Fig. 3. (A) Anatomy of three anatomical types (A–C) of photoreceptor in diurnal (left) and nocturnal (right) geckos (modified from Underwood, 1970). Note the different lengths of the outer segments that cause different quantum captures. (B) Spectral sensitivities of the 5 µm short cones of a diurnal gecko (broken lines) and the 50 µm long cones of a nocturnal gecko (solid lines). UV, UV receptor; B, blue receptor; G, green receptor. (C) Cone mosaic of the nocturnal gecko Teratoscincus scincus (redrawn from Loew et al., 1996). Green circles, green-sensitive cones; blue circles, blue-sensitive cones; blue-green circles, double cones with a green and a blue receptor; grey-green circles, double cones with a green and a UV receptor.