Figure 2

Pigmentary and structural colorations in Phelsuma geckos. (a) Semi-thin cross-sections of skins of different colors. Two types of melanophores are indicated (arrows and arrowheads, respectively), and iridophores are outlined with dashed lines. Ep, epidermis; X, xanthophores; Er, erythrophores. Bar = 10 μm. (b) Pteridin pigments were removed with NH₄OH (here in Phelsuma grandis, individual number 3), revealing the remaining structural color produced by the iridophores. Bar = 0.2 mm. (c) Red pigments in dorsal markings of Phelsuma quadriocellata and Phelsuma lineata can change color when the pH of the Ringer solution is lowered or when an oxidant (NaNO₂) is added, respectively. Bar = 0.2 mm. (d) Representative electron micrographs of iridophores in skin of different colors. Bar = 1 μm. Note the highly disordered guanine crystals in the white and red skin. (e) Mechanical pressure and dehydration (here applied to the green skin of P. grandis, individual number 2 after removal of the yellow pigment) lead to a blue shift of structural green (for supplementary movies, see Additional file 3; see Additional file 4).