A Post from the Past 
Despite the name, shipworm is not a worm but a bivalved mollusc called Teredo navalis Linnaeus. The photograph above shows a piece of driftwood on the sand at Rhossili looking rather like the head of a crocodile. The wood is riddled with tunnels created by the shipworm.
Below, you can see how the entire piece of wood has been attacked until it resembles a honeycomb. You don’t need a lot of imagination to understand how big a threat this pest was to timber-built ships in the past.
Each tunnel is lined with a chalky deposit which you can see in the close-up photograph below.
For more information on the Great Shipworm see the pages of the Marine Life Information Network.
2 Replies to “Shipworms aren’t worms”
The link didn’t work for me, but I learned a lot at the Wikipedia site (https://en.wikipedia.org/wiki/Teredo_navalis). Absolutely fascinating! Thanks, Jessica, for expanding my wonder yet again.
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Thank you, Linda. The link was for the Marine Life Information Network site which has a lot of information about shipworms, including references to key papers on the subject, but lacks images for the time being, hence the crossed-out camera sign. The Wikipedia link is a great alternative. Thank you.