The effects of salt water adaptation on the australian black swan, Cygnus atratus (Latham)

Abstract

1. 1. Body weight, plasma and tear concns, hematocrit, tissue sizes and Na, K, Cl excretion in salt gland secretion (SGS) and cloacal fluid (CF) were studied in fresh water (FW) and salt water (SW) adapted Australian black swan, Cygnus atratus (Latham), cygnets and/or adults. 2. 2. FW cygnet plasma Na, 119 ± 3; K, 4.8 ± 0.3 m-equiv/l were significantly different ( P <0.001) from adult FW swan plasma Na, 142 ± 5; K, 1.0 ± 0.2 m-equiv/l. 3. 3. Salt adaptation increased cygnet plasma Na, 136 ± 1 ( P <0.001) and salt and Harderian gland sizes, but plasma K, hematocrit, tear ion concn., heart, kidney and adrenal gland size were unaffected. 4. 4. Hematocrit and plasma Na, K, Cl and O.P. of adult swans were unaffected by salt water adaptation. 5. 5. The Na and K concn of spontaneously formed SGS of FW and SW adapted cygnets were the same. 6. 6. A SW cygnet stomach loaded with Na, 500; K, 25 m-equiv/l produced SGS at 0.35 ml/min kg, an unusually high rate; adults secreted at about 1 3 this rate. 7. 7. FW adults eliminated 1 2 the imposed salt loads in SGS (Na, 548 ± 3 m-equiv/l) and 1 5 in CF (Na, 137 ± 19 m-equiv/l). SW swans secreted only 1 3 of the load extrarenally (Na, 656 ± 99 m-equiv/l) while cloacal excretion (Na, 266 ± 43 m-equiv/l) increased tod 1 2 the load given. 8. 8. In FW adult swans the first CF sample was obtained 90 min after the salt loading and in SW adults 4 min after loading, suggesting the FW swans absorbed the salt loads more completely and produced more SGS, but that SW swans allowed the loading solution to pass through the gut to be excreted as CF.