Researchers at Duke University have found that the glue secreted by the lowly barnacle, which enables him to hitchhike on the underside of a boat, bears remarkable similarity to the clotting mechanism of human blood.

Curious about the lifestyle of barnacles, Dan Rittschof from Duke University decided to find out how barnacle adhesive polymerizes under water. "The process must be related to something, because glue isn't de novo," Rittschof was quoted as saying. What else coagulates under water, he wondered, and came up with two answers: blood and semen.

Was barnacle glue polymerization really an extreme example of scab formation? Rittschoff teamed up with Gary Dickinson to work out how to collect the unpolymerized glue and keep it fluid. The research team learned to gently lift polymerized glue away from the barnacle pores that secrete the adhesive and collect the minute drops as they oozed from the shell.

Dickinson found that the fluid polymerized rapidly and was packed full of protein. Using atomic force microscopy, Dickinson observed tangled webs of fibers in his glue drops, which were very similar to the tangled fibers in blood clots.

Knowing that blood clots form when certain enzymes trigger a cascade of events that culminates in the formation of the long fibers found in blood clots, Dickinson and Rittschoff searched for the enzyme in the unpolymerized barnacle glue. The researchers were able to see the pattern that suggested the enzyme was present, and when they added an inhibitor to inactivate it, the glue sample failed to set.

They found that one of the barnacle glue proteins was remarkably similar to human factor XIII, an essential human blood clotting factor that cross-links clot fibers to form a scab.

"It seems likely that barnacle glue polymerization is a specialized form of wound healing," said Rittschoff, and he suspects that other marine animals that rely on glue to get a grip may use the same polymerization mechanism.