UC San Diego

Pistol shrimp have one of the fastest, loudest, and deadliest weapons in the ocean. The rapid snap of their modified claw generates a water jet and cavitation bubble that is used to ward off predators, subdue prey, and settle disputes. It is suggested that pistol shrimp can control the volume they let into the socket of their snapping claw, thereby affecting the force of their strikes. The goal of this study was to determine if pistol shrimp exhibit context-dependent snap modulation. We hypothesized that (1) pistol shrimp would snap with different power in response to different stimuli, and (2) that the predator would induce the most powerful snap while the conspecific would induce the least powerful snap. Two species of pistol shrimp, Alpheus clamator and Synalpheus lockingtoni, were presented stimuli in random order: predator (shore crab), prey (red rock shrimp), conspecific, and control (paintbrush). Snaps were recorded with a high-speed video camera (25,000 fps) and hydrophone, from which water jet dimensions and velocity were calculated. Results show that there is great variability in total water jet velocity, with the prey stimulus inducing a weaker snap than all other stimuli. Yet all other snap characteristics were consistent across stimuli. Pistol shrimp appear to modulate their snap based on context, but to a limited extent, thereby supporting our main hypothesis. This study provides deeper insights into the biomechanics of the pistol shrimp snap, and a better ecological understanding of how they use this potent weapon.