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Systematic relationships between representative Leathesia species (i.e. Leathesia difformis, L. japonica, L. pulvinata and L. sphaerocephala) and related taxa (i.e. Corynophlaea cystophorae and Kurogiella saxicola) within the Ectocarpales s.l. were re-examined based on the combined DNA sequences of plastid rbcL and mitochondrial cox3 genes. Resultant molecular phylogenetic trees showed polyphyly of Leathesia species; Leathesia japonica, L. sphaerocephala and L. pulvinata (members of Leathesia section Primariae), which share solid thallus construction, grouped together with Botrytella spp. rather than L. difformis (generitype; section Leathesia), which was close to Elachista tenuis and Cladosiphon okamuranus. Leathesia japonica clustered with Botrytella species rather than L. sphaerocephala and L. pulvinata. A close phylogenetic relationship between L. japonica and Botrytella species was supported by the occurrence of the characteristic free, sympodially branching filaments forming clustered plurilocular zoidangia in L. japonica, resembling Botrytella in culture and field-collected material. Based on these molecular phylogenetic analyses and morphological characteristics, we propose the establishment of Phaeophysema gen. nov. to accommodate L. sphaerocephala and L. pulvinata, and Vimineoleathesia gen. nov. to accommodate L. japonica. [ABSTRACT FROM AUTHOR]

The genetic structure and phylogeography of the brown seaweed Sargassum horneri/filicinum complex in Japan were studied based on the mitochondrial cox3 haplotype. The cox3 haplotypes found were divided into three clades in a statistical parsimony network, among which there were large numbers of steps. Contrary to the reported large amount of drifting S. horneri along the Japanese coast, the three clades were dividedly distributed on the Japanese coast: the northern Pacific, the central Pacific, and western Japan. The western Japan S. horneri had haplotypes that were phylogenetically closer to those of S. filicinum than to the northern and central Pacific S. horneri populations. The S. filicinum populations were included within the western Japan clade and grouped together with the S. horneri samples from western Japan. Taken together with the unstable morphological diagnosis, this result suggests that S. filicinum should be reduced into a synonymy of S. horneri. The TMRCA analysis suggested that the divergence time of each clade may go back to the last interglacial period and a skyline plot suggested that the last glacial maximum had only a small effect on the population size of S. horneri. The geographic subdivision of the three groups, in spite of a large amount of drifting mats, suggests a limited contribution of drifting mats to gene flow on a large geographic scale. On a small geographic scale, a small number of haplotypes were shared between S. horneri-type and S. filicinum-type populations. This result suggests that populations of these two types are partially, though not completely, isolated from each other, possibly by selfing in S. filicinum-type populations or by a difference in peak reproduction. [ABSTRACT FROM AUTHOR]

The presence or absence of gamete fusion in the dioecious and isogamous brown alga Scytosiphon lomentaria (Scytosiphonaceae, Phaeophyceae) was investigated for thalli collected from three localities, Oshoro, Asari and Muroran in Hokkaido, northern Japan. Both sexual and asexual thalli were found in each locality. These sexual (35 samples) and asexual thalli (15 samples) were used to establish unialgal cultures. ITS2 sequences were determined in all cultures, the rbc L-spacer-S in 14, and cox 3 in 25 cultures. Thirteen haplotypes (A1–4, B, C1–4, D, E1–3) were found in ITS2 sequences (241–252  bp). Ten haplotypes (A1–4, B, C1–4 and D) were found in sexual samples: haplotypes A and B were found in Oshoro, C and D in Asari, and C in Muroran. Haplotypes E1–3 were found in asexual samples. Sequence divergence values (including gap information) were less than 4.03% among sexual samples (A, B, C and D types), 0.38–0.77% among asexual samples (E types) and 4.39–5.70% between sexual and asexual samples. In the mitochondrial cox 3 gene region (543  bp), six haplotypes (K1–3, L, M and N) were obtained. Cox 3-K types were found in samples of ITS2-A types, cox 3-L type in ITS2-B type, cox 3-M type in ITS2-C and D types, and cox 3-N type in ITS2-E types. For cox 3 sequences, nucleotide differences were 0.18–4.42% among sexual samples (K, L and M types), but 8.66–10.31% between sexual and asexual samples (N type). In partial rbc L (174  bp)-spacer (188  bp)-partial rbc S (90  bp) sequences, six haplotypes (R–W) were found although there were 1–4  bp nucleotide differences among these haplotypes. R, U and W types were found in sexual samples, and S, T and V types in asexual samples. Results of the sequence analyses suggest that our presumed asexual thalli are genetically different from sexual thalli and may be derived from populations that lack sexual reproduction. [ABSTRACT FROM AUTHOR]

