Head Coral

• At night it unfurls sweeper tentacles far longer than the ordinary ones, with which it attacks neighbouring corals and takes ground from them, a chemical and physical war that decides the final shape of the reef.
• Its skeleton grows in annual layers, like the rings of a tree, allowing the colony to be dated and past sea conditions to be reconstructed.
• It depends on symbiotic algae to feed, and expels them when the water grows too warm: that is when the coral bleaches.
• Each polygon on its surface is a polyp with its own mouth and its own ring of tentacles, housed in a calcareous cup called a corallite.
• At night it extends long tentacles with which it captures zooplankton, so it does not live on the photosynthesis of its zooxanthellae alone.
• And it has tentacles for war: mesenterial filaments and specialised sweeper tentacles with which it attacks neighbouring corals to defend space. Competition for substrate on a reef is a constant chemical and physical war.
• It is one of the best-studied species in the analysis of inter-coral aggression and of the competitive hierarchy among stony corals.
• Its tolerance of turbid, variable environments makes it hardier than many branching corals, and it is a regular presence on degraded reefs.
• Like all stony corals, it is listed in Appendix II of CITES.

Skeleton type

Invertebrate - calcareous skeleton (coral)

Habitat & environment

Coral reefs of the Indo-Pacific and the Red Sea, from 1 to 30 m

Sources consulted: Veron, Corals of the World; Lista Roja de la UICN; CITES; Chadwick, trabajos sobre agresión entre corales