Skip to content

Acropora horrida

A hard coral with arborescent colonies and bristly, bottlebrush branches. 5 9 It is known for keeping its tentacles extended day and night. 10 It lives mainly between 3 and 20 m, on sheltered bottoms, sandy slopes and in lagoons. 3

AcroporidaeSPSIUCN: EndangeredCITES II
Acropora horrida

At a glance

Data from the scientific sources listed at the bottom.

Depth in the wild

3–20 m

0 m4 m8 m12 m16 m20 m

Size

up to 200 cm

04080120160200

maximum colony diameter

Conservation

NEDDLCNTVUENCREWEX

IUCN Red List: endangered (2023). CITES: Appendix II. The listed criterion is A3ce. 3 The CITES listing currently in force dates back to 18 January 1990; in the European Union it is in Annex B. 2

Where it lives

Red SeaWestern Indian OceanEastern Indian OceanCentral Indo-PacificWestern PacificCentral PacificEastern PacificWestern AtlanticEastern AtlanticMediterranean

According to the range dataset of Hughes et al. it runs from about 25° E to about 138° W and from about 31° N to 34° S, covering almost 90 million km². 4 8 WoRMS gives it in the Red Sea, Kenya, Mauritius, South Africa, the western Indo-Pacific and Fiji. 1 Species+ lists 32 countries and territories, including Egypt, Mozambique, the Maldives, Thailand, Indonesia, Japan, Australia and French Polynesia. 2

The coral

Group: SPS

Growth form: arborescent 9, with bristly, bottlebrush branches 5; corallites 0.6-1.5 mm wide 9

Zooxanthellae: yes

How to recognise it

Tap a number on the photo: the key explains what to look for.

123
  1. 1Arborescent colony branching like a small tree 9
  2. 2Bristly branches bottlebrush look 5
  3. 3Extended tentacles visible day and night 10

Life in the wild

Where it is found

The usual range is 3-20 m, on sheltered submerged flats, sandy slopes and lagoons. 3 A 2015 analysis gives 40 m as the lower limit. 4 6 On the Great Barrier Reef it was found down to 35 m, but below 30 m it is rare; in the Coral Sea it was not found at those depths. 5

What it eats

It hosts symbiotic algae (zooxanthellae): in the Andaman Sea, at 2 m, they were types C3 and C3z. 4 12 According to a 2013 study, its always-extended tentacles suggest that it catches more food than other Acropora: this is the authors' hypothesis, not a measurement. 10

Behaviour

It keeps its tentacles extended day and night. 10

Reproduction

A hermaphrodite that releases its gametes into the sea instead of brooding its larvae: data from a study on mass spawning on a high-latitude reef. 4 11 The larvae (planulae) spend a period in the plankton before settling on the bottom. 3

In the aquarium

From the experience of the BallingMania community.

Community rating
Position in the tank
lowmediumhigh
Water flow
lowmediumhigh
Light intensity
lowmediumhigh
Aggression
lowmediumhigh
Care difficulty
lowmediumhigh
Original sheet

It belongs to the family Acroporidae. A very widespread coral in various shades of green, light blue, dark blue, pale yellow and brown. Place of origin: the Red Sea, the Indian Ocean, the Indo-Pacific, the Great Barrier Reef.

In the wild it can be spotted among the reefs and slopes at a depth of 5 to 25 m, where the water is more turbid.

This type of coral forms colonies of considerable size, with arborescent and highly branched growth; the branches are about a centimetre thick. What is special about this animal is the marked extension of its polyps even during the photoperiod.

In the aquarium, with good lighting and medium-strong water movement, its dense polyps can be seen even during the day. It needs excellent water parameters to bring out its magnificent colours.

It is vulnerable to attack by pests and does not tolerate high temperatures well.

Photo by Ciro Murino, text by Massimo Ramognino

Did you know?

It split from its most recent common ancestor at least 5.12 million years ago: for the authors of the study, losing it would mean losing an unusual evolutionary branch. 10
The same study also reports an unusual organisation of its fluorescent pigments. 10
Colonies can reach 2 m in diameter, according to the revision of the genus in Indonesia. 4 7

Sources

  1. Hoeksema B.W., Cairns S., Samimi-Namin K. (2026). Acropora horrida (Dana, 1846). World List of Scleractinia, via WoRMS.
  2. UNEP-WCMC (2026). Acropora horrida, CITES listings and distribution. Species+.
  3. Palomares M.L.D., Pauly D. (eds.) (2026). Acropora horrida, Blue staghorn. SeaLifeBase.
  4. Madin J. et al. (eds.) (2026). Acropora horrida. Coral Trait Database.
  5. Muir P., Wallace C., Bridge T.C.L., Bongaerts P. (2015). Diverse Staghorn Coral Fauna on the Mesophotic Reefs of North-East Australia. PLoS ONE.
  6. Muir P.R., Wallace C.C., Done T., Aguirre J.D. (2015). Limited scope for latitudinal extension of reef corals. Science, reference in the Coral Trait Database.
  7. Wallace C.C., Wolstenholme J. (1998). Revision of the coral genus Acropora (Scleractinia: Astrocoeniina: Acroporidae) in Indonesia. Zoological Journal of the Linnean Society, reference in the Coral Trait Database.
  8. Hughes T.P., Connolly S.R., Keith S.A. (2013). Geographic ranges of reef corals (Cnidaria: Anthozoa: Scleractinia) in the Indo-Pacific. Ecology, reference in the Coral Trait Database.
  9. Wallace C.C., Done B.J., Muir P.R. (2012). Revision and catalogue of worldwide staghorn corals Acropora and Isopora (Scleractinia: Acroporidae) in the Museum of Tropical Queensland. Memoirs of the Queensland Museum, reference in the Coral Trait Database.
  10. Richards Z.T., Miller D.J., Wallace C.C. (2013). Molecular phylogenetics of geographically restricted Acropora species: Implications for threatened species conservation. Molecular Phylogenetics and Evolution.
  11. Babcock R.C., Wills B.L., Simpson C.J. (1994). Mass spawning of corals on a high latitude coral reef. Coral Reefs, reference in the Coral Trait Database.
  12. LaJeunesse T.C., Pettay D.T., Sampayo E.M. et al. (2010). Long-standing environmental conditions, geographic isolation and host-symbiont specificity influence the relative ecological dominance and genetic diversification of coral endosymbionts in the genus Symbiodinium. Journal of Biogeography, reference in the Coral Trait Database.

Sources checked on 5 November 2026. Community texts and ratings are kept separate from the scientific data.

View the original sheet (Italian)All species