SEA ANEMONES (Actiniaria)
Anemones are closely related to reef-building hard corals. Essentially
an anemone is nothing more than an overgrown coral polyp that lacks
a hard skeleton.
As in many types of coral polyps the anemones tentacles
contain a special type of alga known as zooxanthellae. It utilizes
sunlight and carbon dioxide to produce high-energy substances (sugar),
which are leaked to the host anemones, thus providing an important
dietary supplement.
Because of their relationship with zooxanthellae,
most of the large anemones achieve maximum growth in shallow, sun-lit
waters. The alga is also responsible for imparting a greenish or
brown hue to the tentacles.
Anemones can multiply by means of fragmentation.
Sexual reproduction also occurs. Anemones normally feed on planktonic
plants and small animals.
Some species live in symbiosis with fishes.
Most fishes would be stung by the anemone, but clown fishes have
a special mucus coating, which prevents the anemone from stinging
them.
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 Exposed
on hard substrates of drop-offs and slopes. The color is variable,
tentacles greyish with yellowish tips.
Lives in symbiosis
with clown fishes. |
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 Settles
from close to surface down to 30 m.
The body is smooth and
folded. The carpet-like tentacles have strong stings. |
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 Very
common at the Similans, but often unnoticed, because hidden in cracks on hard
substrates.
The tentacles are swollen at the tip. Occurs in
many different colorations, depending on the zooxanthellae. |
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JELLYFISHES (Cnidaria)
The Phylum Cnidaria, besides corals and anemones, also contains
Jellyfishes. Although at first, it appears they have nothing in
common, there are a few similarities that bind them. First and foremost
is the basic body plan. Also, they have the same larval stage known
as a planula.
Basically the medusa and the polyp are very similar
in their organization, consisting of a soft body with tentacles
clustered around a central mouth. In the medusa the mouth and the
tentacles are usually directed downward, but in polyps they are
typically directed upwards or laterally.
The sting of many jellyfishes
is harmless; their stinging cells are not able to penetrate human
skin. However a few species are capable of delivering very painful
stings and a few can cause death. It is best to avoid contact with
all of them, just to be on the safe side.
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 Length:
to 50 cm
These jellies have a thick, fluffy frill between the upper
bell and lower tentacles.
The central frill underneath actually
contains numerous mouths, that are particularly efficient
for trapping small organisms from the surrounding water. |
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