Tube-dwelling anemones or
ceriantharians look very similar to
sea anemones, but belong to an entirely different
subclass of
anthozoans. They are solitary, living buried in soft sediments. Tube anemones live and can withdraw into tubes, which are made of a fibrous material, which is made from secreted mucus and threads of
nematocyst-like
organelles, known as ptychocysts.