Nucleotide-based regenerated fiber production using salmon (Oncorhynchus keta) milt waste by solution spinning.

The use of nucleic acid-derived fibers has not been developed in contrast to the traditional use of polysaccharide- and protein-based fibers in daily life. Salmon, Oncorhynchus keta, is an abundant fishery resource, and its milt contains a huge amount of DNA. Most of the milt is discarded because it degrades easily and is unsuitable for food consumption. DNA-based fibers are expected to possess functionality and mechanical strength because DNA is a polyanion with a high molecular weight. Here, using DNA extracted from the salmon milt, we produced nucleotide-based fibers. A solution spinning system was applied using ethanol as a coagulant. Adding the salt to the dope solution reduced the solubility of DNA, which was essential for the successful spinning of DNA-based fibers. The obtained fibers became insoluble in water by ultraviolet (UV) exposure. Fibril-like structures were detected on the fracture surface, and humidity influenced the conformational structure. This study focuses on the bulk-scale production of biodegradable DNA-based fibers. Therefore, it can be used not only for clothing and filters but also as a functional material to remove harmful pollutants released into the ocean, such as heavy metal ions and aromatic derivatives.

Subcellular localization of Na+/K+-ATPase isoforms resolved by in situ hybridization chain reaction in the gill of chum salmon at freshwater and seawater.

The Na+/K+-ATPase (NKA) α1-isoforms were examined by in situ hybridization chain reaction (ISHCR) using short hairpin DNAs, and we showed triple staining of NKA α1a, α1b, and α1c transcripts in the gill of chum salmon acclimated to freshwater (FW) and seawater (SW). The NKA α1-isoforms have closely resembled nucleotide sequences, which could not be differentiated by conventional in situ hybridization. The ISHCR uses a split probe strategy to allow specific hybridization using regular oligo DNA, resulting in high specificity at low cost. The results showed that NKA α1c was expressed ubiquitously in gill tissue and no salinity effects were observed. FW lamellar ionocytes (type-I ionocytes) expressed cytoplasmic NKA α1a and nuclear NKA α1b transcripts. However, both transcripts of NKA α1a and α1b were present in the cytoplasm of immature type-I ionocytes. The developing type-I ionocytes increased the cytoplasmic volume and migrated to the distal region of the lamellae. SW filament ionocytes (type-II ionocytes) expressed cytoplasmic NKA α1b transcripts as the major isoform. Results from morphometric analysis and nonmetric multidimensional scaling indicated that a large portion of FW ionocytes was NKA α1b-rich, suggesting that isoform identity alone cannot mark the ionocyte types. Both immature or residual type-II ionocytes and type-I ionocytes were found on the FW and SW gills, suggesting that the chum salmon retains the potential to switch the ionocyte population to fit the ion-transporting demands, which contributes to their salinity tolerance and osmoregulatory plasticity.

Insights from a chum salmon (Oncorhynchus keta) genome assembly regarding whole-genome duplication and nucleotide variation influencing gene function.

Chum salmon are ecologically important to Pacific Ocean ecosystems and commercially important to fisheries. To improve the genetic resources available for this species, we sequenced and assembled the genome of a male chum salmon using Oxford Nanopore read technology and the Flye genome assembly software (contig N50: ∼2 Mbp, complete BUSCOs: ∼98.1%). We also resequenced the genomes of 59 chum salmon from hatchery sources to better characterize the genome assembly and the diversity of nucleotide variants impacting phenotype variation. With genomic sequences from a doubled haploid individual, we were able to identify regions of the genome assembly that have been collapsed due to high sequence similarity between homeologous (duplicated) chromosomes. The homeologous chromosomes are relics of an ancient salmonid-specific genome duplication. These regions were enriched with genes whose functions are related to the immune system and responses to toxins. From analyzing nucleotide variant annotations of the resequenced genomes, we were also able to identify genes that have increased levels of variants thought to moderately impact gene function. Genes related to the immune system and the detection of chemical stimuli (olfaction) had increased levels of these variants based on a gene ontology enrichment analysis. The tandem organization of many of the enriched genes raises the question of why they have this organization.

Biochemical indices, gene expression, and SNPs associated with salinity adaptation in juvenile chum salmon (Oncorhynchus keta) as determined by comparative transcriptome analysis.

