Skin resistance to water loss in agamid lizards.

Many desert lizards show reduced rates of cutaneous water loss (CWL) compared to their counterparts from more humid environments. It is not clear yet whether reduced CWL is connected to the taxonomic position of the lizard studied, or is affected more by environmental or experimental conditions. To investigate this, we measured the skin resistance to water transfer, R s, in five closely related lizard taxa of the genus Agama. These diurnal lizards are distributed in Israel from mesic-Mediterranean to extreme desert biotopes. The highest R s (738 s cm-1) and the lowest CWL (0.160 mg cm-2 h-1) were found in Agama sinaita, which lives in the most arid habitat. The lowest R s (234 s cm-1) and the highest CWL (0.548 mg cm-2 h-1) were found in A. stellio ssp., which occupies mesic habitats. In addition, only the desert species were able to change their R s in accordance with the changing experimental conditions. These R s changes, which probably reflect vasomotor responses, were more pronounced in A. sinaita and presumably enable the desert species to control their CWL in a hot and dry environment.