Wednesday, September 20, 2017

Corals as Colonies – Colony Surface

The individual coral animal is called the polyp.  This simple sac-like animal sits in a skeleton cup made of calcium carbonate, called a corallite.  Together the tissue and the skeleton are called the corallum or coralla (plural).  The following article discusses the space between the corallites and polyps: the surface of the colony.  If you want more information on the corallite or polyp key terms check out the Corals as Individuals articles.

Surface of the Colony – Key Terms

Individual corallites may be separated by a section of skeleton with overlying tissue.  Structures that develop in this area are extremely useful when trying to separate corals with similar looking corallites.

Using Surface Characteristics to ID Corals

As with any aspect of coral morphology, it is unwise to rely on any one characteristic when identifying a coral.  But examination of the structures on the coenosteum is a useful step on the identification pathway.  Below is one example of how knowledge of colony surface structures can help with identification:

Echinopora vs. Oxypora

Both of these genera form thin plating colonies in the form of vases or tiers.  Superficially they are similar and may initially be difficult to separate.  However, the surface of Echinopora is beaded, whereas colonies of Oxypora have a rougher more ragged look to them.  These differences may not sound significant but the following close up photos clearly show that examination of the characteristics of the colony surfaces would allow successful identification.

(Photos of echinopora and oxypora close up)

Learning Resources


Suggested Reading

Veron, J. E. N. (2000). Corals of the World. Melbourne: Australian Institute of Marine Science.