Pausing behavior propagates from animal to animal. Animals T1 and T2 cease gliding ~20 sec after the start of the video, followed sequentially by animals T3 – T5. Their movements slow gradually and then, more abruptly, they become essentially stationary, although their edges spread to varying degrees. The animals begin moving again after ~ 5 min, and pause again near the end of the video. Time lapse transmitted light images captured at 4 sec intervals.