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Battle against barnacles goes genetic

Aug. 16, 2010
Courtesy of the University of Gothenburg
and World Science staff

They’re ti­ny sea crea­tures that cause a huge drag on boat­ing and ship­ping act­iv­i­ties world­wide: bar­na­cles. In droves, they latch al­most per­ma­nently on­to sur­faces such as ship hulls. That re­duces ves­sel speed and of­ten drives boat own­ers to use tox­ic hull coat­ings to keep them off.

Members of a barnacle species known as acorn barn­acles. (Image cour­tesy South Caro­lina Dept. of Na­tur­al Re­sources)
Now, sci­en­tists have iden­ti­fied a gene that they say might be the bar­na­cles’ Achil­les Heel when it comes to at­tach­ing them­selves. That knowl­edge, they say, opens up the pos­si­bil­ity of an an­ti­foul­ing paint that goes easy both on bar­na­cles and on the en­vi­ron­ment.

A sub­stance called medeto­mi­dine has al­ready proved ef­fec­tive in pre­vent­ing foul­ing of ship bot­toms, ac­cord­ing to the re­search­ers. They now re­port that that they’ve iden­ti­fied the gene that causes the bar­na­cle to re­act to the medeto­mi­dine, a sed­a­tive used by vet­eri­nar­i­ans.

“We have found that medeto­mi­dine ac­ti­vates spe­cial re­cep­tors in bar­na­cle lar­vae,” said bi­ol­o­gist An­ders Blomberg of the Uni­vers­ity of Goth­en­burg, Swe­den, who worked with col­leagues at the uni­vers­i­ties of Tur­ku and Hel­sin­ki in Fin­land on the study.

Re­cep­tors are com­plexes of mo­le­cules that act as gate­ways on cell sur­faces, con­trol­ling how cells re­spond to spe­cif­ic sub­stances.

The medeto­mi­dine re­cep­tors “emit a sig­nal that causes the lar­va to swim away from the boat sur­face, in­stead of at­tach­ing to it. As the re­cep­tors are al­ready ac­ti­vat­ed at very low con­centra­t­ions of the sub­stance, this means that very low lev­els are al­so needed to be ef­fec­tive,” Blomberg added. 

De­scrib­ing their find­ings in the sci­en­tif­ic jour­nal Mo­lec­u­lar Phar­ma­col­o­gy, Blomberg and col­leagues pro­posed a way that en­gi­neers could de­vel­op an en­vi­ron­men­tally friendly and ef­fec­tive an­ti­foul­ing paint which, rath­er than kill­ing bar­na­cles, simply sends them else­where.

Medeto­mi­dine it­self has al­ready been used as an in­gre­di­ent in an­ti­foul­ing paint, but al­so has been found to be mildly tox­ic to fish.

“Un­der­stand­ing how the sub­stance works when it binds to the re­cep­tor al­so makes it pos­si­ble to de­vel­op se­lec­tive agents that only af­fect bar­na­cles and not oth­er ma­rine or­gan­isms,” said Blomberg.

Bar­na­cles, an evolutionary group that comprises many species, re­sem­ble small crabs early in life and later se­crete a pow­er­fully sticky sub­stance that lets them at­tach them­selves to a sur­face. This serves as their stag­ing zone for feed­ing. They then form a shell around them­selves that may re­sem­ble a ti­ny vol­ca­no, whose “mouth” the bar­na­cle it­self lives in, and whose base is at­tached to the sur­face. The an­i­mal then sticks out lit­tle ap­pendages used to sweep pass­ing food par­t­i­cles to­ward it­self.

* * *

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They’re tiny sea creatures that cause a huge headache for boats worldwide: barnacles. In droves, they latch almost permanently onto surfaces such as ship hulls. That reduces vessel speed and often drives boat owners to use toxic hull coatings to keep them off. Now, scientists have identified a gene that they say might be the barnacles’ Achilles Heel when it comes to attaching themselves. That knowledge, they say, opens up the possibility of an antifouling paint that goes easy both on barnacles and on the environment. A substance called medetomidine has already proved effective in preventing fouling of ship bottoms, according to the researchers, at the University of Gothenburg, Sweden. They now report that that they’ve identified the gene that causes the barnacle to react to the medetomidine, a sedative used by veterinarians. “We have found that medetomidine activates special receptors in barnacle larvae,” said biologist Anders Blomberg at the university, who worked with colleagues at the universities of Turku and Helsinki in Finland. Receptors are complexes of molecules that act as gateways on cell surfaces, controlling how cells respond to specific chemicals that may approach. “The receptors emit a signal that causes the larva to swim away from the boat surface, instead of attaching to it. As the receptors are already activated at very low concentrations of the substance, this means that very low levels are also needed to be effective,” Blomberg added. Describing their findings in the scientific journal Molecular Pharmacology, Blomberg and colleagues proposed a way that engineers could develop an environmentally friendly and effective antifouling paint which, rather than killing barnacles, simply sends them elsewhere. Medetomidine itself has already been used as an ingredient in antifouling paint, but also has been found to be mildly toxic to fish. “Understanding how the substance works when it binds to the receptor also makes it possible to develop selective agents that only affect barnacles and not other marine organisms,” said Blomberg. Barnacles are saltwater animals that resemble small crabs early in life. They later secrete a powerfully sticky substance that lets them attach themselves to a surface, which serves as their staging zone for feeding. They form a shell around themselves that resembles a tiny volcano, whose “mouth” the barnacle itself lives in, and whose base is attached to the surface. The animal then sticks out tiny appendages used to sweep passing food particles toward itself.