Hitchhiking on the surface of a boat hull can be a rough ride, but barnacles seem to do it with ease. How are they able to hang on so tightly? Researchers have been studying the composition of super-strong barnacle glue for years, and a new analysis of the cement reveals that it has many of the same properties as a human blood coagulant, factor XIII, which helps to form scabs.

"It seems likely that barnacle glue polymerization is a specialized form of wound healing," Dan Rittschof of Duke University said in a prepared statement. The glue analysis he headed up was published online today in the Journal of Experimental Biology.

After quickly gathering unpolymerized glue from lab-based mussels before it set (which happens in about five minutes), the research team analyzed it using an atomic force microscope. In the glue, they noticed tangled fiber webs that resembled those found in blood clots.

They also discovered clot-enhancing enzymes similar to the trypsinlike serine proteases found in blood. Using mass spectrometry, the team found that some of the protein sequences in the barnacle glue were quite similar to those in human factor XIII, which causes fibers to crosslink and form clots.

The surprising findings might have interesting evolutionary implications. "The presence of biochemically similar proteins in the two systems suggest that these two processes may be derived from common ancestral elements," Rittschof and his colleagues wrote.
 
Not just a petty problem, a mass of these barnacles can spell a big cut in fuel efficiency for ships as well as trouble for other submerged industries. So figuring what keeps them on boats may help researchers figure out how to take them off—or keep them from getting there in the first place.

Another component of the sticky mixture used by barnacles and mussels, chemists discovered in 2004, is iron. "Understanding how marine glues are formed could be key to developing surfaces and coatings to prevent adhesion," Jonathan Wilker of Purdue University, who authored the 2004 study in Angewandte Chemie International Edition, told ScientificAmerican.com at the time.

Although the authors of the most recent study don't propose a solvent for the cement, other suggestions for keeping boats and other submerged equipment barnacle-free are circulating. They include electrical shocks and fungus-laden paints.

Image of barnacles glued onto a ship courtesy of iStockphoto/Westhoff