It’s like a mole?! Discovery of new behaviors in a species of sea pen.

Okinawa Churaumi Aquarium is proud to announce the world’s first successful recording of undocumented behaviors in a species of sea pen. This was achieved through collaborative research with the University of the Ryukyus and published in an academic journal.

A species of sea pen
Scientific name：Echinoptilum sp.

Sea pens are marine organisms in the phylum Cnidaria, class Anthozoa, and subclass Octocorollia.
This species can burrow through the sand and later emerge from it. The colony has many polyps which feed on plankton that drifts by.
The specimen described in the study was collected in April 2019 at a depth of 120 meters off the coast of Motobu. It’s behavior was filmed from April to May 2019. Collection was achieved with an ROV (Remotely Operated Vehicle) owned by the Churashima Foundation that manages and operates the Okinawa Churaumi Aquarium.

Recording video images of the sea pen enabled the analysis of its movements that revealed many unreported behaviors. We successfully captured footage of it burrowing in the sand similar to a mole several times. Other species of Anthozoans use peristaltic movements to move on the surface of the sand, burrow up and down, and to clear off sediments that have accumulated on its body. However, this was the first time in the world to discover this particular behavior of moving within sand. The worm-like shape of the sea pen, lack of a solid axis, retractable polyps (autozooids) and its three-flanged sclerites are all physical traits that assist in this unusual mole-like behavior.

The recorded footage is shown on the monitor beside the exhibit tank as well as on the Okinawa Churaumi Aquarium’s YouTube channel. (https://www.youtube.com/watch?v=JYtnsjOsdqw)

Place of exhibit

Small Life in the Deep Sea in the Okinawa Churaumi Aquarium

Size of Exhibit

One individual (about 12cm in length)

Exhibit starts from

2019 June 2nd
*Exhibit may close depending on the condition of the animals.

Detailed results are described in the following international academic journal.
Journal: Marine Biodiversity. https://doi.org/10.1007/s12526-020-01054-y
Title：First observation of mole-like burrowing behavior observed in a sea pen.
Authors: Yuka Kushida, Takuo Higashiji and James Davis Reimer