Meeting Abstract
Giant and non-giant axon systems in squid can act individually or in concert to control a diversity of jet-propelled maneuvers. The giant system primarily underlies strong, stereotyped mantle contractions to form fast escape jets, whereas the non-giant system allows graded contractions that enable a wide range of swimming speeds. Swimming speed in turn predicts jet hydrodynamics where impulse increases with speed. Both systems expel water through the siphon, but the connection between neuromuscular control and hydrodynamic output has remained unexplored. We used simultaneous recordings of neural activity in stellar nerves, mantle contractions, and 3D particle tracking velocimetry in restrained Lolliguncula brevis to explore the role these two axon systems play in jet hydrodynamics. Of 258 jets recorded from 3 squid, 228 were initiated by the non-giant system and 30 by the giant. Jet angle did not differ between the two systems (linear mixed effects model, p = 0.91), but the giant axon jet impulse magnitude was significantly greater than non-giant (linear mixed effects model, p = 0.038). However, the distribution of non-giant impulse magnitudes (range = 0.18 to 11.7 mN s) was much broader than that for giant values (range = 1.10 to 7.70 mN s). Thus, graded control of mantle contractions by the non-giant system matched characteristics of the resulting impulse and acted as a variable force generator. Giant system impulses appeared more quantized, reflecting the all-or-none nature of these mantle contractions. Our results suggest that diversity in hydrodynamic output at different jetting speeds is influenced by differential recruitment of the squid’s two neural systems.
