Osmoregulation
In sea turtles, the bladder is one unit and in most freshwater turtles, it is double-lobed.[57] Sea turtle bladders are connected to two small accessory bladders, located at the sides to the neck of the urinary bladder and above the pubis.[58] Arid-living tortoises have bladders that serve as reserves of water, storing up to 20% of their body weight in fluids. The fluids are normally low in solutes, but higher during droughts when the reptile gains potassium salts from its plant diet. The bladder stores these salts until the tortoise finds fresh drinking water.[59] To regulate the amount of salt in their bodies, sea turtles and the brackish-living diamondback terrapin secrete excess salt in a thick sticky substance from their tear glands. Because of this, sea turtles may appear to be “crying” when on land.[60]