Meeting Abstract

62.4  Thursday, Jan. 6  Motoneurons, muscles and movement: Neural control of the pectoral fins during slow and fast swimming. GREEN, M.G.*; HALE, M.E.; Univ. Chicago; Univ. Chicago mhgreen@uchicago.edu

Fishes actuate their pectoral fins for a variety of purposes, from powering forward swimming to sensing the environment. Rhythmic pectoral fin swimming is a common gait at low swim speeds. At higher speeds, the fins are often positioned against the body and locomotion is driven solely by the body axis. Electromyographic records from pectoral fin muscles in several species have shown that, broadly, abductor muscles are active in alternation with adductor muscles during rhythmic fin beats at slow swim speeds. The control of fin position at higher speeds has not been studied. Here we used larval zebrafish, a neurobiological model organism, to describe patterns of motoneuron input to pectoral fin muscles at low speeds and through the gait transition to higher speed axial locomotion. By recording from pectoral fin motoneurons we found that, in agreement with EMG studies of adult fishes, motor drive to the abductor and adductor muscles alternated during slow swimming. During fast swimming adductor motoneurons became tonically active whereas abductor motoneurons were silenced. The gait transition from locomotion that includes pectoral fin movement to axial-only locomotion is discrete with a sudden switch between motor patterns. This switch in the activity pattern of pectoral fin motoneurons shows that, even among young fish, the neural circuitry driving pectoral fin movement can produce multiple output patterns. Understanding the mechanisms producing these basic patterns may inform future work in determining how more complex fin movements are generated and how gait transitions are accomplished. Funded by the Office of Naval Research.