for the endangered fish, L. obesus. The species-specific primers and probe were designed in consideration of single nucleotide polymorphisms between 65 species of freshwater fish living in the Republic of Korea within the cytochrome b (cytb) gene of mitochondrial DNA. The species-specific primers and probe, in the real-time PCR assay, showed high specificity as only the L. obesus genomic DNA (gDNA) was found to be positive in the specificity verification using 65 species gDNA of freshwater fish in the Republic of Korea. In addition, in the detection limit analysis using the serial dilution concentrations of L. obesus gDNA, it was found that it was possible to detect up to 0.2 pg, showing high sensitivity. Afterwards, using the species-specific primers and probe, real-time PCR assay was performed on freshwater samples obtained from 8 stations in the mid-upper basin of Geum River. As a result, the cytb gene of L. obesus was detected in total 5 stations including all 3 stations where this species was collected at the time of field survey. Therefore, the species-specific primers and probe developed in present study, and the real-time PCR assay using them, can accurately detect the cytb gene of L. obesus from eDNA samples, which can be utilized to monitor the existing habitats of this species and to discover potential new habitats.

• Development and Reproduction
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• v.22 no.1
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• pp.9-18
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• 2018

This study was conducted to investigate the skeletal development of bullhead torrent catfish, Liobagrus obesus larvae and to utilize them as basic data for the taxonomic study of Liobagrus larvae. Skeletal development was observed by being divided into cranium, visceral skeleton, shoulder girdle bone, pelvic girdle bone and vertebra. On the first day after hatching, the pre-larvae had an average total length of 7.92 mm, and a line-shaped parasphenoid ossified in the cranium. In the jaw bone, the dentary supporting the lower jaw and the maxillary supporting the upper jaw were ossified. In the anterior abdominal vertebrae of the vertebra, seven centrums began to ossify and five neural spines ossified simultaneously. On the 3 day after hatching, pre-larvae had an average total length of 8.95 mm, and the prefrontal ossified in cranium. The number of abdominal vertebrae was increased to 14, and three parapophysis developed from the front side. On the 24th day after hatching, post-larvae had an average total length of 15.2 mm and the epural bone ossified in coccyx. The parhypural bone was ossified, and ossification of coccyx and pelvic girdle bone was completed. On the 30th day after hatching, the average total length of the juvenile was 17.8 mm, and the ossification of cranium and visceral skeleton was all completed while the preorbital and three suborbitals were ossified in the orbital region of the cranium.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.4
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• pp.338-343
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• 2006

Histological observations of the barbels of torrent catfish (Amblycipitidae) in Korea are reported. The bullhead torrent catfish (Liobagrus andersoni) and Korean torrent catfish (L. obesus) have eight obvious barbels in two pairs each on the maxilla and mandible. Each barbel is composed of an epidermis, dermis, and central cartilagerod. The epidermis of the maxillary and mandibular barbels of the bullhead torrent catfish is thicker than that of the Korean torrent catfish (P<0.05) and is formed of stratified epithelium that contains many cutaneous taste buds and a few small club cells. There are many taste buds on the upper part of each barbel. The dermis consists of loose connective tissue fibers that enclose blood vessels and bundles of nerve fibers. The barbels of these fish can be categorized into stiff and flexible types and are accessory, feeding, and sensory structures. Our results validate the barbels as gustatory receptor organs for these fishes.

• Development and Reproduction
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• v.10 no.1
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• pp.41-45
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• 2006

The spawning behavior of Liobagrus obesus was observed at Kumgang river, Yeongdong-gun, Chungcheongbuk-do from Apirl to July 2004. The fertilized eggs collected by dip net and skimming net were carried to the laboratory of Chonnam National University, and then egg, larvae and juvenils development were studied. Hatching of the embryo began about at 225 hrs 15 mins after morula stage in water temperature of $19.5{\sim}24.9^{\circ}C$(mean $22.8^{\circ}C$). The newly-hatched larvae were $7.30{\sim}7.90mm$(mean 7.66mm) in total length (TL), their mouth and anus were already opened with 14+28=42 myotomes. Sixteen days after hatching, the postlarvae were $13.00{\sim}14.05mm$(mean 13.48mm) TL, the yolk sac was completely absorbed. The juvenile stage was reached when all fin-rays were formed at 24 days after hatching, and $15.31{\sim}17.20mm$(mean 16.31mm) TL.

• Korean Journal of Ichthyology
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• v.19 no.2
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• pp.112-119
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• 2007

A histological study on development and transformation of the oocyte' follicle cell for Korean four sillurid fishes, Liobagrus obesus, L. mediadiposalis, Pseudobagrus koreanus, and P. brevicorpus was performed by light and electron microscopes. The follicular layer surrounding the oocyte consisted of an outer theca cell and an inner follicle cell (granulosa cell). The follicle cells of the oocyte were flatten cells at early oocyte but during vitellogenesis they were transformed it to a single layer of cuboidal cell, then to a single columnar cell layer, and finally to a layer covered with a substance secreted by themselves. Although the development and transformation of the follicle cells was similar to four species, the secreted materials, called an adhesive membrane, were divided into two types in its appearance and nature. Firstly, a jelly coat-like type was found in L. obesus and L. mediadiposalis, which they are presumed to be polysaccharides and mucoproteins in its nature and secondly, a granular type in P. koreanus and P. brevicopus, being mucoprotein. A zona radiata with about $0.6{\sim}3.1{\mu}m$ thin was present below the adhesive material secreted by the transformed-follicle cell's activity. The zona radiata was composed of two layers, a thin externa and a thick interna.

