Waste Collection

Aestivating amphibians face the difficult task of dealing with waste buildup. Since Cyclorana form a cocoon, they are unable to rid themselves of waste. Most terrestrial animals, including aestivating amphibians, excrete urea, a compound synthesized from carbon dioxide and two ammonia ions:

2NH3 + CO2 => CO(NH2)2 + H2O (Withers, 1998).

Terrestrial animals excrete urea as opposed to ammonia (as most aquatic organisms do) because it is not as toxic. Aquatic animals can tolerate excreting ammonia because it is very soluble, making excretion at low concentrations easy when there is excess water. Terrestrial animals, however, do not have such readily available water (1998).

It was once thought that the accumulation of urea may act as a balancing osmolyte, maintaining a balance of water potential between body fluids and the soil. However, studies have shown that Cyclorana do not co-accumulate counteracting solutes. While some anuran species (i.e. Scaphiopus couchii and Heleioporus albopunctatus) do accumulate urea to keep a favorable water balance between themselves and the soil (Withers et al. 1996), Cyclorana appear to retain urea because they cannot waste such an important source of water, especially in case aestivation periods are unusually long (Cartledge et al., 2008).