Renal water and solute excretion in the Atlantic stingray in fresh water

Freshwater, male Atlantic stingrays Dasyatis sabina, from Lake Jesup, Florida, U.S.A., excreted a dilute urine similar in composition to freshwater teleosts and lampreys with the exception that urea was the primary osmolyte. Urine flow rate was 2.5 to 10 fold higher than that reported for freshwater teleosts resulting in high free-water clearance. Mass-specific free-water clearance values from euryhaline elasmobranchs inhabiting freshwater environments greatly exceed those for freshwater teleosts and are nearly equivalent to those of freshwater lampreys. Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.