THE EFFECT OF TOTAL ENVIRONMENTAL CO2 CONCENTRATIONS ON THE ION-PERMEABILITY OF SHORE CRABS, CARCINUS-MAENAS (L)

1. 1. Salt exchange characteristics (permeability, half-time for salinity adaptation and net salt flux after a change in salinity) of adult shore crabs were studied in relation to experimentally increased external CO2 (TCO2 = carbon dioxide, carbonic acid, bicarbonate and carbonate) concentrations. 2. 2. Up to about 15mM TCO2/1, elevated external TCO2 concentrations induce an increase in the salt permeability of shore crabs, resulting in higher passive salt fluxes across the body wall. The effect is most pronounced in larger animals (body weight > 25 g). 3. 3. When external TCO2 concentrations exceed internal TCO2 concentrations, then permeability and salt exchange drop to low values, comparable to those observed in control animals. The results clarify a connection between blood gas transport and salt transport. 4. 4. Elevated CO2 levels are unfavourable by inhibiting the chloride/bicarbanate pump (thus disturbing the removal of metabolically produced CO2 and the salt uptake in a hypotonic environment). High TCO2 levels, up to about 20 mmol TCO2/1, cause stress but Carcinus maenas can survive, at least temporarily, at the expense of metabolic energy. © 1990.