|
CNIDARIANS (Cnidaria)
All members of the phylum Cnidarians are characterized by tentacles
armed with a myriad of stinging cells. Each of these cells is equipped
with a minute safety pin (cnidocil), which acts as a trigger mechanism.
Whenever potential prey touches the tentacles, cnidociles get bent,
which in turn leads to an instantaneous avalanche of stinging cells
being ejected.
In this process, a bundle of knife-like appendages
extend, cutting into the prey’s skin. Immediately thereafter
a long filament from inside the cell penetrates the cut and injects
a toxin to paralyze or kill the prey.
All this is microscopically
small and happens a million times in a few seconds.
STONY CORALS (Scleractinia)
Millions upon millions of tiny coral polyps are the life blood
of the reef. The skeletons they secrete by countless generations
form the solid limestone foundation or platform on which the reef
flourishes.
An individual coral polyp consists of a fleshy sack
topped with a ring of tentacles around a central mouth opening.
It sits in a limestone skeletal case, which is actually secreted
by the polyp. Members of the colony are linked together by living
tissue. Therefore nutrients captured by a section of the colony
can be shared around.
Stony corals have brownish colored, unicellular
algae living within the tissues of the polyps. The algae use sunlight
and carbon dioxide to produce carbon enriched organic compounds
(sugar). These in turn are leaked to the polyp and may provide as
much as 98 percent of its nutritional requirements.
Stony corals
typically grow in clear, sunlit waters. Some are also found in relatively
low light levels. They grow slowly and their diet may be supplemented
by absorbing nutrients directly from the water or by feeding on
bacteria and organic debris.
| |
 Very
common, often the dominant species of lagoons and fringing
reefs. Colonies arborescent, forming thickets.
Occur in different
colors like cream, brown or blue. Branch ends often pale.
|
|
| |
 The
branches of this species form an almost solid plate.
It has
a light skeleton, which allow them to grow quickly and to
overcome their neighbors.
|
|
| |
 Very
common species, not attached, on upper reef slopes exposed
to surge.
The ridges have triangular teeth.
|
|
| |
 Mostly
occurring in single colonies down to 15 m depth.
The colonies
can reach 1,5 m in diameter.
|
|
| |
 The
commonest cup coral seen by divers because it grows in areas
exposed to currents and not in caves like the other genus
members.
|
|
SOFT CORALS & SEA FANS (Alcyoniidae)
Soft corals and their relatives are a prominent part of the reef
scene. In some places they may form extensive growth, like vast
fields of undersea wildflowers. Structurally they are similar to
stony corals.
Both contain colonies of polyps that gather planktonic
food. However, as their name suggests, soft corals lack a hard skeleton.
Instead, the supporting stem consists of fleshy tissue that is reinforced
by a matrix of microscopic calcareous particles.
Soft corals have
tiny side branches on the tentacles in contrast to the smooth tentacles
of hard corals. Moreover, soft corals generally have eight tentacles
compared to six or multiples of six found in hard corals.
Most soft
corals are various shades of green, yellow and brown. The color
is largely attributable to the presence of single celled algae that
live within their tissue.
| |
 This
species has a flexible uni-plane skeleton.
Normally found
growing on drop-offs, reaching far out into the open water.
|
|
| |
 The
colonies are fan-shaped with a thick main stem, dividing in
many sub-branches.
The polyps are distributed over the entire
surface. Coloration is variable, mainly deep red with white
polyps.
Grows on slopes and drop-offs, also on deeper reef
terraces. Feeds on micro plankton.
|
|
| |
 Whip-like
gorgonians with heavily calcified horny axis. Found in groups
on reef slopes.
Sexes are separate, but also asexual reproduction
by budding. Buds fall down and grow to become neighbors of
the parents. |
|
| |
 Wide
spread species of soft coral. Red calcareous sclerites show
as loosely distributed spines in the translucent body wall.
Coloration pink to violet. On hard substrate, nocturnal plankton
feeder.
|
|
| |
 They
show a variety of branched or whip-like forms, which resemble
gorgonians.
The name is derived from the color of the inner
skeleton. Living colonies never appear black under water. |
|
|
