Tube anemones

Scientific name : Cerianthus sp. or Pachycerianthus sp.

Worm shaped anemones, living partially buried in the sand, protected by a membranaceous tube made up from a skeleton of discharged nematocysts. Two crowns of tentacles, the external, long and slender, variously coloured, capture the prey and pass it to the internal (oral) tentacles, short.
The internal taxonomy of tube anemones is based upon microscopical characters: it is not possible to determine even the genus without dissection.
As already said, the taxonomy of order Ceriantharia is based upon microscopical characters: it is not possible to determine even the genus without dissection. Three genera exist, the animals in our photos belong to genus Cerianthus or Pachycerianthus, and this is all we can say from the observation in the field. A third genus, Arachnanthus, is identified by the long and curly external tentacles.

Associated organisms
The phoronid worm Phoronis australis, black, at the right, can be fixed at the tube. The crab Lissocarcinus laevis live inside the tube. Commonly associated with commensal shrimps like Periclimenes magnificus.