How to Perform a Perfect Slime Attack: Lessons from a Worm
Imagine you've come across a slug-like worm just inching along, minding its own business. This little guy isn't exactly intimidating, so you take the time to sit and watch him as he makes his way across the floor. A cricket wanders onto the scene, and you wonder if they are friends... and then suddenly this unassuming worm is firing two jets of slime straight at his 'friend.' The cricket, covered in sticky goo, has nowhere to run, and the once relaxed pace of this worm takes on a foreboding nature - a leisurely stroll to a crunchy cricket dinner.
This nightmarish scene is everyday life for the velvet worm (Onychophora) - an unusual predator that looks like a cross between a slug and a long-legged caterpillar. The animal is slow-moving, but it doesn't rely on speed to catch its prey. Instead, it has evolved to become a master of what can only be described as "slime attack," immobilizing its prey at a distance so that it can catch up at its own pace.
[Watch a National Geographic video of this ingenious attack here.]
Researchers have been fascinated with this predation strategy for as long as entomologists have known about it. Now, according to a study recently published in the journal Nature Communications, a team of experts thinks it knows how exactly it works.
Close examination of the velvet worm's 'slime cannon' apparatus has revealed that it functions much like a syringe - one tipped with a bendy straw that can help slingshot slime out. Given this structure, a slow and gentle squeeze on the worm's slime reservoir is all it takes to eject the adhesive with great speed and force. Even the shape and elasticity of the "bendy straw" end helps ensure that the slime gets practically everywhere in front of the worm - a lot like a long-ranged shotgun blast. (Scroll to read on...)
[Watch the researchers elicit an attack from a massive Peripatus solozanoi worm here.]
[Credit: Cristiano Sampaio-Costa, Bernal Morera-Brenes, Julian Monge-Najera, Andres Concha ]
"The geometry of the system allows the worm to squirt fast and cover a wide area. That's the magic," lead author Andrés Concha, at dolfo Ibañez University in Chile, said in a statement.
The researcher also compares the slime attack to how a water hose flails around when spraying under high pressure. To get that same effect on such a small scale, the apparatus also includes a corrugated shape, which lowers fluid velocity just enough so that it has a chance to shake the "hose" it escapes from.
"Our work... chalks up one more example of how evolution has co-opted a simple physical principle for a behavioral response," added co-author L. Mahadevan of Harvard University.
According to Concha, the team is now planning to examine the glue of the slime attack istelf, creating a host of new questions for future research.
"If you put your fingers close to the mouth of the worm and you get some glue on your fingers, you wait seven seconds and you're stuck," the researcher explained. "So one ambition is to be able to generate a synthetic glue like that, with biotechnological applications. I think there is some chemistry that we have to learn from the worm."
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