Blue-spotted sea urchin (Astropyga radiata)

Classification (WoRMS)

Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Echinodermata · Class: Echinoidea · Order: Diadematoida · Family: Diadematidae · Genus: Astropyga.

Accepted name: Astropyga radiata · Authority: (Leske, 1778) · Taxonomic status: accepted · AphiaID: 213370.

Synonyms and superseded combinations recorded for this taxon: Asteropyga radiata; Astropyga elastica Studer, 1876; Astropyga freudenbergi Sarasin, 1887; Astropyga major (Seba, 1734); Astropyga mossambica Peters, 1853; Cidaris radiata Leske, 1778; Cidarites radiata (Leske, 1778); Diadema radiatum (Leske, 1778); Echinus radiatus (Leske, 1778); Echionanthus major Seba, 1734.

Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=213370 (CC BY 4.0). Accessed 2026-09-25.

Biology and life history (SeaLifeBase)

Measured values published by SeaLifeBase for Astropyga radiata. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.

Depth range: 0–70 m · Habitat zone: reef-associated · Aquarium trade: never/rarely.

SeaLifeBase notes: Maximum diameter: 18.0 cm. Occurs in shallow waters on sand, rubble and in seagrass areas at depths of 0-60 m. Feeds on algae and small invertebrates. Solitary or in groups (Ref. 800).

Source: SeaLifeBase species summary (SpecCode 86746) — https://www.sealifebase.se/summary/Astropyga-radiata.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-25.

Distribution and occurrence records (GBIF)

628 georeferenced occurrence records for Astropyga radiata are published through GBIF from 31 countries or marine areas. The map above plots 128 distinct locations from a sample of 628 records, omitting 32 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.

Most records by country or area: Indonesia (181); Philippines (180); Kenya (60); Australia (42); Tanzania, United Republic of (31); United States of America (22); Mozambique (16); Mauritius (13); Papua New Guinea (10); Madagascar (9); Thailand (9); Réunion (7); Seychelles (7); Mayotte (7); Solomon Islands (5).

Marine regions with a valid WoRMS distribution record: Mozambican Exclusive Economic Zone; Seychellois Exclusive Economic Zone; West Indian Ocean; Mascarene Basin; Eastern Africa & Madagascar; Kenyan Exclusive Economic Zone; Tanzanian Exclusive Economic Zone; South Africa (country); Aldabra; Cargados Carajos; South African Exclusive Economic Zone; Philippine Exclusive Economic Zone.

Source: GBIF Occurrence Search (taxonKey 4341363) — https://www.gbif.org/occurrence/search?taxon_key=4341363&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=213370 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-25.

Description and natural history (Wikipedia)

Astropyga radiata is a large urchin with a test diameter of up to 20 cm, flattened or slightly concave on the aboral (upper) side. The spines are up to 4 cm 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.

Distribution and habitat

Astropyga radiata is found in the Indo-Pacific Ocean at a maximum depth of about 70 m but more normally at 10 to 30 m. Its range extends from the African coast to Hawaii and Australian waters. It is often found in lagoons and bays where the substrate is sand, shingle or coral rubble. Sometimes many urchins collect together in one locality in dense aggregations.

Biology

Astropyga radiata is mostly nocturnal and feeds by grazing on algae. The mouth is at the centre of the oral (under) surface where there are five powerful teeth in an arrangement known as an Aristotle's lantern. This urchin is light sensitive and can angle its spines towards an approaching threatening object.

The sexes are separate in Astropyga radiata. Eggs and sperm are liberated into the water column. After fertilisation, the larvae are planktonic and develop through several stages before settling on the seabed and undergoing metamorphosis into a juvenile urchin.

Ecology

A number of crustaceans and fish live in association with this urchin. These include the commensal shrimps Periclimenes hirsutus and Stegopontonia commensalis and the crab Zebrida adamsii. Another crab, Dorippe frascone is a symbiont and carries the urchin on its back. Certain juvenile fish also live among the spines including young emperor red snappers (Lutjanus sebae), cardinal fish (Apogonidae) and the zebra lionfish.

Relations to humans

Although not deadly to humans, these urchin's quills are quite venomous; capable of inflicting painful wounds. Its overall pain scale rating, according to the "Kings of Pain" pain index is a 12 out of 30. However, being a rather large and brightly colored species of urchin, it is relatively visible to divers, making injuries by accidentally stepping on one comparatively rare. Due to its beauty, it is loved by underwater photographers and some expert fish-keepers.

"Astropyga" comes from ancient Greek, astro meaning "star" and pyga "anus". Hence, it is named because of its star-shaped anus (or more precisely the star-shaped pattern around its anus). "Radiata" comes from Latin and means "radiant", because of its colors and spines. In English, it is also called star urchin, blue-spotted urchin, red sea urchin, or false fire urchin (different from the "true" fire urchin, Asthenosoma varium). It goes by the name of Roter (Diadem)Seeigel in German, Riccio rosso in Italian, Falso erizo de fuego in Spanish, and Oursin rouge in French.

Source: Wikipedia: Astropyga radiata — https://en.wikipedia.org/wiki/Astropyga_radiata (CC BY-SA 4.0). Accessed 2026-09-25.