Comparing the resistance of a number of lesser known species of tropical hardwoods to the marine borer Limnoria using a short term laboratory assay
L M S Borges, S M Cragg, J R Williams
Naturally durable species of timber are used as an alternative to preservative treated timber for marine structures, but many species have not been evaluated for their potential for use in this environment. EN 275 specifies a 5-year test period - too long a period for screening tests to be economically viable. In this study, durability was assessed by measuring the production of faecal pellets by the crustacean Limnoria quadripunctata under forced feeding conditions over a number of days. Small sticks of a wide range of wood species, mainly of South American origin, were leached in seawater for one week then placed in a cell culture chamber with one animal and 4 ml of seawater. At intervals, the number of faecal pellets per chamber was counted, and the dimensions of the faecal pellets were measured. The number of pellets produced by animals feeding on Scots pine sapwood, which is non-durable, was used as a basis for comparison. Mortality rates were also compared. Lower pellet production rates and higher mortality rates were taken as measures of natural durability. Some lesser known species performed as well or better than species with a reputation for durability in the marine environment.