Maintaining the body’s salt and water balance is a problem that herbivorous reptiles have solved through the use of salt excreting glands. The need for the glands is due to the high concentrations of potassium in the plants that they consume, which must be secreted to maintain a balance in the body. This is found in a number of lizards including, Uromastix acanthinurus and the Chuckwalla (Sauromalus obesus). Hazard (2001) found that the rate of secretion by the nasal glands of the Chuckwalla was affected by the level of potassium in the body, which is believed to be of dietary importance as well as for maintaining the body’s salt and water balance. This is not the case for all herbivorous reptiles, with the North American Desert Tortoise (Gopherus agassizzi) having no functional nasal gland (Whitford, 2002). The tortoise is able to tolerate high levels of potassium in its body, which is discarded through its urine when rainwater is available to drink, which refills its bladder. This, as with the camel, is a useful adaption when the availability of water is unpredictable and also allows the tortoise to continue to eat green vegetation that is high in potassium.

Unlike the NaCl-secreting salt glands of many birds and reptiles, the nasal salt glands of lizards can secrete potassium as well as sodium, with either chloride or bicarbonate as the accompanying anion. The factors responsible for initiating secretion by the gland and the rates of cation and anion secretion were studied in the desert iguana, Dipsosaurus dorsalis. Lizards were given combinations of ions for several days, and secreted salt was collected daily and analyzed for sodium, potassium, chloride, and bicarbonate. Maximum total cation secretion rate was 4.4±0.38 mgrmol/g/d. Cation secretion ranged from 24% to 100% potassium; even high NaCl loads did not abolish potassium secretion. Maximum bicarbonate secretion was about 0.5 mgrmol/g/d; chloride was the predominant anion. Secretion rate increased only in response to those treatments that included potassium and/or chloride; sodium ions and other osmotic loads (e.g., sucrose) did not increase secretion. This is in contrast to birds and some other reptiles with salt glands, which initiate NaCl secretion in response to any osmotic load. The specificity of the response of the salt gland of Dipsosaurus may be related to the ecological importance of dietary potassium and chloride for herbivorous desert lizards.