Some Aspects of Electrolyte Excretion in the Green Turtle, Chelonia Mydas Mydas.

Except for the brief period of egg-laying, five species of turtle are strictly marine: namely, the green turtle (Chelonia mydas), the loggerhead turtle (Caretta carettd), Ridley's turtle (Lepidochelys olivacea), the hawksbill turtle (L. imbricatd) and the leatherback turtle (Dermochelys coriacea). Reptiles in the sea, like marine fish and marine birds, have a high intake of electrolytes; yet, as we shall show, the concentrations of sodium and potassium in the blood of the marine turtle are characteristic of vertebrates generally. In view of their evolutionary relationship to the birds, it is not surprising to find that some marine reptiles possess functional' salt glands' (Schmidt-Nielsen & Fange, 1958). These glands, like those of marine birds, produce a secretion considerably more concentrated than sea water with respect to sodium and potassium (Schmidt-Nielsen & Fange, 1958). The 'salt glands' of marine birds were recently shown to be, at least in part, under the control of the adrenal cortex (Holmes, Phillips & Butler, 1961a; Holmes et al. 1961ft; Phillips, Holmes & Butler, 1961). The object of the present study, therefore, was to determine whether a similar pathway of control might exist in the marine turtle, Chelonia mydas.