Genetic characterisation and variation in Gyrodactylus species
The main focus of this investigation here involved three of the four most common salmonid Gyrodactylus species (G. salarism G. thymalli, G. derjavini and G. truttae), with particular attention to discriminating between G. salaris and G. thymalli. This was accomplished by characterising uncharacterised areas of the genome, i.e. the intergenic spacer region and 28S subunit of the ribosomal array, and CO1 and ND1 gene regions of the mitochondrial genome. Once characterisation was completed for these species, the more variable regions that would potentially be used for as a more comprehensive molecular diagnostic test, would, only then, be characterised for further chosen Gyrodactylus spp. The result of this investigation has now successfully documented the degree of both intra- and inter-specific variation within the IGS, 28S, ITS, 18S, CO1 and ND1 genomic regions. As a direct result of this study’s information and techniques, the diagnostic facility at the FRS Marine Laboratory is now able to identify each strain and species of all Gyrodactylus species investigated to date. In addition, the two cryptic species of G. salaris and G. thymalli can now be differentiated using three distinct ribosomal regions, namely the IGS, 5’ 28S and 3’ 28S. This project also displays the ability to perform such characterisation on older Gyrodactylus species specimens, specifically those which have been preserved in ethanol for greater than 3 years, which had not been able to be utilised in the past due to the problems of DNA extraction. The strategy of progressive and strategic characterisation (targeting smaller specific areas of the array and progressing in a certain order of profitability variation) of these specimens, sufficiently enabled the poorer quality of the DNA to be productive, and therefore beneficial in this investigation.