Cultivation of the blue mussel (Mytillus edulis) has grown strongly in Scotland over the last ten years. The further development of sustainable and productive farms is being encouraged but, because knowledge of the species actually living in Scottish waters is limited, this could be made difficult. Joanna Wilson 1*, John B. Taggart 1, Michaël Bekaert 1, Iveta Matejusová 2 and Rebecca McIntosh 2 1 Institute of Aquaculture, University of Stirling (* 2 Marine Scotland Science Marine Laboratory, Aberdeen Three mussel species have been identified: M. edulis, M. galloprovincialis and M. trossulus, which produce hybrid offspring wherever their ranges overlap. Despite the overall increase of mussel cultivation in Scotland, production has suffered in some regions from the appearance of a particularly fragile mussel with poor meat – traits often associated with M. trossulus (and its hybrids). Farmers wishing to cultivate a single species could face problems without monitoring the genetics of their populations: they need to know what species live in Scottish waters in order to effectively manage their stocks and mitigate risks associated with an expansion in hybrid range.

The genetic marker Me15/16 [1] has, to date, been used routinely for genotyping mussels in Scottish populations. Me15/16 only looks at one locus in the genome so it’s possible that not all hybrids or even species are being correctly identified. Developing new markers from Single Nucleotide Polymorphisms (SNPs) could enable more reliable species identification. SNPs are identified through Restriction Site Associated DNA (RAD) sequencing, which generates hundreds of thousands of sequence reads and gives an in depth picture of a genome. New markers are developed by designing primers complimentary to the sequences flanking SNPs and testing their specificity using a Kompetitive Allele Specific (KASP) Assay. Large scale sequencing of the Mytilus genome through RAD sequencing is currently underway. DNA is digested with a restriction enzyme and specific barcodes are ligated to the restriction sites. The resulting fragments are cleaned, amplified and sequenced on an illumina HiSeq TM machine. Each barcode is read multiple times. Stacks software complies matching reads into groups (“stacks”) which represent possible loci in the genome. These “stacks” are compared between individuals and genotypes are assigned according to a maximum likelihood statistical model [2].

USES FOR NEW MARKERS Genotyping of larvae from Loch Ewe Genotyping of families from crossing experiments Updating map of mussel species in Scotland Map showing areas where mussels have previously been sampled [3] and sites that will be covered in the present study. Historical plankton samples contain information about the diversity of Mytilus species. This could be useful in seeing how or if M. trossulus has affected the overall spat settlement of Mytilus species in this location, with Tracking the movement of genes through generations will give an idea of how they accumulate over time, and thus the likelihood of such genes being expressed in hybrid offspring. implications for other sites in Scotland. References [1] Inoue K et al (1995) Biol Bull 189:370–375 [2] Catchen JM (2011) G3 1:171–82 [3] Dias PJ et al (2011) Hydrobiologia 670:127–140 ? ? 1 2 1/2 1