Haemolymph Concentration and Apparent Permeability in Varying Salinity Conditions of Gammarus Duebeni, Chaetogammarus Marinus and Gammarus Locusta

Haemolymph and external medium sodium concentrations have been investigated in three euryhaline amphipods, Gammarus duebeni (Lillje-borg), Chaetogammarus marinus (Leach) and Gammarus locusta (Linnaeus). These were subjected to various salinity regimes, including sudden and cycling salinity changes. The apparent permeability to water of these three species was investigated in various salinity regimes using THO as a marker. Of the three species, only G. duebeni demonstrated large and significant changes in apparent permeability to water. The bulk flow into and out of the animals was calculated showing a variation of responses in the three species, G. duebeni exhibiting the smallest bulk flow and G. locusta the largest. These results were related to the ecology of the three species.