Abstract
Osmotic, sodium and chloride regulations of hemolymph in Hemigrapsus sanguineus were investigated. The crabs exhibited strong hyperosmoregulation in the range of 50-75% SW. Sodium and chloride ions were also well regulated in the same salinity range. The speciffic activity of gill Na++K+-ATPase was higher in the posterior gills than in the anterior gills. In the posterior gills, the Na++K+-ATPase activity showed an increase of 1.5 times with acclimation from 100% SW to 50% SW. Absorption of sodium ion by H. sanguineus in low salinity may be attributed to the function of the posterior gills which have a high level of Na++K+-ATPase activity.
