字幕列表 影片播放 列印英文字幕 This cricket is about to be dinner. New research reveals what makes a frog's tongue such a formidable weapon. This is Scientific American. I'm Lydia Chain. Since the entire attack takes less than a tenth of a second the researchers set up high-speed cameras to capture the action. "Literally in the blink of an eye, the insect is gone and it's only when we look at it in slow-motion can we really see how the tongue is unfurling from the mouth and impacting the insect. That's Alexis Noel at Georgia Tech. Noel and her colleagues studied frog tongues and the fluid mechanics of their spit to understand how frogs slurp up their prey. First, Noel studied the physical properties of the tongue. It was so soft, Noel had to design special equipment to get an accurate softness measurement. "It's even softer than brain tissue. Even softer than a marshmallow." That soft tongue comes in handy. Prey sinks deep into the tongue's surface, increasing contact for a good grip. The softness also absorbs force like a bungee cord so the frog can reel in a cricket rather than giving it a yank that might cause separation. But it's the saliva that temporarily glues the bug to a frog's tongue. Frog tongues are like spit-saturated sponges since their salivary glands are inside the tongue. Noel and her colleagues analyzed the fluid properties of this saliva. "So I scraped about 17 or 18 frog tongues." Those spit samples revealed frog saliva is a shear thinning fluid. The saliva starts out viscous and sticky, but when force is applied, it liquefies. The force of hitting the insect makes the spit splash up around the bug "And it is able to penetrate all the tiny cracks and crevices within the insect increasing its contact area." After that impact, the spit thickens again, trapping the insect in the goo. It's so sticky that the frog needs to shove its eyeballs onto its tongue in order to loosen the spit enough to swallow its morsel. It's that combination of the soft tongue and the sticky saliva that lets frogs scoop up prey in an instant. Of course not even super spit can help the frog if it bites off more than it can chew. For Scientific American, I'm Lydia Chain.