Saturday, April 19, 2014

Acropora


Family Acroporidae

Welcome to the Acropora genus landing page. In this section, you will find general information about this genus and tips on how to identify it. If you are looking to confirm an observation made underwater with the Coral Finder about a branching coral, use the image browser below to get a sense of the variation possible in the genus Acropora. Then consult the ID tips below or choose one of the following links for further comparison with similar genera: Cyphastrea, Anacropora, or Isopora.

Acropora displays an amazing array of forms and, with over 135 species, it is the most species rich hard coral genus.  Do not be put off however, when it comes down to it they share some common characters which make Acropora one of the easiest genera to recognise. Colonies are an arrangement of branches, or branchlets forming a plate, covered in radial corallites with a single differentiated axial corallite at the branch tips.

Vital Statistics

  • 135+ species
  • Coral Finder p. 1, 18, 23c
  • COTW – Vol 1 p.176-433

Distribution

Widespread in Indo-Pacific and Atlantic.

ID Tips

Acropora generally forms branching colonies, or clusters of branchlets forming tables or plates.  Be aware however that young colonies, or colonies in strong wave action, may be encrusting, as the base will form prior to any branches growing up and out.

In all cases look for a distinct axial corallite at branch tips surrounded by  radial corallites (see diagram in gallery below), axial corallites often appear “differentiated” form the radial corallites, being larger, or tubular and extended, (see Acropora tips gallery below).  A second interesting feature of Acropora is linked to their fast growing nature; the axial corallites at the branch tips are often paler or a different shade than surrounding tissue as the symbiotic algae have not yet moved into the new tissue.

Members of the family Acroporidae share a distinctive skeletal feature which is useful to recognise. The skeleton often shows a unique visual texture on its skeleton referred to as reticulate coenosteum. Look for it showing through the tissue in between the corallites in the gallery below.

While Acropora is challenging at the species level it has the benefit of being the easiest genus to recognise full stop! Test yourself! Look for the axial corallite in each image of the gallery below.

Species level identification is generally based on life-form and corallite shape (see COTW Vol. 1 p. 178-179 and Wallace, 1999 for more info).  For help with field ID look at COTW Vol. 1, for help with skeletal ID look at Wallace (1999). The web site http://www.coralsee.org/ is also a very good place to start.

Similar Genera to Acropora (Coral Finder p.1)

The Coral Finder lists Acropora in two key groups with Cyphastrea, Anacropora, and Isopora being potential candidates for confusion.

Comparing Acropora and Cyphastrea

Acropora can be confused with a single unusual species of CyphastreaCyphastrea decadia is the only branching species in that genus and the only coral other than Acropora to have an axial corallite. Most Acropora axial corallites are larger or differentiated in some way from the radials, whereas the axial corallites of Cyphastrea decadia are of a similar size and appearance to the radial corallites. Close inspection also reveals distinctive Cyphastrea-like spinules and costae on the colony surface. By contrast Acropora species have a reticulate coenosteum, (see gallery above).

Cyphastrea decadia

Comparing Acropora and Anacropora

Acropora may be confused with Anacropora which forms similar branching colonies.  Anacropora however, lacks the distinctive axial corallite found on Acropora branches. The radial corallites and the colony surface generally, are usually fairly smooth.

Anacropora sp.

Comparing Acropora and Isopora

For decades Isopora was a sub-genus of Acropora . Recently placed in its own genus, it holds a small number of distinctive looking species. The radial corallites are typically Acropora-like and continue, densely packed and pale, over the branch ends. Axial corallites are absent. Two species, I. cuneata and I. palifera, are typical outer reef slope corals and show astonishing growth form variation in response to light and wave action.

Isopora sp.

Ecology

The 3-D structure of Acropora provides a rich habitat for a wide range of other reef creatures including crabs, brittle stars and fish. Branching Acropora colonies grow from  the axial corallites and can rapidly take over space with their lightly built skeletons. Despite their delicate appearance they are common on upper reef slopes where damage caused by wave action can disperse colony fragments which regrow asexually.

