Slimy and mud-colored, the northern clingfish, Gobiesox maeandricus, won't win any beauty contests. But scientists have declared that the creature (main image), which uses the giant suction cup on its belly to grip rocks along the coast of the western United States, is a champion of stickiness. When the researchers pitted euthanized clingfish against eight manufactured suction cups, the fish held fast to eight materials ranging from glass to the grittiest sandpaper. The suction cups managed to adhere to only the three smoothest surfaces. The fish have a secret weapon, according to a new study: Sticky mucus keeps seawater from leaking under its "adhesive disk" and disrupting the seal. So the researchers tested how well the artificial cups held when immersed in vats of viscous liquid, which is slower to leak under the edges of the cups and so mimics the benefit of mucus. Still, the fish won out. Scanning electron microscope images showed that the clingfish's suction cup is bordered with filaments similar in size to those on the sticky feet of geckos, according to a paper online today in Biology Letters. The researchers argue that the hairs (inset image) increase friction, giving the cup's edges a grip even on very rough objects. That's how the fish serenely sticks to rocks through pounding waves and buffeting currents and when reaching out to snatch its favorite food, the limpet. The researchers hope that the clingfish's superior suction cup may show the way to artificial devices that can better adhere to rough, wet surfaces. Applications could include surgical materials and tags for marine mammals, the researchers say.
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