A dark green sacoglossan to about 5 cm (2 in) whose flaps and back are covered in short papillae, giving the felted texture behind the name. Pale speckling breaks up the outline further, and on the feathery Caulerpa it feeds from the animal effectively disappears.
Caulerpa is chemically defended - it carries caulerpenyne, which deters most grazers - and this slug not only eats it but appears to take the defense along with the meal, becoming unpalatable itself. The chloroplasts are kept too, so the animal photosynthesises while it digests. Sheltered shallow bays with soft sediment and standing weed are where to look; on open reef it is absent. Records here are few, which reflects both a genuinely patchy distribution and the fact that almost nobody searches Caulerpa beds with a torch.
- surface covered in short papillae, giving a felted look
- dark green with pale speckling
- on Caulerpa weed in calm shallow water
- length up to 5 cm
