title: On the fourth Diadema species (Diadema-sp) from Japan.
abstract: Four long-spined sea urchin species in the genus Diadema are known to occur around the Japanese Archipelago. Three species (D. savignyi, D. setosum, and D. paucispinum) are widely distributed in the Indo-Pacific Ocean. The fourth species was detected by DNA analysis among samples originally collected as D. savignyi or D. setosum in Japan and the Marshall Islands and tentatively designated as Diadema-sp, remaining an undescribed species. We analyzed nucleotide sequences of the cytochrome oxidase I (COI) gene in the "D. savignyi-like" samples, and found all 17 individuals collected in the mainland of Japan (Sagami Bay and Kyushu) to be Diadema-sp, but all nine in the Ryukyu Archipelago (Okinawa and Ishigaki Islands) to be D. savignyi, with large nucleotide sequence difference between them (11.0%±1.7 SE). Diadema-sp and D. savignyi shared Y-shaped blue lines of iridophores along the interambulacrals, but individuals of Diadema-sp typically exhibited a conspicuous white streak at the fork of the Y-shaped blue iridophore lines, while this feature was absent in D. savignyi. Also, the central axis of the Y-shaped blue lines of iridophores was approximately twice as long as the V-component in D. savignyi whereas it was of similar length in Diadema-sp. Two parallel lines were observed to constitute the central axis of the Y-shaped blue lines in both species, but these were considerably narrower in Diadema-sp. Despite marked morphological and genetic differences, it appears that Diadema-sp has been mis-identified as D. savignyi for more than half a century.
authors: National Research Institute of Fisheries Science, Yokohama, Kanagawa, Japan.
authors: Seinen
authors: S
authors: Chow
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Yoshikazu
authors: Y
authors: Kajigaya
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Hiroaki
authors: H
authors: Kurogi
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Kentaro
authors: K
authors: Niwa
authors: Yokosuka Laboratory, National Research Institute of Aquaculture, Yokosuka, Kanagawa, Japan.
authors: Takuro
authors: T
authors: Shibuno
authors: Ishigaki Laboratory, Seikai National Fisheries Research Institute, Ishigaki, Okinawa, Japan.
authors: Atsushi
authors: A
authors: Nanami
authors: Seikai National Fisheries Research Institute, Nagasaki, Nagasaki, Japan.
authors: Setuo
authors: S
authors: Kiyomoto
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics*; D005843:Geography; D007564:Japan; D008969:Molecular Sequence Data; D010802:Phylogeny; D012617:Sea Urchins / Q000033:anatomy & histology* / Q000145:classification / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D003576:Electron Transport Complex IV