Black with electric blue lines and two tails, gliding over sand after flatworms.
A headshield slug to about 6 cm, velvet black with two or three lines of intense electric blue running along the body and around the head shield, and with the rear of the foot drawn out into two unequal tails, the left longer than the right. It is not a nudibranch: headshield slugs are cephalaspideans, and the flattened shield across the front of the head is the structure that lets them plough through sediment without it entering the mantle cavity.
Hunts acoel flatworms, following their mucus trails across sand and algae film and engulfing them whole with a muscular pharynx — it has no radula. A slug moving in a purposeful straight line across open sand is following a trail. It is active in daylight, which for a soft animal this conspicuous means the colours are a warning rather than an accident. Recorded from the shallows to about 25 m. Fast for a sea slug, and it does not stop, so the frame is taken by getting in front of it.
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.
