The sea squirt, whose body is attached by it's underside to the surface and consists almost wholly of a gorge, filters out plankton and organic suspension.
The body of ascidia is covered with tunica, that contains tunicin, a special animal cellular tissue resembling a not typical in animal kingdom cellulose.
Rough, like a cat's tongue Halocynthia papillosa has locked it's siphons and tried to shrink when sensed an intent attention.