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Cutaneous Water Acquisition by the Thorny Devil (Moloch horridus: Agamidae)

Philip Withers
Journal of Herpetology
Vol. 27, No. 3 (Sep., 1993), pp. 265-270
DOI: 10.2307/1565146
Stable URL: http://www.jstor.org/stable/1565146
Page Count: 6
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Cutaneous Water Acquisition by the Thorny Devil (Moloch horridus: Agamidae)
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Abstract

The skin of the thorny devil readily absorbs water, like "blotting-paper." The volume of water held in the cutaneous capillary system is about 3.7% of the body mass. Water is conveyed to the mouth by the cutaneous capillary system, where it is imbibed. The low permeability of the skin to evaporative water loss and lack of dyed water absorption suggest that there is not any transcutaneous water absorption across the skin itself. Interscalar channels about 5-50 μm wide, and an overlapping shelf around the edge of the scales that forms a sub-scalar channel, appear to be the primary cutaneous surface features that are responsible for the "blotting-paper" action of the skin. The capillarity force that absorbs water to the skin supports a pressure head of about 10 cm water. This capillary head is not consistent with the inter-scalar capillarity channel dimension of about 5-50 μm, but to about 220 μm. One ecological role of the "blotting-paper" skin of the thorny devil is clearly the direct uptake of rain that falls on the skin or from puddles. In addition, the cutaneous capillary system of the thorny devil enables water absorption from moist sand.

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