Improved plate assay for antifouling substances using blue mussel Mytilus edulis galloprovincialis

An improved plate assay for screening antifoulants against blue mussels, My tilus edulis galloprovincialis, was designed based on an assay contrived by Ina and colleagues. To obtain more reliable results, the number of test mu ssels for one sample was increased from 4 to 10. Cardboard pieces used as t est plates were cut into rectangular shapes to separate the test sample and the blank zone, which are of the same area. Activity was expressed numeric ally. In this improved method, several inhibitors of byssus thread formatio n were isolated by using a smaller amount of sample per area than in the or iginal method. Previously our laboratory developed a foot-stimulating bioas say for the same purpose. This method requires only a small amount of sampl e and is therefore useful for isolating antifouling substances from natural sources, including marine organisms. However, the inhibition of byssus thr ead formation cannot be directly evaluated in the foot-stimulating method. The improved plate assay and the foot-stimulating method were examined and compared using a secosterol from the sponge Dysidea granulosa and CuSO4.