Movie S1.

WT larvae at 24 dpf: Five larvae were placed in the Petri dish. The video starts (00:00) with a close-up view on one larva near the base of the dish. Spontaneous swim behavior is observed after 1-2 seconds (00:01 – 00:02). After ∼3 seconds (00:03), a metal probe was lowered behind the Petri dish (appears as a shadow in the background) to indicate the start of tapping on the rim of the dish. As tapping began (note movement of the liquid surface), the larva in the foreground and other larvae in the background (partially in focus) display swift escape response, consistent with normal hair cell function and hearing.