The osmotic performance of H. nudtls in dilute SW media in the present study was similar to that reported for the same animal by Dehnel (8) in 50% and 75% SW. However, H. nudus examined in the present study did not maintain as large an osmotic gradient in 25% SW as did Dehnel’s. Further, our animals were isosmotic in 100% SW, while Dehnel’s animals were approximately 150 mOsm hyperosmotic to the same medium and to media as concentrated as 125% SW. These differences in osmotic performance may be due to the different osmotic stresses imposed by the crabs’ normal habitats or by the short acclimation times (48 h) used by Dehnel. Dehnel’s animals were routinely exposed in their natural environment to very dilute sea water (as low as 230 mOsm), particularly in summer, while the crabs used in the present study were taken from
the open coast of central Oregon, where they rarely experience media more dilute than 700 mOsm.