|Wood ravaged by shipworms, from Wikimedia Commons|
Now, how a shipworm lives on wood as its diet actually depends on the microorganisms it harbors in its gills - much like a termite relies upon symbiotic bacteria in its gut to digest the wood it consumes. Wood, believe it or not, is mostly a carbohydrate called cellulose, and unlike starch, isn't so easily digested into sugars. Various types of cellulose, from paper to switch grass, represent stores of locked up energy, and the biofuel industry seeks out cellulases for industrial production of ethanol from cellulose rather than starch. And shipworms carry a different set of bacteria for it's cellulosic diet, representing a potentially valuable trove of tools to fuel the ship, even if the mollusc itself dines on the hull.