Natures wonders: highest speed claw snapping (Introduction)

by David Turell , Monday, February 08, 2021, 23:06 (1382 days ago) @ David Turell

In a tiny shrimp-like fellow in water:

https://cosmosmagazine.com/nature/marine-life/quick-claw/?utm_source=Cosmos+-+Master+Ma...

"Turns out that the claws of the male amphipod (Dulichiella appendiculata) can repeatedly snap shut in less than 0.01% of a second, shooting out high-energy water jets and popping sounds.

"That’s some serious speed for such a little critter. Amphipods are tiny, shrimplike crustaceans that only grow to a few millimetres long. They tend to live in cool, scummy water, spending their days scrounging for dead algae and seaweed – and, apparently, snapping their claws.

“'What’s really amazing about these amphipods is that they’re sitting right on the boundary of what we think is possible in terms of how small something can be and how fast it can move without self-destructing,” says lead researcher Sheila Patek from Duke University in the US. “If they accelerated any faster, their bodies would break.”

***

"You might assume that the fastest motions in nature might come from large animals or robots, but in fact they come from much smaller organisms and structures – including cnidarian stinging cells, fungal shooting spores, and the mandible strikes of ants, termites and spiders.

“'These diverse systems share common features: they rapidly convert potential energy — stored in deformed material or fluid — into kinetic energy when a latch is released,” the researchers explain in their paper.

“'However, the fastest and smallest known movements often cannot be used multiple times, because mechanical components are broken or ejected.”

"It’s especially difficult to produce fast motions in water, which has a higher density and viscosity than air.

But the snaps of these amphipods in water were not only ultra-fast, but also repeatable.

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"Intriguingly, the observations also revealed that sometimes the resulting water jets caused “cavitation”, where rapid changes in water pressure cause bubbles to form – and when they pop, they release an immense amount of energy, enough to degrade the steel of boat propellers. (my bold for emphasis)

"But why do amphipods snap their claws in the first place?

“'The claws make up a third of a male’s body weight,” says Patek. “We want to know why they invest so much into this action, whether it plays into male-female interaction or territorial disputes. That’s something we’re excited to pursue.'”

Comment: Is this a slowly developed adaptation, and if so 'why' as the authors pose? If it appeared all at once it had to designed to make everything work and be protected from such force.