SKIN RESISTANCE TO EVAPORATIVE WATER-LOSS IN VIPERID SNAKES - HABITATARIDITY VERSUS TAXONOMIC STATUS

The question whether evaporative water loss in snakes is affected main ly by the habitat aridity or whether it is better attributed to taxono mic position, remains controversial. To answer this question, cutaneou s water loss (E-c) and skin resistance to water loss (R-s) were measur ed under standardized experimental conditions in four species of noctu rnal vipers occupying different habitats. In the mesic-Mediterranean s pecies Vipera, E-c increased from 0.105 to 0.175 mg cm(-2) h(-1) at ai r temperatures of 25 and 35 degrees C, respectively. These values were 2 to 3-fold higher than that of the desert vipers, in which E-c incre ased with temperature very slightly. Values of R-s in the mesic-Medite rranean Vipera (averaged 792 s cm(-1)) were two times lower than those obtained for the desert species and did not change at the different t emperatures. In the desert vipers, R-s increased by different degrees with increasing air temperatures. These temperature-dependent R-s chan ges, which probably reflect vasomotor responses, were more pronounced in Pseudocerastes. Of the four species studied, this snake is least no cturnal and it occupies the most extreme desert habitats. These result s indicate that among closely related species, E-c and R-s correlate w ith habitat aridity. (C) 1998 Elsevier Science Inc. All rights reserve d.