Mai T., Johansen J.R., Pietrasiak N., Bohunicka M., Martin M.P. Revision of the Synechococcales (Cyanobacteria) through recognition of four families including Oculatellaceae fam. nov. and Trichocoleaceae fam. nov. and six new genera containing 14 species // Phytotaxa, 2018. V. 365. N. 1. P. 1-59. https://doi.org/10.11646/phytotaxa.365.1.1
Diagnosis:―Distinguished from the other species of the genus by its meristematic zones and false branching, and by its wide variability in trichome width. Description:—Colony brownish or purplish-brown, forming floating, mucilaginous mats in liquid culture.
Filaments long or short. Mature filaments 2.8–3.7 μm wide (Figs. 16a, g–h), young filaments narrower, 2.3–2.8 μm wide (Figs. 16b–f), occasionally with false branching (Fig. 16a–b). Sheath firm, colorless, thin to occasionally enlarged (Figs. 16c–e) and lamellate (Fig. 16e), up to 4.4 μm wide. Trichomes not or slightly constricted at cross-walls, cylindrical, with compacted coils at meristematic zones (Figs. 16a,g), 1.5–2.1 μm wide in young trichomes and 1.7–3.0 μm wide in mature trichomes. Hormogonia absent. Cells longer than wide and occasionally elongated, (2.2) 3.1–4.5 μm long, or in meristematic regions isodiametric, 2.0–2.6 μm long, with one central granule present in both young and mature cells. Necridia present (Fig. 16h). End cells cylindrical, rounded. D1-D1’ helix 64 nucleotides long, with 3’ unilateral bulge of 7 nucleotides (5’-CAUCCCA-3’). Mid-helix region with a mismatch at position 24/34–35 immediately separated from the terminal loop by a 5’-GC:GC-3’ clamp, and two mismatches at position 9 (C/U) and 21 (G/A) on the 5’ strand. Terminal loop having sequence 5’-AAUCA-3’ (Fig. 6f). Box B helix 34 nucleotides long, with one basal internal loop at position 5/29–30 and one unpaired adenine residue at position 9 of the 5’ strand (Fig. 7e). V2 helix 21 nucleotides long, with terminal loop having sequence 5’-AAUAU-3’ (Fig. 8c). V3 helix 51 nucleotides long, with one large internal loop at position 10–12/39–41 and one unpaired guanine residue at position 46 on 3’ strand. Terminal loop sequence 5’-UUAG-3’ (Fig. 9f).
