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Electrical-Potential Difference and Sodium Ion Fluxes across the Integument of Corophium Volutator (Crustacea; Amphipoda), a Euryhaline Hyperosmotic Regulator
1 Department of Zoology, University of Leicester, University Road, Leicester, LEI 7RH: Department of Zoology, Bedford College, University of London, Regent's Park, London, NW1 4NS.
1. Measurements of electrical-potential difference (TEP) and Na+ efflux, across the integument have been made for Corophium volutator acclimated to 85 or 15%SW.
2. The TEP of acclimated animals in 85 or 15%SW is l.4mV or 11.1 mV respectively (haemolymph negative). For acclimated animals, unidirectional Na+ efflux is 154.3 nmol mg-1 body weight h-1 in 85%SW [efflux rate constant (k) = 0.70 h-1] and approximately 35.5 nmol mg-1 h-1 in 15%SW (k = 0.50h-1 in 10%SW).
3. The results indicate that Na+ and Cl-are passively distributed across the ion-permeable (gill) integument of acclimated animals in 85%SW, but that active uptake of Cl-, and possibly Na+ also, occurs across the gills of acclimated animals in 15%SW. The ion transport mechanisms appear to effect electroneutral transfers across the gill integumental epithelium.
4. Corophium volutator gill integument has a high permeability to ions; permeability to Na+(PNa) is 7.5x10-8ms-1, and the ratio PCl/PNa is 0.45, for animals acclimated to either salinity. The resistance of the gill epithelium of acclimated animals has been calculated to be 5.3x10-3
m2 and 2.0x10-2
m2 in 85 and 15%SW respectively.
Key words: Crustacean, epithelial potential, sodium flux.
Accepted on August 1, 1984