Cutaneous respiration
The skin of amphibians is a major site of respiration in all species for which measurements are available. Cutaneous respiration is the sole respiratory mode of lungless salamanders (family Plethodontidae) which lack lungs entirely yet constitute the largest family of salamanders. Cutaneous respiration in frogs and other amphibians may be the primary respiratory mode during colder temperatures.
Allopumiliotoxin
As stated previously, these alkaloids were first discovered in the skins of frogs. They can be isolated from the frog’s skin by mincing the skin and extracting the compounds by trituration. A series of extractions involving an acid-base extraction are needed to isolate the allopumiliotoxins. The skins of the frogs may contain a number of different allopumiliotoxins. For example, the skin of Dendrobates tricolor was found to contain alkalkoids 251D, 271, 341A, and 323B. Also, different frogs contain different alkaloids in their skin. Dendrobates auratus, for example, was found to contain (+)-allopumiliotoxin 339A (a compound not present in the skin of Dendrobates tricolor).