Figure 19. Untreated wood bait piece riddled by marine borers. 



Wood Panels. All the wood specimens were severely damaged by molluscan 

 borers. As shown in Figures 19 and 20, the wood bait pieces which were fitted 

 around the plastic rods and tubes, as well as the plywood panels, were riddled by 

 the borers. These have been identified as Xylophaga washlngtona Bartsch and 

 Xylophaga duplicata Knudsen. The majority of the borers measured about 1/2 inch 

 in diameter (Figure 21). Some of the damaged wood specimens could easily be 

 broken apart by hand. A complete description of the above-mentioned borers Is 

 presented in References 7 and 8. 



Generally, the wood specimens which were exposed near the sediment were 

 damaged considerably more severely than those specimens which were exposed about 

 3 feet above the sediment. This Indicates that the deep sea borers are very active 

 in large numbers Immediately above the sediment layer and that their numbers tend 

 to decrease in seawater as the distance from the sediment layer increases. A similar 

 phenomenon has been reported in Reference 9. It is possible that these borers may 

 not be present in seawater about 25 feet above the deep sea floor. It is suggested 

 that deep sea currents play an Important role in the distribution and settlement of 

 larvae on wood. 10 



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