|SREL Reprint #0953|
Permeability of the Skin of the Amphibious Snake, Agkistrodon piscivorus
A. Dunson and Joseph Freda
The cottonmouth (A. psicivorus) is a
semi-aquatic fresh water snake which is closely related to the terrestrial
copperhead (A. contortrix). Despite
the differences in habitat preference, both species have similarly low
integumentary water permeability in the summer.
Influx and efflux of water measured between tritiated distilled water and
a 1 M NaCl solution were about 20-50 moles/cm2h.
These are fairly typical values for terrestrial snakes, but abnormally
low for fresh water species. A.
piscivorus were caught soon after emergence from hibernation, and
successive shed skins tested under constant conditions over a five month period
showed significant declines in water permeability with a minimum of about 20
moles/cm2h in June-September. Newborn
A. piscivorus placed in water for three weeks had significantly
lower cutaneous water permeabilities than those dehydrated by about 27% of their
initial body mass in air. Thus
integumentary permeability may vary in response to the state of body fluid
hydrations. Skin water permeability
appears to be controlled by lipids since their extraction causes an enormous
increase in influx and efflux. The
lipid extracted shed skin of A. piscivorus demonstrated a marked
asymmetry in downhill water diffusion, within influx exceeding efflux.
SREL Reprint #0953
Dunson, W.A. and J. Freda. 1985. Water permeability of the skin of the
amphibious snake, Agkistrodon piscivorus. Journal of Herpetology 19:93-98.