Image: Reed College
You're to be forgiven for thinking that cilia are gross. They're the squirmy, wavering appendages found on nearly all of the cells in the human body, helping cells sense and manipulate their environment in some cases—doing the front-line work of the eyes and nose, for example, or keeping your airways clean of snot and assorted bad, nasty things—and in others acting as kind of swimmy propulsion mechanisms. The rhythmic beating of cilia may enable a single-celled creature to move around, like creepy nano-arms.
In one strange case, cilia are used by a relatively large creature for mobility. Ctenophora, aka the "comb jelly," can be found up to over a meter in length, yet still propel themselves around underwater by way of rows of cilia (the "comb"). This variety of jelly creature is likened to the terrestrial spider, just because it's adapted to so many different ways of killing prey. As creepy as they are, the jellies are beautiful too, refracting light through their bodies in unexpected pulses of color. You can see it in the video above, courtesy of Brown University (via Science360).