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Haematological changes by splenic respiratory compensation in the cave salamander, Hydromantes genei



Like other amphibians, the salamander Hydromantes genei, an exclusively terrestrial lungless plethodontid which lives in cold humid caves, possesses a haematological mechanism of respiratory compensation: the spleen can hoard erythrocytes, which are then released into the bloodstream when necessary, analogous to what happens in the Italian crested newt (which, however, is predominantly aquatic). The cave salamander, anaesthetized with chlorobutanol and kept in a humidity-saturated environment at a constant temperature long enough for its haematological conditions to stabilize, presents homogeneous and very low blood parameters at the extreme temperature ranges to which it is adapted (6 °C and 18 °C): about 16 109 red blood cells/1, haematocrit value approximately 12, and haemoglobin concentration slightly below 3g/dl. The increase in temperature triggers the release of erythrocytes into the bloodstream from the spleen, which shrinks from 0.8% of the animal's body weight at 6 °C to 0.25% at 18 °C; however, a parallel increase in blood plasma maintains the blood composition unaltered. At 24 °C, a critical temperature for this species, the erythrocyte parameters increase by 50% owing to plasma loss, as happens in other amphibians in hypoxic conditions.

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