Epaxial and Limb Muscle Activity During Swimming and Terrestrial Stepping in the Adult Newt,Pleurodeles waltl

Abstract

We have investigated the patterns of activation of epaxial musculature during both swimming and overground stepping in an adult newt (Pleurodeles waltl) with the use of electromyographic (EMG) recordings from different sites of the myomeric muscle dorsalis trunci along the body axis. The locomotor patterns of some limb muscles have also been investigated. During swimming, the epaxial myomeres are rhythmically active, with a strict alternation between opposite myomeres located at the same longitudinal site. The pattern of intersegmental coordination consists of three successively initiated waves of EMG activity passing posteriorly along the anterior trunk, the midtrunk, and the posterior trunk, respectively. Swimming is also characterized by a tonic activation of forelimb (dorsalis scapulae and extensor ulnae) and hindlimb (puboischiotibialis and puboischiofemoralis internus) muscles and a rhythmic activation of muscles (latissimus dorsi and caudofemoralis) acting both on limb and body axis. The latter matched the activation pattern of epaxial myomeres at the similar vertebral level. During overground stepping, the midtrunk myomeres express single synchronous bursts whereas the myomeres of the anterior trunk and those of the posterior trunk display a double bursting pattern in the form of two waves of EMG activity propagating in opposite directions. During overground stepping, the limb muscles and muscles acting on both limb and body axis were found to be rhythmically active and usually displayed a double bursting pattern. The main conclusion of this investigation is that the patterns of intersegmental coordination during both swimming and overground stepping in the adult newt are related to the presence of limbs and that they can be considered as hybrid lampreylike patterns. Thus it is hypothesized that, in newt, a chain of coupled segmental oscillatory networks, similar to that which constitutes the central pattern generator (CPG) for swimming in the lamprey, can account for both trunk motor patterns if it is influenced by limb CPGs in a way depending on the locomotor mode. During swimming, the segmental networks located close to the girdles receive extra tonic excitation coming from the limb CPGs, whereas during stepping, the axial CPGs are entrained to some extent by the limb oscillators.

Where are we in understanding salamander locomotion: biological and robotic perspectives on kinematics

“…Moreover, Edwards (1977) estimated that limb retraction supplies 56-62 % of forward propulsion and limb rotation 10-18 % highlighting the importance and bifunctionality of the limbs. Theoretical considerations and descriptions dealt with the movements and mechanics of the hindlimbs (Barclay 1946;Gray 1968;Edwards 1977Edwards , 1989Peters and Goslow 2010) as well as the limb's musculature and activation patterns in relation to the kinematics (Ashley-Ross 1992, 1995Delvolvé et al 1997).…”

“…Typically, salamanders swim at a higher frequency and speed than they step (e.g., swimming: 2.13 ± 0.24 Hz, stepping: 0.88 ± 0.12 Hz, Delvolvé et al 1997).…”

“…Cinematography has been used by many investigators early on (e.g., Gray 1944;Evans 1946) to study the kinematics of salamanders. Force-plate measurements (Barclay 1946;Sheffield and Blob 2011) and electromyography (e.g., Székely et al 1969;Frolich and Biewener 1992;Ashley-Ross 1995;Delvolvé et al 1997;Deban and Schilling 2009) helped to understand their dynamics and muscular activity patterns. Using cineradiography, we were recently able to record and reconstruct the kinematics of the salamander's skeleton in great detail (Karakasiliotis et al, under preparation).…”

Simulation and Robotics Studies of Salamander Locomotion: Applying Neurobiological Principles to the Control of Locomotion in Robots

“…There is a large amount of data available characterizing the kinematics of salamander locomotion, including axial movements (Edwards, 1976;Frolich and Biewener, 1992;Carrier, 1993;Delvolvé et al, 1997;Gillis, 1997;Ashley-Ross and Bechtel, 2004), hindlimb kinematics (Ashley-Ross, 1994a, b), and backward walking (Ashley-Ross and Lauder, 1997).…”

“…1, right). As in the lamprey, the average wavelength usually corresponds to the length of the body (i.e., the body produces one complete wave) and does not vary with the frequency of oscillation (Frolich and Biewener, 1992;Delvolvé et al, 1997).…”