• Korean Journal of Ichthyology
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• v.1 no.1_2
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• pp.64-72
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• 1989

Karyological characteristics were investigated in 3 species of the genus Liobagrus from Korea. The diploid chromosome number in L. andersoni was found to be 28, with 9 pairs of metacentrics and 5 pairs of submetacentric chromosomes, and arm number (AN) was 56. L. mediadiposalis was found with 2n of 42, consisting of 13 pairs of metacentrics and 8 pairs of submetacentric chromosomes (AN=84). In the case of L. obesus 2n was 20, with 20 metacentric chromosomes (AN=40), which was the lowest among the species of the order Siluriformes. Sexual dimorphism or intraspecific polymorphism of the chromosomes was not observed in any species examined.

• Korean Journal of Ichthyology
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• v.20 no.3
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• pp.198-209
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• 2008

During studies of the fish fauna and communities of Mankyeong River, which flows to the Yellow Sea, 14 families in 44 genera and 63 species of freshwater fishes were caught. Zacco platypus (27.7%) was the dominant species and Z. koreanus (11.3%) the subdominant species in this river. Twenty-three species of Korean endemic fishes appeared, and two of these, Pseudopungtungia nigra and Liobagrus obesus, represented endangered Korea species. Community structure of each branch stream was stable, showing appropriate dominant species: Z. koreanus in Jeonju Stream, Z. platypus in Kosan and Soyang Streams, and Carassius auratus in Mankyeong main stream. Three introduced species appeared: C. cuvieri, Micropterus salmoides, and Lepomis macrochirus. Among these introduced species, M. salmoides expanded its territory from midstream to downstream because of its strong carnivorous tendency and it favoring of lentic waters. This distribution of M. salmoides affected the number and distribution of small native freshwater fishes, especially those in the subfamily Acheilognathinae.

• Korean Journal of Ichthyology
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• v.18 no.3
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• pp.209-215
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• 2006

A closely associated set of characteristics was analyzed using both classical and truss dimensions to discriminate the morphometric traits of three species of torrent catfish (Amblycipitidae) in Korea. After arcsine square root transformation, 18 measurements relative to the standard length and three measurements relative to the head length of each species of torrent catfish were compared statistically. Classical and truss dimensions of each of four morphometric traits showed higher values in the bullhead torrent catfish, Liobagrus obesus, than the Korean and south torrent catfish (L. andersoni and L. mediadiposalisa, respectively; P<0.05). Truss dimensions of three morphometric traits were higher in the bullhead and Korean torrent catfish than in the south torrent catfish (P<0.05). There were no significant differences in six morphometric traits among these Amblycipitidae. The dimensions used in this study may be useful as taxonomic indicators to discriminate species of Liobagrus in Korea.

• Korean Journal of Ichthyology
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• v.24 no.3
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• pp.183-190
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• 2012

The spawning site characters in the natural environment of bull-head torrent catfish, Liobagrus obesus, were investigated at the part of the Gosan stream in Korea from April to October 2010 and June 2011. The sex ratio of female to male was 1 : 1.02. Spawning season was from June to July with water temperature in approximately $23^{\circ}C$. The spawning sites were covered by the boulder used upper plate and were composed of gravel and sand. One male lies with the egg mass and guards the developing embryos in the hollow below the boulder. The environmental conditions of the spawning sites were $61.4{\pm}11.97$ (50~85) cm in depth, 0.58${\pm}0.067$ (0.48~0.72) m/sec in surface water velocity, $0.46{\pm}0.098$ (0.27~0.61) m/sec in middle water velocity, $0.27{\pm}0.083$ (0.14~0.41) m/sec in bottom water velocity. The boulder width as spawning sites was $26.2{\pm}5.32$ (20~38) cm in long axis, $20.5{\pm}2.97$ (16~25) cm in short axis and $11.1{\pm}4.02$ (5~19) cm in height. The hollow underneath the boulder was $9.8{\pm}2.32$ (6~14) cm in diameter and $2.8{\pm}1.10$ (1.5~5) cm in depth. The average number of eggs in ovary was $124{\pm}27.7$ (92~180). The matured egg size was $3.40{\pm}0.078$ (3.21~3.56) mm. The average number of spawning eggs in the spawning site was $99{\pm}12.9$ (81~122).

• Korean Journal of Environmental Biology
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• v.17 no.1
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• pp.79-88
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• 1999

The fish fauna, notified species, and fish community was studied at the six stations in a 18km section of the Ungchon stream, a mountain stream in Korea, where a new dam is planned from 1994 to 1996. Twentynine species (11 families, 25 genera) were found. Nine species were endemic to Korea. The Dominant specie in the studied area were Zacco temmincki, Z. platypus and Squalidus gracilis majimae. Some of the korean endemic species (Coreoperca herzi) including the Korean endangered species such as Pseudopungtudgia nigra and Liobagrus obesus were not found in this stream anymore. The average of area density was 0.69 individuals per square meter and the volume density was 1.45 individuals per cubic meter. Species diversity was highest in the middle region. According to community correlation coefficients of six stations, similality coefficients of station one, four, five and six were higher than others, but no significant difference in the composition of fish fauna was found between six study staions.