Potamosiphon G.B. McGregor & B.C. Sendall, 2019

Mcgregor, Glenn B. & Sendall, Barbara C., 2019, Potamosiphon australiensis gen. nov., sp nov. (Oscillatoriales), a new filamentous cyanobacterium from subtropical north-eastern Australia, Phytotaxa 387 (2), pp. 77-93 : 87

Potamosiphon G.B. McGregor & B.C. Sendall gen. nov. ( Fig. 1 )

Diagnosis:— Filaments single, or forming loose aggregations amongst littoral vegetation; straight or slightly flexuous. Sheath colourless, hyaline, lamellated when mature, open at the apex. Trichomes isopolar, cylindrical, not or slightly constricted at the cross walls. Vegetative cells discoid, 7–10 × broader than long; contents finely granular, without aerotopes; apical cell rounded, without calyptra or thickened outer cell wall. Reproduction by motile hormogonia formed by necridia, or by diagonal fragmentation without the formation of necridia.

Etymology:— Potamo (Gr.) river or stream, siphon (Gr.) tube or pipe.

Type species:— Potamosiphon australiensis G.B. McGregor & B.C. Sendall sp. nov.

Potamosiphon australiensis G.B. McGregor & B.C. Sendall sp. nov.

Diagnosis:— Filaments single, or forming loose aggregations amongst littoral vegetation; straight or flexuous, up to 21 μm wide. Sheath colourless, hyaline, lamellated when mature, open at the apex. Trichomes isopolar, cylindrical, not or slightly constricted at the cross walls. Vegetative cells discoid, 7–10 × broader than long, 1.7–2.5 μm long × 15.7–17.8 μm wide; contents finely granular, without aerotopes; apical cell rounded, without calyptra or thickened outer cell wall. Reproduction by motile hormogonia formed by necridia, or by diagonal fragmentation without the formation of necridia.

Etymology:— australiensis , from Australia

Holotype:— Preserved specimen deposited in the Queensland Herbarium , accession number BRI ( AQ826842 ).

Type locality:— Fat Hen Creek at Kilkivan Bush Camp (26 o 06’59” S, 152 o 17’23” E).

Gene sequences:— 16S rRNA gene sequences–GenBank Accession Nos. MH 047860, MH 047861, MH 047862; nifH gene sequences–GenBank Accession Nos. MH 057664, MH 057665, MH 057666.

Figures

FIGURE 1. Morphology of Potamosiphon australiensis (A–F) mature filaments with lamellated sheaths, (C–D) diagonal trichome fragmentation, (B, E, G) trichome fragmentation following formation of necridia; scale bar = 30 μm.