EUGLENOZOAN FLAGELLA 

Almost all eukaryotic flagella have an internal axoneme made of a cylinder of 9 doublets of microtubules, and a central pair of microtubules. The contractile enzyme, dynein, links adjacent peripheral pairs of microtubules. When ATP is consumed, the dynein moleculas change shape, tension develops between adjacent microtubules, the microtubules slide, and the flagellum bends.

Most flagella bend with a sine-wave which progresses from base to tip. The crests of the wave push against the fluid environment and force the cell backwards (away from the tip of the flagellum). In protists there are a variety of variations on this theme. While some euglenids (e.g. Anisonema) have a flagellum that beats with a sine wave, others (e.g. Euglena) drive loops along the flagellum from base to tip, and in others (e.g. Peranema) the flagella stick to the ground and the cells move by sliding against the substrate. These are illustrated in some of the animations.

Protists also embellish the basic '9+2' flagellar structure. They may have hairs or scales on the outside of the flagellum. They may have additional structures alongside the axoneme (paraxonemal structures). The diagram below, of a Peranema flagellum shows two of the peculiarities of euglenozoan flagella. A crystalline paraxial rod (p) adjacent to the axoneme (a) (this occurs on one of the two flagella), and thin hairs (h) attached to the flagellum in a spiral arrangement. These additions make the flagellum of euglenozoa seem to be much thicker than in other types of cells.