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Family MILLEPORIDAE Fleming, 1828

Fire Coral, Hydrocoral

Compiler and date details

6th January 2017 - Narissa Bax (PhD) holds an Adjunct Researcher position at the Institute for Marine and Antarctic Studies (IMAS). Her PhD thesis focused on stylasterid corals (also commonly known as hydrocorals) in the deep sea in Antarctica, and she continues to work on all aspects of deep sea coral biogeography, phylogenetics, connectivity and conservation. Her current project collaboration is Antarctic Seabed Carbon Capture Change (ASCCC), as part of the Antarctic Circum-navigation Expedition (ACE). For more information on this project visit the following website: and please feel free to email: if you have any queries regarding hydrocorals.


Millepora means 'many pores', the family Milleporidae has a single genus, Millepora(/i). Milleporids are tropical calcareous hydrozoans, commonly known as fire corals or hydrocorals. Their calcium carbonate skeleton (coenosteum) is composed of many shapes including; branching, encrusting and plate-like forms. The Milleporidae coenoestum is composed of an internal network of coenosteal tubes. The outer skeleton is covered by a thin epidermal layer perforated by pores. Coenosteal pores have the internal structure of large gastropores surrounded by small dactylopores forming cyclosystems containing polyps. Polyps are polymorphic and contain gastrozooids (for feeding) with an oral wall of four to seven tentacles. Dactylozooids (for prey capture) are long and thin with tentacles extending from dactylopores. Reproductive chambers are embedded in the coenosteum and gonophores (reproductive pores) arise from the coenosarc (the living tissue overlying the skeleton) within chambers embedded in the coenosteum. Polyps reproduce asexually, and medusae are free swimming when released from ampullae. Medusa release eggs and sperm into the water column and larvae develop and settle on the substrate. Millepora species are also known to reproduce by fragmentation. Like most tropical corals, Milleporidae contain photosynthetic symbiotic algal cells (Lewis, 2006).

Fire corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES).

Note on Hydrocoral description:
There are two coral families known commonly as hydrocorals, the Stylasteridae and the Milleporidae. These coral families secrete a calcium carbonate skeleton, and therefore look superficially like cnidarian corals. However, they are hydrozoans - hence the name hydrocoral. Their affinity as hydrocorals was first documented by Agassis (1858) and Moseley (1879), the two were combined in a single order, Hydrocorallina, until Boschma (1956) when they were assigned to the orders Stylasterina and Milleporina (where they are often found in field guides etc). However, there has been sufficient debate since this time to classify them in the suborders of Filifera (Stylasteridae) and Capitata (Milleporidae), order Anthomedusae as defined herein (also see Stylasteridae).



Ecological Descriptors

Sessile, tropical.



Diagnosis from the World Register of Marine Species (WoRMS):

"Hydroid colony forming massive, calcareous exoskeletons (= coenosteum) of varied shape; coenosteum with an internal complex network of coenosarcal tubes and covered externally by a thin ectodermal layer, coenosteal surface perforated by pores; margins of pores not elevated; large gastropores surrounded by smaller dactylopores, forming indistinct cyclosystems; polyps polymorphic; gastrozooids relatively short and stout, with an oral whorl of four to seven short capitate tentacles, arising from gastropores; dactylozooids long, slender, mouthless, with scattered capitate tentacles, arising from dactylopores; cnidome with stenoteles and macrobasic mastigophores; gonophores arising from coenosarc within chambers embedded entirely in the coenosteum.
Medusa free swimming eumedusoids with exumbrellar nematocyst patches, radial and circular canals present, without tentacles and sense organs; gonads occupying the place of an indistinct manubrium."


ID Keys

Colony surface pierced with fine pinholes. No septa present.
• Yes – Millepora spp.


History of changes

Note that this list may be incomplete for dates prior to September 2013.
Published As part of group Action Date Action Type Compiler(s)
HYDROZOA Owen, 1843 06-Jan-2017 ADDED Dr Narissa Bax