| Summary: | Cephalopods evolved during the Cambrian and were once the dominant lifeforms in the world’s oceans. Several groups of the 800 living cephalopod species have diversified due to their rapid response to drivers of evolution and different adaption strategies. My research aims to investigate their evolutionary history and relationships, and answer different questions about cephalopod biology and systematics, using a variety of molecular techniques with the support of morphology. Chapter 2 uses DNA barcoding to determine the diversity and abundance of cephalopods within warm-core eddies in the North Atlantic. I identified different taxonomic groups which need to be reviewed, expanded the known distribution of six species, provided the first sequence for two known species and identified a potential new species Todarodes cf. sagittatus. Chapter 3 investigates the distribution of deep-sea octopuses in the North east Atlantic, also using DNA barcoding. I discuss the taxonomic and systematic issues of the groups represented in this study, extend the known depth range for one species and identify a potential new Muusoctopus species. Chapter 4 uses genome skimming to build a phylogeny of the Octopodiformes. I provide whole mitochondrial genome sequences and 18S rRNA genes and 28S rRNA for twenty Octopoda specimens comprising 18 Cirrata and Incirrata species. Chapter 5 uses CT scanning to investigate the internal anatomy of cirrate octopods. I discuss the non-invasive imaging techniques that have been used in cephalopods, along with their advantages and disadvantages. My research shows how different molecular techniques can be used to answer certain questions and will contribute to improving the cephalopod tree of life.
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