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How Nasal Salt Glands Filter Blood
Marine iguanas consume substantial amounts of ocean water while grazing on underwater algae around the Galápagos Islands. To survive this high intake of salt without becoming dangerously dehydrated, their bodies use specialized nasal glands located in the snout.
These lateral nasal glands continuously extract excess sodium and chloride directly from the bloodstream, concentrating it into a thick saline fluid. When enough fluid accumulates in the nasal cavity, strong muscle contractions force a high-pressure sneeze through the nostrils, blasting the concentrated brine away from the body.
Thermoregulation and Salt Clearance on Shore
Cold ocean currents around the Galápagos rapidly strip body heat from cold-blooded reptiles while they dive. After foraging underwater, marine iguanas return to land and cluster together on sun-warmed volcanic rocks to raise their internal temperature.
As an iguana warms in the sun, its metabolic rate increases, accelerating blood circulation and salt filtration. Consequently, most salt sneezing occurs while the animals are basking on shore, often leaving a powdery white crust of dried salt on their heads and shoulders.
Sneezing as Osmoregulation, Not Illness
Visitors seeing marine iguanas repeatedly snort and spray fluid on beach rocks sometimes assume the reptiles are sick or suffering from a respiratory infection. In reality, this forceful blowing is a healthy biological function known as osmoregulation.
Many ocean-dwelling species face similar challenges with salt balance, using varied biological mechanisms. For instance, seabirds excrete excess salt through specialized glands near their eyes, while sea turtles flush out salt through tear glands. For marine iguanas, sneezing through modified nasal glands is simply the most efficient method to maintain life-sustaining salt balance.
Quick facts
- Marine iguanas are the only modern lizard species adapted to dive and forage in marine environments.
- Modified nasal glands located in the iguana's snout filter excess sodium and chloride directly from the blood.
- The expelled brine frequently dries in the sun, forming a chalky white crust on the iguana's head and neck.
- Iguanas sneeze out salt most frequently while basking on warm volcanic rocks after cold ocean dives.
- Other marine species possess similar adaptations, such as sea turtles that excrete excess salt through tear glands.
Frequently asked questions
They sneeze to eject excess salt absorbed into their blood while feeding on ocean algae, which prevents severe dehydration.
The crust consists of dried salt left behind after concentrated saline spray is sneezed into the air and settles on their scales.
No, sneezing is a natural biological mechanism that clears accumulated salt from their nasal passages rather than a sign of respiratory infection.
