Throughout evolution, organisms repeatedly developed elastic elements to power explosive body motions, overcoming ubiquitous limits on the power capacity of fast-contracting muscles. Seahorses evolved such a latch-mediated spring actuation (LaMSA) mechanism; however, it is unclear how this mechanism powers the two complementary functions necessary for feeding: rapidly swinging the head towards the prey, and sucking water into the mouth to entrain it. Here, we combine flow visualization and hydrodynamic modeling to estimate the net power required for accelerating the suction-feeding flows in 13 fish species. We show that the mass-specific power of suction feeding in seahorses is ~3 times higher than the maximum recorded from any vertebrate muscle, resulting in suction flows that are ~8 times faster than similar-sized fish. Using material testing, we reveal that the rapid contraction of the sternohyoideus tendon can release ~72% of the power needed to accelerate the water into the mouth. We conclude that the LaMSA system in seahorses is powered by two elastic elements, the sternohyoideus and epaxial tendons. These elements jointly actuate the coordinated acceleration of the head and the fluid in front of the mouth. These findings extend the known function, capacity, and design of LaMSA systems.

This is a complete set of data to recreate power, PIV and kinematic result of one strike as in ‘A power amplification dyad in seahorses’. This data set contains and should be run in the following order:

seahorsefry6_video.avi: video of a feeding seahorse strike with increased contrast to better visualize the flow of water. 

DLTdv5_data_xypts.csv: is the manual tracking of the locations needed for calculating the kinematics of the strike. These were recorded using DLTdv5 tracking package and can be easily recreated from the above video. Columns alternating x and y positions for (1) the proximal tip of the upper and (2) lower jaw, (3) the center of the eye socket, and the joint locations of the four-bar lever system: (4) the proximal tip of the hyoid bone (when visible), (5) the ventral attachment of the cleithrum.

run_avi_MatPIV_cj.m: This script runs MatPIV with the set parameters used for this study. The file is annotated and can be run on the provided video to recreate the flow fields.

Radial_transects_cj.m: This script takes the transects radiating from the mouth opening to 2 peak gape distances from the mouth and determines the flow speed along those transects. It is annotated and is the first step in extracting flow velocities from PIV. This script produces 2 files. 

statistics_cj.m: This script extracts the relevant information from the Radial_transects such as peak values of kinematics as well as the timing of these kinematics.

pressureformat_new.m: This script simply rearranges the PIV velocity fields into a format that can be read for power calculations

parametersfish.m: This file stores all the parameter information for the pressure calculations. Currently set to the parameters used in this study but can be adjusted for different situations 

pressure.m: This function calculates pressure fields based on rearranged PIV vector maps using the equations taken from "queen2" by Dabiri et al. (2014) then calculates power. It is annotated for better understanding and uses the parameters defined by parametersfish.m.