Samplings: February 2010

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Left: Amphibalanus amphitrite; X-ray tomographic image shows section of A. amphitrite shell

Gary H. Dickinson; X-ray image: Richard K. Everett

Barnacles make their living clinging to one spot and filter-feeding on plankton. The virtually insoluble, protein-rich cement that anchors them in place has been tricky to study, though not for lack of interest: scraping the crustaceans from ships’ hulls and other marine gear is a huge expense.

“No one ever thought to ask the simple question . . . what is [the] glue related to?” says Daniel Rittschof of Duke University, who, with his then doctoral student Gary H. Dickinson and several colleagues, recently discovered the glue’s surprising biochemical origins. Since compounds essential to survival can be evolutionarily conserved over millennia, Rittschof and Dickinson hypothesized that barnacle glue shares a curing mechanism with another sticky bodily fluid: clotting blood.

Working with the Amphibalanus amphitrite barnacle, Dickinson collected its glue by pricking the base plate of the shell and gently squeezing out droplets. Investigating the glue’s components, the team detected a protein-cutting enzyme, or “protease,” known to be involved in human blood clotting. Then, closely examining cement proteins, they found amino acid sequences that, despite a billion years of evolution, exactly matched sequences in a human blood-clotting protein that cross-links fibers during scab formation.

Rittschof suspects that barnacle-cement bonding is an evolutionary modification of wound healing, and that many other marine invertebrates use the same chemistry to get a grip. (Journal of Experimental Biology)