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Big
Bank Shoals of the Timor Sea
An
environmental resource atlas
| Biological
Environment |
Epi-benthic
communities of the Big Bank Shoals |
CORAL
ECOSYSTEMS
General biology
Like the hard corals, soft corals are colonial organisms made up of numerous
polyp units. Colonies are usually cemented to a hard surface and remain attached
(sedentary) for the whole of their life span. However, some species are capable
of moving. The colony can creep slowly around the reef by extending the tissues
of its base in the direction of travel.
The soft
coral Nephthea sp.
(AIMS) |
A principal architectural difference between hard and soft coral polyps is
the number of tentacles present. While the stony corals have polyps with six
tentacles and mesenteries (or multiples of), soft coral polyps have eight
tentacles. The tentacles are subdivided so that two rows of fine, comb-like
pinnules fringe the length of each one and the polyps are arranged so that they
lie side by side, with their mouths and tentacles facing out to the surrounding
water. A common mass of tissue, called the coenchyme, surrounds and joins the
polyps to form the colony. |
| Octocoral tissues are supported by numerous, small pieces of calcium
carbonate, called sclerites, which are found throughout the coenchyme. These
stiffen the soft tissues and in some species are fused to form a stiff support.
The sclerites may project externally, in bundles that encircle the polyps. The
spiky bunches of sclerites discourage predators, and in some cases may
facilitate more efficient filter-feeding by supporting the polyp tentacles in
swift water currents (Fabricius, 1995). |
Polyps of the soft coral Nephthea sp.
(K. Fabricius) |
|
