A thin, semi-transparent sea cucumber to about 30 cm (12 in), pale with fine dark longitudinal lines and a ring of feathery tentacles at the head end. It has no tube feet - another of the footless group - and its body is soft enough to drape over whatever it is sitting on, which is almost always a sponge.
That habit is what makes it worth knowing. Dozens of individuals gather on the surface of large barrel and rope sponges, sweeping up the organic film and particles the sponge's own currents deliver, and the aggregations are among the more photogenic things on a shallow reef here. The relationship costs the sponge nothing and appears to keep its surface clean. Forsskål described the species in 1775 from material collected on this coast, so it has been on the region's species list for a quarter of a millennium. The skin carries the same anchor-shaped ossicles as its relatives and feels distinctly sticky, and the body tears easily, so the sensible way to enjoy a colony is with a camera.
- thin translucent body, pale with fine dark lines
- lives in groups on sponges, rarely on the bottom
- ring of feathery tentacles at the head end
- no tube feet
