Scallops track moving visual stimuli with their extensible sensory tentacles

Above, a bay scallop (Argopecten irradians) tracks the angular position of a rotating stripe with its sensory tentacles. On the left is a video in which the tips of the scallop’s tentacles are labeled with colored dots. In the video, you can see the scallop extending multiple sensory tentacles towards the isoluminant visual stimulus as it rotates counterclockwise. On the right is the circular distribution of the relative lengths of tentacles extended by the scallop. Each step of the animation corresponds to a frame of the video. From this plot, you can see that the scallop’s response to the rotating visual stimulus is a rotating wave of tentacle extension that closely follows the position of the stripe.