Abstract
Terrestrial isopods, as successful colonizers of land habitats, show a great variety in species distribution patterns on a global, continental, or regional scale. On a local, within-habitat level these patterns reflect the species’ tolerance limits and the presence of suitable hiding places (shelter sites, refugia). Humidity preference reflects a species’ capability for water retention which, in turn, depends on the integumental barrier. Desiccation resistance is a key feature in isopod survival under different environmental conditions. The present study shows a correlation between cuticle thickness and desiccation resistance under three relative humidity (RH) ranges (about 30, 75 and 100% RH) in nine species, relating these to the species’ differences in meso- and microhabitat choices. Habitat preferences are also associated with differences in cuticle surface morphology. The results support our hypothesis that species distribution and desiccation resistance are associated with particular cuticular morphological traits. Phylogenetic relations seem to be less important in desiccation resistance than cuticle thickness and external morphology.
Highlights
Terrestrial isopods (Isopoda, Oniscidea) are successful colonizers of land habitats with over 3700 described species (Sfenthourakis and Taiti 2015)
Under extreme dry conditions (RH ~30%) we found high mass-specific water loss at each investigated species (Figure 1)
Mortality appeared in each species group except A. vulgare (P. politus – 100%, P. pruinosus – 80%, C. convexus – 65%, O. planum – 60%, T. rathkii – 25%)
Summary
Terrestrial isopods (Isopoda, Oniscidea) are successful colonizers of land habitats with over 3700 described species (Sfenthourakis and Taiti 2015). The sclerotized cuticle is the main barrier between oniscidean individuals and their environment. The epicuticular layer is important in inhibiting water loss (CloudsleyThompson 1977). It is divided into sublayers: the cement layer, the surface coat, the waxy layer, and the inner epicuticle. The waxy layer located within the cuticulin layer is not homologous with the external wax layer of insects (Compère 1990). As in insects, the waxy layer of oniscideans probably acts as a waterproofing barrier which reduces the tegumental water loss in terrestrial environments (Hadley 1982). Hadley and Quinlan (1984) detected cuticular lipids in the mesic Porcellio laevis, the amount of lipid present was not effectively reducing the transcuticular water loss As in insects, the waxy layer of oniscideans probably acts as a waterproofing barrier which reduces the tegumental water loss in terrestrial environments (Hadley 1982). Hadley and Quinlan (1984) detected cuticular lipids in the mesic Porcellio laevis, the amount of lipid present was not effectively reducing the transcuticular water loss
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