If the wood panels were treated with preservatives which are effective against 

 shallow water borers, it is possible that they would also resist deep water borers. 

 However, wood panels treated with various kinds of preservatives should be exposed 

 In the deep ocean to confirm this, because the borers found in the deep ocean are 

 different from the ones found in shallow waters. 



Tropical Wood Panels. Tropical wood specimens such as greenheart, Afambeau , 

 and Antidesma pulvinatum were exposed to determine their resistance to marine 

 borers. In northern Europe and in some tropical areas, the use of naturally resistant 

 wood is more common than the use of creosote-treated timbers for pilings. One of 

 the most widely used of the naturally resistant timbers is probably greenheart ( Octea 

 rodiaei ). It is grown commercially in British Guiana and is often called Demerara 

 greenheart. The high resistance of greenheart to marine borers has been attributed 

 to the presence of toxic alkaloids. These alkaloids have been isolated and were 

 found to be quite toxic to Teredo, a molluscan borer, but less toxic to Limnoria , a 

 crustacean borer (Reference 8). 



The three tropical wood specimens were attacked by borers (Figure 25). Of 

 these, greenheart sustained the heaviest damage with 14 borers per square inch. The 

 shells of some borers measured about l/8 inch in diameter, and the borers had pene- 

 trated over 1/4 inch into the wood. Afambeau had 7 immature borers per square inch. 

 The borers had penetrated about 1/32 to l/l6 inch. Antidesma was the most resistant 

 of the three tropical wood specimens, with only 2 immature borers per square inch. 

 These borers had penetrated about 1/32 to 1/16 inch. This information was obtained 

 from an examination of a single panel of each of the tropical wood specimens which 

 were exposed about 1 foot above the sediment layer. 



Rope Specimens. A heavy slime growth was present over the surface of cotton 

 and manila ropes, and a light slime growth was present over the surface of nylon and 

 polypropylene ropes. 



The fibers of cotton were decayed considerably by bacterial action and, as a 

 result, were easily torn apart by one's fingers. The borers were not found on the 

 surface of any of the cotton rope specimens. A test revealed that the cotton rope 

 specimens had lost about 85% of their breaking strength. The l/2-inch-diameter 

 manila rope specimens were completely destroyed by both borers and microorganisms. 

 Borers ranging In size from 1/32 to 1/8 inch in diameter had completely Infested the 

 entire length of the 5-foot-long rope specimens (Figure 26). The rope fibers were 

 severed from deep penetration. The slime bacteria were also responsible for the 

 decay and deterioration of the fiber materials. 



Examination of the nylon and polypropylene ropes under stereoscopic micro- 

 scope showed that the fibers of these ropes were not damaged by marine borers. On 

 the contrary, they were in very good condition (Figure 27). Table 4 compares the 

 breaking strength of these rope specimens before and after deep sea exposure. 



26 



