Sodium regulation during dehydration of a herbivorous and a carnivorous beetle from African dry savannah

The sodium regulation of carnivorous carabid beetles of the genus Cypholoba and herbivorous tenebrionid beetles of the species Phrynocolus petrosus from dry savannah in East Africa was investigated while the beetles went through dehydration in the laboratory. In both species the water loss took place mainly at the expense of the extracellular fluid, and in both species the loss of extracellular water was accompanied by a loss of extracellular sodium. In the carabid beetles the sodium removed from the extracellular fluid was excreted from the body, while in the tenebrionids sodium was kept within the body. It is proposed that the different manners in which the two species handle their sodium reflect differences in their access to dietary water and sodium.