Clingfish lives up to its name
This slightly disgruntled looking individual is a Northern Clingfish (Gobiesox maeandricus). These unassuming fish live on the Pacific coast of North America inhabiting the rather dangerous area known as the rocky intertidal zone. Making your home on a rocky seashore comes with quite a few hazards – crashing waves, strong currents, all the sorts of things that turn lost sailing ships into driftwood. The clingfish though comes prepared with a nifty adhesive disc on the belly, formed from modified pelvic fins, which allows for a remarkably firm attachment to slippery wet rocks.
To find out just how good the clingfish is at staying put on a range of surfaces a team of biologists caught 22 individuals and pitted them against manufactured suction cups. Despite the clingfish being dead (the scientists wanted to make sure it was the actual structure of the disc that made it so effective, not any other tricks the clingfish might have) the result was a resounding victory for the clingfish. On eight surfaces of varying roughness – seven different sandpapers and one smooth glass – suction cups managed to stick to only the three smoothest surfaces, while the clingfish stuck to all eight. To test whether fish mucus might be giving the clingfish an unfair advantage they also carried out the same experiment in viscous solutions, but even then the clingfish still outperformed the suction cups on the roughest surfaces.
These tenacious fish manage this feat thanks to the microstructure of their adhesive discs. An electron microscope revealed that microvilli (tiny finger-like protrusions) around the edges of the disc create higher friction and prevent slippage on rough surfaces. They are also more flexible than a suction cup, allowing them to seal more tightly to the surface. It’s a similar mechanism to the way in which gecko’s feet work, but of course the clingfish can do it underwater. This might end up being a nice example of ‘biomimicry’ – emulating or taking inspiration from the natural world to improve human engineering. Mimicking the clingfish might just provide a way of improving suction devices for rough wet surfaces, which I’m sure might come in handy for all sorts of things!
Reference: Wainwright DK, Kleinteich T, Kleinteich A, Gorb SN, Summers AP: Stick tight: Suction adhesion on irregular surfaces in the northern clingfish. Biology Letters 2013, 9(3).