Disorientation as a marker of neurotrauma in an animal that uses shock waves as weapons

By snapping their claws, snapping shrimp create cavitation bubbles that release supersonic pressure waves when they collapse. Shock waves such as these are dangerous to animals because they can cause blast-induced neurotrauma by transferring kinetic energy to neural tissues. Previously, we discovered that helmet-like orbital hoods protect snapping shrimp from blast-induced neurotrauma by damping the shock waves they generate and use as weapons. To learn how effectively orbital hoods function, we need to be able to compare levels of blast-induced neurotrauma in snapping shrimp. In humans, spatial disorientation is a behavioral hallmark of blast-induced neurotrauma. Here, we develop methods for assessing spatial disorientation in snapping shrimp and ask if shrimp, like humans, demonstrate disorientation following shock wave exposure. To do so, we quantified aspects of the path trajectories taken by snapping shrimp during shelter-seeking including path tortuosity, fractal dimension, distance traveled, and speed. Shock wave exposure caused snapping shrimp without orbital hoods to travel longer, slower, and more tortuous paths compared to shrimp with unaltered orbital hoods. By quantifying shelter-seeking behavior, we show that exposure to shock waves causes spatial disorientation in snapping shrimp without orbital hoods, supporting our hypothesis that orbital hoods mitigate short-term behavioral consequences of blast-induced neurotrauma.