A SPINSTER OF RARE BEAUTY

A species of crustacean makes silk underwater

SPIDER silk is impressive stuff. Stronger than steel, flexible and exceedingly light. Barnacle glue is equally special. It holds an animal whose ancestors swam freely in the sea to rocks that are often battered by powerful waves. What, then, might a combination of the two achieve?

Fritz Vollrath, of Oxford University, hopes to find out. As he describes in Naturwissenschaften, he and his colleagues have found that a small marine crustacean called Crassicorophium bonellii produces a material which has the adhesive characteristics of barnacle glue and the structural properties of spider-silk fibres. It is water-resistant and flexible, but also somewhat sticky, and is employed by the animals to construct tubular homes in the sediments of the sea bed.

Dr Vollrath's examination of Crassicorophium showed that the material is secreted by glands similar to those used by barnacles to make their cement. Given that Crassicorophium and barnacles are both crustaceans, albeit ones whose common ancestor lived 100m years ago, that suggests a single origin for the ability to make this type of goo. Indeed, it might explain the mystery of how barnacles settled down in first place. Possibly, a Crassicorophium-like ancestor used the material to anchor itself to rocks and feed on passing titbits by catching them with its legs, as modern barnacles do. (The protective plates presumably came later.)

To examine the relationship between the newly discovered goo and barnacle glue, Dr Vollrath's colleagues, Katrin Kronenberger and Cedric Dicko, took a look at the chemical composition of both. The proteins of barnacle glue, they discovered, are dominated by amino acids called proline and isoleucine. These like to form cross-links between protein molecules, and thus tend to hold such molecules together. Crassicorophium goo, by contrast, is dominated by lysine, glycine and aspartic acid. These encourage protein molecules to stretch out and form fibres.

In addition, whereas barnacles just ooze out their cement, Crassicorophium processes its material in a spider-like spinning duct. The goo emerges from holes in the crustacean's legs and is spun into gossamer filaments by being stuck to a surface and then pulled out as threads.

This way of spinning silk is remarkably similar to that used by spiders, which pull the material from their bodies using their legs. That similarity, though, is almost certainly the result of convergent evolution rather than a common origin, since the last joint ancestor of Crassicorophium and spiders lived way longer ago than the ancestor of Crassicorophium and barnacles.

Beyond its curiosity value, the discovery of Crassicorophium silk could have practical benefits. There is great interest, in biotechnological circles, in using silk more extensively as an industrial material. Its lightness, flexibility and strength would make it widely deployable. Adding Crassicorophium silk—or, at least, knowledge derived from its analysis—to the mix would extend that range. Dr Vollrath, for example, suggests that Crassicorophium silk's tolerance of salt water means it might find uses in medical applications where it would come into contact with salty bodily fluids. Thus, with luck, can curiosity-driven research of the most esoteric kind lead to good, solid human benefits.

                                                       Source: (The Enconomist)