Identification: five short, sturdy arms and a domed central disc; a row of dark conical horns on each arm and a cluster on the disc, which may wear blunt. Colour varies: cream, light tan, orange, red, brown, sometimes blue or yellow depending on origin; white underside, purple or pale pink tube feet. 15 cm on average, 30 cm according to SeaLifeBase and up to 40 cm according to other sources. The horns do not sting: the animal is harmless.
In the wild it prefers sheltered sandy or muddy bottoms and the seagrass beds of calm lagoons, from the surface to about 30 m, rarely below 10 m; it can be left exposed at low tide. It gathers in aggregations (over 5 individuals per 10 m²) where food is plentiful. It mostly grazes algal and microbial films and seagrass blades, but also attacks large prey, including other stars such as Linckia laevigata. A 2022 revision limits its range to the western Pacific; records from the Indian Ocean probably refer to the sister species Protoreaster lincki.
Reproduction and status: separate sexes, fertilisation in open water, planktonic larvae for a few weeks; mature at about 12 cm, possibly living up to 17 years. Heavily collected as a dried souvenir, it has collapsed locally (not seen on Guam since 1945). It has not been evaluated by the IUCN and is not listed by CITES.
