Information about the density of fish eggs is important to understand the vertical distribution of eggs and survival in early stage, in particular change in egg density is one of major issue in fisheries. This paper describes a practical application of an experimental system for measurement of the fish egg density under laboratory conditions. The device can control the temperature range in each water column, and make different densities at each layer. The density of olive flounder (Paralichthys olivaceus) eggs have ranged from 1,018.49 to 1,020.93 kg/m3 and were aggregated around the density of 1,020 kg/m3. The results show that the device is applicable for measuring the fish egg density under laboratory conditions.

In order to develop a core set and new corn variety in Korea, we evaluated the morphological characteristics of 194 maize accessions by examining eight quantitative characteristics. On the evaluation of quantitative traits for 194 maize accessions, they showed the morphological variations in tassel length (35.1±5.0 cm), plant height (226.1±33.7 cm), ear height (86.3±22.6 cm), stem diameter (2.3±0.6 cm), leaf width (9.3±1.1 cm), ear length (14.5±2.4 cm), ear row number (14.1±1.9 row), and 100 kernel weight (24.9±4.4 g). The results of principal component analysis (PCA) indicated that the tassel length, plant height, and ear height greatly contributed to positive direction on the first principal component axis. One-hundred kernel weight contributed to negative direction on the second principal component axis. Thus these morphological characteristics, which contributed greatly in the first and second principal components, might be useful for discrimination among 194 maize accessions. In our study, seven accessions, such as IT026357, IT026441, IT027321, IT033271, IT033591, IT033597 and IT124273, particularly were measured high on yield-related traits. Consequently, the 194 maize accessions used in this study could be used as promising materials for maize breeding programs such as development of new hybrid in Korea.

Reactive oxygen species (ROS) are produced in organisms as the natural products of oxidative metabolism by environmental stress and pathogen invasion. ROS, such as superoxide anion and hydrogen peroxide, can be toxic to cells and tissues to cause oxidative stress. Recent study revealed that olive flounder (Paralichthys olivaceus) superoxide dismutase (SOD) has been identified as a partial gene and strongly induced to benzoin[a]pyrene and it was deduced indicator of aquatic oxidative stress responses, but its transcriptional response against viral infection has not been investigated. In the present study, spatial and temporal expression profile was analyzed to investigate the function of Of-SOD in the anti-viral response. Of-SOD transcripts were ubiquitously detected in diverse tissues with variable levels using a real-time PCR. The expression of Of-SOD was significantly higher in the muscle, liver and brain, but extremely low in the stomach and spleen. Following VHSV challenge, the expression of Of-SOD increased within 3 hours and subsequently decreased to the original level at 2 days post-challenge in kidney. Although expression pattern and induction time are slight differences depending on the tissue, the transcript of Of-SOD was consistently increased in acute infection response, but expression is low in the chronic response. Collectively, Of-SOD expressions were inducible after VHSV infection and they were probably involved in the immune response against viral challenge. These results suggest that SODs may play important roles in the immune defense system of P. olivaceus and perhaps contribute to the protective effects against oxidative stress in this flounder.

Molecular markers are useful for selecting to include superior character genetic like as strong immune system and rapid growth in fish. The marker is also very important part of breeding technology in Olive flounder (Paralichthys olivaceus). Single nucleotide polymorphisms (SNPs) marker is already in use widely for genomic research and breeding. But this SNPs marker hardly has been validated for screening functional genes in Olive flounder. We study identify single nucleotide polymorphisms (SNPs) on Expressed sequence tag (EST) database, develop usable SNP marker and apply to wild sample and cultured of olive flounder. As a result, Out of total 4.327 ESTs, 693contigs and 514 SNP from total contigs were detected while these substitutions include 297 transitions and 217 transversions. 144 developed markers were applied in 16 samples (wild 8, culture 8), Out of total marker, only 32 markers had detected polymorphic in sample. Polymorphism of 32 markers was observed in the variety genes region involved in immunity and protein synthesis. And the 32 marker were identified 21 transitions, 11 transversions, and indel was not detected in polymorphic SNPs. The analysis on heterozygosity by sample showed 0.34 in wild sample and 0.29 in cultured sample. In conclusion, we was identified SNP and Polymorphism by designed new marker, it supports that development marker is suitable for SNP detection and diversity analysis in Olive flounder. The outcome of this study can be basic data for researches for immunity gene and characteristic with SNP.

Olive flounder (Paralichthys olivaceus) is a most important aquaculture species in Korea. Like most marine fishes, olive flounders are stomachless at first feeding and aquired gastric function during the metamorphosis, so food was mainly digested by pancreatic enzyme from first feeding to premetamorphosis. However, comprehensive analysis of pancreatic and gastric digestive enzyme of olive flounder at early developmental period is still unclear. In the expression study of pancreatic and gastric digestive enzyme by real-time PCR at early developmental stage, pancreatic enzyme such as chymotrypsinogen 2, preproelastase 2 and 4, pancreatic protein somatomedin-B domain (PPSB) mRNA expression were initiated at first feeding and strongly expressed in the pancreas developmental stage, while gastric digestive enzyme signal was not at all detected during same period. Although, trypsinogens were secreted from pancreas and have similar amino acid sequence, trypsinogen 3 expression induction was detected both pancreas and stomach developmental stage, while trypsinogen 2 expression was significantly increased only post-metamorphosis period. Pepsinogen mRNA expression was only detected at metamorphosis according to stomach differentiation. Lipid digestive enzyme, lipase and intestine fatty acid binding protein 1 (I-FABP 1), were already reached a certain level at beginning of hatching and more increased during early developmental stage and then gradually decreased before metamorphosis. These results suggested that feed ingestion of olive flounder was exclusive charged by pancreatic digestive enyme, lipid digestive enzyme and trypsinogen 3 from first feeding and then fully swiched by gastric digestive enzyme and trypsinogen 2 from metamorphosis period.

For the study of population genetic structure with mtDNA, it is essential to measure genetic diversity at each mtDNA regions. Also, to evaluate the variation according to the each region should follow as well as to see if there are differences. In this study, we delved into the variations and dendrogram among samples of seven mtDNA regions (NDⅡ, NDⅤ, NDⅣ, NDⅣL, NDⅥ, NDⅠ, 12SrRNA) from wild Pacific abalone, Haliotis discus hannai collected in Yeosu, Korea. The region with the highest genetic variation was NDⅣ region (Haplotype diversity = 1.0000, Nucleotide diversity = 0.010823) with two to five times higher variation than the others. Furthermore, the study to see if there is a difference between the regions of samples showed that similar aspects of dendrogram in NDⅡ and NDⅠ(divergence of 90% and 87%), which forms a group with hd4, 7, 8 and 10 at bootstrap support, based on 1000 replications. Also, pair-wise FST between clusters within the regions showed high values; 0.4061 (P=0.0000), 0.4805 (P=0.0000) respectively. Therefore we can infer that it is the most efficient and accurate way to analyze the region of NDⅣ with the highest variation in addition to the regions of NDⅡ and NDⅠ, which formed clusters with high bootstrap value, for study of population genetic structure in this species.