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PubMed2001

A model of salmon louse production in Norway: effects of increasing salmon production and public management measures.

Salmon lice Lepeophtheirus salmonis Krøyer have caused disease problems in farmed Atlantic salmon Salmo salar L. since the mid-1970s in Norway. High infection intensities and premature return of wild sea trout Salmo trutta L. were first reported in 1992. Later emaciated wild Atlantic salmon smolts carrying large amounts of lice have been observed both in fjords and offshore. The Norwegian Animal Health Authority regulations to control the problem, which came into operation in 1998, included compulsory louse level monitoring in farms and maximum legal numbers of lice per fish. Here, we present a model of salmon louse egg production in Norway and show that the effect of the current public management strategy is critically dependent on the yearly increase in salmon production. This is because the infection pressure is the product of the number of fish in the system, and the number of lice per fish. Due to the much larger number of farmed than wild salmonids, it is highly likely that lice originating from farmed salmon infect wild stock. Estimated tolerance limits for wild salmonids vary widely, and the level of louse egg production in farms which would be needed to decimate wild populations is not known. Two possible thresholds for total lice egg production are investigated: (1) 1986 to 1987 level (i.e. before adverse effects on sea trout were recorded), and (2) a level corresponding to a doubling of the estimated natural infection pressure. The farm lice per fish limits that would have to be observed to keep louse production within the 2 thresholds are calculated for the period 1986 to 2005. A steady decrease in the permitted number of lice per fish may keep the total louse production stable, but the number of salmon required for verification of lice numbers will increase as the prevalence to be verified is decreased. At threshold (2), the model estimated that lice limits should have been 0.05 louse per fish in 1999. This would require 60 fish from each pen to be collected, anaesthetised and examined for a good estimate at a confidence level of 95%. Such sample numbers are likely to be opposed by farmers. The use of national delousing programs to solve the problem is discussed.

Animals↗
PubMed2002

Effect of poly I:C on the expression of Mx proteins and resistance against infection by infectious salmon anaemia virus in Atlantic salmon.

Mx proteins are induced by type I interferons (IFN alpha and beta) in mice and humans and inhibit the replication of orthomyxoviruses and some other single-stranded RNA viruses. Recently, Mx genes have been cloned from Atlantic salmon. Mx transcripts were shown to be induced in head-kidney, liver and gills of the fish by the synthetic double-stranded RNA polyinosinic polycytidylic acid (poly I:C). In the present work we have studied expression of Mx protein in organs of Atlantic salmon treated with poly I:C. A quantitative immunoblot method was established to monitor expression of Mx protein and to compare relative amounts of Mx protein in different organs. Treatment of Atlantic salmon with poly I:C increased the relative amount of Mx protein in liver, stomach, hindgut, head-kidney and spleen. In gills the levels of Mx protein were similar in control fish and poly I:C treated fish. Immunohistochemistry of tissue sections from liver, head-kidney and gills from poly I:C treated fish was in accordance with the immunoblotting data and showed staining for Mx protein in several different cell types. Classification of infectious salmon anaemia virus as an orthomyxovirus makes it a putative target for Atlantic salmon Mx protein. Atlantic salmon treated with poly I:C showed reduced cumulative mortality compared to the control fish when challenged with infectious salmon anaemia virus (ISAV) by intraperitoneal injection. This demonstrates that poly I:C has some protective effect against ISAV in vivo.

Anemia↗
PubMed2003

Fitness reduction and potential extinction of wild populations of Atlantic salmon, Salmo salar, as a result of interactions with escaped farm salmon.

