Osmoregulation of the grass shrimp (Palaemonetes pugio) exposed to polychlorinated biphenyls (PCBS). Part I - Effect on chloride and osmotic concentrations and chloride - and water - exchange kinetics.
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Grass shrimp, Palaemonetes pugio, were capable of hypo- and hyper-osmotic regulation of body fluids. Hemolymph chloride and osmotic concentrations were maintained at relatively stable levels over a wide salinity range. Following an abrupt transfer from intermediate (14 and 17 parts per thousand by weight) to high (31 and 35 parts per thousand by weight) salinities, hemolymph cloride levels exhibited initial overshoot and undershoot, respectively, of new steady- state levels. Changes in chloride space following salinity transfer paralleled those of hemolymph chloride levels. Rate constants for chloride turnover indicated independent exchanges of sodium and chloride ions. Water-turnover measurements showed that permeability of P. pugio was greatest at the isosmotic salinity (17 ppt by wieght) and reduced at salinities which were associated with active osmoregulation. Exposure to sublethal and 96-h LC^50 levels of Aroclor 1254 did not seriously alter hemolymph chloride and osmotic concentrations, chloride space or chloride - exchange kinetics in adult shrimp.