Most of you reading this have seen serpulid worms but most likely did not know what you were looking at.  These are small, curling, tubes of calcium carbonate (the same material oyster and snail shells are made of) found on rocks, seawalls, hermit crab shells, driftwood, and more.  Most who see them immediately think of corals, or a mollusk of some sort.  But they are actually tubes built by an annelid worm – a serpulid worm.

Annelids are worms whose bodies are segmented (think earthworm).  The annelids are divided into three groups – the oligochaetes (earthworms), the hirudineds (leeches), and the polychaetes (marine worms).

The polychaetes are divided into three additional groups – those that are free-moving/swimming, those that live in tubes but can leave and forge, and those that live in tubes but cannot leave them.  The last two groups are what are known as “tubeworms” – and serpulids belong to the group of tubeworms who cannot leave.

As mentioned, the serpulid worms secrete a calcium carbonate tube on such things as rocks, shells, seawalls, driftwood, even algae.  The worms live within the tube, extend appendages that resemble antenna with small hairs along them to collect food, and can close the hole so they are completely withdrawn in.  They secrete additional calcium carbonate to make the tube longer as they grow.  Serpulids can also secrete a mucous to make turning over within the tube easier.

Again, most of you have probably seen the calcium carbonate tubes of the serpulid worms on rocks and shells around our beach – but probably did not know they were produced by segmented worms – they were not what you thought they were.

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