Sailors, shipwrights, and those who build docks and piers have known about shipworms for centuries.  These creatures bore tunnels through the wood forming numerous holes throughout making the pilings on docks less stable and causing ships to sink.  The ancient mariners really disliked shipworms and tried numerous things to keep them from eating the wood – including metal plating and a very toxic resin soaked into the wood called creosote.  Today these worms are still troublesome for dock owners, and many have seen evidence of shipworms when they find a piece of driftwood, or a piece of timber that has been in the water for some time.

But here is the thing.  Shipworms are not what you think… they are not worms… but rather a type of clam.  Did not see that one coming did you…

Yep – “shipworms” are in the Phylum Mollusca (which includes the clams, snails, and octopus) and in the Class Bivalvia (mollusk that have two shells – like clams, oysters, and… shipworms).  Typical bivalves include clams, oysters, mussels, and scallops.  Clams move by using a muscular foot, oysters and mussels do not move, and scallops can “swim” using the adductor muscle to create jet propulsion.  But there is a group of boring bivalves, ones that can penetrate firm substrate such as peat, clay, sandstone, shell, coral, and wood.

Boring bivalves settle on a hard substrate as planktonic larvae and begin their burrow.  Once the burrow begins, they are locked in there for the rest of their lives, only the breathing tube known as the siphon extends out of the opening.  If it is removed from the burrow, it cannot begin creating a new one.  The drilling process involves using the two valves (shells) which are serrated.

The body of a shipworm is greatly elongated and cylindrical.  The valves are greatly reduced in size.  Mollusk possess a thin tissue called the mantle from which their shells are secreted.  The mantle of the shipworm secretes a thin shell which will cover the lining of the burrow itself.  These burrows can be quite long – ranging from 7 inches to over 6 feet.  They can live from one to several years.

The sawdust created during excavation is used as a food source.  For those who feed primarily on sawdust, nitrogen-fixing bacteria within the gut compensate for the low protein levels.  The other source of food would be plankton.

So… shipworms were not what you thought they were.

0