44-1 10:00 - 10:15 Starting to snap: the development and kinematics of spring-driven strikes in juvenile snapping shrimp Harrison, JS*; Patek, SN; Duke University; Duke University email@example.com
Organisms use latch-mediated spring actuation (LaMSA) to enhance their mechanical power output, allowing them to achieve ultrafast motion. Interestingly, repeated-use (i.e., not self-destructive) LaMSA is only found in mechanisms larger than ~1 µg. For example, jellyfish nematocysts (~1 ng) use LaMSA, but once fired cannot be used again, while Dracula ant mandibles (~86 µg) can be repeatedly loaded and fired. Establishing a lower size limit requires examining transitions from a non-LaMSA to a LaMSA mechanism across a size-range either within an organism (during development) or across species. We leveraged the development of LaMSA mechanisms across ontogeny to determine at what size organisms transition to using LaMSA. We establish the development of the LaMSA mechanism in snapping shrimp. Snapping shrimp are a clade of decapod crustaceans that fire cavitation bubbles at opponents during interspecific contests. Snapping shrimp form cavitation bubbles using a LaMSA mechanism in their claw. We raised juvenile Alpheus heterochaelis using eggs collected from gravid adults. The snapping claw develops 1-2 months after settlement when the claws are ~1 mg. We collected high speed video of strikes from developing snapping claws and found larger juvenile snapping shrimp have larger claws, which are more likely to produce strikes than smaller claws (n=281 strikes, 20 individuals). Power densities approximated from juvenile strikes show the claw uses a LaMSA mechanism. Juvenile A. heterochaelis are among the smallest repeated-use LaMSA mechanisms and generate some of the highest accelerations measured for repeated-use, ultrafast movements (5.8 x 105 m s-2). These findings reveal the scaling and onset of ultrafast motion in snapping shrimp as well as a size-based transition to LaMSA that is congruent with the other tiniest, repeated-use LaMSA systems.