Iguanas sneeze to eject excess salt from their bodies.

Marine iguanas (Amblyrhynchus cristatus) and many terrestrial species possess specialized lateral nasal glands located just above their eyes. These glands are highly efficient at extracting sodium chloride and potassium from the bloodstream. This adaptation is crucial because iguanas often consume high-salt diets, particularly marine iguanas that feed on seaweed and algae in the ocean.The process is known as extrarenal salt excretion. Since reptilian kidneys are not efficient enough to produce concentrated urine like mammalian kidneys, these nasal glands do the heavy lifting. When the salt concentration in the blood reaches a certain threshold, the glands secrete a brine-like fluid into the nasal cavity. The iguana then forcefully exhales, or sneezes, to propel the fluid out of its nostrils.Research published in journals like 'Comparative Biochemistry and Physiology' highlights that this mechanism allows iguanas to conserve fresh water while disposing of unwanted minerals. The white crust often seen on an iguana's snout is actually crystallized salt left behind after the moisture evaporates. This biological 'desalination plant' is a remarkable example of evolutionary adaptation to harsh or specialized environments.