A small prostrate filamentous brown alga, isolated from the warm temperate Pacific coast of Japan, was cultured to investigate its life history, morphology, ultrastructure and molecular phylogenetic position. The isolate had an isomorphic, diphasic life history with anisogamous sexual reproduction. Gametogenesis was regulated by temperature and occurred only at temperatures =14°C. At higher temperatures, gametophytes reproduced by means of asexual zoids. All swarmers from plurilocular and unilocular zoidangia lacked an eyespot. Both sporophytes and gametophytes had oligostichous filamentous axes, lateral hairs with a basal sheath and no erect thalli. Three to eight oblong chloroplasts, each with a protruding pyrenoid, aggregated to form a stellate chloroplast configuration. All these morphological features suggested that this alga belongs to the genus Asterocladon . Plurilocular gametangia produced in an intercalary or terminal position and zoids lacking eyespots, are, however, unlike those of Asterocladon lobatum , formerly the only member of the genus. Therefore, we described the alga as a new taxon, Asterocladon interjectum sp. nov. Molecular phylogenetic analyses based on the large RUBISCO subunit ( rbc L) and partial SSU nuclear ribosomal RNA gene sequences showed that A. interjectum , A. lobatum and Asteronema rhodochortonoides together formed a monophyletic clade, sister to the Ectocarpales sensu lato . Because the molecular phylogenetic analyses showed Asteronema to be paraphyletic, but monophyly of Asterocladon spp. and Asteronema rhodochortonoides was supported by the absence of cytoplasmic invaginations in pyrenoids, Asteronema rhodochortonoides was transferred to Asterocladon and an emended generic circumscription of Asterocladon was included. [ABSTRACT FROM AUTHOR]

Describes the morphological features of the red algae Hypnea cornuta and compares the chloroplast-encoded rbcL sequence to that of the type variety and the additional species of the genus. Taxonomic status of red alga; Description of the species of the Ceramiales recorded from Malaysia.

A taxonomic study of two brown algal species, Elachista nigra Takamatsu and Elachista orbicularis (Ohta) Skinner (Elachistaceae), was performed on the basis of morphological observations of field-collected and laboratory cultured specimens from Japan (including their type localities) and molecular phylogenetic analyses. The two species had been distinguished by developmental patterns of paraphysis- and plurizoidangium-bearing erect filaments, such filaments of E. nigra developing from wide erect filaments and those of E. orbicularis developing directly from basal prostrate filaments. However, many specimens investigated in the present study showed forms intermediate between these two patterns. Molecular phylogenetic analyses (including five additional elachistacean species) based on the internal transcribed spacer (ITS)2 region of the nuclear ribosomal RNA (nrRNA) gene showed a close relationship between all samples of E. nigra and E. orbicularis, and that the developmental patterns of paraphysis- and plurizoidangium-bearing erect filaments were homoplasious. On the basis of these morphological and molecular data, E. orbicularis was reduced to synonymy with E. nigra. The ITS2 sequences of E. nigra were significantly different between samples from the Sea of Japan and those from the Pacific Ocean with several insertion/deletion and substitution mutations. [ABSTRACT FROM AUTHOR]

SUMMARYElachista fucicola (Velley) Areschoug (Elachistaceae, Phaeophyceae) is newly recorded from Japan, and compared with three previously described species, Elachista coccophorae Takamatsu, Elachista mollis Takamatsu and Elachista okamurae Yoshida. All species showed direct-type life histories in culture without sexual fusion. Prostrate filaments of E. fucicola formed globular plurilocular zoidangia similar to those reported from Atlantic isolates of this species. However, these were different from uniseriate plurilocular zoidangia of the three Japanese species. Furthermore, the position of a meristematic region in assimilatory filaments and the morphology of paraphyses can easily distinguish these from E. fucicola. Previously emphasized differences in cell length: width ratios in assimilatory filaments showed only slight differences. Elachista coccophorae is characterized by thick-walled assimilatory filaments and curved paraphyses, and the absence of downwardly growing rhizoidal filaments. Elachista mollis and E. okamurae are very similar. However, germlings from plurizoids formed on erect filaments of E. mollis showed characteristic pseudodiscoid growth in culture. Halothrix coccophorae Ohta and Elachista zosterae Noda are reduced to synonyms of E. coccophorae and E. mollis, respectively. [ABSTRACT FROM AUTHOR]