Invertebrates
Fire Coral
Millepora · also called fire corals
Fire coral earns its name honestly. Brush against a colony that looks for all the world like an ordinary chunk of reef, and the burning sting that follows can linger for hours, a clear signal that whatever just made contact was never a true coral at all, but a much closer relative of the jellyfish drifting somewhere nearby.
Overview
Fire coral, genus Millepora, is a hydrozoan found on reefs throughout tropical and subtropical oceans worldwide. Despite its hard, coral-like skeleton, it is more closely related to jellyfish and the Portuguese man o’ war than to true reef-building coral.
A convincing disguise with a painful catch
Fire coral’s encrusting, branching growth so closely mimics true coral that even experienced divers can mistake it at a glance, a resemblance that makes knowing what not to touch on a reef considerably more important than it might first appear.
Status
Least Concern — common and widespread across suitable reef habitat throughout tropical and subtropical oceans worldwide.
Fire Coral: common questions
Is fire coral actually a type of coral?
No, despite its name and its hard, coral-like skeleton, fire coral is a hydrozoan, placing it in the same broader group as jellyfish and the Portuguese man o' war rather than with true stony corals, making the resemblance between fire coral and actual reef-building coral a case of superficial similarity rather than close biological relationship.
Why does fire coral's sting hurt so much?
Fire coral's surface is covered in tiny pores containing specialised stinging cells that deliver a painful, burning sensation on contact, and the resulting discomfort and welts can persist for hours or occasionally longer, a defensive and prey-capturing mechanism inherited from its closer relationship to stinging jellyfish and siphonophores rather than to true corals.
How can divers avoid accidentally touching fire coral?
Because fire coral's hard skeleton and encrusting growth pattern can closely resemble true reef-building coral, divers and snorkelers are generally advised to avoid touching any unfamiliar hard reef surface, wear appropriate protective clothing when diving near reefs, and maintain careful buoyancy control to reduce the risk of accidental contact.
Does fire coral get energy the same way as true coral?
Yes, similar to many true reef-building corals, fire coral hosts photosynthetic algae within its tissue and gains a significant portion of its energy from that relationship, while also actively capturing small planktonic organisms using its stinging cells, combining both strategies despite belonging to a different broader animal group than true coral.