“Tube Anemone” (Cerianthus filiformis)
…a species of tube-dwelling anemone (Ceriantharia) which is widespread throughout tropical waters in the Indo-west Pacific. Unlike the unrelated sea anemones tube-dwelling anemones have specialized cindocytes known as ptychocysts which create a sticky surface which helps the “anemone” create the tube which it dwells in. However like sea anemones Cerianthus filliformis also feeds on passing organic materials which passes by its tentacles. If disturbed C. filliformis can retract itself inside its tube for safety.
Image: Massimiliano De Martino