Sea
anemones
Class Actiniaria
| Sea anemones are plentiful on Chek
Jawa. The most obvious ones are the huge carpet anemones that
often amaze first-time visitors. |
|
There
are about 800 species of sea anemones
|
|
Many of the commonly seen sea anemones of Chek Jawa have yet to be
studied. Thus they are still unidentified. Here is a gallery of some
of them.
Sea anemones are solitary, large polyps. Most sea anemones are made
up of a thick body column topped by a broad, flat oral disc covered
with hollow tentacles. The other end of the body column often ends
in a flat muscular pedal disc that attaches to a surface or buries
part or most of the body column in sand or mud. The mouth is in the
centre of the oral disc. To protect themselves from danger and drying
out, sea anemones can retract in such a way that the outside of body
column closes around the oral disc, like a draw-string purse.
Many sea anemones have tentacles armed with nematocysts, stingers
that can inject toxins. They also have stingers that produce only
a long adhesive threads (called spirocysts). These make the tentacles
sticky and are used to capture hard-bodied prey such as crabs. Tentacles
then move the meal to the central mouth, which can expand wide to
swallow it whole. Like other cnidarians, sea anemones lack an anus
so indigestible bits are later spat out through the mouth.
Anemone Food: Most anemones eat
marine invertebrates, some eat small particles, detritus and plankton
that they gather from the water. But large ones can capture and eat
fish. Many sea anemones also harbour in their tentacles, zooxanthallae
(symbiotic single-celled algae) that photosynthesise. In exchange
for safety and nutrients, the zooxanthallae provide the sea anemone
with some products of photosynthesis.
Anemone Haven: Some creatures
have adapted to live among the tentacles of sea anemones. The Anemonefish
(Amphiprion sp.) is coated with mucous that does not trigger
off the host sea anemone's stingers. The fish enjoys protection in
the sea anemone's tentacles, and may feed off the host's leftovers.
In return, the fish may defend the sea anemone from some predators,
remove dead tissues and by its constant swimming about, keep the tentacles
free of sediments. Each species of Anemonefish lives in a specific
species of sea anemone. In fact, it is believed that the sea anemone
releases chemicals that attract juvenile Anemonefish of the right
species to take up residence in it. Other creatures that also make
their homes in sea anemones include shrimps, crabs, brittle stars.
Anemone Babies: Most sea anemones
are hermaphrodites, but act as one gender at any one time. That is,
they produce either sperm or eggs during one reproductive period.
Fertilisation may be external, or the eggs may be fertilised inside
the anemone. The eggs develop into free-swimming larvae that eventually
settle to the bottom and develop tentacles. Some sea anemones can
reproduce by detaching a portion of their body, such as the pedal
disk, or even by dividing into two. The detached portion eventually
grows into new sea anemones. |
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Carpet anemone
Unidentified anemone
Unidentified anemone
Unidentified anemone
Unidentified anemone
Anemone with tentacles retracted
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