title: Osmotic and ionic regulation in different populations of the new zealand freshwater crayfish Paranephrops zealandicus.
abstract: 1. Some features of the osmoregulatory mechanism are compared in four populations of Paranephrops zeal andicus White collected form freshwaters of different ionic concentrations. 2. Crayfish from freshwaters of ca, 2-0 mM-NaCl concentration show a sustained decrease in blood concentration of ca. 8% when placed in 0-2 mM-NaCl. 3. Populations from freshwaters of ca. 0-2-0-4 mM-NaCl show lower rates of net salt loss in distilled water and higher rates of net salt uptake form dilute NaCl solutions than do populations from freshwaters of ca. 0-8-2-0 mM-NaCl. 4. Renal salt losses over the first 24 h in distilled water account for ca. 18% of the total salt loss. 5. It is suggested that P. zealandicus from environments of lowest concentration shows a similar degree of adaptation to freshwater as do crayfish of the northern hemisphere. It differs in possessing a substantially higher blood concentration.
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D002712:Chlorides / Q000097:blood / Q000378:metabolism; D005618:Fresh Water; D007668:Kidney / Q000502:physiology; D007700:Kinetics; D011188:Potassium / Q000097:blood; D012623:Seawater; D012964:Sodium / Q000097:blood / Q000378:metabolism; D014882:Water-Electrolyte Balance
chemical_list: D002712:Chlorides; D012964:Sodium; D011188:Potassium