Fire Coral

Millepora exaesa is a colonial hydrozoan, not a true coral, though it builds calcium carbonate skeletons that contribute to reef structure alongside scleractinian corals. Colonies form encrusting, branching, or plate-like growths with a characteristic pale mustard to cream coloration and a smooth to finely textured surface. The skeleton is perforated by pores containing polyps equipped with potent nematocysts, capable of delivering a painful sting to humans, which gives the genus its common name.

As a colonial organism, it feeds on zooplankton captured by its stinging polyps while also hosting symbiotic zooxanthellae that supply energy through photosynthesis. Within reef ecosystems it adds structural complexity, providing habitat and contributing to reef accretion.

The species inhabits marine neritic zones across the Indo-Pacific, with recorded populations in Papua New Guinea, the Solomon Islands, American Samoa, the Philippines, Madagascar, Micronesia, Australia, Indonesia, Thailand, Vietnam, Yemen, Japan, Fiji, and Guam, typically on shallow reef flats and slopes.

Populations are declining due to a combination of pressures. Fishing and harvesting activities damage colonies directly, while disease outbreaks and problematic native species affect colony health and survival. Habitat shifting and alteration, linked to broader reef degradation, reduce suitable substrate, and unspecified pollution sources add further stress. These threats compound the general vulnerability of reef-building organisms to warming seas and ocean acidification.

Conservation efforts rely largely on broader marine protected area networks and reef management programs across its range states, though species-specific interventions remain limited. No detailed population counts are available.

Given ongoing habitat degradation and multiple concurrent stressors, the species' trajectory remains negative, consistent with its Endangered listing and the general decline observed across Indo-Pacific reef systems.