Scientists at UCSB, with the help of a species of somewhat malevolent mollusks, may soon find a sticky solution that can allow people to glue things together under water.
Getting a Strong Grasp With Mussels
Mussels, which have been known to cling strongly to wet, stony surfaces, produce a compound on their foot that allows them to attach themselves to the metals within rocks. According to Herbert Waite, senior author and professor of molecular, cellular and developmental biology at UCSB, the compound binds quite strongly to metals and can reattach to the rock if the bond is broken.
“When the [researchers] tested the compound, it formed a strong bond [to the metals] under water,” Waite said. “The bond was about half as strong as a covalent bond. They also noticed … when they broke the bond, the bond would reform. This would not happen with a covalent bond.”
The compound’s abilities have piqued the interests of researchers such as Waite, since the sticky substance can perform underwater adhesion, which is still a somewhat unresolved issue in the field of materials science.
“Everyone should be able to empathize with someone trying to put Scotch tape on a wet table or a Band-Aid on a cut finger after washing dishes,” Waite said. “Adhesion, when left to human technology, is very difficult when surfaces are wet.”
While the compound found in most mussels is a good adhesive in water, pollutants within the water tend to react with the molecule, causing it to lose its binding ability. Luckily, at least for certain shellfish, nature’s solution to this problem can be found within the green mussel, a strong yet pesky mollusk that uses an alternative molecule to stick itself to rocks.
Mean Green Gluing Machine
The molecule used by most other mussels uses a compound similar to the human neurotransmitter dopamine, which becomes unstable when pollutants enter the system. According to Waite, a six-year study into the chemical binding method of green mussels showed the mollusks use a complicated compound similar to serotonin that bonds to metals in a similar fashion but is stable enough to resist contamination.
Unfortunately, the green mussel’s sticky skills and aggressive nature have made it a highly invasive species, according to Waite.
“The green mussel is invasive. … They started in Southeast Asia and like warm water. In the course of the last 15 years, [the mussel] has invaded the Asian west coast up to Japan,” Waite said. “Once they get into cold water, [their growth tends to stop].”
However, the growth of modern industry and overseas transportation has allowed the green mussels to infest other ecosystems, causing environmental damage on a global scale.
“Coastal power plants need to be cooled. … Usually, river or ocean water is used. The water used comes out warm and warms up the local area, [making it habitable for green mussels],” Waite said. “Green mussels can get around by hitchhiking on [ship] hulls [or ballast water] and spawning when a ship gets to another port.”
According to Waite, the ability for the green mussel to flourish even in increasingly polluted waters makes it both intriguing to marine scientists
and dangerous to the environment.
“One aspect that is kind of scary is that the green mussel is more successful than other kinds of mussels at living in polluted water,” Waite said in a press release. “Once they get a foothold, they stay.”
The malicious mollusk has already become a huge pest in Florida and the Gulf of Mexico, where it has pushed out local mussel populations and fouled surrounding boats and piers, leading to action by affected governments and environmental groups. While there is a happy abundance of available specimens due to the widespread success of the shellfish sea critter, Waite said California has banned live specimens from its soil in an effort to protect its shores from infestation, leaving researchers at UCSB with only frozen samples to work with.
What the Future Holds
The studies currently being done on mussels are highly interdisciplinary and span a variety of interests, so the goals of the projects are many. The researchers hope to understand how the mussel does what it does as well as utilize the information to synthesize the next generation of biologically-based materials, but the environmental consequences of the green mussel’s biological fitness have now also become a critical target for future research.