Meeting Abstract
Ultrafast appendage movements have evolved in many arthropod groups including snapping shrimp, mantis shrimp, trap-jaw ants and smashing-mandible termites. We discovered such motions in another arthropod group: maerid amphipods. We confirmed prior anecdotal reports that male amphipods of the genus Dulichiella produce a snapping sound with their second gnathopod. This massively hypertrophied gnathopod, which occurs primarily on the right side, exhibits pronounced positive allometry and in large males of Dulichiella appendiculata may exceed 20% of the total body weight. Preliminary high-speed video recordings of gnathopod closing (more than 200,000 fps) and synchronized audio recordings revealed a) angular velocities among the highest known in animals, b) surprisingly large appendage recoil motions, c) occasional formation of cavitation bubbles, and d) hints of an unexpected mechanism for sound production. Much remains to be learned about how this small animal achieves such remarkable claw closing speeds and produces an audible snap.
