Effects of acute fresh water exposure on water flux rates and osmotic responses in Kemp’s ridley sea turtles ( Lepidochelys kempi)

Water flux rates and osmotic responses of Kemp’s Ridley sea turtles ( Lepidochelys kempi) acutely exposed to fresh water were quantified. Salt-water adapted turtles were exposed to fresh water for 4 d before being returned to salt water. During the initial salt water phase, absolute and relative water flux rates were 1.2±0.1 l d −1 and 123.0±6.8 ml kg −1 d −1, respectively. When turtles were exposed to fresh water, rates increased by approximately 30%. Upon return to salt water, rates decreased to original levels. Plasma osmolality, Na +, K +, and Cl − decreased during exposure to fresh water, and subsequently increased during the return to salt water. The Na +:K + ratio was elevated during the fresh water phase and subsequently decreased upon return to salt water. Aldosterone and corticosterone were not altered during exposure to fresh water. Elevated water flux rates during fresh water exposure reflected an increase in water consumption, resulting in a decrease in ionic and osmotic concentrations. The lack of a change in adrenocorticoids to acute fresh water exposure suggests that adrenal responsiveness to an hypo-osmotic environment may be delayed in marine turtles when compared to marine mammals.