Motor control of tongue movement during prey capture in plethodontid salamanders

Four species of salamander of the family Plethodontidae were examined using electromyographic (EMG) recording during prey-capture behavior to test the hypotheses that the tongue retractor, tongue protractor and jaw depressor muscles are activated simultaneously and in a stereotyped pattern, as was f ound in other salamanders, and to determine whether species with different tongue morphologies and tongue protraction abilities exhibit different moto r control strategies. The results show that sequential activation was obser ved far more frequently than simultaneous activation; the jaw depressor mus cle was activated first, followed by the tongue protractor and then the ton gue retractor, Species with short, attached tongues (Desmognathus quadramac ulatus and Plethodon jordani) showed simultaneous activation more often tha n species with long, free tongues (Pseudotriton ruber and Hydromantes supra montis), which showed strongly non-simultaneous activation, Most EMG variab les showed no effect of prey-capture success, suggesting that sensory feedb ack is not involved in modulating the motor pattern during the prey-capture strike. Hydromantes supramontis was examined for modulation of its motor p attern in response to prey distance, and several EMG variables were found t o be positively correlated with tongue protraction distance. The motor patt ern of strongly non-simultaneous activation of antagonistic tongue muscles has evolved along with the evolution of long, free tongues in plethodontids . The variable motor patterns observed provide further evidence that amphib ian feeding in general is not as highly stereotyped as has been previously thought.