The Salt Gland in a Sea Snake (Laticauda)

Abstract

ONE marine lizard and several marine turtles possess salt glands capable of secreting highly concentrated solutions of sodium chloride¹. The salt gland appears to be of adaptive advantage to reptiles exposed to electrolyte loads, because the kidney is unable to excrete urine hyperosmotic to the blood. A sea snake (Laticauda semifasciata) follows the general pattern of ionic regulation found in marine turtles and a marine lizard². The work reported here was designed to identify the salt glands of Laticauda semifasciata and compare it with the homologous gland of another sea snake, Pelamis platurus. Laticauda excretes a relatively dilute urine (7–148 mmolar sodium) from the kidney and a concentrated sodium chloride solution (380–625 mmolar) orally². The rate of excretion of extrarenal sodium chloride increases to as much as 72 μmoles/ 100 g/h after injection of a sodium chloride or sucrose load². This response must be due to a salt gland. In all lizards the salt gland is the nasal gland; secretions pass from the nasal passage out through the external nares^1,3,4. In turtles, salt gland secretion elaborated by the Harderian gland is discharged under the eyelid¹. Crocodiles may have a similar route of extrarenal electrolyte excretion².