Figure 2.

Percentage of behaviours displayed in response to shadows of different velocities. Crayfish produce only one of two discrete defensive responses when exposed to approaching shadows: tail-flipping, which is always mediated by activity in the medial giant (MG) interneurons or freezing behaviour. Tail-flipping behaviour decreases and freezing behaviour increases as shadow velocities increase. The measured differences in displayed behavioural patterns are statistically significant. ** = p ≤ 0.01. Grey bars, freezing; black bars, tail-flipping.