Regulation of haemolymph sodium and potassium during dehydration in the cricket Teleogryllus oceanicus

Male crickets ( Teleogryllus oceanicus ) when dehydrated for 3 days lost 51% of their body water, and 65% of their haemolymph volume. Haemolymph osmolality rose from 391 to 572mOs/kg; [Na + ] from 149 to 289 HIM; and [K + ] from 13.0 to 26.3 mM. During dehydration 385 μig Na (expressed as NaCl) and 41 μug K (expressed as KCI) were removed from the haemolymph. Rehydration of the dehydrated insects failed to restore the Na + and K + concentrations to near their original levels. Approximately 62% of the missing Na + was excreted, whilst five times the amount of K + removed from the haemolymph was excreted. It is presumed that the excess represents K + removed from intracellular fluid.