Asthenosoma varium
Encounter Rate
Spotting Difficulty
Best Season
Year-round
Depth Range
5-35 meters
The fire urchin is one of the most visually striking and painful-to-touch echinoderms found in Komodo National Park. Unlike the rigid, globe-shaped sea urchins most people picture, the fire urchin has a soft, flexible body in vivid shades of red, orange, and purple, covered with two types of spines — long, slender spines and shorter, thicker ones tipped with venom-filled sacs. Contact with these venomous spines causes an immediate, intense burning sensation that gives the animal its common name and can persist for hours. Despite its fearsome defences, the fire urchin is one of the most fascinating invertebrates in Komodo for a surprising reason: it hosts an extraordinary array of commensal creatures. Coleman shrimp, zebra crabs, and various other small animals have evolved to live among its venomous spines, gaining protection while the urchin provides a mobile fortress. In Komodo, fire urchins are found at macro-rich dive sites, typically on rubble slopes and among sponge gardens. Every fire urchin encountered should be carefully examined for resident commensals — they are living apartment buildings for some of the reef's most sought-after macro subjects.
Average Size
10-15cm diameter
Size Range
5-20cm diameter
Maximum Size
20cm diameter
Omnivore that grazes on algae, detritus, and encrusting organisms on the reef surface. Uses its tube feet and Aristotle's lantern (jaw structure) to scrape food from substrates.
The fire urchin is one of the most visually striking and painful-to-touch echinoderms found in Komodo National Park. Unlike the rigid, globe-shaped sea urchins most people picture, the fire urchin has a soft, flexible body in vivid shades of red, orange, and purple, covered with two types of spines — long, slender spines and shorter, thicker ones tipped with venom-filled sacs. Contact with these venomous spines causes an immediate, intense burning sensation that gives the animal its common name and can persist for hours. Despite its fearsome defences, the fire urchin is one of the most fascinating invertebrates in Komodo for a surprising reason: it hosts an extraordinary array of commensal creatures. Coleman shrimp, zebra crabs, and various other small animals have evolved to live among its venomous spines, gaining protection while the urchin provides a mobile fortress. In Komodo, fire urchins are found at macro-rich dive sites, typically on rubble slopes and among sponge gardens. Every fire urchin encountered should be carefully examined for resident commensals — they are living apartment buildings for some of the reef's most sought-after macro subjects.
This species plays an important role in the marine ecosystem of Komodo National Park. Responsible diving practices help protect these animals and their habitat for future generations.
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Very painful. Contact causes immediate, intense burning that can last several hours. The venom sacs on the spine tips burst on contact. Treatment involves hot water immersion and vinegar application. While not life-threatening, it will certainly ruin a dive.
