Aquatic C-start escape responses in teleost fishes are driven by a well-studied network of reticulospinal neurons that produce a motor pattern of simultaneous contraction of axial muscle on the side of the body opposite the threatening stimulus, bending the fish into the characteristic C shape, followed by a traveling wave of muscle contraction on the contralateral side that moves the fish away from the threat. Superficially, the kinematics of the terrestrial tail-flip resemble the C-start, with the anterior body rolling up and over the tail into a tight C shape, followed by straightening as the fish launches off of the caudal peduncle into ballistic flight. We asked whether similar motor control is used for both behaviors in the amphibious mangrove rivulus, Kryptolebias marmoratus. Fine-wire bipolar electrodes were percutaneously inserted into repeatable paired axial locations in five individual fish. Electromyograms synchronized with high-speed video were made of aquatic C-starts, immediately followed by terrestrial tail-flips. Tail-flips took longer to complete than aquatic escapes; correspondingly, muscles were activated for longer durations on land. In the tail-flip, activity was seen in contralateral posterior axial muscle for an extended period of time during the formation of the C shape, likely to press the caudal peduncle against the ground in preparation for launch. Tail-flips thus appear to be produced by modification of the motor pattern driving the aquatic C-start, with differences consistent with the additional requirement of overcoming gravity.
The authors declare no competing or financial interests.
B.M.P. carried out the lab work and data and statistical analyses. B.M.P. and M.A.A.-R. conceived of the study, designed the study, coordinated the study and helped draft the manuscript. Both authors gave final approval for publication.
The Department of Biology at Wake Forest University provided financial support.
Raw data for this study can be found in the WakeSpace repository at https://wakespace.lib.wfu.edu/handle/10339/58894.
Supplementary information available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.128744/-/DC1
- Received July 17, 2015.
- Accepted March 24, 2016.
- © 2016. Published by The Company of Biologists Ltd