메기 (Silurus asotus)를 대상으로 210일간 기아 시 계측 형질 및 체 절단면 형질을 측정하여 그 기아 효과를 조사하였다. 실험 종료시 섭이군의 생존율은 92.2±0.47% 였으며, 기아군에서는 74.4±2.59%의 생존율을 보였다. Ls, DALPO/Ls, DADOP/Ls, ED/Ls, CH/Ls, BDAA/Ls, BDMA/Ls 및 BWAA/Ls의 8개 항목에서 유의한 차이를 보 였으며 (p<0.05), 다른 16개 항목 DALAD/Ls, DPDPL/ Ls, HPLAA/Ls, HALAV/Ls, HALOP/Ls, DAUPO/Ls, DADAV/Ls, DADAA/Ls, Max BL/Ls, Man BL/Ls, LD/Ls, HWOP/Ls, DAUF/HL, DAUS/HL, IW/HL 및 DAUE/HL 에서는 초기군, 섭이군 및 기아군의 세 그룹 간 유의한 차이가 없었다 (p>0.05). 섭이군은 각 체 절단면에서 기아군 보다 더 높은 전체 높이 (THX), 더 넓은 너비 (WX) 및 더 넓은 면적 (AX)을 보였다. 본 연구는 메기의 기아 상태에 대한 외형 및 체 절단면 형질에 대한 정보를 제공한다. 이는 메기에 대한 먹이 조절에 대한 방법을 보조하고 영양상태를 나타내는 기본 기초자료로 활용될 수 있을 것이다. 또 한, 본 연구에서 사용한 조사 분석 방법을 타 어종에서 적용 시 그 영양 상태에 대한 정보를 파악하는 데 유용하게 활용될 수 있을 것으로 사료된다.

A 210-day experiment was conducted to examine the effects of starvation on survival, the gonadosomatic index (GSI), hepatosomatic index (HSI), and the intestinosomatic index (ISI), and histological changes in the renal tubule epithelium, midgut epithelium, and hepatocytes in Far Eastern catfish (Silurus asotus). The survival rate decreased to 92.2±0.47% in the fed group and 74.4±2.59% in the starved group during the 210-day experimental period. GSI, HSI, and ISI were lowest in the starved group (p<0.05). The hepatocyte nuclear area, hepatocyte cell area, the nuclear height of the midgut epithelium, and the nuclear height of the kidney were highest in the fed group (p<0.05). The hepatocyte nuclear area, nuclear height of the midgut epithelium, and nuclear height of the kidney were lowest in the starved group (p<0.05). The numbers of melano-macrophages (MMs) found in the kidney cells increased during starvation in this species. This suggests that thinner body cavity regions, the contraction of hepatocyte nuclear sites, and the spreading of kidney cell MMs in this species could be used as alternative indicators for identifying starvation conditions. Therefore, the results from our study provide accurate indications of the nutritional status of Far Eastern catfish.

This study identified the differences in the morphometric characteristics of the truss and classical dimensions between diploid and triploid Far Eastern catfish, Silurus asotus, and provided methods for sorting diploid and triploid Far Eastern catfish based on morphometric observations. The significant variables were the direct distance between the anterior edge of the lower lip and the anterior insertion of the dorsal fin (DALAD), the horizontal distance between the anterior edge of the lower lip and the anterior insertion of the ventral fin (HALAV), the direct distance between the anterior edge of the upper lip and the first nostril (DAUF), the direct distance between the anterior edge of the upper lip and the second nostril (DAUS), the interorbital width (IW), and the mandible barbel length (ManBL). The more significant variables were HALAV, DALAD, DAUF, IW, and DAUS. The most useful combination of variables for separating the two groups was DALAD, IW, and DAUF, which correctly classified 85% of the catfish as triploid or diploid, and that percentage was the maximum degree of value possible (p<0.05). Triploid Far Eastern catfish had a high rate of growth in the head region and body depth during the first year after hatching. Triploid Far Eastern catfish had smaller heads and shorter mandible barbels than diploid Far Eastern catfish.

The aim of study is to contribute to this knowledge-base by investigating the respiratory function, the metabolic rate and the difference of physiological responses un-der low water temperature (20℃→15℃) stress be-tween diploid and triploid far eastern catfish, Silurus asotus. During the 48 hrs of water temperature stress exposure time, the respiratory frequencies, CO₂ and NH₄+ concentrations of diploid had higher values than those of triploid (p<0.05). However, pH of triploid was higher than those of diploid (p<0.05), and oxygen consumption rate was not different between diploid and triploid (p>0.05). The level of plasma cortisol and plasma glucose of triploid was lower than those of the diploid (p<0.05). However, in case of lactic acid, there were not significant between triploid and diploid (p>0.05). These results suggest that diploid was more sensitive for low water temperature stress response than triploid in this species.

