Motor basis of suction feeding performance in largemouth bass,Micropterus salmoides

Abstract

We examined the relationship between cranial muscle activity and buccal pressure during suction feeding by the largemouth bass, Micropterus salmoides. Buccal pressure was recorded simultaneously with electromyograms (EMG) from four muscles that function prominently during the strike, including three expansive phase muscles (levator arcus palatini, epaxialis, and sternohyoideus) and the major compressive phase muscle, the adductor mandibulae. Feeding behavior was analyzed in 145 strike sequences from five individuals. EMG from each muscle was quantified with four variables (integrated area of rectified EMG, burst duration, intensity of activity, and onset time of activity), and pressure pulse was characterized with seven variables (area of subambient pressure curve, area of superambient pressure curve, minimum pressure, maximum pressure, pressure pulse duration, time to minimum pressure, and time to maximum pressure). Correlation, multiple regression, and a principal components analysis (PCA) were used to investigate the relationship between muscle activity and buccal pressure patterns. About 50% of the correlations among muscle variables were significant, while fewer than 25% of the correlations between muscle activity and buccal pressure variables were significant. Multiple regression models accounted for about 50% of the variance in each pressure variable, although substantial differences were found among individual fish in the success of these models. A PCA performed on the correlation matrix of EMG variables yielded a first principal component that accounted for 33% of the overall variance in strikes and was significantly correlated with the timing variables of buccal pressure. A general trend was apparent in which Micropterus modulated the magnitude of suction pressure and the timing of the pressure pulse during the strike by altering the extent of activity (i.e., integrated area and burst duration) in cranial muscles. This study shows that suction performance is moderately influenced by cranial muscle activity. However, extensive strike-to-strike and inter-individual variation suggest that the relationship between muscle activity patterns and buccal pressure is not precise, and bass are able to use a variety of motor strategies to generate strikes with similar suction pressures. J. Exp. Zool. 277:1–13, 1997. © 1997 Wiley-Liss, Inc.