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Dolichospermum (Ralfs ex Bornet & Flahault) P. Wacklin, L. Hoffmann & J. Kom��rek, emend. G.B. McGregor & B.C. Sendall Emended description:��� Filaments planktonic, solitary or aggregated into floccose masses; trichomes isopolar, uniseriate with facultative T-type true branching, metameric with respect to the position of heterocytes, straight, flexuous, circinate, spirally coiled or irregularly twisted, constricted at the cross walls, without firm sheaths, generally with fine diffluent mucilage. Vegetative cells spherical, ellipsoidal, barrel-shaped, quadrate or cylindrical, with aerotopes. Apical cells undifferentiated, morphologically similar to the vegetative cells. Heterocytes intercalary, solitary, exceptionally in pairs; developing from vegetative cells in �� metameric position. Akinetes spherical to cylindrical in shape, developing paraheterocytically, rarely adjacent to heterocytes, generally separated from them by one or more cells, solitary or in series. Mature akinetes usually three or more times larger than vegetative cells. Dolichospermum brachiatum G.B. McGregor & Sendall, sp. nov. (Figs. 1���2, 4) Diagnosis:��� Filaments planktonic, generally straight, and surrounded by a broad hyaline mucilage up to 6.5 ��m wide; facultatively produce T-type true branching (Fig 2). Branching is homothallic, progressing from a lateral bulge in vegetative cells perpendicular to the main filament, and through subsequent cell divisions, continue to elongate; vegetative cells of branches generally similar to, or only slightly broader than the parent filament, apical cells barrelshaped and hyaline. Vegetative cells with aerotopes, �� vacuolate, longer than broad (L: W 1.9 ���6.3) ranging from short cylindrical to elongated club-shaped; 7.7���21.1 ��m long �� 2.8���5.2 ��m broad. Apical cells �� hyaline, elongated and club-shaped (L: W 2.6 ���6.5); 10.8���47.8 ��m long �� 2.6���7.3 ��m broad. Heterocytes spherical to slightly longer than broad; 5.4���11.2 ��m long �� 4.4���7.5 ��m broad. Akinetes solitary or up to two in series, and remote from heterocytes; ovate to elongated cylindrical (L: W 1.2 ���4.2); rounded at the ends; 13.1���33.8 ��m long �� 6.3���10.9 ��m broad (Figs 1 & 4). Etymology:��� The epithet is from the Latin brachiatus ��� branched, in reference to the facultative formation of true branching. Holotype:��� Preserved specimen deposited in the Queensland Herbarium (BRI), accession number AQ1018975. Type locality:��� Waranga Basin, Victoria, Australia (36��33.18���S; 145��6.0���E). Gene sequences:��� 16S���23S rRNA gene sequences���GenBank Accession Nos. MT 535756, MT 535757, MT 535758, MT 535759., Published as part of Mcgregor, Glenn B. & Sendall, Barbara C., 2021, True branching and phenotypic plasticity in the planktonic cyanobacterium Dolichospermum brachiatum sp. nov. (Nostocales, Aphanizomenonaceae), from south-eastern Australia, pp. 93-114 in Phytotaxa 491 (2) on page 105, DOI: 10.11646/phytotaxa.491.2.1, http://zenodo.org/record/5757363

Mcgregor, Glenn B., Sendall, Barbara C. (2021): True branching and phenotypic plasticity in the planktonic cyanobacterium Dolichospermum brachiatum sp. nov. (Nostocales, Aphanizomenonaceae), from south-eastern Australia. Phytotaxa 491 (2): 93-114, DOI: 10.11646/phytotaxa.491.2.1, URL: http://dx.doi.org/10.11646/phytotaxa.491.2.1

Reliable identification of cyanobacterial isolates has significant socio-economic implications as many bloom-forming species affect the aesthetics and safety of drinking water, through the production of taste and odour compounds or toxic metabolites. The limitations of morphological identification have promoted the application of molecular tools, and encouraged the adoption of combined (polyphasic) approaches that include both microscopy- and DNA-based analyses. In this context, the rapid expansion of available sequence data is expected to allow increasingly reliable identification of cyanobacteria, and ultimately resolve current discrepancies between the two approaches.In the present study morphological and molecular characterisations of cyanobacterial isolates (n=39), collected from various freshwater sites in Australia, were compared. Sequences were obtained for the small ribosomal subunit RNA gene (16S rDNA) (n=36), the DNA-dependent RNA polymerase gene (rpoC1) (n=22), and the phycocyanin operon, with its intergenic spacer region (cpcBA-IGS) (n=19). Phylogenetic analyses identified three cyanobacterial orders: the Chroococcales (n=8), Oscillatoriales (n=6), and Nostocales (n=25). Interestingly, multiple novel genotypes were identified, with 22% of the strains (17/77) having