The photographs in this post show a small piece of water-logged driftwood about 30 cm long and riddled with holes and tunnels caused by two different types of wood-boring sea creatures. The larger borings are about 1 cm in diameter and many are lined with a smooth calcareous material that has become stained through burial in the beach sediments. These larger borings may be familiar to beachcombers as being made by Shipworms, Teredo navalis Linnaeus. I have talked about these worms – which are not really worms but bivalved molluscs – elsewhere in the blog.
Less familiar, are the much smaller holes and burrows in this piece of soft wood. These have been made by Gribbles, Limnoria lignorum (Rathke). Gribbles are very small marine isopod crustaceans. Crustacea is the major grouping that includes the crabs, prawns, and sandhopper types of animal. Isopods are a bit like the terrestrial woodlice that you see in gardens – they have an ‘armoured’ body with lots of limbs and joints; and their body is flattened from top to bottom – compared with amphipods such as sandhoppers in which the body is flattened from side to side. Gribbles are very small and their length rarely exceeds 3.5mm.
Shipworms can burrow into hard wood but Gribbles prefer wet, cool and soft wood, like the bases of exposed pilings on piers and jetties. The pictures here show the infestation damage caused by both Gribbles and Shipworms that leads to the destruction and disintegration of the timber.
Revision of a post first published 29 May 2010
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Jessica's Nature Blog 
So bad for the boats, and yet the little gribbles are just trying to make a living. I’m glad they have a cute name, at least. Sorry to sound so shallow! But everything is beautiful when looked at for itself, isn’t it?
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“Gribble” sounds like something from a Dr Suess story, doesn’t it? They are a real pest because of their eating habits but I dare say they are quite cute in their own way. I haven’t seen one yet but I’ll post a picture when I do – then we can see whether they are beautiful or not.
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I went to school with a girl who rejoiced in the name Rosemary Gribble….and now I know what a gribble is!
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I hope she didn’t look like a gribble or share with it in any nasty eating habits! Did she chew the ends of her pencils?
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I can’t really remember! She was one of the nicer girls and I have very occasionally seen her when visiting my home town.
I had an acquaintance at university who used to destroy any pens/pencils he was loaned by chewing them to nothing; I never loaned him anything again after I was presented with the remains at the end of a lecture. In my final year, he was sectioned as a result of a siege where he held one of the lecturers hostage to try and prove that he was Jesus Christ come back; the lecturer was an ex-monk… What larks, what larks!
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Viv, you have had some incredibly colourful experiences in your life. I hope that chewing wood is not a sign of madness – otherwise there are a lot of crazed gribbles, piddocks and beavers out there.
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The gribble and shipworm of course are inspirational to me as an artist .the piece of wood i collected sometime back on the beach is being worked at to have a new dimension.
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It would be interesting to see what you have created when it is finished. Art and nature.
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Gribble are salt water creatures. The British “Hearts of Oak” warships were periodically brought up river in places like Bucklers Hard on the Beaulieu river to spend some time in the fresh water to kill off the gribble.
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That is very interesting. I did not know that the old warships were treated this way. Thank you, John.
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