Reciprocal inhibition between feeding and withdrawal behaviors inPleurobranchaea

Abstract

1. The interaction between two discrete behavioral acts, feeding and withdrawal from tactile stimulation, was examined in 32 specimens of the marine molluskPleurobranchaea. The experimental paradigm (Fig. 2) incorporated gradation of the intensity of the respective sensory stimuli for both behaviors over a wide range. 2. Withdrawal amplitude was suppressed during simultaneous feeding in individual animals (Figs. 5 and 7) and in grouped data from all 32 subjects (Fig. 9). The suppression of withdrawal was greater with increased feeding intensity (Fig. 9). 3. Feeding intensity declined during simultaneous withdrawal in individual animals (Figs. 6 and 8) and in grouped data from all subjects (Fig. 10). The suppression of feeding during withdrawal was greater with increased withdrawal intensity, and less with increased feeding intensity (Fig. 10). 4. It is concluded that feeding and withdrawal interact reciprocally rather than hierarchically, and a modified scheme for the overall organization ofPleurobranchaea's behavioral hierarchy is presented (Fig. 11). The findings are discussed from an evolutionary, ethological and neurophysiological view point.