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The Function of Salt Glands
Salt glands perform two functions, one primary and one secondary. The primary function is for secreting excess salt that has collected in the turtle's system. Salt accrues within turtles by absorption through the animal's skin and by entering through their mouth, nose, eyes and other apertures as they move through the sea. The secondary function of the salt gland is to coat the eyes with a mucus-like substance for protection.
The Reason Behind the Function
The salt content of ocean water is about three times the amount of salt found in the sea turtle's body. If sea turtles don't excrete a large amount of salt that enters their bodies the animals suffer physiological imbalance with serious consequences. Sea turtle livers are incapable of creating hypertonic urine, which is urine with a higher concentration of solubles, such as salt, than an organism's blood. Because sea turtle blood contains significantly less salt than sea water, its ingestion leads to hypertonic urine. Thus, the animals must secrete salt to maintain a healthy balance between urine and blood.
What Salt Glands Really Do
Specialized cells comprise the salt glands of sea turtles. These cells extract sodium (Na) and chlorine (Cl), the compositional elements of salt, from the blood and direct it to small tubes leading into the secretion glands. The solution excreted by the glands is composed almost entirely of sodium chloride (salt), meaning the salt glands extract little else from the turtle's blood stream. If the salt in a turtle's system increases or decreases, the frequency of secretions changes accordingly.
Salt Gland Inhibition
The inhibition of the salt gland causes serious health risks for sea turtles, according to the authors of "The Biology of Sea Turtles, Volume 2." Adult turtles experience potentially lethal ion imbalances when the salt gland stops functioning or functions improperly.
Studies show that baby sea turtles require the regular intake of seawater and resultant excretion of excess salt to achieve optimum health. Baby sea turtles with inhibited salt glands stay away from the sea and suffer substantial loss in body mass as a result. According to the article "Salt and Water Regulation by the Leatherback Sea Turtle Dermochelys coriacea," sea turtle hatchlings lose as much as 5 percent of their body mass when away from seawater for 12 hours.