Keelworm tubes are common under stones and on hard surfaces on probably
all our shores. Keelworms also encrust ship keels (thus their common
name) and in fact, any hard surface that is immersed in the sea, including
shells and bodies of hard animals. For this reason, they are often
What are keelworms? Keelworms
are segmented worms belonging to the Family Serpulidae, Class Polychaeta,
Phylum Annelida. The polychaetes include bristleworms, and Phylum
Annelida includes the more familiar earthworm.
Not all tubeworms are polychaetes and not all polychaetes are
tubeworms. More about tubeworms
Features: Tubes about 0.5cm in diameter and 5-8cm long,
usually under stones. The keelworm secretes a hard tube out of calcium
carbonate to protect their soft bodies. These hard tubes allow them
to settle in tough places such as the underside of a stone. A little
knob on a stalk, called the operculum, seals the opening from predators
and reduces water loss at low tide. The operculum is actually a modified
tentacle. The worm's head is topped by a fan of feathery tentacles
(called a radiole) that is extended at high tide. They also breathe
through these feathery tentacles.
Sometimes confused with
snails that also build tubes on rocks. Tubes made by worms such
as keelworms are dull on the inside and made up of two layers. Tube
worms have segmented bodies. Tubes made by snails such as vermetids
are glossy on the inside because of a deposit of nacre, and made up
of three layers. Vermetid snails do not have segmented bodies. Here's
more on how to tell apart animals
that make hard coiling tubes.
What does it eat? The keelworm
is a filter feeder, using its feathery tentacles to gather edible
bits from the water.
Similar worm: The popular 'Chrismas
tree fan worms' that are often photographed by divers belong to this
family. These worms have large spiral fans and build hard tubes out
of calcium in rocks and dead and living corals. The fan worms that
we see more often on the intertidal belong to the Family
Sabellidae and these build soft tubes out of mucus.
Human uses: Keelworms are among
the important animals that form the fouling community. These encrusting
animals grow on the undersides (keels) of ships, piers and other hard
surfaces in the sea. Fouling animals can affect the efficiency of
these structures and equipment and thus affect human activities.
Growing on a living small crab.
Changi, Oct 11
Growing on a shell occupied by a hermit
Changi, Jul 08
difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of
on Singapore shores
- 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.
- Jones, R.E.
(Ed.) et al. 2000. Polychaetes and Allies: The Southern Synthesis
Australian Biological Resources Study, Canberra. 465pp.