Acropora

Acropora is a genus of small polyp stony coral in the phylum Cnidaria.[3] Some of its species are known as table coral, elkhorn coral, and staghorn coral. Over 149 species are described.[4] Acropora species are some of the major reef corals responsible for building the immense calcium carbonate substructure that supports the thin living skin of a reef.

Acropora
Temporal range: Late Paleocene - recent[1]
Acropora pulchra
Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Scleractinia
Family: Acroporidae
Genus: Acropora
Oken, 1815[2]
Species

See text

Synonyms
List
  • Heteropora Ehrenberg, 1834
  • Madrepora (Conocyathus) Brook, 1893
  • Madrepora (Distichocyathus) Brook, 1893
  • Madrepora (Eumadrepora) Brook, 1893
  • Madrepora (Lepidocyathus) Brook, 1893
  • Madrepora (Odonthocyathus) Brook, 1893
  • Madrepora (Polystachys) Brook, 1893
  • Madrepora (Rhabdocyathus) Brook, 1893
  • Madrepora (Trachylopora) Brook, 1893
  • Madrepora (Tylopora) Brook, 1893

Anatomy and distribution

Depending on the species and location, Acropora species may grow as plates or slender or broad branches. Like other corals, Acropora corals are colonies of individual polyps, which are about 2 mm across and share tissue and a nerve net. The polyps can withdraw back into the coral in response to movement or disturbance by potential predators, but when undisturbed, they protrude slightly. The polyps typically extend further at night to help capture plankton and organic matter from the water.

Threats

Symbiodinium, symbiotic algae, live in the corals' cells and produce energy for the animals through photosynthesis. Environmental destruction has led to a dwindling of populations of Acropora, along with other coral species. Acropora is especially susceptible to bleaching when stressed. Bleaching is due to the loss of the coral's zooxanthellae, which are a golden-brown color. Bleached corals are stark white and may die if new Symbiodinium cells cannot be assimilated. Common causes of bleaching and coral death include pollution, abnormally warm water temperatures, increased ocean acidification, sedimentation, and eutrophication.

In 2014 the U.S. Fish and Wildlife Service has listed[5] 10 Acropora species as Threatened. The species are distributed in the Indo-Pacific (over 100 species) and Caribbean (3 species). However, the true number of species is unknown: firstly, the validity of many of these species is questioned as some have been shown to represent hybrids, for example Acropora prolifera;[6] and secondly, some species have been shown to represent cryptic species complexes.[7]

Reef-keeping
Close-up of a network of Acropora polyps

Most Acropora species are brown or green, but a few are brightly colored, and those rare corals are prized by aquarists. Captive propagation of Acropora is widespread in the reef-keeping community. Given the right conditions, many Acropora species grow quickly, and individual colonies can exceed a meter across in the wild. In a well-maintained reef aquarium, finger-sized fragments can grow into medicine ball-sized colonies in one to two years. Captive specimens are steadily undergoing changes due to selection which enable them to thrive in the home aquarium. In some cases, fragments of captive specimens are used to repopulate barren reefs in the wild.[8]

Acropora species are challenging to keep in a home aquarium. They require bright light, stable temperatures, regular addition of calcium and alkalinity supplements, and clean, turbulent water.

Common parasites of colonies in reef aquariums are "Acropora-eating flatworms" Amakusaplana acroporae,[9] and "red bugs" (Tegastes acroporanus).

Species
Acropora (Acroporidae) at French Frigate Shoals, northwestern Hawaiian Islands

The following species are recognised in the genus Acropora:[10]

References
  1. Wallace, C. C; Rosen, B. R (2006-04-22). "Diverse staghorn corals (Acropora) in high-latitude Eocene assemblages: implications for the evolution of modern diversity patterns of reef corals". Proceedings of the Royal Society B: Biological Sciences. 273 (1589): 975–982. doi:10.1098/rspb.2005.3307. ISSN 0962-8452. PMC 1560246. PMID 16627283.
  2. WoRMS (2010). "Acropora Oken, 1815". WoRMS. World Register of Marine Species. Retrieved 2012-02-10.
  3. "Acropora". Integrated Taxonomic Information System.
  4. Archived 2011-08-12 at the Wayback Machine Acropora at Encyclopedia of Life
  5. U.S. Fish and Wildlife Service. "Endangered and Threatened Wildlife and Plants; Adding 20 Coral Species to the List of Endangered and Threatened Wildlife" (PDF). Federal Register. 79 (219): 67356–67359.
  6. Vollmer, S.; Palumbi, S. (2002). "Hybridization and the Evolution of Reef Coral Diversity". Science. 296 (5575): 2023–2025. doi:10.1126/science.1069524. PMID 12065836.
  7. Ladner, Jason T.; Palumbi, Stephen R. (2012). "Extensive sympatry, cryptic diversity and introgression throughout the geographic distribution of two coral species complexes". Molecular Ecology. 21 (9): 2224–2238. doi:10.1111/j.1365-294X.2012.05528.x. PMID 22439812.
  8. "Restoration". The Global Coral Repository. 2011. Archived from the original on 2011-12-19. Retrieved 2011-12-08.
  9. Rawlinson, K. A.; Gillis, J. A.; Billings, R. E.; Borneman, E. H. (2011). "Taxonomy and life history of the Acropora-eating flatworm Amakusaplana acroporae nov. sp. (Polycladida: Prosthiostomidae)". Coral Reefs. 30 (3): 693–705. doi:10.1007/s00338-011-0745-3.
  10. "WoRMS - World Register of Marine Species - Acropora Oken, 1815". www.marinespecies.org. Retrieved 2018-05-28.

Further reading
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