The high level of escapes from Atlantic salmon farms, up to two million fishes per year in the North Atlantic, has raised concern about the potential impact on wild populations. We report on a two-generation experiment examining the estimated lifetime successes, relative to wild natives, of farm, F(1) and F(2) hybrids and BC(1) backcrosses to wild and farm salmon. Offspring of farm and "hybrids" (i.e. all F(1), F(2) and BC(1) groups) showed reduced survival compared with wild salmon but grew faster as juveniles and displaced wild parr, which as a group were significantly smaller. Where suitable habitat for these emigrant parr is absent, this competition would result in reduced wild smolt production. In the experimental conditions, where emigrants survived downstream, the relative estimated lifetime success ranged from 2% (farm) to 89% (BC(1) wild) of that of wild salmon, indicating additive genetic variation for survival. Wild salmon primarily returned to fresh water after one sea winter (1SW) but farm and 'hybrids' produced proportionately more 2SW salmon. However, lower overall survival means that this would result in reduced recruitment despite increased 2SW fecundity. We thus demonstrate that interaction of farm with wild salmon results in lowered fitness, with repeated escapes causing cumulative fitness depression and potentially an extinction vortex in vulnerable populations.

Animals↗
PubMed1994

Localization of salmon gonadotropin-releasing hormone mRNA and peptide in the brain of Atlantic salmon and rainbow trout.

The decapeptide gonadotropin-releasing hormone (GnRH) is a key hormone for the central regulation of reproduction. The distribution of salmon GnRH (sGnRH), which is the major form in salmonids, has been studied in different fish species by immunocytochemistry. Discrepancies in data concerning the distribution of sGnRH perikarya led us to investigate this problem in two species, the Atlantic salmon and the rainbow trout, with in situ hybridizaiton of sGnRH messenger, a highly specific molecular tool. By Northern blot analysis, the rainbow trout sGnRH messenger appears to be about 500 bases in length, which is close to those isolated from Atlantic salmon or masu salmon and characterized previously. In situ hybridization with riboprobes generated with Atlantic salmon sGnRH cDNA demonstrated that sGnRH perikarya are restricted to the ventral part of olfactory bulbs, telencephalon, and preoptic area. They are distributed on a nearly continuous line extending from the olfactory bulbs to the preoptic area in both salmonid species studied. Despite the presence of GnRH-like immunoreactivity in the preoptic magnocellular nucleus (NPOm) and in the tegmentum of the midbrain (MT), the sGnRH mRNA is not present in these two structures. Stained cells in NPOm could be target cells for GnRH and immunoreactive neurons in MT are likely to be chicken GnRH-II containing cells. Our study not only gives a precise distribution of the sGnRH system in two salmonids, Atlantic salmon and rainbow trout, but also clarifies the ambiguous data published up to now in rainbow trout.

Animals↗
PubMed1991

Seasonal changes in seawater adaptability and plasma levels of prolactin and growth hormone in landlocked sockeye salmon (Oncorhynchus nerka) and amago salmon (O. rhodurus).

In order to clarify the roles of prolactin (PRL) and growth hormone (GH) in the development of seawater adaptability in salmonids, seasonal changes in salinity tolerance, plasma PRL, and plasma GH were examined in juvenile landlocked sockeye salmon (Oncorhynchus nerka) and amago salmon (O. rhodurus). Assessed by the 24-hr seawater-challenge test, the landlocked sockeye salmon possessed seawater adaptability as underyearlings in spring, which was maintained throughout the year, and a further increase was observed as yearlings the next spring. An increase in seawater adaptability was observed in silvery juvenile amago salmon as underyearlings from autumn to winter, when some of the wild population migrate to the sea. Precociously mature amago salmon, which did not develop a silvery body color but maintained distinct parr marks, also showed an improvement in seawater adaptability during autumn to winter, although plasma sodium levels after transfer to seawater were still higher than those of the silvery juveniles. In both sockeye and amago salmon, seasonal changes in plasma levels of PRL and GH were not correlated with development of seawater adaptability. In both species, acclimation to seawater resulted in decreased plasma levels of PRL irrespective of their adaptability to seawater, in agreement with the inhibitory effects of PRL in seawater adaptation. On the other hand, plasma GH levels increased only when seawater adaptability was high, in agreement with previous observations indicating an important role of GH in seawater adaptation of salmonids.

