Cladosiphon umezakii sp nov (Ectocarpales, Phaeophyceae) from Japan

The new species Cladosiphon umezakii Ajisaka (Ectocarpales, Phaeophyceae) is described from Japan based on morphology and DNA sequences. The species resembles Cladosiphon okamuranus Tokida in its gross morphology; somewhat slimy, cylindrical, multiaxial and sympodial erect thallus, arising from a small disc-shaped holdfast, and branching once to twice. However, C. umezakii has considerably longer assimilatory filaments (up to 840 mu m long, composed of up to 90 cells) than any known taxa of the genus. The species is a winter to spring annual, growing on lower intertidal to subtidal rocks of more or less exposed sites on the north-eastern coast of Kyushu and on both the Pacific and the Sea of Japan coasts of Honshu. Specimens from the Sea of Japan coast had both unilocular and plurilocular zoidangia, whereas those from Kyushu and from the Pacific had only unilocular zoidangia. Unilocular zoidangia were formed on the basal part of assimilatory filaments, and plurilocular ones were transformed from the distal part of assimilatory filaments. DNA sequences of the Rubisco-spacer (rbc-spacer) region and the nuclear rDNA ITS region (ITS1, 5.8S and ITS2) supported the distinctness of the species.