Chum salmon (Oncorhynchus keta) migrate from freshwater to saltwater, and incur developmental, physiological and molecular adaptations as the salinity changes. The molecular regulation for salinity adaptation in chum salmon is currently not well defined. In this study, 1-g salmon were cultured under 0 (control group, D0), 8‰ (D8), 16‰ (D16), and 24‰ (D24) salinity conditions for 42 days. Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities in the gill first increased and then decreased in response to higher salinity environments where D8 exhibited the highest Na+/K+ATPase and Ca2+/Mg2+-ATPase activity and D24 exhibited the lowest. Alkaline phosphatase (AKP) activity was elevated in all salinity treatment groups relative to controls, while no significant difference in acid phosphatase (ACP) activity was observed across treatment groups. De novo transcriptome sequencing in the D0 and D24 groups using RNA-Seq analysis identified 187,836 unigenes, of which 2,143 were differentially expressed in response to environmental salinity (71 up-regulated and 2,072 down-regulated). A total of 56,020 putative single nucleotide polymorphisms (SNPs) were also identified. The growth, development, osmoregulation and maturation factors of N-methyl-D-aspartate receptors (nmdas) expressed in memory formation, as well as insulin-like growth factor 1 (igf-1) and igf-binding proteins (igfbps) were further investigated using targeted qRT-PCR. The lowest expression of all these genes occurred in the low salinity environments (D8 or D16), while their highest expression occurred in the high salinity environments (D24). These results provide preliminary insight into salinity adaptation in chum salmon and a foundation for the development of marker-assisted breeding for this species.

Transcriptional Contribution of Transposable Elements in Relation to Salinity Conditions in Teleosts and Silencing Mechanisms Involved.

Fish are an interesting taxon comprising species adapted to a wide range of environments. In this work, we analyzed the transcriptional contribution of transposable elements (TEs) in the gill transcriptomes of three fish species exposed to different salinity conditions. We considered the giant marbled eel Anguilla marmorata and the chum salmon Oncorhynchus keta, both diadromous, and the marine medaka Oryzias melastigma, an euryhaline organism sensu stricto. Our analyses revealed an interesting activity of TEs in the case of juvenile eels, commonly adapted to salty water, when exposed to brackish and freshwater conditions. Moreover, the expression assessment of genes involved in TE silencing mechanisms (six in heterochromatin formation, fourteen known to be part of the nucleosome remodeling deacetylase (NuRD) complex, and four of the Argonaute subfamily) unveiled that they are active. Finally, our results evidenced for the first time a krüppel-associated box (KRAB)-like domain specific to actinopterygians that, together with TRIM33, might allow the functioning of NuRD complex also in fish species. The possible interaction between these two proteins was supported by structural prediction analyses.

Significance of sea entry pathway of chum salmon Oncorhynchus keta fry, inferred from the differential expressions of Na+,K+-ATPase α-subunit genes in the gills.

Na+,K+-ATPase (NKA) α-subunit 1a (α1a) and 1b (α1b) gene expressions in the gills are changeable in response to ambient salinity in a few salmonids. In this study, the expressions were compared among ambient salinities and used to infer sea entry migration of chum salmon Oncorhynchus keta fry. The expression of α1a decreased from the 2 days after seawater (SW) transfer from freshwater (FW) and was significantly lower in SW-acclimated fry than that in FW-fry. On the other hand, the expression of α1b peaked on the first to second day after SW transfer and then settled to a level 2-fold higher than in FW-fry. In fry caught in the waterfronts of the beaches, the expression levels were quite similar to those on the first and second days after SW transfer, whereas, in fry caught off beach, the expressions were identical to those of SW-acclimated fry. These suggest that fry adapt to SW with moving along the shoal in the bay, and move to off beach after completing SW adaptation. One of the physiological significances in a usage of waterfront may be to transform the gills to SW type. Only fry on the 2 days after SW transfer failed to exhibit condition factor-dependency of burst swimming, probably due to physiological perturbation, which may be related to poor predation avoidance. The physiological approach used in this study inferred sea entry migration of fry; furthermore, it shows the possible significance of adaptation to SW in the shoal is to reduce predation risk.

Gene expression levels of synaptic exocytosis regulator synaptophysin in the brain and the olfactory organ of anadromous salmon.

