These large tangled masses of tentacles are basket stars, some of the more complex looking brittlestars. Reaching up to about a meter in diameter, they hide away in dark holes in the reef by day and emerge at night to stand facing into the current on rocky or coral outcrops with their branching, many tendriled arms forming the shape of a radar dish to capture passing plankton. At the base of the arms is a ball of curling, branching tentacles. They are very light sensitive; even pointing a flashlight at them causes them to start folding up and running for cover. At Kwajalein, they are relatively common at night on the seaward reef slope at depths of about 10 to at least 30m.
The mass of branching tentacles at the base of the arms. Sometimes you can spot the commensal shrimp Lipkemenes lanipes moving through the tangle of tentacles.
By day, they live folded up in dark holes in the reef like the one below.
Sometimes a diver's bubbles will sufficiently irritate one to make it come out to look for another place to hide.
Created 16 January 2019