A large southern sea star that splits itself in two to reproduce, so most animals have arms of several different lengths.
To about 50 cm across. Usually eleven arms, though seven to fourteen occur, and characteristically of unequal length because the animal reproduces by splitting in two. Mottled orange, blue, green, grey and red-brown with rows of spines.
The other large southern sea star has five arms.
Surface to a hundred and fifty metres on rock and sand. What a diver sees is the regenerating short arms — a large disc with a few long arms and several stubs, which is a comet, not an injury. It preys actively on mussels and scallops and is treated as a keystone predator. It sheds arms readily if handled.
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.