A flat ctenophore that lives on soft corals and sea stars, fishing with two long tentacles.
A soft flattened animal to about 3 cm across, spread as a thin sheet over the surface of its host and usually close to it in colour, so that a red-orange one on Dendronephthya and a white one on a sea star are both easy to pass over. Two long branched tentacles are extended from openings on the upper surface and trail into the water, reaching fifteen centimetres or more, and they are what is normally noticed first. They are withdrawn completely into sheaths when the animal is disturbed, at which point almost nothing is left to see.
It is a ctenophore and not a flatworm and not a nudibranch, though it is filed with both by divers. The tentacles carry colloblasts, adhesive cells that hold small prey rather than stinging it, and the tentacle is drawn in and wiped across the mouth on the underside once something is caught. The comb rows that give the group its name are present only in the larva and are gone in the adult, which crawls on a ciliated sole instead of swimming.
Hosts recorded include soft corals, sea whips, sponges, sea stars and sea cucumbers, and the animal is found by searching the host rather than the ground. Recorded from about 5 to 30 m.
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.