ceriantharians

Ceriantharians are a group of marine invertebrates belonging to the order Ceriantharia. They are commonly known as tube-dwelling anemones or, more accurately, as "keniops" or "flower animals." These animals are distinct from true sea anemones (order Actiniaria) and are characterized by their solitary, elongated bodies that are housed within a protective tube.

The tube itself is not secreted by the ceriantharian but is constructed from mucus and a secreted chitinous material, reinforced with sand, shells, and other debris collected from the surrounding environment. Ceriantharians anchor themselves in soft substrates such as sand or mud, with their tubes extending vertically. The oral end of the animal, bearing two distinct whorls of tentacles, protrudes from the tube. The outer whorl of tentacles is typically longer and used for capturing prey, while the inner whorl is shorter and may play a role in feeding or respiration.

Ceriantharians are found in marine environments worldwide, from shallow coastal waters to the deep sea. They are carnivorous, feeding on small planktonic organisms and small invertebrates that drift within reach of their tentacles. Reproduction can be both sexual and asexual, with some species exhibiting budding. Their classification within the phylum Cnidaria is still debated, but they are generally placed within the class Anthozoa, alongside corals and true anemones. Despite their anemone-like appearance, their unique tube-dwelling lifestyle and tentacle arrangement set them apart.