Astropyga radiata is a large urchin with a test diameter of up to 20 cm (8 in), flattened or slightly concave on the aboral (upper) side.
The spines are up to 4 cm (1.6 in) long and are grouped in five vertical clusters in between which are V-shaped areas with no spines corresponding to the interambulacral plates.
These bare areas are red with lines of iridescent blue dots while the colour of the rest of the test and spines varies from reddish brown to purple, dark brown or nearly black.
The spines are long and hollow; they are of two kinds, the shorter being venomous.
The anal sac is prominent, brown with a dark tip.
Juveniles have spines with transverse banding and this characteristic sometimes persists into adulthood.
Astropyga radiata is a large urchin with a test diameter of up to 20 cm (8 in), flattened or slightly concave on the aboral (upper) side. The spines are up to 4 cm (1.6 in) long and are grouped in five vertical clusters in between which are V-shaped areas with no spines corresponding to the interambulacral plates. These bare areas are red with lines of iridescent blue dots while the colour of the rest of the test and spines varies from reddish brown to purple, dark brown or nearly black. The spines are long and hollow; they are of two kinds, the shorter being venomous. The anal sac is prominent, brown with a dark tip. Juveniles have spines with transverse banding and this characteristic sometimes persists into adulthood.
Astropyga radiata