Hemolymph ion composition and volume changes in the supralittoral isopod Ligia pallasii Brandt, during molt

J Comp Physiol B. 2000 Jun;170(4):329-36. doi: 10.1007/s003600000108.


We analyzed ion composition and volume of the hemolymph of Ligia pallasii in four different stages of the molt cycle using capillary electrophoresis and 3H-inulin. The main ions in the hemolymph were Na+, K+, Mg2+ , Ca2+, and Cl-. The Ca2+ concentration increased significantly during the molt by 47% from intermolt to intramolt and by 37% from intermolt to postmolt, probably due to resorption of Ca2+ from the cuticle and sternal CaCO3 deposits. The K+ concentration increased significantly by 20% during molt. The hemolymph volume normalized to the dry mass of the animals decreased by 36% from intermolt to late premolt. This was due to a reduction in the hemolymph volume and to an increase in dry mass of the animals during premolt. A sudden increase in the hemolymph volume occurring between late premolt and intramolt served to expand the cuticle. Since the Na+, K+, Mg2+, and Cl- concentrations did not change significantly from late premolt to intramolt, the increase in hemolymph volume suggests an uptake of seawater rather than freshwater.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Volume / physiology
  • Calcium / analysis
  • Calcium / metabolism*
  • Chlorides / analysis
  • Chlorides / metabolism
  • Crustacea / physiology*
  • Electrophoresis, Capillary
  • Hemolymph / chemistry
  • Hemolymph / metabolism*
  • Magnesium / analysis
  • Magnesium / metabolism
  • Molting / physiology*
  • Potassium / analysis
  • Potassium / metabolism
  • Seawater
  • Sodium / analysis
  • Sodium / metabolism
  • Water-Electrolyte Balance / physiology*


  • Chlorides
  • Sodium
  • Magnesium
  • Potassium
  • Calcium