Dynamics of Information Exchange in Zebrafish: The Role of U-Turns in Visual Communication and Behavior Modulation

Motions of visually coupled zebrafish pairs are studied to understand the effects of information exchange on their behavior as a function of their minimal separation ($d$). We find that when $d$ is small, the pair can display a leader-follower relation (LFR) with trajectories of almost synchronized form. However, with larger $d$, although the same LFR is still maintained, the originally similar trajectories turn into different forms. Detailed analysis of their motion trajectories suggests that the pair might be using U-turns (UTs) to exchange information and to maintain a LFR at the same time. A simulation model based on UTs with inferred and proposed rules is able to reproduce prominent features of observed trajectories; indicating that the transition of trajectories can be understood as the result of a change in information exchange between the fish as $d$ increases. Our finding that UTs as important visual signals is consistent with the fact that UTs can induce a large amount of firings in retinas of observing fish.