A small flattened worm, under 1.4 cm (0.6 in), its back covered in overlapping scales and coloured to match the feather star it lives on - banded when the host is banded, dark when it is dark. It walks along the arms and among the grasping cirri underneath, and is found nowhere else.
Feather stars carry a whole household of small animals that copy them: this worm, a squat lobster, shrimps and clingfish, each matched to its host and each nearly impossible to see until it moves. The worm takes particles the crinoid has caught and gives nothing in return, though it costs so little that the arrangement persists. Finding one means picking a feather star, waiting for it to unfurl at dusk, and watching the arms rather than the animal as a whole.
How to recognise it
- flattened body covered in overlapping scales
- colour and banding copy the host feather star exactly
- walks along an arm rather than swimming
- length up to 1.4 cm