Adaptation, Physiological↗
PubMed2001

Phagocytosis of Loma salmonae (Microsporidia) spores in Atlantic salmon (Salmo salar), a resistant host, and chinook salmon (Oncorhynchus tshawytscha), a susceptible host.

The in vitro phagocytosis of Loma salmonae spores by macrophages of Atlantic salmon and two strains of chinook salmon were investigated. Opsonisation of L. salmonae with plasma factors increased uptake by head kidney macrophages. Macrophages of Atlantic salmon, which are resistant to the parasite, had a significantly higher phagocytic index (PI) than those of chinook salmon, a susceptible species. This may indicate a possible mechanism contributing to resistance in Atlantic salmon or that L. salmonae is able to evade or suppress initial binding by macrophages of chinook. Non-specific binding or lectinophagocytosis was also suggested by significantly higher PI of spores from EDTA treated plasma when compared with no plasma or heat treated plasma. In comparison, uptake of Baker's yeast Saccharomyces cerevisiae by phagocytes was not significantly different between fish species and strains for all treatments.

Animals↗
PubMed2000

Localization of salmon cardiac peptide (sCP) in the heart of salmon (Salmo salar L.).

We have previously cloned and characterized a novel cardiac hormone from the salmon (Salmo salar) which has a uniquely heart-specific distribution and a low structural similarity with any other known natriuretic peptides. Specific antibodies were raised in goat against the salmon cardiac peptide. For localization and quantification, four different methods were applied: immunohistochemistry (avidin-biotin peroxidase), transmission electron microscopy, cryoimmunoelectron microscopy (protein A-gold), and a specific radioimmunoassay. Both atrial and ventricular myocytes stained immunohistochemically. The staining was similar in all myocytes and no specific myoendocrine cells were found. Within a single myocyte, both atrial and ventricular, the staining was stronger near the nucleus. Transmission electron microscopy revealed that both the atrium and the ventricle contained small sarcoplasmic granules of similar type with a diameter of 100 to 200 nm and an electron-dense core with a clear halo. The granules were typical vesicles which can be found in secretory cells utilizing the regulatory pathway. The highest number of granules was found near the nucleus, but granules were located also near the Golgi apparatus, between myofilament bundles, and in subsarcolemmal positions. Gold particles, conjugated to antibodies raised against the salmon cardiac peptide, were deposited on similar sarcoplasmic granules found in transmission electron microscopy. Among the sarcoplasmic granules with gold particles there were granules which did not show any cardiac peptide immunoreactivity. A significantly (Student's t test, P < 0.05) higher concentration of cardiac peptide was found in the heart atrium than in the ventricle, 16.2 +/- 3.5 pmol/mg tissue (n = 8) and 4.5 +/- 1.7 pmol/mg tissue (n = 8), respectively. The findings show that the salmon cardiac peptide is localized in secretory granules in both compartments of the heart. The morphology of the granules suggests that both the atrium and the ventricle utilize the regulatory pathway to release salmon cardiac peptide.

Animals↗
PubMed1995

Salmon HNF1: cDNA sequence, evolution, tissue specificity and binding to the salmon serum albumin promoter.

cDNA clones coding for the transcription factor HNF1 have been isolated from Atlantic salmon (Salmo salar L.). The 559 amino acid residue long encoded protein shows high conservation, with respect to other species, of the domains necessary for DNA-binding: the HNF1 atypical homeodomain, the POU related sequence and the dimerisation domain. Alignment with rat HNF1 protein reveals that the transcription activation domains ADI and ADIII are relatively conserved in the fish sequence whereas ADII is not. Phylogenetic analysis indicates that higher vertebrate HNF1s and the related variant HNF1s (vHNF1s) are more closely related to each other than any of them is to Salmon HNF1, suggesting that the duplication event from which HNF1 and vHNF1 genes arose occurred after the divergence of the tetrapod and teleost ancestors. Northern blot analysis show a single transcript, of about 2.6 kb, which is not exclusive to liver but is also present in intestine, kidney and spleen. Using polymerase chain reaction (PCR) we have isolated the salmon albumin gene promoter which contains, upstream of the TATA box, a potential binding site for HNF1. The salmon HNF1 protein synthesized by in vitro transcription-translation of the full-length cDNA is able to bind specifically with equivalent affinities to either the rat or salmon albumin promoter.