Anadromous Pacific salmon (genus Oncorhynchus) are known for their homing behavior based on olfactory imprinting, which is formed during their seaward migration. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE/Snare) complex is a minimum unit of vesicle exocytosis from the pre-synaptic membrane. Its component genes (synaptosome-associated protein 25, syntaxin 1, and vesicle-associated membrane protein 2) are more strongly expressed in the olfactory nervous system (olfactory epithelium, olfactory bulb, and telencephalon) at the migration stages related to olfactory imprinting and/or retrieval in salmon. This study focused on the mRNA synthesis of synaptophysin (Syp), one of the Snare regulatory factors. syp is strongly expressed in chum salmon (Oncorhynchus keta) olfactory nervous system during the seaward migration and temporarily increased during the homeward migration. In reference to our previous studies, these expression changes were similar to the snare genes in the chum salmon. Therefore, syp and Snare component genes were synchronously expressed reflecting the development and short-term plasticity of the olfactory nervous system that is essential for olfactory imprinting.

Molecular characterization of transient receptor potential vanilloid 4 (TRPV4) gene transcript variant mRNA of chum salmon Oncorhynchus keta in response to salinity or temperature changes.

Transient receptor potential vanilloid 4 (TRPV4) is an osmosensory cation channel that respond to an increase in cell volume and participates in various physiological functions. Among organisms in aquatic environments, euryhaline teleost is are suitable experimental models to study ion channel proteins related to physiological functions involving osmosensing. Among the studies of various regulatory molecules that mediate osmotic regulation in fish, however, information is lacking, particularly on the TRP family. This study investigated the structural characteristics of theTRPV4 gene of chum salmon (Oncorhynchus keta) and their responses to changes in salinity and temperature. Interestingly, TRPV4 generates transcript variants of the intron-retention form through alternative splicing, resulting in a frameshift leading to the generation of transcripts of different structures. In particular, TRPV4 x1 and TRPV x2 mRNAs were predominant in the gill and skin including at the lateral line. The expression levels of chum salmon TRPV4 x1 were significantly increased with increase in salinity and temperature, whereas TRPV4 x2 mainly responded to temperature decrease. Overall, these results demonstrate for the first time the effects of salinity and temperature on the expression of two salmonid TRPV4 transcript variants, suggesting their contribution to the regulation of hydromineral balance.

A Confocal Microscopic Study of Gene Transfer into the Mesencephalic Tegmentum of Juvenile Chum Salmon, Oncorhynchus keta, Using Mouse Adeno-Associated Viral Vectors.

To date, data on the presence of adenoviral receptors in fish are very limited. In the present work, we used mouse recombinant adeno-associated viral vectors (rAAV) with a calcium indicator of the latest generation GCaMP6m that are usually applied for the dorsal hippocampus of mice but were not previously used for gene delivery into fish brain. The aim of our work was to study the feasibility of transduction of rAAV in the mouse hippocampus into brain cells of juvenile chum salmon and subsequent determination of the phenotype of rAAV-labeled cells by confocal laser scanning microscopy (CLSM). Delivery of the gene in vivo was carried out by intracranial injection of a GCaMP6m-GFP-containing vector directly into the mesencephalic tegmentum region of juvenile (one-year-old) chum salmon, Oncorhynchus keta. AAV incorporation into brain cells of the juvenile chum salmon was assessed at 1 week after a single injection of the vector. AAV expression in various areas of the thalamus, pretectum, posterior-tuberal region, postcommissural region, medial and lateral regions of the tegmentum, and mesencephalic reticular formation of juvenile O. keta was evaluated using CLSM followed by immunohistochemical analysis of the localization of the neuron-specific calcium binding protein HuCD in combination with nuclear staining with DAPI. The results of the analysis showed partial colocalization of cells expressing GCaMP6m-GFP with red fluorescent HuCD protein. Thus, cells of the thalamus, posterior tuberal region, mesencephalic tegmentum, cells of the accessory visual system, mesencephalic reticular formation, hypothalamus, and postcommissural region of the mesencephalon of juvenile chum salmon expressing GCaMP6m-GFP were attributed to the neuron-specific line of chum salmon brain cells, which indicates the ability of hippocampal mammal rAAV to integrate into neurons of the central nervous system of fish with subsequent expression of viral proteins, which obviously indicates the neuronal expression of a mammalian adenoviral receptor homolog by juvenile chum salmon neurons.

Spatiotemporal distribution of juvenile chum salmon in Otsuchi Bay, Iwate, Japan, inferred from environmental DNA.

