UAlberta scientists solve mystery of snapping shrimp's 'spectacular' claws
Prof. Richard Palmer says his team has uncovered 'one of the holy grails of research questions'— how the snapping shrimp uses its claws to create one of the loudest noises on the ocean floor.
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Researchers at the University of Alberta say they've solved the mystery of one of the loudest noises in the ocean.
The snapping shrimp is a tiny crustacean that lives in coral reefs. But don't let its small size fool you — when it snaps its large claw shut, the jet of water that results is louder than a gunshot, and is more than enough to defend against predatory salmon, crabs and seagulls.
“This puzzle that we have now solved, is one of the holy grails of research questions, which is to reconstruct the evolutionary history origins of these absolutely spectacular claws,” said Richard Palmer, a professor of biological sciences at the University of Alberta.
Palmer spent a decade studying shrimp. In the last two years he focused on the snapping aspect of the claw, studying 119 species to understand the 150 million years of evolution that produced that claw.
He said they used high resolution imaging tools to look at the claw's joint structure.
When the shrimp snaps, it shoots a stream of water so fast it leaves a tiny vacuum behind, and when the water rushes back to fill that space, the bubble breaks, causing the loud clap.
By studying ancient lineages, researchers found that shrimps have been squirting water long before the evolution of snapping claws.
"What they seem to do is they were somehow squirting water using their claws, and they get better and better at squirting water," he said. "It's an really an increased ability to squirt water faster over 150 million years."
Imaging showed the unique system of joints that slowly evolved to create the powerful snap, Palmer explained.
“We saw two novel joints, two novel ways that the fingers on the claws move that were set the stage for the final stop which would be the evolution of snapping,” he said.
“What we found in some of these shrimp joints, the finger moves so far back that some of the muscle is on the wrong side of the hinge.”
He said a contracting muscle is responsible for opening the claw--similar to pulling back an arrow in a bow. Then, another muscle lets it slide back, releasing all the stored energy, which causes the super fast snap.
Palmer said without that first joint that causes the energy storage system, it would be like throwing an arrow using only your arm.
“It can throw it a fair distance but it doesn’t go very far or very fast.”
The three to five centimeteres long shrimp with one claw disproportionately bigger than the other, are fairly popular online, with videos of them snapping having accumulated thousands of views on YouTube.
“They are fairly charismatic, people have them in aquariums and there (are) wonderful nature videos about them snapping as they use this snap to communicate or kill prey,” Palmer said.
He said this was big news for them to uncover what gave rise to the super specialized claw.
“Snapping is such an amazing adaptation it’s really one of the most spectacular adaptations in shrimp,” he said.