Federico engels

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G. W. LIGGINS and G. C. GRIGG School of Biological Sciences, The University of Sydney, NSW, Australia, 2006. Telephone: (02) 692-2433 Abstract-1. Adult cane toads, B. marinus, survived in salinities up to 40% sea-water (SW). 2. Pre-exposure to 30, then 40% SW, increased the survival time of toads in 50% SW. 3. Plasma from toads acclimated to salt water is hyperosmotic to the environment - a result of increased plasma sodium, chloride and urea concentrations. 4. When toads were placed in tap-water and 20% SW, all significant changes to plasma sodium, chloride, urea and osmotic pressure occurred within the first 2 days of exposure. 5. When toads were placed in 30 and 40% SW
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The animals were kept in 56 x 36 x 27 cm plastic tanks tilted to provide the animals with a choice of sitting in shallow tap-water or on the dry plastic substratum ("pre-treatment conditions"). Lids with small ventilation holes prevented escape of the animals. The tanks were kept in a room temperature of 24 ± 2°C and the tank water was changed daily. The toads were not fed. Experiments were carried out between July and October 1982 by exposing B. marinus to aqueous environments of various salinities, achieved by filling the plastic tanks with an appropriate mixture of tap-

water and sea-water to a depth of 2.5 cm. The tanks were not tilted so that the toads had no choice but to sit with their ventral surfaces immersed: Collection and storage of plasma and urine Urine was obtained by gently inserting a glass tube (4 mm OD) into the animal's cloaca and pushing it up through the muscular sphincter into the bladder. Urine then flowed freely into a plastic vial. Blood was obtained by cardiac puncture of a double-pithed animal using a 26-gauge needle attached to a heparinized 2 ml syringe. Approximately 75 μl of this blood were transferred to a micro-hematocrit capillary tube for hematocrit determination. The remainder was centrifuged and the plasma transferred to a plastic vial. Plasma and urine were kept refrigerated pending determination of osmotic pressure (within 3 hr). Samples were then frozen for later determinations of sodium, potassium, chloride, urea

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