Iningainema pulvinus G.B. McGregor & B.C. Sendall (2017: 17)

Mcgregor, Glenn B., 2018, Freshwater Cyanobacteria of North-Eastern Australia: 3. Nostocales, Phytotaxa 359 (1), pp. 448-450 : 448-450

Iningainema pulvinus G.B. McGregor & B.C. Sendall (2017: 17) Figs. 70 A–E, 71 A–F, 72 A–B .

Filaments densely arranged, radiating from the centre of spherical to discoid, blue-green to olive-green colonies, 5–25 mm in diameter. Filaments isopolar, uniseriate, cylindrical, straight or flexuous, 20–39 μm in diameter, main filament generally wider than the lateral filaments which gradually taper to a bluntly conical end; with single or geminate false-branching. Sheath firm, lamellated, uncoloured to yellowish or yellow-brown, closed at the apex. Vegetative cells isodiametric to shorter than broad, slightly constricted at the cross walls, 3.3–8.2 μm long × 18.0–27.5 μm wide in the main filament, 3.5–5.0 μm long × 4.2–12.0 μm wide in lateral branches, with granular contents. Heterocytes basal and intercalary, solitary, spherical to compressed-ovoid, 6.3–9.5 μm long × 11.0–19.0 μm wide. Akinetes absent.

Specimens examined:—Edgbaston Reserve.

Observations:—Morphologically, Iningainema is most like Scytonematopsis Kiseleva and Scytonema Agardh ex Bornet & Flahault.All three genera have isopolar filaments enveloped by a firm, often layered and coloured sheath; false branching is typically geminate, less commonly singly ( Komárek et al. 2013). In Iningainema and Scytonematopsis , filaments gradually narrow towards the apices. The false branching ontogeny in Iningainema is distinctive. It initiates via trichome fragmentation through the formation of a necridic cell, however rather than forming a lateral protrusion at the site of fragmentation, the trichome continues parallel growth within the sheath for a short distance, often leading to trichome contortions and filament bulging, prior to lateral protrusion. Subsequently the filaments can be thickened or have a slight nodular appearance at the branching sites. This species is known to produce the hepatotoxin nodularin (McGregor & Sendall 2017).

HETEROSCYTONEMA

Figures

FIGURE 72. Colonies of Iningainema pulvinus growing on the benthos in shallow wetlands.