Osmolality and electrolyte concentration of hemolymph and the problem of ion and volume regulation of cells in higher insects

Abstract

1. 1. The study was carried out on 22 species of insects from 5 orders. The osmolality of their hemolymph varied from 319 to 421 mOsm/kg H 2O, concentration of Na + 4.6 to 118 mM/l, K + 6.3 to 73mM/l, Ca 2+ 3.6 to 12.9 mM/l, Mg 2+ 2.3 to 76 mM/l. The most abundant cation in the hemolymph of insects from higher orders is either K + or Mg 2+. 2. 2. In the muscles of lower and higher insects K + is usually within 80–120 mM/kg wet wt. 3. 3. Most Ca 2+ and Mg 2+ in hemolymph is bound with protein and low molecular anions, concentration of free Ca 2+ is 0.9-2.1mM/l Mg 2+ 3.7–8.0 mM/l. 4. 4. It is concluded that, in insects, potassium hemolymph, cell volume regulation and accumulation of ions in the cell, are ensured by an increased osmolality of hemolymph due to a high percentage contribution of low molecular organic substances which are retained in the hemolymph due to the absence of filtration apparatus in the Malpighian tubules.