Shipworms 

 and 



Gribbles: 

 The 



Wooden 



■Boat 



Eaters 



By Lundie Spence 



Tiny marine borers eating their 

 way into the hulls of ships may have 

 changed the course of civilization. 



In February 1588, the Spanish 

 Armada sailed with 196 ships to 

 attack England. It had taken months 

 to outfit the ships with guns and 

 crews. Once under way, the fleet was 

 buffeted by North Sea winds in the 

 English Channel and sent back to 

 ports for emergency repairs. 



Months later, the ships again 

 sailed toward England. But the 

 victory that King Philip II of Spain 

 thought he had won was lost as 

 storms and Queen Elizabeth's navy 

 sank ship after ship. By August 1588, 

 the fleet was in shambles and scat- 

 tered around the shores of the British 

 Isles. Was it the North Sea winds, 

 inept Spanish strategy, a superior 

 British navy or Philip's hole-riddled 

 ships that cost Spain the war and 

 altered the course of history? 



Four hundred years later, some 

 naval historians speculate that vessels 

 in the Spanish Armada, infested with 

 shipworms, were unable to withstand 

 the heavy weather. 



Marine borers are typically two 

 types of animals. Shipworms, or 

 teredos, are mollusks, tiny clams with 

 long, soft bodies — perhaps a foot in 

 length. Boat repairers describe them as 

 worms with bony heads. The hard 

 parts are actually the two valves of the 

 shell. Gribbles, also called sand fleas 

 along parts of the Atlantic coast, are 

 arthropods — crustaceans like shrimp 

 and lobsters, although much smaller. 

 Adults measure only about 5/8 inch in 

 length. Gribbles are closely related to 

 the wood lice or marine roaches that 

 run around piers and floats. 



Although both borers are vegetar- 

 ians, their styles of dining differ. 

 Shipworms, like termites, have 

 bacteria in their gut to break down 

 wood fibers. But their main source of 

 food is the plankton drawn into their 

 burrows. 



Gribbles nibble on wood, using 

 the digestive enzyme cellulase. They 

 tend to follow in the path of wood rot 

 or fungus, and fungi are the principal 



Was it the North Sea 

 winds, inept Spanish 

 strategy, a superior 

 British navy or Philip's 

 hole-riddled ships 

 that cost Spain the 

 war and altered the 

 course of history? 



food of these crustaceans. Their 

 tunnels provide a safe haven for 

 shelter and reproduction. 



Shipworms can make large 

 tunnels throughout wood. Gribbles 

 make numerous, very small passage- 

 ways just below the surface of wood. 

 Shipworms can weaken wood much 

 faster than gribbles, but each is an 



Continued 



COASTWATCH 17 