To understand the ecology of juvenile chum salmon during early marine life after their downstream migration, we developed a quantitative PCR-based environmental DNA (eDNA) method specific for chum salmon and investigated the spatiotemporal distribution of eDNA in Otsuchi Bay, Iwate, Japan. Indoor aquarium experiments demonstrated the following characteristics of chum salmon eDNA: (1) the eDNA shedding and degradation were time- and water temperature-dependent and the bacterial abundance could contribute to the eDNA decay, (2) fecal discharge may not be the main source of eDNA, and (3) a strong positive Pearson correlation was found between the number of juveniles and the eDNA amounts. As we discovered strong PCR inhibition from the seawater samples of the bay, we optimized the eDNA assay protocol for natural seawater samples by adding a further purification step and modification of PCR mixture. The intensive eDNA analysis in the spring of 2017 and 2018 indicated that juvenile chum salmon initially inhabited in shallow waters in the shorefront area and then spread over the bay from January to June. The eDNA data also pointed out that outmigration of juvenile chum salmon to open ocean temporarily suspended in April, possibly being associated with the dynamics of the Oyashio Current as suggested by a previous observation. The eDNA method thus enables us large-scale and comprehensive surveys without affecting populations to understand the spatiotemporal dynamics of juvenile chum salmon.

Enhanced osmoregulatory ability marks the smoltification period in developing chum salmon (Oncorhynchus keta).

The freshwater (FW) life of chum salmon is short, as they migrate to the ocean soon after emergence from the substrate gravel of natal waters. The alevins achieve seawater (SW) acclimating ability at an early developmental stage and the details of smoltification are not clear. We examined the stage-dependent SW acclimating ability in chum salmon alevins and found a sharp increase in SW tolerance during development that resembles the physiological parr-smolt transformation seen in other salmonids. Perturbation of plasma Na+ after SW exposure was prominent from the hatched embryo stage to emerged alevins, but the plasma Na+ became highly stable and more resistant to perturbation soon after complete absorption of yolk. Marker gene expression for SW-ionocytes including Na/K-ATPase (NKA α1b), Na-K-Cl cotransporter 1a (NKCC1a), Na/H exchanger 3a (NHE3a), cystic fibrosis transmembrane conductance regulators (CFTR I and CFTR II) were all upregulated profoundly at the same stage when the alevins were challenged by SW, suggesting that the stability of plasma Na+ concentration was partly a result of elevated osmoregulatory capability. FW-ionocyte markers including NKA α1a and NHE3b were consistently downregulated independent of stage by SW exposure, suggesting that embryos at all stages respond to salinity challenge, but the increase in SW osmoregulatory capability is restricted to the developmental stage after emergence. We propose that the "smoltification period" is condensed and integrated into the early development of chum salmon, and our results can be extrapolated to the future studies on hormonal controls and developmental triggers for smoltification in salmonids.

Unexpected insertion of carrier DNA sequences into the fission yeast genome during CRISPR-Cas9 mediated gene deletion.

OBJECTIVES: The fission yeast Schizosaccharomyces pombe is predicted to encode ~ 200 proteins of < 100 amino acids, including a number of previously uncharacterised proteins that are found conserved in related Schizosaccharomyces species only. To begin an investigation of the function of four of these so-called microproteins (designated Smp1-Smp4), CRISPR-Cas9 genome editing technology was used to delete the corresponding genes in haploid fission yeast cells. RESULTS: None of the four microprotein-encoding genes was essential for viability, meiosis or sporulation, and the deletion cells were no more sensitive to a range of cell stressors than wild-type, leaving the function of the proteins unresolved. During CRISPR-Cas9 editing however, a number of strains were isolated in which additional sequences were inserted into the target loci at the Cas9 cut site. Sequencing of the inserts revealed these to be derived from the chum salmon Oncorhynchus keta, the source of the carrier DNA used in the S. pombe transformation.

Quantitation of residual host cell DNA in protaminesulfate drug product by qPCR.

Protamine sulfate (PS) is an FDA approved drug used to reverse heparin-induced anticoagulation in patients. Protamine sulfate is a mixture of primarily four ∼4 kDa arginine-rich cationic polypeptide chains derived from chum (Oncorhynchus keta) salmon sperm. Because the presence of residual host cell salmon DNA (resDNA) in PS drug product can pose safety concerns, processing steps during PS manufacturing are designed to target the reduction of these impurities. However, given protamine's positively charged structure, isolating and measuring negatively charged residual DNA is challenging. Here, the development of a sensitive detection method using real-time quantitative polymerase chain reaction (qPCR) assay for a multicopy gene (5S ribosomal DNA) using custom-designed primers and TaqMan probes is described. The PS qPCR standard curve was accurate over a linear range of 0.0025-156.25 pg/µL using protease-digested research grade salmon sperm DNA (neat) as the reference standard. DNA present in PS drug products was extracted using an optimized two-hour procedure achieving ∼85% recovery values from 1 to 125 pg reference DNA spiked into PS (1 mg) samples. The procedure lower limit of quantitation (LLOQ) of 5 pg of DNA per mg of PS or 250 pg of DNA per 50 mg dose of PS was determined from DNA spike recovery curves using the acceptance criteria of 70-130% recovery with % CV ≤ 25%. Seven pharmaceutical-grade lots of PS were evaluated and the detectable amount of resDNA was below the LLOQ. This qPCR method demonstrated sensitivity 40-fold above the current guidelines for resDNA (10 ng DNA per dose). Overall, the approach offers a promising tool for monitoring resDNA in PS and potentially other challenging complex drug products with cationic character.

