Water, Nitrogen and Ion Balance in the African Treefrog Chiromantis petersi Boulenger (Anura: Rhacophoridae), With Comments on the Structure of the Integument

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Physiological and anatomical investigations were carried out on Chiromantis petersi, an African rhacophorid treefrog, with the following results:

1. The minimum rate of evaporative water loss (EWL) was 0.41±0.25 mg/g.h.

2. The maximum rate of water uptake in dehydrated frogs averaged 75% body weight/h in the first 10 min of rehydration.

3. The low EWL correlates with the unique structure of the chromatophore units of the dorsum, the sides and the gular region.

4. The high rates of water uptake correlate with the structure of the verrucae hydrophilica of the abdominal and femoral surfaces. These verrucae are not unique to this species.

5. When denied water and force-fed mealworms for 30 days, plasma osmotic concentrations increased from 210 mosM to 384 mosM, with Na+, Cl− and urea contributing most to the increase.

6. The ratio of urinary K+∶Na+ excretion is 3∶1.

7. Excretion totaled 155 mg N/kg·day with 97% as uric acid, 2% as ammonia and 1% as urea.

8. Since urea accumulated in the body at the rate of 58.5±6.1 mg N/kg·day, total nitrogen production was 213 mg N/kg·day. Uric acid formed 70% thereof.

9. Chiromantis petersi is capable of surviving without free water for prolonged periods and is as well adapted to its xeric environment as are many desert reptiles.



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