Cutaneous water collection by a moisture-harvesting lizard, the thorny devil (Moloch horridus).
Moisture-harvesting lizards, such as the Australian thorny devil, Moloch horridus, have the remarkable ability to inhabit arid regions. Special skin structures, comprising a micro-structured surface with capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and transport it to the mouth for ingestion. The ecological role of this mechanism is the acquisition of water from various possible sources such as rainfall, puddles, dew, condensation on the skin, or absorption from moist sand, and we evaluate here the potential of these various sources for water uptake by M. horridus The water volume required to fill the skin capillary system is 3.19% of body mass. Thorny devils standing in water can fill their capillary system and then drink from this water, at approximately 0.7 µl per jaw movement. Thorny devils standing on nearly saturated moist sand could only fill the capillary channels to 59% of their capacity, and did not drink. However, placing moist sand on skin replicas showed that the capillary channels could be filled from moist sand when assisted by gravity, suggesting that their field behaviour of shovelling moist sand onto the dorsal skin might fill the capillary channels and enable drinking. Condensation facilitated by thermal disequilibrium between a cool thorny devil and warm moist air provided skin capillary filling to approximately 0.22% of body weight, which was insufficient for drinking. Our results suggest that rain and moist sand seem to be ecologically likely water sources for M. horridus on a regular basis.
RWTH Aachen University, Institute of Biology II, Worringerweg 3, Aachen 52074, Germany philipp.comanns@rwth-aachen.de.
Philipp
0000-0002-2020-0515
P
Comanns
University of Western Australia, School of Animal Biology, 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
Philip C
PC
Withers
RWTH Aachen University, Institute of Biology II, Worringerweg 3, Aachen 52074, Germany.
Falk J
FJ
Esser
Johannes Kepler University Linz, Institute of Biomedical Mechatronics, Altenberger Strasse 69, Linz 4040, Austria.
Werner
W
Baumgartner
D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D008116:Lizards / Q000502:physiology*; D012867:Skin / Q000378:metabolism*; D012987:Soil; D014867:Water / Q000378:metabolism*; D017155:Wettability
D012987:Soil; D014867:Water
Capillary; Lizard; Micro-ornamentation; Moist sand; Skin; Water uptake