• Parasites, Hosts and Diseases
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• v.28 no.3
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• pp.183-194
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• 1990

In an attempt to develop prophylactic and therapeutic measures of the intestinal giant-cystic disease caused by Thelohanellus kitauei in the Israel carp, Cyprinus carpio nodus, pathological observations were conducted upon the carps which were hatched in May 1988 and raised in a net cage fish farm at the Soyang lake, managed by Horim Fisheries for the period of 21 months with 1~2 months interval. After a gross inspection of the carps, necropsy was carried out periodically in order to clarify the pathological changes in various internal organs and muscular tissues. Also. the prevalence of the disease was checked during the period from 1988 to 1990. Gross inspections revealed that the infected carps showed some degree of fading in body and gill color, back-emaciation symptoms, reddish anus accompanying erosion and relaxation and pot-belly, as well as discharge of yellowish white mucoid material from the anus. However, most carps died eventually of intestinal obstruction. Other significant necropsy fadings included cyst formation of various size in the intestinal mucosa, ascites, anemic condition through internal organs and muscular tissues, hyperemia and dilation of intestines with decreased tension, thinness and fragility, and full contents of semi-fluid or yellowish white mucoid material in the intestinal canals. Based on the morphological characteristics of the spores found in the cysts, parasitic location in the intestines, macro- and microscopic findings of the lesions, the parasites were identised as Thelohanellus kitauei Egusa os Nakajima, 1981. Although monthly changes of water temperature were distinct, the extrusion rates of the polar filaments of the spores stayed constant throughout the year with an exception of a lower rate in July, The lesions initiated from mucosa and submucosa in early July became large swellings and then complete mature (orms following the peracute course. From late August the upper cysts were gradually opened and most of the spores were dispersed from anus into the surrounding water through December but only a few lasted until next April. The cysts were completely recovered until next September. Comparing the incidence and prevalence of the disease by year tremendous infection and death rates were checked in the first prevalent year, 1988, but the rates were significantly decreased in the second year, and showed an almost normal status in the third year, 1990. As the above summarized results showed, the disease entity might come to an end in three years after the first prevalent year, however, the spores must be strictly prevented because they could be infective in the water for one year.

• Korean Journal of Environment and Ecology
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• v.27 no.4
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• pp.487-497
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• 2013

This study was conducted to suggest vegetation management plan for Gugok landscape maintenance and improvement by deducing the vegetation landscape factors inherent in Yongha Gugok and understanding vegetation structure through the investigate of existing vegetation and plant community structure of Yongha valley in Woraksan National Park. There were broad and flat rocks, natural layered stones, clear water, light stones, stream, valleys, waterfalls, Pinus densiflora and Acer pseudosieboldianum as a result of deducing natural factors on poetry. There were P. densiflora and A. pseudosieboldianum appeared as one of main vegetation landscape elements. The actual vegetation analysis results were as followed. The natural vegetation occupied 67.5% and it was classified as P. densiflora community, Quercus variabilis community, Q. variabilis-P. densiflora community, Q. variabilis-Q. serrata community, Q. serrata community, Q. mongolica community, Q. mongolica-P. densiflora community, Deciduous broad-leaved tree community. The artificial vegetation(18.7%) was classified as Q. serrata community-Larix kaempferi community, Q. mongolica- Castanea crenata community, L. kaempferi community, L. kaempferi-C. crenata community, fruticeta, L. kaempferi-Q. mongolica community. The grassland area(2.0%) was classified as Miscanthus sinensis community, Phragmites communis community, and other areas were classified as landscape tree planting area, farm, orchard, residential area. The representative vegetation were P. densiflora community, Q. variabilis-Q. serrata community, L. kaempferi community, Deciduous broad-leaved tree community in Yongha Gugok. The species diversity index of Shannon was 0.6274~0.9908 on the whole. Yongha Gugok, as a symbol of succession on confucianism and reverence for nature, should be preserved natural valley landscape being clean and wijungchuksa at the end of Joseon Dynasty and Japanese Colonial era. In this historical and cultural Gugok, vegetation landscape management plan is needed to landscape maintenance with P. densiflora community, density control with L. kaempferi community. And it is considered when natural disasters and artificial damages happened, P. densiflora-oriented vegetation restoration plan should be applied in order to restore.

• Korean Journal of Poultry Science
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• v.16 no.2
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• pp.61-71
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• 1989

The purposes of this study were to investigate the genetic variations by backcrossing in commercial chickens. Backcrossing was carried out successively back to parent stock (P.S). Heritabilities and genetic correlation coefficients were estimated to verify the genetic variations. The data obtained from a breeding programme with commercial chickens (I strain) were collected from 1955 to 1987 at Poultry Breeding Farm, Seoul National University. Data came from a total of 1230 female offspring. The results obtained are summarized as follows： 1. The general performance ($Mean\pmStandard deviation$) of each trait was $663.94\pm87.11$g for 8 weeks body weight, $1579.1\pm155.43$g for 20 weeks body weight, $2124.1\pm215.3$g for 40 weeks body weight, $2269.1\pm242.94$g for 60 weeks body weight, $168.43\pm12.94$ day for a9e at sexual maturity (SM), $214.52\pm29.82$ eggs , for total egg number to 60 weeks of age (TEN), $61.45\pm3.48$ g for average weight (AEW), $13180.7\pm1823.22$ g for total egg mass to 60 weeks of age(TEM). All traits, except 10 weeks body weight and AEW, were significant for the degrees of backcross (p＜0.01). 2. The pooled estimates of heritabilities derived from the sire, dam and combined variance components were 0.47~0.52 for age at sexual maturity (SM), 0.07~0.37 for total egg number (TEN), 0.40~0.54 for average egg weight (AEW), 0.18~0.27 for total egg mass (TEM). High heritability estimates were found for SM and AEW. TEN and TEM were estimated to be a lowly heritable traits. Heritability estimates from dam components were higher than those from sire components. These differences might be due to non-additive genetic effect and maternal effect. 3. The estimates of heritabilities and standard errors derived from combined variance components for different degrees of backcross were $0.47\pm0.11$ (BCO), $0.42\pm0.16$ (BC1), $0.51\pm0.29$ (BC2) for TEN, $0.59\pm0.20$ (BCO), $0.43\pm0.17$ (BC1), $0.35\pm0.18$ (BC2) for AEW, $0.28\pm0.12$(BC0), $0.20\pm0.11$(BC1), $0.18\pm0.14$ (BC2) for TEM. Heritability estimates for AEW and TEM were decreased by backcrossing while those for SM and TEN remained constant. Since backcrossing contributes to increased homozygosity, the genetic variation of the traits (AEW and TEM) decreased . 4. The pooled estimates of genetic correlation coefficients were -0.55 between SM and TEN, 0.20 between SM and AEW, -0.29 between TEN and AEW, 0.82 between TEM and TEN, 0.31 between TEM and AEW, -0.42 between TEM and SM. The genetic correlation between TEM and TEN was higher than that between TEM and AEW, and it was suggested that egg mass was strongly affected by egg number. Also, age at sexual maturity(SM) contributes to egg mass(TEM). 5. When backcrossing was carried out successively, the genetic correlation between TEM and TEN increased (BC0：0.79, BC1：0.82, BC2：0.91) but those between TEM and SM decreased (BC0：-0.54, BC1：-0.36, BC2：-0.09) with successive backcrosses.