Identification: tentacles all alike, densely packed, finger-like, up to 75 to 100 mm, with a blunt tip often marked by a small dot. The column is fully visible and brightly coloured (purple, red, orange, blue, green, white or brown); its verrucae are inconspicuous, the same colour, and do not hold debris. When disturbed it curls into a ball, leaving only a tuft of tentacles. Stichodactyla haddoni has similarly shaped but shorter, denser tentacles; S. mertensii can exceed it in diameter but has short tentacles. The genus Radianthus was reinstated by England (1988): these species lack the macrobasic nematocysts of Heteractis aurora.
In the wild it occupies prominent spots with its foot on hard substrate, mostly on fore reefs but also on calm patch reefs and reef flats shallower than 1 m. It is the only host anemone whose column and pedal disc are regularly fully exposed. The shallowest individuals do not always host clownfish.
Reproduction: sexual and asexual (longitudinal fission). It lives alone or in clonal beds of dozens to hundreds of identically coloured individuals; according to Fautin and Allen, large solitary animals dominate the centre of the range (eastern Indonesia, Great Barrier Reef, Papua New Guinea), clusters the edges (western Indonesia, Malaysia, Tahiti).
Status and trade: not evaluated by the IUCN and not CITES-listed. A 2018 survey of aquarists ranked it among the three most wanted anemones. Fautin and Allen advise against collecting host anemones: they survive poorly in captivity, rarely recruit successfully in the wild and are probably very long-lived, so harvesting outpaces replacement.
