The apparent absence of salt glands in marine and estuarine Crocodilia has long been a puzzle. However, we have identified glands in the tongue of Crocodylus porosus which exude a concentrated secretion of sodium chloride. The glands are similar in ultrastructure to other reptilian salt glands and undoubtedly play a major role in electrolyte regulation.

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. . The estuarine environment of crocodiliansUnlike the marine turtles and sea snakes, none of the extant crocodilians can be considered truly marine in habits. Even the sea-going Estuarine Crocodile, Crocodylus porosus, is principally an inhabitant of estuaries and rivers rather than the open ocean. We tend, therefore, to think of the salt-water crocodilians as 'estuarine ' rather than 'marine', and allow the term 'estuarine' to imply a less osmotically stressful Caiman crorodilus C a . latirostris Melanosuchus niger Palaeosuchus palpebrosus P. trigonatus Family Gavialidae Gavialis gangeticusPrimarily fresh waters. Subspecies C. c . crocodilus and C . c. fuscus not uncommon in brackish and salt water and known from offshore islands. C . c. apaporiensis restricted to fresh water. C. c. jacarereported to avoid salt waters in coastal salt waters Alvarez del Toro (1975); Varona (1976); S. Gorzula (in litt.); Medem (1981 a , b) Primarily fresh waters. Not uncommon Apparently restricted to fresh waters Apparently restricted to fresh water. Found close to the coast in places suggesting some tolerance of salt water Brazaitis (1973); Brazaitis cit. Medem (19810, b) Medem (1981 a , b) Groombridge (1982); Medem ( 1 9 8 1 b) As for P . palpebrosus Medem ( I 98 I a, b ) Apparently restricted to fresh waters. Reputedly occurred historically in a brackish coastal lagoon Singh & Bustard (1982); Whitaker & Basu (1983); R. Whitaker (pers. comm.) TAPLIN, L. E. (1984a). Homeostasis of plasma electrolytes, sodium and water pools in the Estuarine Crocodile, Crocodylus porosus, from fresh, saline and hypersaline waters. Oecologia 63, 63-70. TAPLIN, L. E. (19846). Drinking of fresh water but not seawater by the Estuarine Crocodile, Crocodylus porosus. Comparatioe Biochemistry and Physiology 77 A, 763-767. TAPLIN, L. E. ( 1 9 8 4~) . Evolution and zoogeography of crocodilians: a new look at an ancient order. In . Lingual salt glands in Crocodylus acutus and C. johnstoni, and their absence from Alligator mississipiensis and Caiman crocodilus. Journal of Comparative Physiology 149, 43-47. TAPLIN, L. E. & LOVERIDGE, J . P. (1988). Nile Crocodiles, Crocodylus niloticus and Estuarine Crocodiles, Crocodylus porosus, show similar osmoregulatory responses on exposure to seawater. Comparative Biochemistry and Physiology. 89A: 443-448. Copperhead and Mocassin. Biologia Generalis I , 482-500. A. Brodal and R. Fange), pp. 503-515. Universitetsforlaget, Oslo. 745-75 1 ' Chemistry 116, 81-86. Specialists Group, Gland, Swizerland. Physiological Zoology 25, 84-98. Rwiews of Biophysics 2 (3), 283-304.Science 159, I 105-1 108. 1045-7.

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