Physiological Bases of Feeding Behaviour in Salamanders: Do Motor Patterns Vary with Prey

Muscle activity patterns (motor patterns) of the jaw musculature of all vertebrates studied to date (primarily fishes and amniotes) vary considerably when they feed on different types of prey. Previous data on buccal pressure patterns suggested that feeding in the aquatic salamander, Ambystoma mexicanum (Shaw), is highly stereotyped. This hypothesis was tested by quantifying the motor pattern used during feeding on two prey types: earthworms and guppies. Twenty-nine variables were measured from the activity pattern of six cranial muscles in the feeding mechanism of Ambystoma mexicanum. These variables included the area under the electromyogTam of each muscle, relative muscle onset times, and the amplitudes and durations of muscle bursts. Univariate and multivariate statistical analyses demonstrate that the feeding motor pattern of Ambystoma mexicanum is stereotyped and does not change with prey type, in contrast to motor patterns of other vertebrates studied to date. Individual salamanders use significantly different motor patterns from one another during feeding, but do not alter their motor pattern during feeding on different prey.