The effect of ambient chloride concentration changes on branchial chloride-bicarbonate exchanges and hemolymph acid-base balance of crayfish.
In crayfish Astacus leptodactylus maintained in 13 degrees C ambient water of constant oxygenation and acid-base balance, water chloride concentration was varied while the concentration of other ions, except sulfate, were maintained at constant values. The effects of wide variations of the ambient Cl- concentration, CCl, on the branchial titration alkalinity, delta TA, on delta CCl, delta CCO2, delta CO2 between inspired and expired water, and on the prebranchial hemolymph CCl and pH were studied. The branchial changes of TA, CCl and CCO2 were dependent on the ambient CCl, and a decrease of CCl led to a fall of CO2 excretion. Hemolymph acid-base balance closely depended on ambient CCl, particularly when CCl was less than 1 meq . L-1; when ambient CCl fell from 1 meq . L-1 to 0.1 meq . L -1, pH increased from 7.87 to 8.30. Since hemolymph PCO2 was not affected by the variations of CCl, the changes of pH are mainly explained by the concomitant changes of the hemolymph HCO3- and CO32- concentrations. During an 18-day exposure of crayfish to dechlorinated water, hemolymph CCl decreased progressively whereas its pH increased. The extreme values for CCl were 193 meq . L-1 at day 1 and 96 meq . L -1 at day 18, and the corresponding pH extremes were 7.87 and 8.65. Since the observed modifications of the branchial exchanges and the hemolymph acid-base balance were not related to the small changes of ambient osmolarity or of the SO42- or Na+ concentrations, it is inferred that they depended on a modified Cl-/HCO3- exchange mechanism in the gills.
D000136:Acid-Base Equilibrium / Q000187:drug effects*; D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D001639:Bicarbonates / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology* / Q000502:physiology; D005260:Female; D005880:Gills / Q000502:physiology*; D006458:Hemolymph / Q000502:physiology*; D008297:Male; D012119:Respiration / Q000187:drug effects*; D013997:Time Factors
D001639:Bicarbonates; D002712:Chlorides