Wood borers are highly specialised animals which penetrate
wooden structures such as boats, wharves, jetties, driftwood and
even living mangrove trees. Many can digest the wood owing to
cellulose-digesting bacteria or protozoa living in their guts.
Only a few species can actually produce their own cellulose-
digesting enzymes (cellulases). These are actually bivalves, the
body being worm-like and protected within a calcium-lined
tunnel. At the posterior end, the siphons stick out of the wood
at high tide and have two calcium plugs (pallets) to seal the
entrance of the tunnel at low tide. At the front end, the
original shell valves are used to grind away the wood. In the
days when wooden ships were important, shipworms were major
pests. These bivalves drill holes into wood, usually at very
high tidal levels. They can cause extensive damage to structures
like floating fish farms. They drill through mechanical action,
using the two shell valves as abrasive surfaces. (Length 1-2cm)
Wood-boring isopods drill holes