An interim report on studies of the tolerance by Sphaeroma (Crustacea: Isopoda) of CCA-treated timber
S M Cragg, J D Icely
In Papua New Guinea any untreated timber exposed to seawater close to mangrove stands is liable to be attacked in the intertidal zone by the crustaceans Sphaeroma terebrans or Sphaeroma triste. Even CCA-treated timber is sometimes vulnerable. The mouth-parts of these animals are adapted for boring, but whether wood particles are ingested remains to be resolved. Some limbs of Sphaeroma terebrans appear to be adapted for filter-feeding. In both species a portion of the gut, the hepatopancreatic caeca, contains cells in which large quantities of copper are concentrated. Specimens of Sphaeroma terebrans taken from CCA-treated piles had an average of 35 mg copper per gram dry weight of hepatopancreatic caeca: the corresponding figure for Sphaeroma triste was approximately 7 mg/g. Specimens of Sphaeroma terebrans taken from mangroves had much less copper in them than those from treated wood. No such clear-cut difference was evident in the case of Sphaeroma triste. Analyses of CCA-treated piles infested with Sphaeroma showed that Cu, Cr and As levels were high at the surface, but that levels in the interior of the pile had dropped since installation Further studies of Sphaeroma gut function are in progress.