• Korean Journal of Ichthyology
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• v.18 no.1
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• pp.20-26
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• 2006

Bagrid catfish hybrid between Korean bullhead (Pseudobagrus fulvidraco) and Ussurian bullhead (Leiocassis ussuriensis) was produced by artificial fertilization. Modal chromosome numbers of Korean bullhead, Ussurian bullhead and their hybrid were the same as 2n=52. The karyotypes were 22 metacentric (M), 22 submetacentacentric (SM), and 8 acrocentric (A) chromosomes for Korean bullhead, 22M+14SM+16A for Ussurian bullhead and 22M+18SM+12A for their hybrid. The hybrid bullhead karyotype consisted of each haploid set of parental species chromosomes. Erythrocytic sizes and DNA contents of hybrids were intermediate between two parental species.

• Korean Journal of Ichthyology
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• v.13 no.4
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• pp.248-253
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• 2001

An histological study was conducted to determine the initial treatment time and treatment duration in the use of sex-reversal hormones in relation to gonadal development and sexual differentiation in the bagrid catfish, Leiocassis ussuriensis. The primordial germ cell, which could be recognized from one-day-old fry, began to protrude into the peritoneal cavity between the mesonephric duct and the gut. The primordial gonad with a genital ridge was developed at 5~10 days after hatching. Sex differentiation of the ovary was identified by the ovarian cavity and meiotic oocytes from 20-day-old larvae. Testicular differentiation was also identified by spermatogonial cells from 20-day-old larvae. It may therefore be concluded that this species belongs to the differentiated type of gonochoristic teleost.

• Journal of Aquaculture
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• v.20 no.3
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• pp.190-193
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• 2007

Viability, early growth and sex ratio of induced gynogenetic diploid bagrid catfish (Leiocassis ussuriensis, Siluriformes) were examined. Survival rates of gynogenetic diploids and normal bi-parental diploids up to 180 days post hatching were not significantly different (P>0.05), and consequently resulted the mean percent survivals of 76% (gynogens) and 78% (bi-parental progeny) at the end of growth trial. Growth in both body weight and total length of gynogenetic diploids was also similar to those of normal diploid controls (P>0.05). Gynogenetic bagrid catfish displayed a similar level of ovarian development when compared to bi-parental diploid females, as judged at 10 weeks post hatching. Sex ratio of bi-parental progeny was normal 1:1 whereas all-femaleness was observed in gynogenetic progeny (P<0.05), suggesting that the genetic sex determination mechanism of this species should be XX-XY based female homogamety.

• Journal of Aquaculture
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• v.22 no.1
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• pp.74-78
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• 2009

Backcross hybridization between Korean bullhead Pseudobagrus fulvidraco female and Korean bullhead P. fulvidraco $\times$ Ussurian bullhead Leiocassis ussuriensis hybrid male was performed, and early viability and karyotype of the backcross hybrids were examined along with their parental species. Mean fertilization rate (86.8%), hatching success (70.7%) and early survival rate (76.4%) of backcross hybrids were similar with those found in the maternal species, the Korean bullhead. From the chromosome analysis, modal chromosome numbers of Korean bullhead, Ussurian bullhead, their hybrid and backcross hybrid were the same as 2n = 52. However, their karyotypes were different among genotypes. The karyotype of backcross hybrid was 22 metacentric + 18 submetacentacentric + 12 acrocentric chromosomes.

• Korean Journal of Ichthyology
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• v.2 no.2
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• pp.117-137
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• 1990

The morphological characters of the family Bagridae living in the river systems flowing into the south and western seas of Korea were reviewed and a taxonomic revision was made. The family Bagridae was classified into two genera: Pseudobagrus and Leiocassis. Species corresponding to genus Pseudobagrus were P. fulvidraco, P. koreanus Uchida, sp. nov., P. brevicorpus, and genus Leiocassis were L. nitidus, L. ussuriensis, and L. longirostris. Among them Pseudobagrus koreanus Uchida, sp. nov. and P. brevicorpus are endemic species of Korea. As the intergeneric taxonomic characters, the outstanding morphological differences between genera Pseudobagrus and Leiocassis were distinguished in following characters; the serrated structure of pectoral spine, the length of barbels, the number of pectoral fin rays, the structure of cranial lateral line system and the fused state of 3-4 hypurals. Pelteobagrus fulvidraco and Coreobagrus brevicorpus recorded previously in Korea were classified as Pseudobagrus fulvidraco and P. brevicorpus, respectively. Pelteobagrus nitidus and Pseudobagrus ussuriensis are also changed to genus Leiocassis. The characters of interspecific classification belonging to genera Pseudobagrus and Leiocasis were the shape of caudal fin, the form of body, the length of body, the number of anal fin ray and the number of gill rakers. Pseudobagrus sp. was named into Pseudobagrus koreanus Uchida, sp. nov..

