Mastigonemes are lateral "hairs" found covering the flagella of heterokont and cryptophyte algae^[1]. They are approximately 15 nm in diameter, and usually consist of a tubular shaft that itself terminates in smaller "hairs". It is believed that they assist in locomotion by increasing the surface area of a flagellum.

References

1. ↑ Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). Algae : An introduction to phycology, Cambridge University Press, UK.