Fig. 7. Transverse sections through the central cornea showing the pigment layer during light- (A) and dark-adaptation (B). Scale bar, 1 µm. (C) Differences in width of the central iridescent layer (IR), the cells in the reservoir (RC), the central pigment layer (PL) and individual pigment processes (PP) in the central cornea in both species in the light- (LA) and dark-adapted (DA) condition. The difference between the widths of the iridescent layer is significant for both species (T. pleurogramma, F=2400, P<0.001; T. hamiltoni, F=33.3, P<0.001). Note that the IR width in T. pleurogramma is larger during dark-adaptation compared to light-adaptation, whereas the opposite is true for T. hamiltoni. During dark-adaptation, the cells in the reservoir of both species swell, the pigment processes in the central cornea empty leading to a decrease in width of the pigment layer. During light-adaptation, the central pigment processes swell, leading to an increased width of the pigment layer and a decreased size of the peripheral pigment reservoir cells.

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