Amino Acid Sequence↗
PubMed2002

Immunolocalization of cysteine proteinases (cathepsins) and cysteine proteinase inhibitors (salarin and salmon kininogen) in Atlantic salmon, Salmo salar.

Tissue localization of cysteine proteinases (cathepsins) and their inhibitors (salarin, salmon kininogen) was performed in tissues of the Atlantic salmon. In skin, both epidermis and dermis were strongly stained by antisera against salarin and salmon kininogen. In epidermis the intercellular space seemed to be heavily stained (salarin). In kidney, the inhibitors were mainly localized to the interstitial capillaries. Also, some epithelial cells of the tubules (salarin) and some cells of the interstitium were stained. Mostly, the staining had a diffuse cytoplasmic localization. In the liver some hepatocytes were strongly positive for salarin and salmon kininogen. Purified fish cysteine proteinase inhibitors were not found to inhibit the growth of fish pathogenic bacteria and viruses. In the trunk kidney cathepsins B and L were localized in epithelial cells of the tubules (proximal part) and in cells of the interstitium. Mostly, the staining showed a prominent lysosomal localization. In head kidney large macrophage-like cells were positively stained for cathepsin B. The staining was localized to granula/vacuoles in the cytoplasm. In the liver, some hepatocytes were strongly stained and some were less strongly positive for cathepsin B and L. Mostly, the hepatocytes showed lysosomal staining. Cathepsin L was found in some big macrophage-like cells in the spleen. Mucosal epithelial cells of the esophagus and intestine seemed to be strongly stained for cathepsin B and L. The results show that cathepsins and their inhibitors are specifically and widely distributed in the Atlantic salmon skin indicating that they perform some biologically important and specific but so far unknown functions.

Animals↗
PubMed1997

Multiplication and haemadsorbing activity of infectious salmon anaemia virus in the established Atlantic salmon cell line.

Infectious salmon anaemia virus (ISAV), which previously had never been isolated in any of the commercially available established fish cell lines, was successfully propagated in the continuous cell line Atlantic salmon (AS). The yield of infectious ISAV increased with the incubation time of virus-inoculated cells, demonstrated by in vivo infectivity trials in groups of Atlantic salmon. Trypsin treatment of the virus was not necessary for primary infection of AS cells with salmon-grown ISAV. The infection was non-cytopathic, but it was possible to detect virus-infected cells by a haemadsorption centre assay using Atlantic salmon erythrocytes. Pleomorphic enveloped virus particles were seen by transmission electron microscopy of infected AS cells. Elongated forms were observed, but spherical particles with diameters of 90-130 nm were commonest. Growth of ISAV was inhibited by actinomycin D but not by 5-bromo-2-deoxyuridine treatment, which indicates that ISAV may be an aquatic orthomyxovirus.

Animals↗
PubMed1995

[The thyroid gland of humpback salmon (Oncorhynchus gorbuscha) fry and of humpback and cherry salmon (Oncorhynchus masu) hybrids during smoltification].

Thyroid gland follicular cells were studied morphofunctionally on different stages of juvenile humpback salmon migration from the spawning sites into the sea. Salmon hybrids kept in laboratory conditions in fresh and salt water were exposed to the same examination. Juvenile humpback salmon fished out from the river mouth, when coming to the sea water had significant increase of follicular epithelium height and decrease of follicular diameter and amount of the deponated colloid. Thyroid glands follicle topography of hybrids is close to those of juvenile humpback salmon although it is more compact in hybrids. Completely formed follicles were found in three-month-old fish. Microscopic and morphometric studies revealed the increase of thyroid gland activity in hybrids in April: follicular diameter grew smaller, epithelial height significantly increased and amount of colloid in the follicles decreased. In May increased activity of the gland remained and went smaller in June. Ten days after hybrids transferation into the sea water activity of the gland cells significantly increased. Thus, thyroid gland activity is an important characteristics of smoltification both for the juvenile salmon from natural population and hybrids kept in laboratory conditions.

