Amphibians are excellent models to understand vertebrate
chemosignaling. Amphibian chemical communication is amenable to
study atmolecular, developmental, physiological, behavioral, ecological,
and evolutionary levels. Urodele (salamanders, including newts)
reproductive behavior is orchestrated by a rich array of chemosignals.
Anurans (frogs and toads) are best known for their remarkable calling
behavior during breeding, butmany anuran species possess specialized
glands that emit chemosignal-like substances. Amphibians are sometimes
viewed as transitional between fish and reptiles, or as stand-ins
for basal tetrapods, but these are not correct views. Instead, the major
families of amphibians diversified very early in their evolutionary
history, andmodern representatives, especially anurans, havemany derived
characters (Duellman and Trueb, 1994; San Mauro et al., 2005).
Amphibians are well known for their complex life cycles,where aquatic
larvae metamorphose into terrestrial or semi-aquatic adults. However
in some species, individuals are aquatic or terrestrial their entire lives
while in other species, adults transition between terrestrial and aquatic
life styles for breeding every year. Thus, chemical signaling can be compared
and contrasted in aquatic versus terrestrial environments from a
developmental perspective (within a species) and froman evolutionary
perspective (across species). Another advantageous feature is that
many amphibian chemosignals are peptides or proteins so there is a relatively
direct link between the chemosignal and the genome. In this
way, the evolution of chemosignal sequence, structure, and function
can be studied.