Soft, black and abundant in the shallows; the fine red margin line is the useful mark.
A soft-bodied dorid to about 6 cm and usually smaller, uniformly black to very dark brown with a fine red to orange line round the mantle edge, which flares and ripples as the animal crawls. Young animals often carry scattered white spots that are lost as they grow. The soft body separates it from Phyllidiella nigra, which is hard and rubbery, carries raised pink tubercles and has no gill plume at all. Dendrodoris fumata is the harder problem: dark individuals of that species are not reliably separable from this one in the water, and the two are regularly swapped in photo libraries.
Dendrodorids have no radula. They feed by pressing the mouth against a sponge, releasing digestive fluid into it and drawing the liquefied tissue back up, which is why an animal can sit apparently motionless on one patch of sponge for a long time. Recorded from the intertidal to about 15 m on rubble, dead coral and jetty structure, and one of the commonest sea slugs in the first few metres.
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.
