Corals as Colonies – Life-forms
Although some coral genera are solitary, i.e. they form separate individuals (e.g. Cycloseris, p. 24 of the Coral Finder), the majority of scleractinian corals form colonies made up of a number of individuals. These individuals reproduce asexually by budding (see asexual reproduction article for more information), so that over time the colony becomes larger and is composed of more and more individuals (e.g. Acropora, p. 1 of the Coral Finder). The colonial nature of corals has wide ranging implications for coral ecology, biology and identification. One of the main consequences is that colonies may grow into a wide range of shapes or morphologies as new individuals are added and grow. These shapes are termed life forms or growth forms, and can be used as the first step in identifying corals, as certain genera and species grow into specific life forms.
Life form describes the overall shape of the coral, and is synonymous with growth form or morphology. It is important to be aware that there are three sources of confusion when discussing a coral’s life form: 1) many different terms exist for similar life forms, 2) a single colony may exhibit more than one life form; in this instance the predominant life form is generally used, 3) these shapes exist on a continuum rather than being clear cut, separate definitions, so a degree of subjectivity is inherent to the topic.
- links inside these captions for more info.
Hover over the main image to pause slideshow." title="entry4" width='170' height='135' />
- attached to the seafloor." title="slide4-1-new" width='170' height='135' />
- free-living - the genus Zoopilus." title="slide4-2-new" width='170' height='135' />
- free-living corals on soft sediment. Clockwise from top: Heteropsammia, Heterocyathus, Cycloseris x2 & Heteropsammia." title="slide4-3-new" width='170' height='135' />
- free-living as adults - the genus Fungia." title="slide4-4-new" width='170' height='135' />
- solitary polyp or clone to form a colony of many polyps. Solitary corals can be as large, or larger, than colonies. The genus Ctenactis (left) and Moseleya (right). Note: both of the corals illustrated are also free-living." title="slide4-5" width='170' height='135' />
- Free-living corals can be solitary or colonial - the genus Fungia (left) & Halomitra (right)." title="slide4-6-new" width='170' height='135' />
- Branching corals take many forms - fingers, needles, blades and plates of branchlets - to name a few. Clockwise from top left: Acropora, Seriatopora, Pocillopora & Acropora." title="slide4-7" width='170' height='135' />
- digitate. Corals with thicker "fingers" form columnar growth forms - the genus Acropora (left) and Isopora (right)." title="slide4-8" width='170' height='135' />
- massive, sub-massive, thick encrusting & thin encrusting." title="slide4-9" width='170' height='135' />
- Meandering corallites produce distinctive colony life forms. Corallites with common walls are meandroid while meandering corallites with separate walls are known as flabello-meandroid. The genus Symphyllia (left) and Euphyllia (right)." title="slide4-10-new" width='170' height='135' />
- Meandering corallites produce distinctive life forms. Coral genera can be strongly or weakly meandering e.g. two species of the genus Platygyra." title="slide4-11" width='170' height='135' />
- Meandering corallites may be very subtle (note scale) and difficult to see when tentacles are extended - the genus Psammocora." title="slide4-12-new" width='170' height='135' />
- plates can take many forms e.g. tiers and vases - two species of the genus Montipora." title="slide4-13-new" width='170' height='135' />
- plates can be leafy or form spires - the genus Pavona (left) and Pectinia (right)." title="slide4-14" width='170' height='135' />
- Veron, J. E. N. (2000). Corals of the World. Melbourne: Australian Institute of Marine Science.