Purple lines on a pale ground, and the inverse of the commoner lined nembrotha.
A polycerid to about 7 cm, the body cream to pale grey-green and carrying several dark purple longitudinal lines running from the head to the tail, the lines broad, well spaced and sometimes broken. The rhinophores and gill plume are dark purple to maroon. Nembrotha lineolata is the species it is confused with, and the confusion runs both ways in the older literature; the two invert each other, since lineolata carries many fine pale lines on a dark ground while this one carries a few dark lines on a pale one. The question to settle in front of the animal is which of the two, ground or line, is the darker, and how many lines there are.
Feeds on colonial ascidians and is normally found on or immediately beside a colony rather than crossing open ground, often with the oral tube everted into it. It takes up the ascidian’s defensive compounds and secretes them in its mucus, which is the usual explanation for a soft-bodied animal of this size grazing in daylight without cover. Egg masses are cream spiral ribbons laid on the same colony.
Recorded from about 5 to 30 m on the harder ground of a muck site — rock, rubble and jetty structure — wherever the ascidian colonies are.
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.
