Fig. 1. Images and silhouettes of withdrawal behavior in Erpetoichthys calabaricus. All images and silhouettes are oriented with the fish's head to the right. (A) Time series of withdrawal to a head-directed stimulus. The head initially rotates to one side (20 ms) in the pre-transition stage of movement. After the transition point, the head is pulled back from the stimulus and continues to rotate. (B) Silhouettes show examples of four withdrawals to head-directed stimuli. One silhouette is shown for each of the study animals. For an individual withdrawal, the silhouettes get darker through the response. (C) Time series of withdrawal to a tail-directed stimulus. (D) Silhouettes show examples of four withdrawals to tail-directed stimuli. One silhouette is shown for each of the study animals. The response to tail stimulation results in greater movement during withdrawal than the response to head stimulation. In addition, unlike for responses to head stimulation, responses to tail stimulation generally involve a post-withdrawal propulsive stage of movement.