Sea pen

This sea pen is a colonial Cnidarian in the subclass Octocorollia. The colonies are tapered into a finger-like form and the base of the colony stands upwards on sandy and muddy areas. Polyps, spread along the axis, catch plankton that drifts by.  Usually sea pens in the order of Pennatulacea retract into the sand when disturbed. Through observing a specimen at the Okinawa Churaumi Aquarium, it became clear that it moves within the sand after burrowing itself. This behavior is likely to occur when it is fleeing from a predator or when it needs to move.  Through deep-sea surveys conducted using the aquarium’s remotely operated vehicle, this sea pen has been confirmed in waters off of the main island of Okinawa at depths from 90 to 120 meters. Descriptions of its behavior and its colonial structural features have been published in the international academic journal Marine Biodiversity.

Yuka Kushida, Takuo Higashiji, James Davis Reimer. 2020. First observation of mole-like burrowing behavior observed in a sea pen. Marine Biodiversity. 50: 29."