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Fig. 4. Evidence that cuttlefish discriminate depth in checkerboard patterns. This
study used the same 20 juvenile cuttlefish as in the pebble study
(Fig. 3), and again we analysed
the response of each animal to each of the three experimental backgrounds,
giving a total of 60 images (Fig.
2B). (A) The cuttlefish were settled on a Perspex floor above a
checkerboard in which the dark and light squares were either in the same depth
plane (flat) or in different depth planes separated by 10 mm. (B) Light
squares above dark were most effective in eliciting the disruptive body
pattern (PC1; Figs 1 and
2). The expression of PC1
(disruptive) was stronger when the light check pattern was in the upper plane
(Student's t-test, t19=–2.635,
P<0.05). Similarly an ANOVA showed a significant interaction of
the backgrounds (flat and depth with light checks on the upper surface) with
the expression of PC1 and 2 (F1,19=0.5711,
P<0.05). There is no apparent effect of the experimental
treatments on PC3 and PC4 (not illustrated).
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