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The diversity of eight microsatellite DNA loci was analyzed to assess the contemporary level of reproductive isolation between the sockeye salmon with lower numbers (sparse) and higher numbers (dense) of gill rakers cohabiting the landlocked Lake Kronotskoe and its tributaries (Kamchatka Peninsula). We found a significant difference among three groups: the sparsely-rakered fish with lacustrine spawning, the sparsely-rakered fish with riverine spawning and the densely-rakered fish with both types of spawning. The interannual and spatial genetic structure of the three fish groups was found to remain stable, and the sparsely-rakered fish with riverine spawning exhibited a decreased level of microsatellite diversity and heterozygosity. [ABSTRACT FROM AUTHOR]

Lacustrine sockeye salmon ( Oncorhynchus nerka) are listed as an endangered species in Japan despite little genetic information on their population structure. In order to clarify the genetic diversity and structure of Japanese populations for evaluating on the bottleneck effect and an endangered species, we analyzed the ND5 region of mitochondrial DNA (mtDNA) and 45 single nucleotide polymorphisms (SNPs) in 640 lacustrine sockeye salmon in Japan and 80 anadromous sockeye salmon in Iliamna Lake of Alaska. The genetic diversity of the Japanese population in both mtDNA and SNPs was significantly less than that of the Iliamna Lake population. Moreover, all Japanese populations had SNP loci deviating from the HWE. In spite of low genetic diversity, the SNP analyses resulted that the Japanese population was significantly divided into three groups. These suggest that Japanese sockeye salmon populations should be protected as an endangered species and genetically disturbed by the hatchery program and transplantations. [ABSTRACT FROM AUTHOR]

Abstract: The olfactory system of salmonids is essential for imprinting and the subsequent homing migration. Olfactory imprinting-related genes were identified in the olfactory system of 1- and 3-year-old lacustrine sockeye salmon (Oncorhynchus nerka) using a subtractive hybridization technique of representational difference analysis (cDNA-RDA). We have obtained a partial clone from a subtractive cDNA library of 1-year-old fish that contains a 756 bp open reading frame coding for a putative protein with 252 amino acid residues named the Sockeye salmon Olfactory system Imprinting related Gene (SOIG). By northern hybridization, the SOIG mRNA was only expressed in the olfactory epithelium and not in other tissues. In situ hybridization showed that the expression of SOIG mRNA was observed in the olfactory receptor cells and basal cells of the olfactory epithelium. This suggests that SOIG could have specific and important roles in olfactory system. [Copyright &y& Elsevier]

It was demonstrated that pregnenolone (P5) and 17a-hydroxypregnenolone (17a-OH-P5) were identified as cholesterol metabolites in the brain and pituitary gland of lacustrine sockeye salmon (Oncorhynchus nerka) during sexual maturation. Moreover, 17a-OH-P5 was determined as the major cholesterol metabolite. The conversion of P5 to 17a-OH-P5 in the brain and pituitary gland showed a clear regional difference, and their productivity were dramatically changed during sexual maturation. From these data, it was suggested that steroid converting enzyme in the brain and pituitary gland of lacustrine sockeye salmon might be involved in brain region-dependent roles on sexual maturation. [ABSTRACT FROM AUTHOR]