Animals↗
PubMedDate not supplied

Rapid liquid chromatographic method to distinguish wild salmon from aquacultured salmon fed synthetic astaxanthin.

Analytical methods are needed to determine the presence of color additives in fish. We report a liquid chromatographic (LC) method developed to identify the synthetic form of the color additive astaxanthin in salmon, based on differences in the relative ratios of the configurational isomers of astaxanthin. The distributions of configurational isomers of astaxanthin in the flesh of wild Atlantic and wild Pacific salmon are similar, but significantly different from that in aquacultured salmon. Astaxanthin is extracted from the flesh of salmon, passed through a silica gel Sep-Pak cartridge, and analyzed directly by LC on a Pirkle covalent L-leucine column. No derivatization of the astaxanthin is required-an important advantage of our approach, which is a modification of our previously described method. This method can be used to distinguish between aquacultured and wild salmon. The method has general applicability and can also be used to identify astaxanthins derived from other sources such as Phaffia yeast and Haematococcus pluvialis algae.

Animal Feed↗
PubMed2002

Effect of double-stranded RNA and interferon on the antiviral activity of Atlantic salmon cells against infectious salmon anemia virus and infectious pancreatic necrosis virus.

Type I interferons (IFN) establish an antiviral state in vertebrate cells by inducing expression of Mx and other antiviral proteins. We have studied the effect of Atlantic salmon interferon-like activity (AS-IFN) and poly I:C on the Mx protein expression and antiviral activity against infectious salmon anaemia virus (ISAV) and infectious pancreatic necrosis virus (IPNV) in the Atlantic salmon cell lines SHK-1 and TO. The double-stranded RNA poly I:C is an inducer of type I IFN in vertebrates. A cell cytotoxicity assay and measurements of virus yield were used to measure protection of cells against virus infection. Maximal induction of Mx protein in TO and SHK-1 cells occurred 48 h after poly I:C stimulation and 24 h after AS-IFN stimulation. TO cells pretreated with AS-IFN or poly I:C were protected from infection with IPNV 24 to 96 h after stimulation. Poly I:C or AS-IFN induced a minor protection against ISAV infection in SHK-1 cells, but no protection was induced against ISAV in TO cells. Western blot analysis showed that ISAV induced expression of Mx protein in TO and SHK-1 cells whereas IPNV did not induce Mx protein expression. These results suggest that ISAV and IPNV have very different sensitivities to IFN-induced antiviral activity and have developed different strategies to avoid the IFN-system of Atlantic salmon. Moreover, Atlantic salmon Mx protein appears not to inhibit replication of ISAV.

Animals↗
PubMed2000

Effects of salmon gonadotropin-releasing hormone on follicle stimulating hormone secretion and subunit gene expression in coho salmon (Oncorhynchus kisutch).

