Research on Southern Ocean octopuses has provided evidence of cryptic speciationand endemic radiation (Allcock, 2005) with one genus, Pareledone, proving to beparticularly diverse with at least 10 species occurring sympatrically at ElephantIsland, South Shetland Islands (Allcock et al., 2008). Circumpolarity has beenproposed for several species (e.g., Dell, 1972), but the evidence is equivocal.Taxonomic workshops have tended to question circumpolarity, but a paucity ofspecimens from areas other than the South Shetland Islands (where a CCAMLRsponsored groundfish survey regularly yields an abundance of octopuses) hashampered progress. In this collaborative study, we have used sequences of themitochondrial COI gene (the designated Barcode of Life gene) from over 500specimens of Pareledone from a range of locations throughout the SouthernOcean. Targeting material from James Clark Ross, Tangaroa, Aurora australis andPolarstern, we have obtained collections from the South Shetland Islands, the SouthOrkney Islands, the eastern Weddell Sea, the coast of Adelieland, the coast of GeorgeV Land, the Ross Sea, the Amundsen Sea and the Bellinghausen Sea. Combining ourgenetic data with the extensive morphological systematics knowledge of Pareledonearound Elephant Island (Allcock, 2005; Allcock et al., 2007) gained from the frequentand intensive trawl surveys in this area gives us an insight into the variability of thebarcode gene in this group. Thus we are able to draw firm conclusions about thediversity of this group elsewhere based on COI data alone. Our results indicate thatcircumpolar species do exist (but are not the rule) and we examine the relationshipbetween range extent and other habitat parameters such as depth distribution. Ourresults also indicate a number of undescribed species and we interpolate our data tomake estimates of the yet undiscovered biodiversity in this group. We also evaluatethe usefulness of COI sequences in this context and consider the applicability ofbarcoding to other groups.