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worms
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worms > Phylum Annelida >
Class Polychaeta
> Order Sabellida > Family Sabellidae
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| Fan
worms Family Sabellidae updated Oct 08
Where 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 stealthily. 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 tubeworms. 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 are eaten. Andy 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. Similar 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 purpose. 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 food. 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 |
These worms are segmented like the more familiar earthworm.
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non-fluorescing orange fan worm @ sekudu - Oct2011 from SgBeachBum on Vimeo. |
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white spiral fan worm @ sekudu - Oct2011 from SgBeachBum on Vimeo. |
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Sabellidae recorded for Singapore from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. and A Guide to Singapore Polychaetes by Lim Yun Ping 1997-2000
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Links
References
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The Nature Society (Singapore), Singapore. 343 pp.|
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