This is a rather large species of Oscillatoria, a cyanobacteria. Most species are so fine that it is difficult to see the striations even under high magnification. Each filament is made up of sections called homogonia. You can see a division in this speciment. The entire filament is called a trichrome. The tip of the trichrome is swung from side to side using very fine filaments, which can also propel the trichrome.
Images made through a microscope. All subject types.