Folds into a fist all day and opens into a metre-wide net after dark.
A brittle star with a central disc to about 10 cm and five arms that branch repeatedly — each division splitting again, and again, to a final count in the tens of thousands of tips. Cream, tan or brown. By day the whole animal is contracted into a tight ball wedged into a crevice or at the base of a sea fan, and it is easily taken for a lump of dead sponge.
After dark it climbs onto a gorgonian or an exposed edge, orients across the current and unfolds the arms into a filtering net that can span a metre. Prey — small crustaceans and larvae — is caught on hooks along the branchlets, and individual branches curl to pass it inward. A light held on an open animal makes it begin folding within a minute, so the working method on a night dive is to find it, back off, light it obliquely and shoot early, rather than to move in and watch the net close. Recorded from about 5 to 40 m, always where there is current.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.
