Snapping Shrimp

Snapping shrimp can drive you crazy. The noise starts abruptly, and if you are at anchor in a secluded cove, far from mechanics or boat yards or someone with an explanation for that “crinkly, snap-crackle-pop noise” coming from somewhere deep in the hull, the first time you hear it can be quite disconcerting (Can it be water? Is there a leak somewhere? Did rats get in last time we were docked up? Are they chewing through the insulation or wiring? Did that bird that was hitching a ride find its way into the storage lockers? What IS that noise!?). Turns out it is only a shrimp, Alpheus heterochaelis, capturing its dinner, defending its territory, or just talking with its mates. According to Detlef Lohse, Michel Versluis (University of Twente in Enschede, The Netherlands) and Barbara Schmitz of the Technical University of Munich, Germany (Nature, October 4, 2001), the shrimp snaps its large claw together with such force that a jet of water, traveling at speeds up to 100 kilometers an hour (62 mph), creates a bubble that implodes with the heat of the sun (probably up to 5000 degrees Kelvin [8540 degrees Fahrenheit]) and a green flash (the researchers have dubbed the flash shrimpoluminescence). It’s the implosion* that causes the snapping noise we hear, and the power it generates stuns the shrimp’s prey—small crabs or other shrimp. There are over 100 varieties of this shrimp prowling the tropics, lunching on other crustaceans, interrupting sonar on submarines, or creating puzzles for new cruisers.

*The physics of the process involve cavitation, where liquid moving above a certain speed causes a drop in pressure, allows air bubbles in it to expand, and, when it slows, results in the bubbles imploding and creating a shock wave (Bernoulli’s principle).