Oxygen consumption, heart rate and respiratory movements are maintained almost unchanged in toads (Bufo viridis) on soil without access to free water

The terrestrial toadBufo viridiswas maintained on soil (12–14% water content) without access to free water for periods lasting over 10 weeks. The weight of the animals stabilized after some loss of water (15–25%) which was accompanied by a large increase in plasma osmolality (from about 400 to 950 mOsm kg−1H2O). Oxygen consumption of toads kept on soil for over 4 weeks was 3•39 ± 0•29 ml h−1(mean ± SE of 10 toads weighing 35•8 ± 2•6 g), which was lower by about 15% as compared to control, water-access conditions. Rate of respiratory movements and heart rate were quite variable, and were similar in control conditions and on soil without free water. AQ10of 1•8 was calculated for heart rate over a temperature range of 10–30°C. Acute dehydration (15% in 24 h) resulted in a small (10%) but insignificant increase in the heart rate. It is concluded that activeBufo viridison soil, in water restricted condition, maintains its aerobic metabolism at a level that is reduced by no more than 15–25% of the control, despite large changes (more than doubling) in the osmolality and composition of its body fluids.