Congruent population structure across paralogous and nonparalogous loci in Salish Sea chum salmon (Oncorhynchus keta).

Whole-genome duplications are major evolutionary events with a lasting impact on genome structure. Duplication events complicate genetic analyses as paralogous sequences are difficult to distinguish; consequently, paralogs are often excluded from studies. The effects of an ancient whole-genome duplication (approximately 88 MYA) are still evident in salmonids through the persistence of numerous paralogous gene sequences and partial tetrasomic inheritance. We use restriction site-associated DNA sequencing on 10 collections of chum salmon from the Salish Sea in the USA and Canada to investigate genetic diversity and population structure in both tetrasomic and rediploidized regions of the genome. We use a pedigree and high-density linkage map to identify paralogous loci and to investigate genetic variation across the genome. By applying multivariate statistical methods, we show that it is possible to characterize paralogous loci and that they display similar patterns of population structure as the diploidized portion of the genome. We find genetic associations with the adaptively important trait of run-timing in both sets of loci. By including paralogous loci in genome scans, we can observe evolutionary signals in genomic regions that have routinely been excluded from population genetic studies in other polyploid-derived species.

Hybrids between chum Oncorhynchus keta and pink Oncorhynchus gorbuscha salmon: age, growth and morphology and effects on salmon production.

Mature hybrids between chum salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha, which were identified by an intermediate colour pattern, were caught at the Kurilsky Hatchery, Iturup Island, Russia. Most of them were female and 3 years old (a partial freshwater year and 2 marine years), which is intermediate between the ages of maturity of the parental species. The hybrids exceed both parental species in the rate of growth, are large in size and robust and might successfully compete for mating in the wild or be chosen for artificial reproduction. The ratio of the scale length over width, R, is oblate (R < 1), whereas scales of the parental species are prolate (R > 1). From scale analyses, the c.v. in body size of hybrid females at the second marine year is twice that of O. keta, which suggests developmental instability in the hybrid. A dynamic model predicted that continuing hybridization at a low rate does not produce a substantial hybrid load due to selection against advanced-generation hybrids and backcrosses. A high hybridization rate, however, may be an additional risk for genetic management and should be taken into account in programmes of artificial reproduction of Pacific salmon Oncorhynchus spp., although such hybrids might have commercial use in confined production systems.

Effects of seawater transfer and fasting on the endocrine and biochemical growth indices in juvenile chum salmon (Oncorhynchus keta).

Insulin-like growth factor (IGF)-I, IGF-binding protein (IGFBP)-1 and RNA/DNA ratio are endocrine and biochemical parameters used as growth indices in fish, however, they are subjected to environmental modulation. Chum salmon (Oncorhynchus keta) migrate from freshwater (FW) to seawater (SW) at fry/juvenile stage weighing around 1g and suffer growth-dependent mortality during the early phase of their marine life. In order to reveal environmental modulation of the IGF/IGFBP system and establish a reliable growth index for juvenile chum salmon, we examined effects of SW transfer and fasting on IGF-I, IGFBP-1 and RNA/DNA ratio, and correlated them to individual growth rate. Among serum IGF-I, liver and muscle igf-1, igfbp-1a, igfbp-1b and RNA/DNA ratio examined, muscle RNA/DNA ratio and muscle igfbp-1a responded to SW transfer. Serum IGF-I, liver igf-1 and liver RNA/DNA ratio were sensitive to nutritional change by being reduced in 1week in both FW and SW while muscle igf-1 was reduced 2weeks after fasting. In contrast, igfbp-1a in both tissues was increased by 2weeks of fasting and igfbp-1b in the liver of SW fish was increased in 1week. These results suggest that the sensitivity of igf-1 and igfbp-1s to fasting differs between tissues and subtypes, respectively. When chum salmon juveniles in SW were marked and subjected to feeding or fasting, serum IGF-I showed the highest correlation with individual growth rate. Liver igfbp-1a and -1b, and muscle igf-1 exhibited moderate correlation coefficients with growth rate. These results show that serum IGF-I is superior to the other parameters as a growth index in juvenile chum salmon in term of its stability to salinity change, high sensitivity to fasting and strong relationship with growth rate. On the one hand, when collecting blood from chum salmon fry/juveniles is not practical, measuring liver igfbp-1a and -1b, or/and muscle igf-1 is an alternative.

