Asymmetrical Muscle Activity During Feeding in the Gar, Lepisosteus Oculatus

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Abstract
Prey capture in the spotted gar, Lepisosteus oculatus, was studied by high-speed cinematography synchronized with electromyographic recordings of cranial muscle activity. Muscle activity patterns were recorded during each of the three major phases of feeding: the initial strike at the prey, manipulation of the prey following capture, and swallowing. With one exception, the obliquus superioris, all muscles at the strike are active in a bilaterally symmetrical pattern. During the manipulation phase two distinct muscle activity patterns occur: one is characterized by symmetrical activity in the epaxial muscles and obliquus inferioris, the other by complete asymmetry between the right and left sternohyoideus, obliquus superioris, and epaxial muscles. Low-amplitude manipulatory movements are characterized by activity in one side of the sternohyoideus only, all other muscles being generally inactive. The adductor mandibulae and obliquus inferioris are always active symmetrically. Asymmetrical activity in the sternohyoideus, epaxial muscles, and obliquus superioris correlates with lateral head movements during feeding and acts to rotate prey into the preferred orientation for swallowing. The pattern of asymmetrical activity between right and left side muscles is discussed in relation to previous studies of feeding which utilized only unilateral muscle recordings.