Courtesy of the Department of Applied Physics, University of Twente
Snapping shrimp are crustaceans that are found in tropical and temperate seas. These shrimp, usually a muddy green color, grow to about 5 cm (2 inches) long. Their most noticeable physical feature is a claw that can grow to be half the size of the entire body length. It is this claw that gives snapping shrimp their most remarkable attribute. A snapping shrimp will quickly close its claw to produce a loud “snap” as a way to stun its prey, deter predators, and communicate with others. For at least one species of snapping shrimp, the actual sound is generated by the formation and subsequent popping of a bubble, and not by the physical contact of the claw striking together. The bubble appears when the shrimp closes the two parts of the enlarged claw at lightning speed, causing the water to cavitate. Scientists have also found that light is produced when the bubble pops due to the high temperatures and pressure inside the bubble. Alpheus heterochaelis is the only known species to produce sound using this cavitation process. The combined sound of large aggregations of snapping shrimp is so prevalent in certain areas of the world that it interferes with interferes with underwater communications and research.
Drawing of a snapping shrimp showing the top view of the whole shrimp and the dorsal and lateral views of the large claw. In the lateral view, part of the claw is removed to show the water jet groove that plays a critical role in sound production. (Adapted from Figure 1 from Knowlton and Moulton. 1963. Biol. Bull. 125:311-331. Reprinted with permission from the Marine Biological Laboratory, Woods Hole, MA.