Skin Morphology of Five Species of Rock Lizards of the Genus Darevskia (Lacertidae, Squamata)

The microstructure of the tuberculate dorsal and lamellar ventral skin of the body in rock lizards of different ages (Darevskia raddei, D. nairensis, D. valentini, D. dahli, and D. armeniaca) was described for the first time. The thickness of the skin in the most xerophilic species (D. raddei) is less than that in the more hygrophilic species. Rock lizards have single or paired longitudinal skin folds that are not closed from the side, which stretch along the inner side of the scutes to the distal edge. Small folds are also present in the lining of the squamous pocket; they consist of all layers of the skin and subcutaneous tissue. A large fold can completely block the cavity of the squamous pocket, the volume of which changes with contraction of the subcutaneous muscle bundles reaching the bases of the scutes. Small folds are also present on the scales of tuberculate skin. In mesophilic lizards (Zootoca vivipara), similar formations appear at later stages of postnatal ontogenesis than in rock lizards. The likely functional significance of the described skin structures is discussed.