An adaptation 150 million years in the making

Just how do snapping shrimp snap? This was the question plaguing scientists who set out to uncover the mysterious mechanisms producing big biology in tiny crustaceans.

Graphical abstract of slip joints in snapping shrimp [Credit: Rich Palmer, University of Alberta]

"All we've known until now is the endpoint of these super snapping claws," said Rich Palmer, biological science professor at the University of Alberta and senior author on a new study on snapping shrimp claws. "What we now know is that a series of small changes in form led to these big functional changes, which essentially allow these shrimp the ability to break water, or snap."

Through the course of two years of research investigating 114 species from 19 different shrimp families -- exploration that took the scientists from the far reaches of Panama to advanced imaging facilities in Germany -- the researchers discovered that this ability to break water or snap was preceded by evolution and adaptation millions of years in the making. The shrimp use the snapping for multiple reasons including communication, killing prey, territorial defense, and defending against predators.

"We realized that this spectacular ability to break water by making cavitation bubbles had to have been preceded by maybe millions of years of shrimp just shooting water. Somehow as they continue to shoot water, they got faster and faster, and they eventually broke the cavitation threshold to produce these snaps. It's pretty extreme biology," said Palmer.