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Title: MHC, parasite burden and heterozygosity in the blue shark (Prionace glauca, L.1758)
Author: McMillan, Heather Anne
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2013
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The blue shark (Prionace glauca) is a highly migratory pelagic elasmobranch that inhabits ocean basins globally. As a result, this shark is exposed to intensive ocean exploitation by commercial target fisheries, by-catch and for recreational pursuits globally. This top predator is therefore at high risk of becoming overfished. Advances to current knowledge of genetic population structure and diversity of this species would provide vital information required to initiate co-operative management approaches. In this study, the major histocompatibility complex (MHC) class IIa and IIβ genes were successfully isolated and characterised from blue sharks. Phylogenetic trees of the class II genes showed three major clades; one of teleost fish, one of tetrapods and one of sharks. The MHC class IIβ gene exon 2 primers successfully amplified partial sequences in blue sharks from several global locations. Analysis of sequences using denaturing gradient gel electrophoresis (DGGE) suggested the assay resolved different sequences up to one basepair, making the assay potentially very useful with further development. The class II genes presented in this study show conflicting evidence for the presence of more than one class II locus. To explore inheritance patterns of MHC exon 2 diversity, a single blue shark litter (mother + 19 pups) was cloned and sequenced, revealing evidence to suggest the possibility of more than one locus for class IIβ. Statistical analysis of parasite loads and diversities from blue shark spiral valves revealed no definitive population structure, supporting global and North Atlantic mtDNA and microsatellites genetic analyses presented here. The size (fork length) of sharks was found to be potentially influential when modelled with individual microsatellite heterozygosity and fork length. International co-operation will be required to prevent this species becoming extinct from global marine ecosystems. Reductions in numbers could lead to reduced genetic diversity, decreased immunity and ultimately an 'unhealthy' population.
Supervisor: Not available Sponsor: Biotechnology and Biological Sciences Research Council (BBSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Blue shark ; Major histocompatibility complex ; Heterozygosity