Stream macroalgae of Hawai`i: an identification guide - Hawaii.gov

Scytonema
Classification: Cyanobacteria (Family
Scytonemataceae)
General habit: a falsely branched cyanobacterium
that forms thick mats or tufts than can be
abundant in streams, often yellowish-brown in color
from pigmentation, most commonly attached to rock
surfaces
Species in Hawai‘i: S. archangelii, S. chiastum, S.
coactile, S. crispum, S. figuratum, S. fritchii, S.
guyanese, S. hofmannii, S. myochrous, S. ocellatum,
S. rivulare, S. stuposum, S. tolypothricoides, S.
varium, Scytonema sp.
Island distribution: Kaua‘i, O‘ahu, Maui, Hawai‘i
Distinguishing features: false branches normally
occur in pairs in this genus (Figs B, D, E), only a
single filament is contained within the surrounding
sheath, sheath can be thick and layered in
appearance and often highly pigmented in Hawaiian
specimens
Compare with: Dichothrix, Tolypothrix
21
A. A tuft of Scytonema as viewed under a dissecting
microscope. Scale bar = 1cm. B. Filament of
Scytonema under a compound microscope illustrating
double false branching. Scale bar = 25µm.
C. A heterocyst of Scytonema. Scale bar = 25µm.
D, E. Double false branching of Scytonema filaments.
Scale bar = 25µm (D), 30µm (E).