Barnacles are capable of attaching themselves to virtually any underwater surface; from whale skin and turtle shells to ship hulls and pier structures. Just how they manage to keep themselves anchored has remained a mystery; a multimillion mystery since barnacles increase fuel consumption by adding additional drag to the submerged parts of marine vessels. Scientists knew that the barnacles used a type of glue, but they didn’t understand how it worked and why it was so strong.

Traditionally, toxic paint has been used to keep the barnacles away but dry-docking huge cargo ships every so often to have them repainted is naturally expensive. Also, the toxic paint is not only affecting the barnacles; it is causing problems for entire ecosystems and many countries have therefore decided to ban or limit the use of some of the most harmful ones.

Using modern techniques such as force microscopy and mass spectrometry, a team of scientists from Duke University’s Marine Laboratory in Durham has now managed to find out how barnacles stick to surfaces; a discovery which they hope will lead to the development of more environmentally friendly anti-barnacle remedies.

The research team unveiled that barnacle glue from the species Amphibalanus amphitrite binds together much the same way as red blood cells bind together when our blood clots. When our blood clot, several different enzymes work together to form protein fibres that bind the cells together. In barnacle glue, similar enzymes – known as trypsin-like serine proteases – do the same thing. Interestingly enough, one of these enzymes are remarkably similar to Factor XIII, and essential blood clotting agent present in human blood.

“We’ve found homologous enzymes in barnacles and humans, which serve the same function of clotting proteins underwater, despite roughly a billion years of evolutionary separation,” says research team member Dr Gary Dickinson.

Another team member, Professor Dan Rittschof, explains that this similarity does make evolutionary sense.

“Virtually no biochemical pathway is brand new. Everything is related and really important pathways are used over and over,” says Rittschof. “Really key parts of those pathways can’t change because if they do, the pathway fails and the animal dies.”

According to Dickinson, it wouldn’t be surprising to find this glue in other organisms besides the barnacles.

“The enzymes are highly conserved because they are very effective at what they do, ” says Dickinson. “There are bound to be a number of other organisms that use the same enzymes for the same purpose.”

For more information, read the article in The Journal of Experimental Biology.

http://jeb.biologists.org

North Carolina State University engineers have created a non-toxic ship hull coating that resists the build up of barnacles.

Barnacles that colonize the hull of a ship augment the vessel’s drag which in turn increases fuel consumption. After no more than six months in salt water, the fuel consumption of a ship has normally swelled substantially, forcing the ship owner to either spend more money on fuel or to remove the ship from the water and place it in a dry dock where it can be cleaned. Both alternatives are naturally costly, and for many years ship owners fought barnacles by regularly coating ship hulls with substances toxic to barnacles. Unsurprisingly, these substances turned out to be toxic to a wide range of other marine life as well, including fish, which caused most countries to ban their use.

Ships are not the only ones colonized by barnacles. In the wild, it is common to see barnacles attached to a wide range of marine species, such as whales and sea turtles. One type of animal is however usually free of barnacles: the sharks. Unlike the smooth-skinned whales, sharks tend to have rough and uneven skin, and this might prove to be the salutation for ships as well.

The new hull coating created by Dr. Kirill Efimenko, research assistant professor in the Department of Chemical and Biomolecular Engineering, and Dr. Jan Genzer, professor in the same department, contains nests of different-sized “wrinkles” which makes the surface rough and uneven, just like the skin of a shark.

The wrinkly material was tested in Wilmington, N.C and remained free of barnacles after 18 months of exposure to seawater. Flat coatings made of the same material were on the other hand colonized by barnacles within a month.

“The results are very promising,” says Efimenko. “We

are dealing with a very complex phenomenon. Living

organisms are very adaptable to the environment, so

we need to find their weakness. And this hierarchical

wrinkled topography seems to do the trick.”

Efimenko and Genzer created the wrinkles by stretching a rubber sheet, exposing it to ultra-violet ozone, and then relieving the tension, causing five generations of “wrinkles” to form concurrently. After that, the coating was covered in an ultra-thin layer of semifluorinated material.