INCREASED VASCULARITY OF THE LINGUAL SALT-GLANDS OF THE ESTUARINE CROCODILE, CROCODYLUS-POROSUS, KEPT IN HYPEROSMOTIC SALINITY

Methyl methacrylate corrosion casts were made of the blood-vascular sy stem of the lingual salt glands of the estuarine crocodile, Crocodylus porosus, and examined with light and scanning electron microscopy. Th e 28-40 individual salt glands, each opening separately via a single p ore onto the dorsal surface of the tongue, are supplied by a pair of l ingual arteries. Each gland is richly vascularized and is composed of 14-20 lobular sub-units, each having a dense network of capillaries. T he blood flow in each gland is from the centre to its periphery, oppos ite to the direction of the flow of secretions in the ducts of the gla nd. The main collecting duct leading from the gland to the external po re was well vascularized. The blood supply to the glands of juvenile c rocodiles raised in 20 parts per thousand salt water was more dense th an in freshwater and, from cast masses, had a three-fold greater vascu lar volume. This study provides the first evidence which shows that th e salt glands of crocodiles are morphologically labile and can adapt t o the environmental salinity. (C) 1993 Wiley-Liss, Inc.