Seasonal changes in the water and electrolyte metabolism of Amphibolurus lizards in the field

• 1.

  1. Survival of Amphibolurus lizards in the field is enhanced by sodium retention during periods of water deprivation.

• 2.

  2. The water and electrolyte physiology of A. ornatus is conditioned by the growth rate of the individual.

• 3.

  3. Slow-growing A. ornatus are exceptionally tolerant to hypernatraemia and resist plasma sodium levels of almost 300 mmM/l for long periods in the field without loss of condition.

• 4.

  4. Fast-growing A. ornatus are unable to restrict indefinitely the sodium load to the extracellular fluid and penetration of the cells by sodium ions is accompanied by drastic weight losses which lead ultimately to death.

• 5.

  5. During weight loss the circulating fluid volume in maintained at the expense of other fluid compartments. Sodium levels in the tissues increase progressively but potassium levels are regulated by excretion.

• 6.

  6. Desert-living Amphibolurus species have a reduced rate of evaporative water loss which is evident in both cutaneous and pulmonary components.