Linkage mapping with paralogs exposes regions of residual tetrasomic inheritance in chum salmon (Oncorhynchus keta).

Gene sequence similarity due to shared ancestry after a duplication event, that is paralogy, complicates the assessment of genetic variation, as sequences originating from paralogs can be difficult to distinguish. These confounded sequences are often removed prior to further analyses, leaving the underlying loci uncharacterized. Salmonids have only partially rediploidized subsequent to a whole-genome duplication; residual tetrasomic inheritance has been observed in males. We present a maximum-likelihood-based method to resolve confounded paralogous loci by observing the segregation of alleles in gynogenetic haploid offspring and demonstrate its effectiveness by constructing two linkage maps for chum salmon (Oncorhynchus keta), with and without these newly resolved loci. We find that the resolved paralogous loci are not randomly distributed across the genome. A majority are clustered in expanded subtelomeric regions of 14 linkage groups, suggesting a significant fraction of the chum salmon genome may be missed by the exclusion of paralogous loci. Transposable elements have been proposed as drivers of genome evolution and, in salmonids, may have an important role in the rediploidization process by driving differentiation between homeologous chromosomes. Consistent with that hypothesis, we find a reduced fraction of transposable element annotations among paralogous loci, and these loci predominately occur in the genomic regions that lag in the rediploidization process.

Early human use of anadromous salmon in North America at 11,500 y ago.

Salmon represented a critical resource for prehistoric foragers along the North Pacific Rim, and continue to be economically and culturally important; however, the origins of salmon exploitation remain unresolved. Here we report 11,500-y-old salmon associated with a cooking hearth and human burials from the Upward Sun River Site, near the modern extreme edge of salmon habitat in central Alaska. This represents the earliest known human use of salmon in North America. Ancient DNA analyses establish the species as Oncorhynchus keta (chum salmon), and stable isotope analyses indicate anadromy, suggesting that salmon runs were established by at least the terminal Pleistocene. The early use of this resource has important implications for Paleoindian land use, economy, and expansions into northwest North America.

Effect of salinity changes on olfactory memory-related genes and hormones in adult chum salmon Oncorhynchus keta.

Studies of memory formation have recently concentrated on the possible role of N-methyl-d-aspartate receptors (NRs). We examined changes in the expression of three NRs (NR1, NR2B, and NR2C), olfactory receptor (OR), and adrenocorticotropic hormone (ACTH) in chum salmon Oncorhynchus keta using quantitative polymerase chain reaction (QPCR) during salinity change (seawater→50% seawater→freshwater). NRs were significantly detected in the diencephalon and telencephalon and OR was significantly detected in the olfactory epithelium. The expression of NRs, OR, and ACTH increased after the transition to freshwater. We also determined that treatment with MK-801, an antagonist of NRs, decreased NRs in telencephalon cells. In addition, a reduction in salinity was associated with increased levels of dopamine, ACTH, and cortisol (in vivo). Reductions in salinity evidently caused NRs and OR to increase the expression of cortisol and dopamine. We concluded that memory capacity and olfactory imprinting of salmon is related to the salinity of the environment during the migration to spawning sites. Furthermore, salinity affects the memory/imprinting and olfactory abilities, and cortisol and dopamine is also related with olfactory-related memories during migration.

Efficiency of the inbreeding coefficient f and other estimators in detecting null alleles, as revealed by empirical data of locus oke3 across 65 populations of chum salmon Oncorhynchus keta.

A survey of 65 populations of chum salmon Oncorhynchus keta across the species range revealed homozygote excess (947 homozygotes in 2954 fish) at a polymerase chain reaction (PCR)-based simple sequence repeat (SSR) locus oke3 with multiple alleles, whereas re-designed PCR primers indicated that 328 of these homozygotes were actually heterozygotes. Statistically significant high positive values of inbreeding coefficients, f, in multiple populations appeared to be a reliable predictor of null alleles. Based on these data, three methods were checked for their ability to estimate null-allele frequencies.