The Influence of Environmental Salinity on the Water Fluxes of the Amphipod Crustacean Gammarus Duebeni

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Abstract
1. The effect of salinity on the apparent permeability to water of Gammarus duebeni has been studied. 2. The apparent permeability when the animals are acclimatized to sea water or 150% sea water is more than twice that when they are in dilute media. The change from the level of permeability found in sea water to that in dilute media occurs largely in the range 75-50% sea water. 3. Permeability change occurs within 5 min when animals acclimatized to sea water are transferred to dilute media. 4. When animals from sea water are transferred to a mannitol solution isotonic with sea water the permeability changes to a level close to that found in animals in dilute salines. 5. This last observation is taken to indicate that the stimulus initiating the change in apparent permeability is not an osmotic one. Other possibilities are discussed and the value to the animals of changes in its permeability to water are considered.