Taxonomic Changes

Taxonomic changes in Acropora and its species have developed with the advent of molecular tools; check out some of the references in ‘Learning Resources’ for more info.  The genus Isopora used to be considered as a sub-genus of Acropora (see COTW p.184), but it is now considered its own separate genus (see Wallace et al. 2007, for more details).

Learning Resources

Coral Hub

  • Acroporidae family page

Links

Suggested Reading – Identification Tools

  • Ayre, D. J., Veron, J. E. N., & Dufty, S. L. (1991). The corals Acropora palifera and Acropora cuneata are genetically and ecologically distinct. Coral Reefs, 10(1), 13-18.
  • Bernhard, R. (1995). Description of four new species in the hard coral genus Acropora Oken, 1815 (Scleractinia: Astrocoeniina: Acroporidae) from south-east Africa. Zoological Journal of the Linnean Society, 113(3), 229-247.
  • Bernhard, R. (1995). A revision of the hard coral genus Acropora Oken, 1815 (Scleractinia: Astrocoeniina: Acroporidae) in south-east Africa. Zoological Journal of the Linnean Society, 113(3), 249-288.
  • Davie, P. J., & Phillips, J. A. (2009). 13th International Marine Biological Workshop, The Marine Fauna and Flora of Moreton Bay, Queensland. Memoirs of the Queensland Museum, 54(2), 1-118.
  • Fukami, H., Omori, M., & Hatta, M. (2000). Phylogenetic relationships in the coral family Acroporidae, reassessed by inference from mitochondrial genes. Zoological Science, 17(5), 689-696.
  • McMillan, J., Mahony, T., Veron, J. E. N., & Miller, D. J. (1991). Nucleotide sequencing of highly repetitive DNA from 7 species in the coral genus Acropora (Cnidaria, Scleractinia) implies a division contrary to mophological criteria. Marine Biology, 110(3), 323-327.
  • Richards, Z. T., & Wallace, C. C. (2004). Acropora rongelapensis sp nov., a new species of Acropora from the Marshall Islands (Scleractinia : Astrocoeniina : Acroporidae). Zootaxa(590), 1-5.
  • Riegl, B. (1995). Description of four new species in the hard coral genus Acropora Oken, 1815 (Scleractinia: Astrocoeniina: Acroporidae) from South-East Africa. Zoological Journal of the Linnean Society, 113, 229-247.
  • van Oppen, M. J. H., McDonald, B. J., Willis, B., & Miller, D. J. (2001). The Evolutionary History of the Coral Genus Acropora (Scleractinia, Cnidaria) Based on a Mitochondrial and a Nuclear Marker: Reticulation, Incomplete Lineage Sorting, or Morphological Convergence? Mol Biol Evol, 18(7), 1315-1329.
  • Veron, J. E. N. (1985). Corals of Australia and the Indo-Pacific. Sydney: Angus and Robertson.
  • Veron, J. E. N. (2000). Corals of the World. Melbourne: Australian Institute of Marine Science.
  • Veron, J. E. N. (2002). New species described in ‘Corals of the World’: Australian Institute of Marine Science.
  • Veron, J. E. N., & Wallace, C. C. (1984). Scleractinia of Eastern Australia.  Part 5, Family Acroporidae.
  • Wallace, C. C. (1978). The coral genus Acropora (Scleractinia: Astrocoeniina: Acroporidae) in the central and southern Great Barrier Reef Province. Memoirs of the Queensland Museum, 18, 273-319.
  • Wallace, C. C. (1994). New species and a new species group of the coral genus Acropora from Indo-Pacific locations. Invertebrate Taxonomy, 8, 961-988.
  • Wallace, C. C. (1997). New species and new records of recently described species of the coral genus Acropora (Scleractinia: Astrocoeniina: Acroporidae) from Indonesia. Zoological Journal of the Linnean Society, 120, 27-50.
  • Wallace, C. C. (1997). Scleractinia of Taiwan. IV Review of the coral genus Acropora from Taiwan. Zoological Studies, 36, 288-324.
  • Wallace C. C. (1999). Staghorn corals of the world: a revision of the genus Acropora. CSIRO Publishing, Collingwood, Victoria, Australia.
  • Wallace, C. C. (2008). New species and records from the Eocene of England and France support early diversification of the coral genus Acropora. Journal of Paleontology, 82(2), 313-328.
  • Wallace, C. C., Chen, C. A., Fukami, H., & Muir, P. R. (2007). Recognition of separate genera within Acropora based on new morphological, reproductive and genetic evidence from Acropora togianensis, and elevation of the subgenus Isopora Studer, 1878 to genus (Scleractinia : Astrocoeniidae; Acroporidae). Coral Reefs, 26(2), 231-239.
  • Wallace, C. C., & Rosen, B. R. (2006). 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.
  • Wallace, C. C., & Wolstenholme, J. (1998). Revision of the coral genus Acropora (Scerlactinia: Astrocoeniina: Acroporidae) from Indonesia. Zoological Journal of the Linnean Society, 123, 199-384.
  • Wells, J. W. (1985). Notes on Indo-Pacific Scleractinian corals. Part 11: A new species of Acropora from Australia. Pacific Science, 39, 338-339.

