A new species of Cistopus Gray, 1849 (Cephalopoda: Octopodidae) from the East and South China Seas and phylogenetic analysis based on the mitochondrial COI gene

Abstract

Cistopus chinensis sp. nov. is a small benthic octopod. The primary diagnostic character for the genus Cistopus is the possession of eight mucous pouches set in the oral surface of the webs, with one located between each of the arm bases. This study describes the morphological characters of Cistopus chinensis sp. nov. from the East China Sea and the South China Sea. Cistopus chinensis sp. nov. can be distinguished from Cistopus indicus and Cistopus taiwanicus by enlarged suckers in mature males and lower sucker counts on normal arms and the hectocotylized arm. The 10th and/or 11th suckers on arms I, II and IV in mature males are enlarged. The mature females produce large eggs. Fragments 658 base pairs in length were obtained from the mitochondrial cytochrome c oxidase subunit I (COI) gene of six specimens of Cistopus chinensis sp. nov. Estimated base frequencies were A = 0.3050, C = 0.1991, G = 0.1418 and T = 0.3541. A + T content was 65.91%. There were two haplotypes that differed by a single nucleotide transition at site 305(A→G). The genetic distance ranged from 0.000 to 0.002 among the individuals of the new species. The closest taxon with respect to genetic distance was C. indicus (0.118–0.121), and the most distant in the genus was C. taiwanicus (0.124–0.126). High bootstrap supported the monophyly of the Cistopus well (bootstrap maximum likelihood 91%, neighbour joining 89%, maximum parsimony 83%).