Figure 1.

Description of samples for histomorphometric analysis. Aquatic axolotl salamanders with webbed digits, external gills and tail fins (A). Spontaneously metamorphosed terrestrial axolotl salamander, characterized by a loss of external gills, tail fins and the webbing between the digits (B). (C) Right forelimb of an aquatic axolotl salamander differentially stained for bone (red) and cartilage (blue). Framed and outlined areas illustrate the selection perimeters for bone length and area measurements.