Meeting Abstract
All animals face an overriding constraint on their ability to produce fast movements – muscles contract slowly and over small distances. Repeatedly over evolutionary history, animals have overcome this limitation through the use of power amplification mechanisms. These mechanisms decrease the duration of movement and thereby increase speed and acceleration. The only known example of power amplification in fish is pivot feeding in the Syngnathidae family, whose members are able to rotate their snout towards the prey at exceptionally high speeds of ~1.56 ms-1. While the mechanism of power amplification that permits these exceptional speeds is well documented, the consequences of power amplification for suction feeding are poorly understood. Specifically, there have been no studies documenting the magnitude or spatio-temporal patterns in the suction flows produced using power amplification. Using a high-speed flow visualization technique, we characterized the spatio-temporal patterns in the flow fields produced during pivot feeding in 4 species of the Syngnathidae family. We found that the power amplification provides 8x greater flow velocities, compared to fish with no such mechanism. Both between and within species, shorter snout lengths were correlated with faster flow speeds. Peak flow speeds occurred early in the gape cycle (~60% of time to peak gape), and mid-way through head rotation. We used the observed flow fields to estimate the pressure fields in front of the mouth and calculate net suction power (power used to accelerate the water outside of the mouth) in both power amplified and non-amplified fish species. We further compare the net suction power to the power required for head rotation in our species. Our results reveal a neglected role for power amplification in Syngnathidae.