Previous work has indicated that, during the process of gametogenesis in salmon, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are differentially synthesized and released. Although substantial information is available on the regulation of LH in many fish species, relatively little is known about the regulation of FSH biosynthesis and secretion or the regulation of two types of alpha subunit in salmon. In this study, the effects of salmon gonadotropin-releasing hormone (sGnRH) on in vitro secretion of FSH, and alpha1, alpha2, LH beta, and FSH beta subunit gene expression were investigated in coho salmon (Oncorhynchus kisutch) using primary pituitary cell cultures. To quantify FSH beta, LH beta, alpha1, and alpha2 subunit transcript levels, a multiplex RNase protection assay (RPA) was developed. Probes for the beta subunits of coho salmon FSH and LH were available from previous studies. To generate probes for the alpha subunit RPAs, alpha1 and alpha2 subunit cDNAs were cloned using reverse transcriptase PCR. Release of FSH and LH into cell culture medium was quantified by radioimmunoassays. The effects of sGnRH on gonadotropin release and gene expression were tested at two points during the spring (April and May) prior to spawning in the autumn; a period when plasma and pituitary FSH levels are increasing and females are in early stages of secondary oocyte growth. In both experiments, sGnRH increased steady-state mRNA levels of FSH beta, alpha1, and alpha2, whereas LH beta mRNA levels were not detectable. Secretion of FSH was stimulated by sGnRH in a concentration-dependent manner. Medium LH was not detectable in the first experiment (April) and was measurable only after sGnRH treatment in the second experiment (May). Control levels of medium FSH and transcripts for FSH beta and alpha1 subunits increased approximately fourfold between April and May, whereas alpha2 transcript levels remained relatively constant, suggesting that the seasonal increase in FSH release may involve increased production of alpha1. Therefore, sGnRH has direct stimulatory effects on both secretion of FSH and FSH subunit biosynthesis, most likely due to increased transcription. However, alterations in rates of transcript degradation cannot be ruled out.

Amino Acid Sequence↗
PubMed1988

Regulation of gonadal steroidogenesis in Fundulus heteroclitus by recombinant salmon growth hormone and purified salmon prolactin.

The effects of recombinant salmon growth hormone (sGH) on plasma sex steroid levels and gonadal function were investigated in hypophysectomized Fundulus heteroclitus. Effects of sGH were compared to those of purified chum salmon prolactin (sPRL), Atlantic salmon gonadotropin (sGTH), and salmon pituitary extract (sPE). Treatment with sGH significantly increased plasma concentrations of testosterone in males and estradiol-17 beta in females; sPRL had similar effects on testosterone levels in males. Further, treatment with these hormones prevented the decline in gonadal weight observed after hypophysectomy in both males and females. In vivo treatment of male fish with sGH also augmented testosterone and 11-ketotestosterone production by testis tissue subsequently incubated in vitro. Direct action(s) on gonadal steroidogenesis was examined by incubating gonadal tissues from hypophysectomized fish in vitro with various hormones. sGH significantly stimulated the in vitro production of testosterone and 11-ketotestosterone by testis, and estradiol-17 beta by ovary. sPE and sGTH also stimulated gonadal steroidogenesis, whereas sPRL and bovine GH had no significant effect. By comparison, rainbow trout gonads also produced increased amounts of steroids when treated with sGH in vitro. The use of a cloned GH rules out contamination by other pituitary hormones. These results, therefore, demonstrate that recombinant salmon growth hormone possesses steroidogenic and gonadotropic activity. Purified sPRL also has steroidogenic and gonadotropic actions. However, the significance of these effects of teleost GH and PRL is not known.

Animals↗
PubMed2006

Expression of MHC class I pathway genes in response to infectious salmon anaemia virus in Atlantic salmon (Salmo salar L.) cells.

Infectious salmon anaemia virus (ISAV) is the causative agent of an important viral disease threatening Atlantic salmon aquaculture. Although its structure and pathogenesis is well described little is known about its immunomodulatory effects on the host. Cellular immunity is critical in the host control of virus infections, an event attributable to antigen presentation through the MHC class I pathway, whose genes are transcriptionally activated by interferons (IFN) and other cytokines. In this study we analysed the regulation and kinetics of key genes in the salmon MHC class I pathway in relation to type I IFN during ISAV infection and poly I:C stimulation in the permissive Atlantic salmon kidney cell line (ASK). As measured by quantitative real-time PCR, ISAV induced an mRNA shut-off equivalent to 2.5-5.5-fold reduced levels of housekeeping genes at 7 days post infection. Relative to this shut-off (by normalising to beta-actin) transcription increased to peak levels at 2.8-fold for MHC class I, 10-fold for beta 2 microglobulin (beta 2m), 5.9-fold for the peptide transporter ABCB2, 8.8-fold for the proteasome component PSMB8 and 4.6-fold for the proteasome component PSMB9, presumably by activation of the IFN system as a 26-fold induction was observed for type I IFN-alpha. Expression of Mx protein was also induced 17-fold at peak level. Similar kinetics and activation levels of these genes were seen in poly I:C stimulated cells. We also isolated the salmon MHC class I UBA*0301 promoter and identified a conserved interferon-stimulated response element (ISRE) and GAAA-elements plus several GAS- and IRF-sites, all supporting IFN-inducible properties. In summary, we demonstrate a concerted induction of the MHC class I pathway and type I IFN by ISAV comparable to levels induced by the synthetic double-stranded RNA (dsRNA) poly I:C. Thus, unlike influenza and several other viruses ISAV does not seem to interfere with MHC and IFN expression.

