Scytonemataceae, Rabenhorst ex Bornet et Flahault, 1886

Da Anunciação, Raylane R., Paulino, Jonatas M., Moura, Ariadne N., Iv, H. Dail Laughinghouse & Gama, Watson A., 2024, Morphometric Characterization And The First Taxonomic Synthesis Of Terrestrial Cyanobacteria From The Atlantic Forest In Northeastern Brazil, Phytotaxa 646 (1), pp. 1-31 : 22

Scytonemataceae sp. ( Fig. 13M–O ; 14A–C ).

Filaments entangled with apical portion erected, 7.13–31.08 µm wide. Trichomes heteromorphic, cylindrical, slightly attenuated, with intense scytonematoid geminate or single branched and tolypotrichoid branched, not constricted or constricted in meristematic zones. Sheath firm, 0.86–6.77 µm wide, one lamella present or absent, hyaline to brown. Apical cell rounded-conical. Cells isodiametric, sub-quadratic to short in meristematic zones, 4.32–28.64 µm wide, 2.47–8.92 µm long. Cell content homogeneous to granulated, blue-green to grayish-purple. Basal heterocyte elliptical or cylindrical to short when intercalary, 7.5–20.92 µm wide, 2.35–9.16 µm long. Necridia present. Hormogonia slightly constricted or not constricted, attenuated, with basal heterocyte or not, cell short, apical cell rounded.

Habitat: —Tree bark.

Notes: —The corticolous habitat, heteromorphic filaments, intense scytonematoid branching are the diacritical features that distinguish this morphotype from Scytonemataceae species. This morphotype taxa is similar to Scytonematopsis Kisseleva bur differs from not have trichomes distinctly narrowed towards end.

Studied material:— PEUFR 55793, PEUFR 56636

Family Stigonemataceae (Bornet et Flahault) Borzì (1892: 43) .

Stigonema corticola Sant’Anna, Kaštovský, Hentschke & Komárek (2013: 15) ( Fig. 14D–F ).

Filaments multiseriate, erect, 20–30.49 µm wide, filaments and branches not clearly distinguishable. Sheath firm, non-lamellated, brown. Cell irregular elongated or ± rounded, 5.54–15.65 µm wide. Cell content granulated, blue-green. Heterocyte rounded to semi-spherical, lateral to intercalary, 5.82–11.33 µm wide. Hormogonia numerous, developed in the apical branches.

Habitat: —Tree bark associated with Gloeocapsa sp.1 , Gloeocapsopsis sp. and Dapisostemon sp.

Studied material: — PEUFR 55774

Figures

FIGURE 13. A–C. Scytonema guyanense; D–E. Scytonema javanicum; F–I. Scytonema schmidtii. False branch (arrow); J–L. Scytonema stuposum; M–O. Scytonemataceae sp. Scale: 50 μm (G); 10 μm (to the others).

FIGURE 14. A–C. Scytonemataceae sp.; D–F. Stigonema corticola; G–I. Stigonema fremyi; J–N. Stigonema minutum. O–S. Mastigocladopsis sp.—O. details of the arrangement of the filaments; P. Apical cell; Q. Akinete; E–F. the filament details. Scale: 50 μm (D; G; J; O); 10 μm (to the others).