Note:

Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 80-94.

No description available.

Real-time PCR was utilised to measure the expression of several host immune genes in response to experimental infection with either ISAV or infectious pancreatic necrosis virus (IPNV). Probes targeting transcripts produced during type I and type II interferon (IFN) responses demonstrated these viruses induced both responses and peaked by day 6 post infection. The high mortality in ISAV infected fish highlighted the ineffective nature of the response and suggested the virus possesses IFN antagonistic capabilities to circumvent the host defence mechanisms. Viral proteins were studied using transfection-based methodologies to elucidate potential IFN antagonist capabilities with emphasis on the 7i protein as a putative analogue to the non-structural (NS1) protein of influenza. Results of two independent assays demonstrated the 7i protein caused a reduction induction of the interferon stimulated gene, Mx. In addition, RNA binding experiments suggested the 7i protein also possessed an RNA binding function. A surveillance programme with analysis by real-time PCR and sequencing looking for the presence of the putatively avirulent ISAV HPR0 strain, which contains an extra long highly polymorphic region (HPR) with the haemagglutinin-esterase (HE), was performed to demonstrate the extent of this strains presence in Scottish marine Atlantic salmon stocks. A transfection-based system combined with haemadsorption studies was utilised to examine differences in receptor binding and esterase activity of HE proteins obtained from an HPR0 type, a pathogenic virus and a specific combination of the two. The HPR0 HE protein was shown to be functional with respect to both receptor binding and esterase activity although no difference in function could be attributed to the presence of the full-length HPR in comparison to a protein from a pathogenic variant. This suggests the phenotypic variation of HPR0 may lie in another aspect of the viral life cycle.

Whole salmon scales were analysed using inductively coupled plasma mass spectrometry (ICP-MS) to test for differences in elemental compositions between salmon stocks. The investigation was structured to address stock variation based on fish origin (wild or farmed), farm populations, river origin of wild fish and sea fishery origin (Farces or Greenland). Initial studies were conducted to determine optimal analytical methods and to quantify the effects of fish size, sex, age and interannual variability on trace element composition within a single stock. Although a large number of trace elements were measured in fish scales, only a small number were found to be important predictor elements. The trace element composition of scale samples from wild and farmed fish enabled identification of origin (wild/farmed) to a high degree of accuracy (98 %), with Mn found in significantly higher concentrations in farmed fish and identified as the most influential element. Farmed fish taken from six sites around the west coast of Scotland were also correctly classified with a surprisingly high accuracy using discriminant analysis (87 %). The ability to discriminate between wild stocks was tested using scales from returning fish caught in 12 rivers from around Scotland. Overall classification success was 59 %, but this was found to depend on sample sizes, with elimination of samples comprised of small numbers of individuals improving the classification success to 90 %. The elements showing the highest predictive power differ according to the origin of fish, Mn carries most weight distinguishing farmed from wild fish, Ba, Mn, Zn, Co, Li, Ni and V are important in distinguishing between farms, Li, Sr and Ba strongly influence classification of wild wish and U was found to be the most important predictor element separating out samples recovered from the Farces and West Greenland fisheries. It is suggested that differences in Li and Ba i Abstract contents in scales reflect natural differences in river or catchment water chemistry, Zn, Ni, Co and V are likely to reflect differences in anthropogenic loading within industrialised settings and the high levels of Mn found in farmed fish scales predominantly reflects dietary uptake from supplementation of feed.

No description available.

Yeast cell wall (YCW) extracts have long been regarded as beneficial supplements in aquaculture feeds, especially with respect to immunomodulation. Previous studies have shown that supplementing salmon diets with YCW extracts increases resistance to sea lice. During the series of three trials, different sea lice challenge models and YCW extracts were studied. In Trial 1, fish fed a diet containing 0.4% YCW #a exhibited a significant reduction in sea lice burden of 23% compared to the control diet. The skin and skin mucus samples from Trial 1 were hence used for high-throughput screening of altered transcripts and proteins, while searching for candidate biomarkers for YCW extracts. Samples from Trials 2 and 3 were used for testing the candidate transcripts in independent biological samples, hence confirming or otherwise their suitability as biomarkers. Due to the lack of skin-specific libraries in the salmonid EST database, Roche-454 sequencing was used to describe the skin transcriptome of Atlantic salmon and form the basis of successive experiments. The resulting transcriptome assembly included 4,108 transcripts that were previously unknown for salmon, which include both skin-specific and low-expression transcripts. Analysis of the mucus proteome by 2D gels of Trials 1 and 2 samples showed that 27 and 49 proteins, respectively, exhibited a change in expression due to dietary treatment (p<0.05). Of these, calreticulin-like protein showed greatest potential as a biomarker since its expression was changed in both Trials 1 and 2 at the proteomic level and Trials 2 and 3 at the transcriptomic level. RNAseq was carried out on Trial 1 skin samples and 375 transcripts were significantly altered in expression across dietary treatments (p<0.05). Validation of this data by qPCR was successful and yielded similar fold changes to the RNAseq output. However, when the expression of a selection of genes was studied in Trial 2 samples, no correlation was found and hence, no candidate biomarker molecules were discovered. While further work is required to deduce the underlying mechanisms of immunomodulation due to dietary YCW extracts, this project has yielded two skin-specific transcriptomic databases which may be used to enhance the genomic data for salmonids.

This study examined three aspects of the processes of host location and initial attachment of the infective copepodid stage of the sea louse, <i>Lepeophtheirus salmonis</i> Krøyer 1838, to its host Atlantic salmon, <i>Salmo salar </i>(L.). The role of host and non-host odours and derived chemicals in modifying copepodid behaviour was identified in laboratory bioassays. Seasonal and stage-specific changes in the energetics of the eggs and the free-living larval stages were investigated through respiration experiments and chemical analyses. The influence of realistic physical factors, light intensity, salinity and host swimming speed, on determining the sites of initial copepodid attachment were identified in flowing water conditions, by the use of flume studies. Exposure to original odours and extracts of host odours resulted in significant changes in non-oriented behaviour and movement patterns which would increase the probability of host encounter, whilst exposure to original and extracts of host odour gave near-significant levels of oriented movement to the odour source. The host-derived chemicals isophorone and 1-octen-3-ol appeared to induce activated and limited arrested behaviours in the copepodid, respectively. During all stages of embryonic and larval development a gradual reduction in weight and energy content with developmental stage of larvae was noted, as lipid and protein stores were preferentially catabolised to provide energy for morphological changes and increased locomotion of the later larval stages, as revealed by an observed increase in respiration rates with developmental stage. Seasonal changes in embryonic dry weight, energy and biochemical composition were masked by the presence of seasonally variable proteinaceous egg cases. The free living stages showed a mixed trend in reproductive strategy, similar to previous studies of <i>L. salmonis </i>eggs in response to seasonal changes in temperature and photoperiod, but also similar to trends observed in food-unlimited holopelagic copepod species. Light intensity, salinity and host swimming speed independently and interactively altered the distribution and total initial attachment of <i>L. salmonis</i> copepodids on host Atlantic salmon smolts.

Thesis (M.S.) in Zoology--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 78-86).

Thesis (M.R.M.)--Simon Fraser University, 2001. / Includes bibliographical references (leaves 73-78).