This study was conducted to investigate egg development and larvae morphological development of catfish and to provide basic data to clarify the genetic relationship with Siluriformes fish. The mother fish that was used in this study was caught in the stream of Nakdong River in Uiseong-gun, Gyeongbuk. The temperature range of the breeding was 23.0- 25.0℃ (mean 24.0±1.0℃) and egg size was 1.62-1.70 mm (mean 1.66±0.05, n=30). Eggs of catfish began hatching at 54 hours and 40 minutes after fertilization. Immediately after hatching, the total length of larvae was 3.60-3.65 mm (mean 3.62±0.03, n=5) and had an egg yolk without swimming ability. On the third day after hatching, the larvae at the medium stage was 8.00-8.65 mm (mean 8.32±0.45) in total length, and two pairs of whiskers formed around the mouth were elongated. On the 12th day after hatching, the larvae at the juvenile stage was 16.5-17.0 mm (mean 16.7±0.35) in total length, and the stem of each fin was in the range, and the juvenile at this period was morphologically similar to the mother fish.

The purpose of this study is to investigate the differences fatty acids and hormonal parameters in the spawning and non-spawning season between the diploid and induced triploid Far Eastern catfish, Silurus asotus. The measured triploids were produced by cold shock for 50 min at 4℃ in May 2014, the spawning season of diploid was in May, and the nonspawning season was designated in January. Estradiol and testosterone and gonadosomatic index of diploid were higher than those of induced triploid in spawning season (P<0.05), and those of diploid in spawning season were higher than nonspawning season. On the other hand, thyroid stimulating hormone and thyroxine of induced triploid were higher than those of diploid in spawning season (P<0.05). Erythrocyte count of diploid was higher than that of induced triploid in spawning season and non-spawning seasons. Mean corpuscular volume and mean corpuscular hemoglobin of induced triploid were higher than those of diploid in both seasons (P<0.05). Percentages of total saturated fatty acids and n-3 polyunsaturated fatty acids of induced triploid were higher than those of diploid in spawning season, but those of diploid were higher in non-spawning season (P<0.05). Percentages of total mono unsaturated fatty acids and total n-6 polyunsaturated fatty acids of diploid were higher than those of induced triploids in spawning season, while those of induced triploid in non-spawning season were higher (P<0.05). Therefore, induced triploids in the spawning season tend to concentrate on growth and lipid-synthesization, whereas, diploids concentrate on reproduction and gonadal maturation rather than on growth. In non-spawning season, growth and lipid- synthesization were not significantly different between diploid and induced triploid.

The influence of triploidization on histological characteristics of retina, trunk kidney, liver and midgut tissue, and cell cycle of tail fin and gill tissue in far eastern catfish, Silurus asotus were analyzed. In the infertile triploid fish, the nucleus and/or cell size of secondary proximal tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger than those of the corresponding cells in the diploid fish (P<0.05). However, triploid tissue showed fewer number of outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk kidney than those for diploid tissue. The mean percentages of the Gl-, the S- and the G2+M-phase fractions were 92.5%, 3.2% and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of triploid, respectively. There were no significant differences in the percentages of each cell cycle fraction between diploid and triploid. The mean percentages of each phase fractions were 75.1%, 11.1% and 13.8% in gill tissue of diploid and 85.2%, 8.9% and 5.9% in those of triploid, respectively. The differences of cell cycle between tail fin tissue and gill tissue were statistically significant in diploid and triploid (P<0.05). Also, the differences between diploid and triploid were statistically significant in tail fin tissue and gill tissue (P<0.05). Cyclin D1 and cyclin E expressions were not significantly difference between gill tissue and tail fin tissue, and protein expressions of induced triploid were higher than those of diploid. Results from this study suggest that some characteristics in the triploid exhibiting larger cell and nucleus size with fewer number of cell than diploid can be used as an indicator in the identification of triploidization and ploidy level in far eastern catfish.

