MOTOR BASIS OF SUCTION FEEDING PERFORMANCE IN LARGEMOUTH BASS, MICROPTERUS-SALMOIDES

We examined the relationship between cranial muscle activity and bucca l pressure during suction feeding by the largemouth bass, Micropterus salmoides. Buccal pressure was recorded simultaneously with electromyo grams (EMG) from four muscles that function prominently during the str ike, 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 w ith 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 c urve, area of superambient pressure curve, minimum pressure, maximum p ressure, pressure pulse duration, time to minimum pressure, and time t o maximum pressure). Correlation, multiple regression, and a principal components analysis (PCA) were used to investigate the relationship b etween 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 v ariables were significant. Multiple regression models accounted for ab out 50% of the variance in each pressure variable, although substantia l differences were found among individual fish in the success of these models. A PCA performed on the correlation matrix of EMG variables yi elded a first principal component that accounted for 33% of the overal l variance in strikes and was significantly correlated with the timing variables of buccal pressure. A general trend was apparent in which M icropterus modulated the magnitude of suction pressure and the timing of the pressure pulse during the strike by altering the extent of acti vity (i.e., integrated area and burst duration) in cranial muscles. Th is study shows that suction performance is moderately influenced by cr anial muscle activity. However, extensive strike-to-strike and inter-i ndividual variation suggest that the relationship between muscle activ ity patterns and buccal pressure is not precise, and bass are able to use a variety of motor strategies to generate strikes with similar suc tion pressures. (C) 1997 Wiley-Liss, Inc.