The Fire Urchin (Asthenosoma varium) is a tropical urchin species that can be found through the Indo-western pacific region. It is a member of the echinoderm family Echinothuriidae and has been recorded in various tropical countries including Indonesia, Philippines, Papua New Guinea, Thailand, Vietnam and northern Australia. It can be found living on coral reefs, in coastal bays and lagoons and on sandy or rubble bottoms. This is a large urchin species and it has small short spines that inflict a considerable amount of pain and discomfort if a diver is unfortunately stung. The test of this species is quite flexible which allows it to squeeze into tight crevices and holes. There are many different species that can be found living on Asthenosoma varium including the commensal shrimps Periclimenes colemani, Allopontonia iaini, the parasitic gastropod Leutzenia asthenosomae, the Striped Urchin Crab Zebrida adamsii and the Urchin Cardinalfish Siphamia unicolour.
The Fire Urchin (Asthenosoma varium) grows to a maximum width of at least 25 cm.