Published online by Cambridge University Press: 31 January 2011
The freshwater Zebra Mussel, Dreissena polymorpha, was accidently released into the Great Lakes approximately 20 years ago. Since then it has spread rapidly, thanks in part to its ability to adhere to hard substrates, resulting in serious environmental and economic consequences. Like the marine mussels, attachment of the Zebra Mussel is achieved by means of its byssus, a series of proteinaceous threads that connect the animal to surfaces via secreted adhesive plaques. While the byssus of the Zebra Mussel is superficially similar to those of its marine counterparts, significant structural and compositional differences suggest that further investigation of the adhesion mechanisms in this freshwater species is warranted. Here we examine for the first time the detailed distribution of DOPA (3,4-dihydroxyphenylalanine)-containing proteins in the Zebra Mussel plaque and threads, as well as the enzyme responsible for their cross-linking. We show that the plaque-substrate interface retains the greatest amount of DOPA after aging, consistent with an adhesive role, while in the threads and bulk of plaque DOPA is presumably cross-linked for cohesive strength. We report also on a remarkably uniform layer ˜10 nm thick on the underside of the plaque, which is most likely responsible for adhesion.