Water Relation and Internal Body Temperature of Isopods from Mesic and Xeric Habitats

Abstract

The rate of water loss by evaporation was measured in several isopod species fArmadillidium vulgare, Cylisticus convexus, Venezillo arizonicus]. One of them Venezillo arizonicus, which lives in xeric habitats in southern Arizona, has a very low rate of water loss. At temperatures higher than 38[degree]C there was a substantial increase in the rate of evaporation even when exposed to constant vapor pressure deficit. A similar temperature effect was not found in any of the other species studied. The internal body temperature of the isopods was found to be inversely related to the rate of water loss. The ability to survive high temperatures was not related to the rate at which the isopod could lower its body temperature. Accordingly, V. arizonicus survived high temperatures but was unable to depress its body temperature. Evaporation seems therefore to play a more important role in regulating the body temperature of isopods from mesic habitats than it does in isopods from xeric habitats.