A marine iguana removes salt from its body through salt glands located in the cranial cavity. These glands connect to the marine iguana's nasal cavity, allowing for expulsion when the marine iguana blows forcefully.
Salt is concentrated in the salt gland as the marine iguana feeds on algae in salty seawater. The concentrated salt water, separated into sodium chloride and potassium chloride, then secretes into the marine iguana's nasal cavity for expulsion. On land, the marine iguana blows the solution out of its nostrils until its nasal passages are clear of salt.
The marine iguana can rid itself of unwanted salt faster when it is warm. It is not unusual to see a marine iguana lying on a rock to sun itself before feeding. This allows the marine iguana to raise its body temperature before it dives into deep, cold water to feed. The warmer the marine iguana is, the easier it is to expel the salt from its body.
The need for salt glands relates directly to the marine iguana's insufficient kidney function. It is not the only animal to make use of salt glands; these glands appear in various marine mammals, reptiles and seabirds. These glands appear in different places on different animals.