Partial migration of juvenile temperate seabass <Emphasis Type="Italic">Lateolabrax japonicus</Emphasis>: a versatile survival strategy

Partial migration describes intrapopulation variation in the migratory behavior, i.e. some individuals from a population migrate to low-salinity river areas, while others remain in coastal areas. This paper reviews the partial migration pattern of juvenile temperate seabass Lateolabrax japonicus, which is a migration pattern not commonly seen in Japan. Seabass spawn offshore, and eggs and larvae are transported to coastal areas. Some of these juveniles then ascend rivers, while others remain in coastal areas. Juveniles efficiently use physical structures in their habitat; they use tidal currents to ascend rivers in macrotidal estuaries, while they use the salt wedge in microtidal estuaries. Once juveniles ascend the river, they can feed on the abundant prey and attain more rapid growth than those remaining in coastal areas. As estuaries are highly productive areas, they play significant roles as nurseries for juveniles of various fishes. However, compared with coastal areas, the relative area of estuaries is considerably smaller and its environmental conditions are more variable. For example, nearly 40% of adult seabass in Tango Bay were estimated to use estuarine areas as a nursery, while the other 60% use coastal areas during their juvenile stage. Using both estuaries and coastal areas through partial migration during the juvenile stage is concluded to contribute to the stabilization and yield of seabass populations.     

Genetic and molecular analysis of the restoration of fertility ( Rf ) genes for Ogura male-sterility from a Japanese wild radish ( Raphanus sativus var. hortensis f. raphanistroides Makino)

Ogura male-sterile cytoplasm is one of the most extensively studied cytoplasms in Brassicaceae. In this study, in order to gain better understanding of the variation and evolution of the restoration of the fertility (Rf) gene for Ogura male-sterile cytoplasm, the nucleotide sequence of the orf687 homologue in the Japanese wild radish (Raphanus sativus var. hortensis f. raphanistroides Makino) was analyzed using an F₂ population made with a cross between a Japanese wild radish plant containing the Rf gene and ‘Uchiki-Gensuke’ (a maintainer of Ogura-male sterility). Segregation of male-fertile/-sterile plants in the F₂ generation suggested that another unidentified Rf gene unlinked to orf687 exists in the Japanese wild radish. The genotype of orf687 was determined for each F₂ plant by Southern hybridization with an orf687 gene probe, mismatch-specific endonuclease digestion of PCR products, and direct sequencing of a PCR product. Genotyping revealed that some fertility-restored plants are homozygotic for the ‘Uchiki-Gensuke’ type orf687 allele, supporting the idea that another gene different from orf687 also functions as an Rf gene for Ogura male-sterility. Protein analysis using an antibody raised against the Ogura-specific ORF138 protein suggests a mechanism of fertility restoration by the unidentified Rf similar to that by orf687. Sequence analysis of orf687 from a Japanese wild radish plant and ‘Uchiki-Gensuke’ revealed that both orf687 regions encode a mitochondrially-targeted protein consisting of 687 amino acids with 16 PPR motifs. Comparison of the deduced amino acid sequences with those of the known orf687 sequences from ‘Yuan hong’ and ‘Kosena’ containing Rf and recessive one (rf), respectively, showed that three unique amino acid replacements are present in ORF687 of the Japanese wild radish. Two of the three replacements, that from lysine to isoleucine at position 232 and from asparagine to asparate at position 240, confer negative charges to the protein. Since the Rf of ‘Yuan hong’ was reported to have a unique replacement that confers a negative charge to ORF687 (from asparagine to aspartate at position 170), it is proposed that the amino acid replacements conferring a negative charge to ORF687 are important for determining the status of the Rf/rf gene.     

Prevention of hypermelanosis by rearing Japanese flounder Paralichthys olivaceus in net-lined tanks

Fisheries Science - In artificially reared flatfish, especially the Japanese flounder Paralichthys olivaceus, pigmented skin (hypermelanosis) frequently appears on the fish’s blind side after...     