The influence of triploidization on histological characteristics of retina, trunk kidney, liver and midgut tissue, and cell cycle of tail fin and gill tissue in far eastern catfish, Silurus asotus were analyzed. In the infertile triploid fish, the nucleus and/or cell size of secondary proximal tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger than those of the corresponding cells in the diploid fish (P<0.05). However, triploid tissue showed fewer number of outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk kidney than those for diploid tissue. The mean percentages of the Gl-, the S- and the G2+M-phase fractions were 92.5%, 3.2% and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of triploid, respectively. There were no significant differences in the percentages of each cell cycle fraction between diploid and triploid. The mean percentages of each phase fractions were 75.1%, 11.1% and 13.8% in gill tissue of diploid and 85.2%, 8.9% and 5.9% in those of triploid, respectively. The differences of cell cycle between tail fin tissue and gill tissue were statistically significant in diploid and triploid (P<0.05). Also, the differences between diploid and triploid were statistically significant in tail fin tissue and gill tissue (P<0.05). Cyclin D1 and cyclin E expressions were not significantly difference between gill tissue and tail fin tissue, and protein expressions of induced triploid were higher than those of diploid. Results from this study suggest that some characteristics in the triploid exhibiting larger cell and nucleus size with fewer number of cell than diploid can be used as an indicator in the identification of triploidization and ploidy level in far eastern catfish.

The aim of this study was to compare the efficacy of cryopreservation methods for ex situ conservation of spermatozoa from far eastern catfish, Silurus asotus. The spermatozoa activity index (SAI) and hatching rates were higher in spermatozoa stored in Alserver’s solution than those of spermatozoa stored in glucose solution. The SAI and hatching rates in all experimental groups gradually decreased with increasing duration of storage. Additionally, the SAI and hatching rates gradually decreased with increasing thawing temperatures at all storage durations (P<0.05). Based on the SAI and hatching rates, our results suggest that the optimal cryopreservation conditions of catfish spermatozoa involve storage in Alserver’s so-lution with 15% ethylene glycol, and thawing at 25℃. Cryopreservation of spermatozoa is a useful and reliable technique for conserving gene resources and for artificial propagation of far eastern catfish.

For the 2 years of farming, at the indoor circulating aquaculture system, four kinds of skeletal deformities were found among 60 Far Eastern catfish, Silurus asotus. Deformities saw jawbone’s luxation, abnormality of upper lip and malocclusion. Spinal deformity was most fatal deformities with low weight and small length. Jawbone’s luxation had 1 maxilla and 2 mandibles. Abnormality of upper lip had just lip was back over. Malocclusion’s left maxilla and right maxilla were not balanced. This experiment was any deformities in this species through the deformity can grasp how it affects.

The influence of triploidization on histological characteristics of retina, trunk kidney, liver and midgut tissue, and comparative analysis of cell cycle and expression of cell cycle protein from tail fin and gill tissue in Far Eastern catfish, Silurus asotus were analyzed. In the infertile triploid fish, the nucleus and/or cell size of secondary proximal tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger than those of the corresponding cells in the diploid fish (P<0.05). However, triploid tissue showed fewer number of outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk kidney than those for diploid tissue. The mean percentages of the G1-, the S- and the G2+M-phase fractions were 92.5%, 3.2% and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of triploid, respectively. There were no significant differences in the percentages of each cell cycle fraction between diploid and triploid. The differences of cell cycle between tail fin tissue and gill tissue were statistically significant in diploid and triploid (P<0.05). Also, the differences between diploid and triploid were statistically significant in tail fin tissue and gill tissue (P<0.05). Results from this study suggest that some characteristics in the triploid exhibiting larger cell and nucleus size with fewer number of cell than diploid can be used as an indicator in the identification of triploidization and ploidy level in Far Eastern catfish.

The present study determined the differences in the morphometric characteristics of truss and classical dimensions between diploid and triploid Far Eastern catfish, Silurus asotus and provided methods for separating diploid and triploid Far Eastern catfish based on morphometric observations. Significant variables were the direct distance between the anterior edge of the lower lip and the anterior insertion of the dorsal fin (DALAD), the horizontal distance between the anterior edge of the lower lip and the anterior insertion of the ventral fin (HALAV), the direct distance between the anterior edge of the upper lip and the first nostril (DAUF), the direct distance between the anterior edge of the upper lip and the second nostril (DAUS), the interorbital width (IW), and the mandible barbel length (ManBL). The more significant variables were DALAD, HALAV, DAUF, DAUS, and IW. The most useful combination of variables for separating the two groups was DALAD, IW, and DAUF, which correctly classified 85% of the catfish as triploid or diploid, the maximum degree of separation obtained (P<0.05). The triploid catfish had high head region and body depth growth rates during the first year after hatching. Triploid catfish had smaller heads and shorter mandible barbels than diploid catfish.