Fig. 2

Operculum behavior becomes more consistently patterned at 4 and 5 days postfertilization (dpf). At both (a) 4 dpf (n = 15) and (b) 5 dpf (n = 15), all subjects produced bouts of rhythmic operculum movement, followed by a large burst of operculum movement associated with attempted whole-body movement (indicated by arrows), followed by a pause before rhythmic movement resumed. Note that rhythmic movements could occur as couplets, as shown for the example in panel (b). In both panels (a) and (b), a microscopic image of the operculum is shown in the upper left, and a representative trace of dorsoventral operculum position over time is shown in the upper right. The location of the landmark used to track movements in this subject is indicated by an asterisk. A histogram (bottom) shows the distribution of inter-movement intervals for this subject across trials (excluding intervals during and immediately following attempted whole-body movements). The histogram has been divided into smaller (<5 s, left) and larger (>5 s, right) intervals.