Animals↗
PubMed2004

The effect of light on the settlement of the salmon louse, Lepeophtheirus salmonis, on Atlantic salmon, Salmo salar L.

The salmon louse, Lepeophtheirus salmonis, is an ectoparasitic copepod that infests both wild and farmed salmonid fish. Salmon lice are a major disease problem in the farming of Atlantic salmon, Salmo salar L., and the possibility of salmon lice playing a role in the decline of wild anadromous stocks has also been raised. Lepeophtheirus salmonis can detect a range of stimuli (pressure/moving water, chemicals and light) in the external environment. However, the response thresholds to various stimuli, and the spatial and temporal scales over which they operate in the context of host location, are largely unknown. In this context, we attempted to determine whether salmon lice copepodids settle onto hosts more effectively, or at different locations on the fish's body, under different qualities of light. Lice settlement trials were conducted under three lighting conditions; L1: unpolarized under ultraviolet A (UVA)-through visible; L2: unpolarized without UVA (control); L3: 100% linearly polarized without UVA. A dark control was also conducted. No statistically significant difference in lice settlement was found. While changes in light intensity are involved in host detection at spatial scales on the order of metres, the results presented here suggest that it is not the primary sensory modality underlying host location at smaller spatial scales (cm to mm).

Animals↗
PubMed2005

A highly redundant BAC library of Atlantic salmon (Salmo salar): an important tool for salmon projects.

BACKGROUND: As farming of Atlantic salmon is growing as an aquaculture enterprise, the need to identify the genomic mechanisms for specific traits is becoming more important in breeding and management of the animal. Traits of importance might be related to growth, disease resistance, food conversion efficiency, color or taste. To identify genomic regions responsible for specific traits, genomic large insert libraries have previously proven to be of crucial importance. These large insert libraries can be screened using gene or genetic markers in order to identify and map regions of interest. Furthermore, large-scale mapping can utilize highly redundant libraries in genome projects, and hence provide valuable data on the genome structure. RESULTS: Here we report the construction and characterization of a highly redundant bacterial artificial chromosome (BAC) library constructed from a Norwegian aquaculture strain male of Atlantic salmon (Salmo salar). The library consists of a total number of 305,557 clones, in which approximately 299,000 are recombinants. The average insert size of the library is 188 kbp, representing 18-fold genome coverage. High-density filters each consisting of 18,432 clones spotted in duplicates have been produced for hybridization screening, and are publicly available 1. To characterize the library, 15 expressed sequence tags (ESTs) derived overgos and 12 oligo sequences derived from microsatellite markers were used in hybridization screening of the complete BAC library. Secondary hybridizations with individual probes were performed for the clones detected. The BACs positive for the EST probes were fingerprinted and mapped into contigs, yielding an average of 3 contigs for each probe. Clones identified using genomic probes were PCR verified using microsatellite specific primers. CONCLUSION: Identification of genes and genomic regions of interest is greatly aided by the availability of the CHORI-214 Atlantic salmon BAC library. We have demonstrated the library's ability to identify specific genes and genetic markers using hybridization, PCR and fingerprinting experiments. In addition, multiple fingerprinting contigs indicated a pseudo-tetraploidity of the Atlantic salmon genome. The highly redundant CHORI-214 BAC library is expected to be an important resource for mapping and sequencing of the Atlantic salmon genome.

Animals↗