Oscillatoria Vaucher ex Gomont, 1892
Key # 8
1.) Classification: Order Oscillatoriales, Family Oscillatoriaceae. There are >60 described
species, of which about 35 are unclear. Many of the planktonic cyanobacteria that were
originally placed in the genus Oscillatoria and had thinner filaments and differing cellular
structure have been reclassified into the genera Planktothrix, Pseudanabaena, or
Limnothrix (Komárek and Johansen 2015b).
2.) Form: Filamentous.
3.) Groups: Forming fine, smooth, layered, slimy mats on submerged surfaces. These mats
can be up to several centimeters in diameter.
4.) Sheath: Observed only in the early transitional stages of a hormogonium developing
into a filament.
5.) Filaments: Uniseriate, straight or wavy, 8–60μm wide, unbranched; apical end tapered,
basal end truncated.
6.) Cells: Short, discoid, shorter than wide, with variable crosswall constriction.
End cells are rounded, capitate, and with a calyptra. Filaments tremble and oscillate.
Heterocysts: Absent.
Akinetes: Absent.
Aerotopes: Absent.
7.) Color: Varies from blue green to brownish or pinkish.
8.) Replication: Filament disintegration into short, motile hormogonia by necridic cells.
Cells divide perpendicular to the long axis; most cells can divide; no meristematic zones.
9.) Habitat: Mostly in mats on substrates in shallow freshwater or marine littorals;
rarely on wet soils. Clusters can be found floating at the surface. They are distributed
worldwide, but several are limited geographically.
10.) Similar genera: Lyngbya and Phormidium cells are discoid; no heterocysts or akinetes.
Oscillatoria has no sheath; both Lyngbya and Phormidium have sheaths.
Oscillatoria mats break up easily; Lyngbya and Phormidium mats are tougher; cohesive.
Oscillatoria cells are shorter than wide; Phormidium cells are more evenly square.
Oscillatoria filaments are motile; Lyngbya and Phormidium filaments are not motile.
Nodularia and Oscillatoria both have discoid cells. The distinction is that Oscillatoria
cells are regularly arranged in their filaments: they are stacked straight. Oscillatoria
filaments also do not taper very much toward their ends. Nodularia cells are not directly
centered on top of the preceding cell in the filament, the cells are off-axis, they are not
"stacked straight". The filaments tend to taper toward their ends.
11.) Toxins: Anatoxin-a, microcystins, aplysiatoxins, saxitoxins, and lyngbyatoxin-a reported.
12.) Distinguishing features: Oscillatoria has discoid cells that are wider than tall and no
heterocysts, akinetes, or sheath. The filaments oscillate and tremble and the mats are
easily pulled apart. MAN
Oscillatoria_01
Oscillatoria is a very diverse group of motile, filamentous cyanobacteria. The
cells are shorter than wide with the end cells rounded. No heterocysts. They are
mostly found in the form of mats on submerged surfaces in shallow water.
This is from a shallow water sample taken from Camp Ernst Lake, Burlington,
KY, USA on October 16, 2014. 400X Magnification.
Oscillatoria_02
Same information as Oscillatoria_01.
Oscillatoria_03
This is a still image of a thinner Oscillatoria filament (O) winding its way around
a larger, green alga filament. This is from a shallow water sample taken from
A.J. Jolly Lake, Alexandria, KY, USA on October 21, 2014. 400X Magnification.
Oscillatoria_04
This is a good comparison/contrast between Oscillatoria (O) and a somewhat
similar genus, Nodularia (N). Both are filamentous with discoid cells. The
Oscillatoria cells are arranged in a very regular “stack” within the filament
with little/no tapering. The Nodularia cells are not so; they are not stacked
straight and begin to taper in size. Also present are the cyanobacteria
Pseudanabaena (P), Spirulina (S) plus a variety of Diatoms (d). This
specimen was found in a shallow water sample from north shore of
Lake Yambo, Ecuador, taken in 2014. 400X Magnification.