EFFECTS OF DEHYDRATION ON WATER-CONTENT, METABOLISM, AND BODY-FLUID SOLUTES OF A CARABID BEETLE FROM DRY SAVANNA IN EAST-AFRICA

Carabid beetles of the genus Cyphaloba, which live on dry savanna in E ast Africa, were investigated with respect to water balance, metabolis m and regulation of body fluid solutes during dehydration. The beetles seemed to reduce their cuticular water permeability in the same manne r as other dry habitat carabids and tenebrionids, but their high metab olic rates gave them relatively high rates of transpiratory wafer loss . The water loss appears to be limited by a substantial depression of the metabolism at daytime, when high temperatures and high vapor satur ation deficit values in the air favor a high evaporative water loss. T he basis of this depression is not clear, but it may in part be due to reduced physical activity. The beetles have high extracellular concen trations of sodium, but because evaporative dehydration causes the hem olymph volume to drop, sodium is removed from the hemolymph and deposi ted elsewhere in the body. A similar change takes place for free amino acids. (C) 1997 Elsevier Science Inc.