A green slug to about 3 cm (1.2 in) that still carries a shell - a small thin one at the rear, partly covered by the mantle, which is unusual in a group that has otherwise abandoned it. The tail is long and pointed, the side flaps small, and the animal is invariably found on Caulerpa.
That dependence is total: the slug feeds on nothing else, colors itself with the alga's chloroplasts and lays its eggs on the same fronds. Disturbed, it secretes a white sticky mucus and can shed the tip of its tail, which writhes and holds attention while the animal moves off. The genus is also chemically armed, carrying compounds derived from Caulerpa's own defenses. Sheltered bays with standing Caulerpa in the top few meters are the place to look, at night, and the search is for the weed first and the slug second.
- carries a small thin internal-looking shell at the rear
- green body with a long pointed tail
- flaps small relative to the body, not leaf-like
- always on Caulerpa weed
