Meeting Abstract

P3.155  Monday, Jan. 6  Scaling of water loss, diffusion and ventilation in Scarab beetles at rest and during hypoxia CAMPBELL, JB*; DUELL, ME; KLOK, CJ; HARRISON, JF; Arizona State University jacob.campbell.1@asu.edu

Due to the scaling of surface-to-volume ratios and metabolic rates, smaller insects desiccate more rapidly than those larger. Water loss occurs through multiple avenues (i.e. cuticle, excretory, respiratory), and as yet it is unclear whether body size affects the proportion of water loss that is associated with respiration. The fact that larger insects have lower metabolic rates per gram would suggest similarly lower mass-specific water loss rates associated with gas exchange; however, some data indicates that larger insects require greater mass-specific ventilation, which should be associated with greater mass-specific ventilator water loss. To test the mass-scaling of water loss for insects at rest and during challenged gas exchange, we measured water loss and CO₂ emission rates at rest and at reduced atmospheric oxygen for individuals of 12 species of Scarabaeidae beetles spanning 5 orders of magnitude in body size, ranging in size from 0.001-30g. For individuals exhibiting discontinuous gas exchange, we were able to separate cuticular, trans-spiracular, maximum diffusive (during anoxia), maximum ventilation-associated water loss. Preliminary analyses suggests that the scaling of CO₂ emission rates and water loss rates were similar. Maximal mass-specific diffusive water loss rates scaled hypometrically and maximal ventilatory water loss rates scaled isometrically, consistent with an increasing reliance on ventilation relative to diffusion in larger beetles. Funded partially by NSF 1122157.