Ionic regulation and Na(+)-K(+)-ATPase activity in gills and kidney of the freshwater stingray Paratrygon aiereba living in white and blackwaters in the Amazon Basin

J Fish Biol. 2009 Mar;74(4):956-60. doi: 10.1111/j.1095-8649.2008.02156.x.


During low-water period, freshwater stingray Paratrygon aiereba collected in the whitewater (WW) of the River Amazon showed higher urea content, osmolality, Na(+) and Cl(-) concentrations in plasma and perivisceral fluid than those caught in blackwater (BW) of the River Negro. Gills and kidney Na(+)-K(+)-ATPase activities were significantly lower in WW than in BW fish. The high level of kidney Na(+)-K(+)-ATPase activity in P. aiereba may minimize ion loss and generate diluted solute-free urine in ion-poor BW environment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blood Glucose / analysis
  • Blood Proteins / analysis
  • Gills / enzymology*
  • Kidney / enzymology*
  • Rivers*
  • Skates, Fish / metabolism*
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Urea / blood
  • Water-Electrolyte Balance / physiology*


  • Blood Glucose
  • Blood Proteins
  • Urea
  • Sodium-Potassium-Exchanging ATPase