Amphibians occupy a wide range of habitat types from arid
deserts to deep freshwater lakes;
they may spend most of their life underground or high in cloud
forest canopy. Some are found
north of the Arctic Circle and can tolerate freezing conditions, while
others have evolved a
range of adaptations to avoid desiccation in some of the hotter
areas of the world. The skin
plays key roles in the everyday survival of amphibians and their
ability to exploit a wide range
of habitats and ecological conditions. The normal functions of the
skin are surveyed and
Eisner's biorational approach to chemical prospecting –
seeking clues from an animal's
behaviour and its interactions with its environment to reveal
the presence of chemical
compounds with potential medical or veterinary applications –
is applied to amphibians. The
biology and natural history of amphibian skin, its glands and their
secretions are briefly
reviewed. Four categories of compounds are found in the granular or
poison glands, these are:
biogenic amines, bufodienolides (bufogenins), alkaloids and steroids,
peptides and proteins.
Toads, particularly members of the genus Bufo, are identified
as a particularly convenient and
useful source of granular gland secretions. The potential
medical-pharmaceutical significance
of products derived from amphibian skin secretions is discussed.
The need for a humane approach to this work is noted.