worms > Phylum Annelida >
> Order Sabellida > Family Sabellidae
learn only 3 things about them ...
These worms are segmented like the more familiar earthworm.
They disappear rapidly into their tubes. Don't step on
feathery fan is actually made up of modified tentacles.
It gathers food.
seen? Even those who find worms icky will be delighted
by these elegant feathery creatures. They are more commonly seen on
our Northern shores but also encountered on the Southern shores. They
are found mainly in or near coral rubble areas. Some are found in
the sand. There are large ones (about 8cm in diameter), small ones
(2-3cm in diameter) and even tinier ones that can hardly be seen.
These worms are wary, though, and will disappear instantly into their
tubes are the slightest sign of danger. So you have to approach them
What are fan worms? Fan worms
are segmented worms belonging to Family Sabllidae, Class Polychaeta,
Phylum Annelida. The polychaetes include bristleworms, and Phylum
Annelida includes the more familiar earthworm. The segmented portion
of the fan worm is usually well hidden inside the tube like other
Fan worm features: The feathery
fan that we see is stuck on the top of the worm's head! The circular
fan is actually made up of two halves. Each long 'feather' of the
fan is actually a modified tentacle called a radiole. Each radiole
has many pinnules (feathery branches).
Each pinnule is covered with cilia (tiny beating hairs). The cilia
generate a current, sucking water from below the fan, through the
pinnules and out through the centre of the fan (indicated by the blue
arrows). Cilia on the pinnules gather tiny food particles from the
current and send these to a groove along the length of each radiole.
Cilia in the groove sort out food particles by size as they bring
these particles to the central mouth.
A pair of palps near the mouth removes particles which are too large:
cilia on the palps carry these particles to the centre of the fan
and toss them into the outgoing current. Only suitably small particles
Dinesh took video clips of some of these
animals flourescing under black light!
Down the Tubes: Fan worms live
in a flexible, leathery tube. The tube is often much longer than the
worm. Some fan worms have eye spots on their tentacles to detect movement.
Fan worms will slip instantly into their tubes at the slightest sign
of danger. The tubes also keep them moist and safe on the rare occasions
when they are exposed at low tide. Fan worms don't have an operculum
to close off their tube entrance. Instead, when they retreat into
their soft tube, the tube entrance collapses to seal the opening.
How does a fan worm make its tube?
Sand grains of suitable size are collected and stored in a sac. The
sand is mixed with mucus and extruded as a string of tube material.
The worm rotates its body to apply this string to the tube, to lengthen
or repair it.
It moulds the string with a special fleshy fold of tissue near the
top of its body (which looks like a shirt collar), almost like building
a pot out of clay ropes.
worm: Feather-duster or 'Christmas tree fanworms' more
familiar to divers belong to Family Serpulidae.
These worms build hard tubes out of calcium, while fan worms' don't.
Feather duster worms usually have an operculum to cover the tube opening,
while fan worms don't. More on how to tell apart animals
with a ring of feathery tentacles.
Human uses: Unfortunately, fan
worms are popular in the live aquarium trade and collected for this
A fan worm (Sabella spallanzanii) introduced to Australian
harbours and coasts is affecting some mussel farms because they grow
on the lines meant for mussel larvae settlement. Dense growths of
these worms foul up dredges and nets, overgrow seagrass and are such
effective filter feeders that they deprive native filter feeders of
Status and threats: Like other
fish and creatures harvested from the wild, most die before they can
reach the retailers. Without professional care, most die soon after
they are sold. Often of starvation as owners are unable to provide
the small creatures and plants that these fishes need to survive.
Those that do survive are unlikely to breed. Like
other creatures of the intertidal zone, they are affected by human
activities such as reclamation and pollution. Poaching by hobbyists
can also have an impact on local populations.
Tuas, Dec 03
This fan worm is out of water. Its fan is
collapsed, and its body segments clearly visible.
Changi, Jul 04
Pulau Hantu, Aug 04
Current generated by the worm is
in the direction of the blue arrows
Collar on a fan worm that is
used to create the tube.
Pulau Sekudu, Aug 05
Sabellidae recorded for Singapore
from Wee Y.C. and
Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
Guide to Singapore Polychaetes by
Lim Yun Ping 1997-2000
worms seen awaiting identification
are difficult to positively identify without close examination.
On this website, they are grouped
by external features for convenience of display.
- Wee Y.C.
and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore.
National Council on the Environment. 163pp.
- Ng, P. K.
L. & Y. C. Wee, 1994. The
Singapore Red Data Book: Threatened Plants and Animals of Singapore.
The Nature Society (Singapore), Singapore. 343 pp.
Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral
Reef Animals of the Indo-Pacific: Animal life from Africa to Hawai’I
exclusive of the vertebrates
Sea Challengers. 314pp.
- Allen, Gerald
R and Roger Steene. 2002. Indo-Pacific
Coral Reef Field Guide.
Tropical Reef Research. 378pp.
- Edward E.
Ruppert, Richard S. Fox, Robert D. Barnes. 2004.Invertebrate
Brooks/Cole of Thomson Learning Inc., 7th Edition. pp. 963
Jan A., 2005. Biology
of the Invertebrates.
5th edition. McGraw-Hill Book Co., Singapore. 578 pp.