Freshwater migration and feeding habits of juvenile temperate seabass <Emphasis Type="Italic">Lateolabrax japonicus</Emphasis> in the stratified Yura River estuary,the Sea of Japan

Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were particularly abundant in areas with aquatic vegetation in the freshwater zone. This distribution pattern suggests that the early life history of the temperate seabass depends more intensively on the river (freshwater) than previously considered. Small juveniles in the freshwater zone fed on copepods and chironomid larvae and upon reaching a standard length (SL) of approximately 20 mm did they fed on mysids. In contrast, juveniles (approx. 17–80 mm SL) in the surf zone fed mainly on mysids.     

Comparison between surface-reading and cross-section methods using sagittal otolith for age determination of the marbled sole <Emphasis Type="Italic">Pseudopleuronectes yokohamae</Emphasis>

To find an appropriate method for age determination in the marbled sole Pseudopleuronectes yokohamae in Tokyo Bay, Japan, sagittal otoliths of 1,343 individuals were observed by surface-reading and cross-section methods and the results were compared. Opaque zones occurred once a year and were regarded as annuli in both methods. The surface-reading method sometimes provided a lower count of the number of annuli than the cross-section method, and the frequency of this discrepancy was highest in older fish (males above 5 years, females above 4 years). The oldest female fish was estimated to be age 10 years by the cross-section method but 8 years by the surface-reading method. The cross-section method could provide a more accurate estimate of age and is therefore likely to be indispensable to estimations of longevity. In contrast, the surface-reading method is superior in terms of cost and time efficiency but is likely to underestimate the ages of older fish. However, growth equations based on age estimated by the surface-reading method were sufficiently accurate if males ≥5 years and females ≥4 years were combined as specific, single age groups of 5+ and 4+, respectively.     

Identification of divergently selected regions between Japanese Black and Holstein cattle using bovine 50k SNP array

Differences between average allelic frequencies of genes that relate to traits suggest that it would be evidence of artificial selections. Sliding window approach is a useful method to identify genomic regions that have been differently selected between two breeds. The objective of this study was to identify the divergently selected regions between Japanese Black (JB) and Japanese Holstein (JH) cattle based on genotypic information obtained through a high‐density single nucleotide polymorphism (SNP) panel. After genotyping of 54 001 SNP markers on 100 animals (50 JB and 50 JH), 40 635 SNPs were suitable for the analysis. For each of these SNPs, the absolute difference between allelic frequencies of JB and JH was calculated. In the current study, 10 consecutive SNPs were defined as components of a window. For each window, the average difference in allelic frequency was calculated. This was termed sliding window average difference (SWAD). Among 40 055 windows, we focused on 39 windows with the largest SWAD. This was equivalent to 0.1% of all windows and the SWAD was more than 0.435. Some of these windows overlapped and were distributed in 11 regions. These regions were in good agreement with reported quantitative trait locus, therefore would be selection signatures and good candidates that harbor the causative mutations.     

Microfibril angle and density of hinoki (Chamaecyparis obtusa) trees in 15 half-sib families in a progeny test stand in Kyushu, Japan

It was previously believed in Japan that the wood qualities of hinoki (Chamaecyparis obtusa) were superior to sugi (Cryptomeria japonica). However, few studies of wood properties such as MFA (microfibril angle of S₂ layer in secondary wall of tracheid) have been completed for hinoki. Some reports have found that hinoki plus tree families have similar mechanical properties to sugi. Here we report the characteristics of MFA and density of hinoki half-sib families in a progeny test stand. There were significant differences in MFA and density between families. The wood properties of two families, Nakatsu 3 and Kanzaki 5, are stable in radial pattern and suitable for structural use. Early selection of hinoki families by MFA and density may be difficult. Effects of MFA and density on E _d (dynamic modulus of elasticity) of logs differed between families. The effects of growth rate on MFA and density differed between families and also between juvenile and mature wood. The faster growth rate in Nakatsu 3 appeared to improve wood properties and increase E _d of logs, although in many other families, faster growth rate had negative effects on desirable wood properties for structural use.     

