title: Rubidium uptake is increased in shore crabs, Carcinus maenas, acclimated to dilute seawater.
abstract: In dilute seawater, Carcinus maenas hyperosmoregulates by actively absorbing Na, K, and Cl. Here we characterize K uptake using a novel technique. Rb was used as a tracer for K transport, and hemolymph Rb levels were measured using cation chromatography. Hemolymph Rb was detectable at 0.1 mmol L(-1), which enabled determination of initial rate of Rb uptake. Crabs maintained for 3 wk in dilute artificial seawater (35% ASW crabs) maintained Na and K above the level of the external media and had elevated Na-K-ATPase activity in the posterior gills. In assay conditions matched to 100% ASW, Rb uptake was the same in 35% ASW crabs (0.45+/-0.04 micromol g(-1) h(-1)) and in crabs acclimated to normal seawater (100% ASW crabs, 0.49+/-0.05 micromol g(-1) h(-1)). In assay conditions matched to 35% ASW, Rb uptake was greater in 35% ASW crabs (0.28+/-0.03 micromol g(-1) h(-1)) compared with 100% ASW crabs (0.10+/-0.04 micromol g(-1) h(-1)). Low external [Rb] or reduced salinity were found to contribute independently to the difference between 100% ASW and 35% ASW crabs. Thus, whole-body Rb uptake in crabs can be measured by cation chromatography, and Rb uptake is greater in 35% ASW crabs than in 100% ASW crabs.
authors.affiliation: Department of Biology, Kenyon College, Gambier, OH 43022, USA.
authors.forename: N E
authors.initials: NE
authors.lastname: Colburn
authors.forename: S G
authors.initials: SG
authors.lastname: Gage
authors.forename: C M
authors.initials: CM
authors.lastname: Gillen
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D003386:Brachyura / Q000502:physiology*; D002845:Chromatography; D011188:Potassium / Q000493:pharmacokinetics*; D012413:Rubidium / Q000493:pharmacokinetics*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014018:Tissue Distribution; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium