Tolerance of Sea Water by the American Crocodile, Crocodylus acutus

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Abstract
Plasma Na concentrations of C. acutus captured in sea water are similar to the Na levels seen in this species in freshwater and typical of fresh water reptiles in general. In sea water starved C. acutus lose weight as an inverse function of total body volume. Large crocodiles are capable of prolonged sustenance in marine environments, particularly if free water is gained from vertebrate prey in the diet. Young or small animals may avoid a rapid increase in body osmolality from sea water either by avoiding hyperosmotic salinities or by utilizing terrestrial microhabitats of high relative humidity. NaCl loading of 1 mmol Na/100 g of body wt evokes an elevated blood Na concentration coupled with an apparent reduction of cloacal flow rate. These responses act to conserve body water and would be beneficial to a species that has only periodic access to fresh water. No evidence was found to suggest that a salt gland capable of compensating for an induced salt load is functional in this species.

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