Hyperosmotic readjustment of the crab,Hemigrapsus edwardsi

Summary Daily changes in the composition of the haemolymph and muscle tissue ofHemigrapsus edwardsi, following transfer to hyperosmotic saline, were investigated. The haemolymph approached a new equilibrium, with respect to ionic constituents, within 48 h. The muscle fibre water content, expressed in kg/kg dry weight, fell initially and then rose. This was associated with a rise in the amount (per kg tissue dry weight) of intracellular ninhydrin-positive substances (mainly amino acids) which was substantially complete within four days. It was concluded that this crab is capable of relatively rapid intracellular readjustment to hyperosmotic stress.