• Development and Reproduction
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• v.19 no.4
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• pp.189-196
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• 2015

This study was examined the ovogenesis of Ussurian bullhead, Leiocassis ussuriensis and the morphological development of its larvae and juveniles and to use the results as basic information for the preservation of species and resource enhancement. For artificial egg collection, human chorionic gonadotropin (HCG) was injected at a rate of 10 IU per gram of fish weight. During breeding period, water temperature maintained at $24.5{\sim}26.5^{\circ}C$ (mean $25.0{\pm}0.05^{\circ}C$). The process of ovogenesis reached the two-cell stage in 50 minutes after fertilization. In 73 hours of fertilization the movement of the embryoid body became active state and the larvae began to hatch from the tail through the oolemma. Length of prelarvae were 6.33~6.50 mm long (mean $6.40{\pm}0.06mm$) just after hatching having yolk with their mouth not opened. After thirty eight days of hatching, juveniles were 30.6~32.5 mm long (mean $31.5{\pm}0.65mm$). The color was dark yellowish brown throughout the entire body, and the number of caudal fin rays developed to thirty six perfectly.

• Korean Journal of Ecology and Environment
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• v.33 no.4 s.92
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• pp.405-412
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• 2000

The fine structure of spermatozoa of Leiocassis ussuriensis was examined with scanning and transmission electron microscopies. The spermatozoon of L. ussuriensis is approximately $68.8\;{\mu}m$ in length and a relatively simple cell with a spherical nucleus, a short midpiece and a tail. The ultrastructure of spermatozoa of L. ussuriensis is characterized by the following features. The nuclear fossa, the length of which is about two-thirds of the nuclear diameter, contains two centrioles. The centrioles are orientated approximately $180^{\circ}$ to each other. The mitochondria are arranged in two layers and their number is 12 or more. The axoneme is the 9+2microtubular pattern and has inner but no outer dynein arms as in other bagrids. The two axonemal fins are in the same plane with the two central microtubules, the doublets 3 and 8. The axonemal fins and the inner dynein arm are shared in Bagridae and the deep nuclear fossa is shared in Siluriformes. The axonemal finsobse observed in Bagridae and Amblycipitidae of Siluriformes might be the apomorphic character in Ostariophysi. They are not reported in Cyprinidae and Characiformes.

• Journal of Aquaculture
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• v.20 no.3
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• pp.184-189
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• 2007

Treatment conditions for the induced diploid gynogenesis, a maternal-exclusive form of artificial parthenogenetic reproduction, were optimized in bagrid catfish (Leiocassis ussuriensis, Siluriformes). Optimal amounts of ultraviolet (UV) irradiation for the genetic inactivation of spermatozoa in bagrid catfish and Pseudobagrus fulvidraco were proven to be ranged from 3,600 to 4,800 $ergs/mm^2$ based on the examination of viability of embryos and haploid incidence. Haploid embryos were restored to diploidy by preventing the extrusion of the second polar body using cold shock treatment. Thermal treatments (4 or $6^{\circ}C$ for 30, 40 or 50 min) were carried out 3, 5 or 7 min post insemination. Best scores for embryo viability (38.6% of total eggs taken) and incidence of normal diploidy (87.9% of hatched larvae) were observed at the embryo group treated at $4^{\circ}C$ for 40 min, 5 min after insemination. Restoration of gynogenetic diploidy was confirmed based on the absence of haploid syndrome, cell size and/or nucleolar organizing region (NOR) counts.

• The Korean Journal of Zoology
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• v.32 no.3
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• pp.252-257
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• 1989

The five species of family Bagridae in Korea were analyzed by numerical taxonomic method based on the twelve osteological characters of 110 cleared specimens. Family Bagridae of Korea was classified into genera Pseudobagrus and Leiocassis. Genus Pseudobagrus has P. fulvidraco, Pseudobagrus sp. and P. brevicorpus, and Leiocassis also has L nitidus and L ussuriensis. P. brevicorpus represented more closely relationships to P. fulvidraco rather than Pseudobagrus sp. in the morphological features of skeleton.

• Development and Reproduction
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• v.17 no.4
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• pp.427-434
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• 2013

The histological changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidraco, were observed during the early period of growth. The retinas size of both species increased in the 9 days post-hatching (DPH) (p<0.05). In the just-hatched Ussurian bullhead, the retina already consisted of six layers: the epithelial layer, ganglion cell layer, inner nuclear layer, inner plexiform layer, outer limiting membrane layer, and rod and cone layer. The Korean bullhead had the same components. At 50 DPH, the thickness of the retina was $538.0{\pm}7.19{\mu}m$ in the Ussurian bullhead and $558.9{\pm}9.44{\mu}m$ in the Korean bullhead. The relative thickness of each layer of the retina did not differ significantly in the two species. Although the growth of the Korean bullhead's retina was faster, the relative thickness of each layer in the retina did not change during early development. After hatching, some parts of the tissue gradually became denser. Immediately after hatching, the kidney and midgut epithelium of the Ussurian bullhead and Korean bullhead were already formed and grew gradually thereafter. From 0 DPH to 30 DPH, the nuclear height in the midgut epithelium did not differ significantly between the two species, but at 50 DPH, it was $11.4{\pm}2.45{\mu}m$ in the Korean bullhead and $9.9{\pm}2.13{\mu}m$ in the Ussurian bullhead. During the experimental period, the major axes, minor axes, surface areas, and volumes of the proximal tubule cells in the kidney did not differ significantly between the two species. Thus, the early histological development of the Ussurian bullhead is similar to that of the Korean bullhead.