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The distribution ofOctopus vulgarishas not yet been completely clarified. For a long time, a cosmopolitan distribution with unknown distribution limits had been assumed. This assumption has recently been questioned and it has been postulated that the distribution is restricted to the Mediterranean and the northeastern Atlantic. However, as our previous studies show, the existence ofO. vulgariscan be confirmed for the Mediterranean and the whole eastern Atlantic, and evidence is provided for its occurrence in the western Atlantic. The aim of the present work is to extend our previous data matrix and to clarify whetherO. vulgarisexists in the northwestern Pacific. Therefore, the sequence variation in ostensibleO. vulgarisfrom 13 localities in the Mediterranean (France), the Atlantic Ocean [Lanzarote, Senegal, South Africa (Atlantic, Indian Ocean), Tristan da Cunha, north, middle and south Brazil], the Caribbean Sea (Venezuela) and the Pacific Ocean (Taiwan, Japan and Costa Rica) was examined using the mitochondrial genes coding for the 16S rRNA and cytochrome oxidase subunit III (COIII). Sequence divergence was relatively low between populations ofO. vulgarisfrom the Mediterranean, the eastern and western Atlantic (except north Brazil), Venezuela, Taiwan and Japan compared with other species of the genusOctopus. Trees constructed by using maximum likelihood, neighbour joining and maximum parsimony algorithms (PAUP) show the above-mentioned populations from the Mediterranean, the western and eastern Atlantic, Venezuela and the northwestern Pacific (Japan and Taiwan) as a monophyletic cluster. Thus, even if theOctopus vulgaris-like octopus from north Brazil should turn out a cryptic species, the data of this work not only support our hypothesis of the distribution ofO. vulgarisin the Mediterranean, the eastern and western Atlantic but also show thatO. vulgarisis present in the northwestern Pacific, namely in the waters of Taiwan and Japan. [ABSTRACT FROM AUTHOR]