Fig. 4.
Demonstration of one cycle for each of the multifunctional behaviors. Bold arrows at the bottom of each schematic indicate changes in grasper position from one behavioral phase to the next, whereas bold arrows at the top indicate changes in head position. A A schematic representation of the simplified model during biting. No seaweed or tube is present and only the grasper moves throughout the cycle. B A schematic representation of the simplified model during swallowing. Seaweed is present and fixed to a force transducer. Of particular note is the motion of the head during swallowing. Because the seaweed is fixed to the rigid force transducer, the activation of the I3 muscle when the seaweed is being firmly grasped results in the head being pulled forwards along the seaweed (B, Retraction panel), so long as the force on the seaweed does not exceed the force threshold. C A schematic representation of the simplified model during rejection. Rather than seaweed, a tube is simulated to provide mechanical stimulation without any chemical cues. The tube is not fixed to an external object and is therefore free to be pushed forward during the rejection. Note the outward movement of the marks on the tube after the rejection cycle concludes (C, Rest panel). For both biting and rejection, there is a slight forward motion of the grasper from the fully retracted position to the rest configuration shown here