Figure 4.

The selective disadvantage of a Cx57 gene loss. (A) Movie of an approaching predator, filtered through the frequencies available to the wild-type animal, as provided by Figure 3D left. In day conditions, the predator can be seen both when it is moving (when the movie is dominated by high temporal frequencies), and when it is still (when the movie is dominated by low temporal frequencies). In night conditions, the signal is weaker, but the predator can still be seen both when moving or still. The visibility in the still condition is possible because of the shift to low temporal frequencies that occurs in the dark. The traces below the figures provide the intensity of each pixel in a horizontal slice through the image; the location of the slice is indicated by the arrow. (B) Same movie, filtered through the frequencies available to the knockout animal. In night conditions, the predator vanishes, see trace below figures. The wild-type's continued visual detection of the predator gives it an obvious selective advantage. (For the frequencies available to each genotype, see Figure 3D left: specifically, the range of frequencies seen by the knockout at night (red curves in 3D bottom left) is a subset of the range seen by the wild-type (blue curves); the lack of low frequency sensitivity in the knockout (below ∼0.3 Hz) causes the predator, when it is still, to disappear. Note that the temporal filtering was applied to the entire movie; only a representative frame from each filtered version is shown here. For the complete filtered versions, see Supplementary Material).