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Clingfish Stick Like Geckos

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Science  20 Jan 2012:
Vol. 335, Issue 6066, pp. 277
DOI: 10.1126/science.335.6066.277
CREDIT: THOMAS KLEINTEICH

On the Pacific Northwest coast, the northern clingfish braves the breaking waves and lives up to its name by prying limpets off the rocks for dinner, thanks to modified fins that form a suction cup on its belly. The unusual body feature outdoes synthetic suction cups, as it can stick even on rough surfaces, Dylan Wainwright of Duke University in Durham, North Carolina, reported at the meeting. “This goes against what you would think,” says Frank Fish, a biomechanicist at West Chester University in Pennsylvania. “You would expect [suction] to fail” on rough surfaces.

Wainwright, an undergraduate, tested the sticking ability of 22 freshly killed Gobiesox maeandricus on eight surfaces mimicking the range of sandpaper grades and found that the fish adhered to them all with an average force 180 times their body weight. (In contrast, rubber suction cups fell off rougher surfaces, sticking only to the three smoothest ones.) Scanning electron microscopy of the clingfish's belly fins revealed that the secret to its staying power may be a rim of microscopic hairs akin to what geckos utilize on their toes to enable them to walk upside down on ceilings (Science, 9 June 2000, p. 1717). Wainwright suspects that clingfish hairs help the edge of the suction cup conform to uneven surfaces and provide more surface area in which weak attractive forces between molecules in the cup and the surface can operate.

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