Tube-dwelling anemoneCeriantharia

Tube-dwelling anemones are solitary, cylindrical cnidarians recognized by two distinct tentacle whorls. The longer, outer tentacles extend widely, reaching a span of 15-30 cm (6-12 in). An inner whorl of shorter, upright tentacles, typically 2-5 cm (1-2 in) long, surrounds the central mouth. Their elongated, worm-like body is housed within a unique, fibrous tube buried vertically in soft sediments. This protective tube is constructed from secreted mucus and specialized stinging cells (ptychocysts). Colours vary, often appearing translucent white, brown, or purple.

These anemones inhabit soft sediments such as sand, rubble, or mud, occurring on sandy flats around reefs and in seagrass beds from shallow depths of 5 m down to 40 m. The long outer tentacles capture small plankton and detritus from the water column, which the inner tentacles then manipulate towards the mouth. When disturbed, tube-dwelling anemones rapidly withdraw their entire body into their tube. Many species are primarily nocturnal, extending their tentacles to feed after dusk.