Detection of Feline calicivirus (FCV) from Vaccinated Cats and Phylogenetic Analysis of its Capsid Genes

We analysed genogroups of four feline calcivirus (FCV) isolates (FCV-S, H10, Ao198-1 and ML89) obtained from cats that experienced FCV infection after having been vaccinated against FCV. New PCR primer sets (8F/8R, Ao-S/Ao-A, cp-S/cp-A) were also designed, since the conventional Seal primer failed to amplify the target sequences in two samples. The genogroups of the four isolates as well as eight global and 17 domestic strains were determined by phylogenetic analysis of their amino acid sequences. One out of the four strains (25%) isolated in this study, H10, was grouped into genogroup I, along with the vaccine strains F9 and FCV-255. The other three isolates (75%) belonged to genogroup II. Thus, there were more isolates in genogroup II than in genogroup I. However, the antibody values of the four isolates against cat anti-F9 antisera were significantly decreased. There may be no relationship between the neutralizing antibody titre and genogroup. Amino acid sequence alignment of the four isolates showed that only a single amino acid in region C, which is involved in neutralization epitopes, was different in ML89 strain from that of F9. The other three strains, H10, Ao198-1 and FCV-B, shared the same amino acid sequence with F9. Alignment of amino acids for linear epitopes in the F9 strain, which are located at regions D and E, showed variations in 5' hypervariable region (HVR) of E, whereas D and conE had only synonymous substitutions i.e. no change in the amino acid sequence. This mutation in 5' HVR of region E suggested a vaccine breakdown, as the region is known to be essential for antigenicity. The genogroup II FCV is likely to be the cause of the FCV infection in this study, while the vaccine strains belong to genogroup I. Thus, the existing vaccine may need reevaluation for its effectiveness.     

Imatinib elicited a favorable response in a dog with a mast cell tumor carrying a c-kit c.1523A>T mutation via suppression of constitutive KIT activation

Target therapy using the tyrosine kinase inhibitor imatinib is one of the new therapeutic approaches for canine mast cell tumors (MCTs). In the present report, we demonstrate a clinical response to imatinib in a dog with MCT carrying a c-kit c.1523A>T mutation. Moreover, the effect of this mutation on the phosphorylation status of KIT and the inhibitory potency of imatinib on the phosphorylation of the mutant KIT were examined in vitro. A dog with a MCT tumor mass on the right forelimb sole with lymph node metastasis and mastocytemia was treated with imatinib. The MCT mass markedly shrank and mastocytemia became undetectable with 2 weeks of treatment. The lymph node enlarged by metastasis became normal in size with 5 weeks of treatment. From the sequencing analysis of c-kit in tumor cells, a substitution mutation c.1523A>T that alters the amino acid composition (p.Asn508Ile) within the extracellular domain of KIT was identified. The mutant KIT expressed on 293 cells showed ligand-independent phosphorylation and imatinib suppressed this phosphorylation in a dose-dependent manner. From these findings, imatinib was considered to elicit a clinical response in a canine case of MCT via inhibition of the constitutively activated KIT caused by a c-kit c.1523A>T mutation.     

Variations in nitrogen uptake and nitrate-nitrogen concentration among sorghum groups

Nitrogen uptake and nitrate-N concentration in forage sorghums, which are related to ground water pollution or feed quality under conditions of crop fertilization by only animal wastes, were examined. Seventy-four genotypes of sorghum and Sudan grass were tested. They were classified into 4 groups; grain type and dual purpose type sorghums (6 and 13 genotypes, respectively, Sorghum bicolor Moench), sorgo type sorghum (21, S. bicolor), Sudan type sorghum (22, S. bicolor × S. sudanense (Piper) Stapf), Sudan grass (12, S. sudanense). There was a strong correlation between dry matter (DM) yield and N uptake, with the sorgo type producing the highest DM matter yield and showing the highest N uptake. Nitrate-N, which causes nitrate poisoning of ruminants, was detected mostly in the stem of all the genotypes. The nitrate-N concentration based on DM could be calculated accurately by multiplying the nitrate-N concentration of stem on a fresh matter basis by the DM partitioning ratio of stem divided by the DM concentration of stem. The grain type and the dual purpose type of sorghums with dry stem showed the lowest nitrate-N concentration because these plants had a lower DM partitioning ratio of stem and higher DM concentration of stem. Sudan grass and Sudan type sorghum with the genetic background of Sudan grass showed higher nitrate-N concentrations owing to their ability to accumulate nitrate-N.