Suggested Reading – Other Topics

  • Bak, R. P. M., Nieuwland, G., & Meesters, E. H. (2009). Coral growth rates revisited after 31 years: what is causing lower extension rates in Acropora palmata? Bulletin of Marine Science, 84(3), 287-294.
  • Kenyon, J. C. (2008). Acropora (Anthozoa : Scleractinia) reproductive synchrony and spawning phenology in the northern Line Islands, central Pacific, as inferred from size classes of developing oocytes. Pacific Science, 62(4), 569-578.
  • Nakajima, Y., Nishikawa, A., Isomura, N., Iguchi, A., & Sakai, K. (2009). Genetic Connectivity in the Broadcast-Spawning Coral Acropora digitifera Analyzed by Microsatellite Markers on the Sekisei Reef, Southwestern Japan. Zoological Science, 26(3), 209-215.
  • Nothdurft, L. D., & Webb, G. E. (2007). Microstructure of common reef-building coral genera Acropora, Pocillopora, Goniastrea and Porites: constraints on spatial resolution in geochemical sampling. Facies, 53(1), 1-26.
  • Nozawa, Y., & Harrison, P. L. (2007). Effects of elevated temperature on larval settlement and post-settlement survival in scleractinian corals, Acropora solitaryensis and Favites chinensis. Marine Biology, 152(5), 1181-1185.
  • Okubo, N., Taniguchi, H., & Omori, M. (2009). Sexual Reproduction in Transplanted Coral Fragments of Acropora nasuta. Zoological Studies, 48(4), 442-447.
  • Strychar, K. B., Coates, M., & Sammarco, P. W. (2004). Loss of Symbiodinium from bleached Australian scleractinian corals (Acropora hyacinthus, Favites complanata and Porites solida). Marine and Freshwater Research, 55(2), 135-144.
  • Suzuki, G., Hayashibara, T., Shirayama, Y., & Fukami, H. (2008). Evidence of species-specific habitat selectivity of Acropora corals based on identification of new recruits by two molecular markers. Marine Ecology-Progress Series, 355, 149-159.
  • Tanaka, Y., Miyajima, T., Umezawa, Y., Hayashibara, T., Ogawa, H., & Koike, I. (2009). Net release of dissolved organic matter by the scleractinian coral Acropora pulchra. Journal of Experimental Marine Biology and Ecology, 377(2), 101-106.
  • Victor, S., Golbuu, Y., Yukihira, H., & van Woesik, R. (2009). Acropora size frequency distributions reflect spatially variable conditions on coral reefs of Palau. Bulletin of Marine Science, 85(2), 149-157.
  • Work, T. M., Aeby, G. S., & Coies, S. L. (2008). Distribution and morphology of growth anomalies in Acropora from the Indo-Pacific. Diseases of Aquatic Organisms, 78(3), 255-264.