• Development and Reproduction
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• v.4 no.2
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• pp.147-152
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• 2000

Four clonal lines of ayu, Plecoglossus altivelis, were produced through gynogenesis, mixed before hatching and reared communally. After 10 months, a randomly taken sample was subjected to a standardized shallow water stressor. Hematocrit, hemoglobin, red blood cells count (RBC) and mean corpuscular volume (MCV) were obtained from stressed and non-stressed fish. DNA fingerprinting was used to confirm the clonal nature of the organisms and to identified the clonal line to which each fish belonged. 1 observed significant differences between clona] lines mostly in the hematocrit and MCV measured under no-stress conditions. Such differences are suggested to represent mainly genetic variance, on account of the common environment provided to all the experimental groups. The stress response ratio was lower than expected, mainly due to some unexpectedly high non-stress values. Heritability values (h$^2$) were medium to high for the no-stress measurements (mean 0.238) and very low or zero for the stressed groups'traits (excepting one high value of 0.484). 1 conclude that the use of communally reared clonal lines represents a good tool for the characterization of the physiological traits, thus allowing for their utilization as genetic selection criteria.

• Korea journal of population studies
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• v.35 no.1
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• pp.131-149
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• 2012

This study examined the effect of parental socioeconomic position on the association between birth outcomes and infant mortality in early and late 2000's. Linked Birth and Infant Death data sets from 2001 to 2003 (T1) and from 2006 to 2008 (T2), provided by the Korea National Statistical Office, were used for analysis. Birth outcomes were categorized into four groups: normal term, small-for-gestational age (SGA), large-for-gestational age (LGA) and intrauterine growth retardation (IUGR). Infant death was defined as the death of a live-born child under one year of age; indicators of parental socioeconomic position were limited to parental education and occupation. The results showed that T2 infant mortality hazard ratios of SGA and IUGR have increased compared to T1. Particularly, preterm and low birth weight babies with shorter gestational age and lighter birth weight than T1 have elevated in T2, possibly indicating that population quality might be continuously aggravated. Moreover, the effect of maternal age on infant mortality has disappeared, rather that of parents' socioeconomic position has increased during the periods, which entailed growing disparities in infant mortality by their social class. Further studies should be therefore done to estimate the effect of parental socioeconomic position on the relationship between birth outcomes and infant mortality in the near future.