| Abstract: | The new species Tinocladia sanrikuensis sp. nov. H.Kawai, K.Takeuchi & T.Hanyuda (Ectocarpales s.l., Phaeophyceae) is described from the Pacific coast of the Tohoku region, northern Japan based on morphology and DNA sequences. The species is a spring–summer annual growing on lower intertidal to upper subtidal rocks and cobbles on relatively protected sites. T. sanrikuensis has a slimy, cylindrical, multiaxial erect thallus, slightly hollow when fully developed, branching once to twice, and resembles T. crassa in gross morphology. The erect thalli are composed of a dense medullary layer, long subcortical filaments, and assimilatory filaments of 11–35 cells, up to 425 μm long and curved in the upper portion. Unilocular zoidangia are formed on the basal part of assimilatory filaments. The species is genetically most closely related to T. crassa and has the same basic thallus structures but differs in having thinner and longer assimilatory filaments. DNA sequences of the mitochondrial cox1 and cox3, chloroplast atpB, psaA, psbA and rbcL genes support the distinctness of this species. |
