- In some parasitic flagellates such as trypanosomes and trichomonads, undulating membrane is a fin-like extension usually associated with the flagellum. The presence of undulating membrane enhances motility of the parasite in a viscous fluid, such as blood. (Minchin 2003)
- In some ciliates such as Tetrahymena, an undulating membrane is made up of a row of fused cilia and assumed to aid in capturing food. (Minchin 2003)
- In spermatozoon of some animals such as some sarcopterygian fish and toads (Bufo marinus). ( Birkhead and others 2009)
- Birkhead TR, Hosken, DJ, Pitnick, S. 2009. Sperm biology an evolutionary perspective. Amsterdam: Elsevier/Academic Press, p.112-113.
- Minchin E. 2003. Protozoa microbiology & guide to microscopic identification. Palm Springs (CA): Wexford College Press, p. 55-56.