How a penguin turns blood salt into brine
Seawater and salty prey add sodium and chloride—the main ingredients of table salt—to a penguin’s body. The bird’s kidneys help regulate water and dissolved waste, but removing a large salt load through urine alone would also cost valuable water. Penguins therefore rely on specialized salt glands, paired organs above the eyes that provide another route for disposing of excess salt.
Blood flows through tiny vessels in each gland. Specialized cells move salt from the blood into narrow channels, producing a concentrated salty fluid. In effect, the gland separates salt from the circulation and packages it for removal, rather than making the penguin’s entire body fluid as salty as the sea.
A route out through the nostrils
The fluid travels from the glands into ducts that open into the nasal passages. From there it can drip out or be expelled in a shake or sneeze. The glands sit above the eyes, but their output does not need to pass through the eyes: ducts carry it toward the nostrils.
This system is useful because it lets penguins take in salt with seawater or food while keeping the salt concentration in their bodies under control. It also shows why a sneeze can have a job beyond clearing irritation: in this case, it helps carry concentrated brine out of the nose. The visible spray is the last step of a process that began in the blood.
