Fig. 1.

Salamanders display complex life cycles in both terrestrial and aquatic habitats. A typical salamander life cycle (exemplified here by that of Notophthalmus viridescens) involves both terrestrial and aquatic stages. Adult newts alternate facultative aquatic/terrestrial lifestyles, but they mate and lay fertilized eggs in the water. These eggs then develop into embryos that hatch as aquatic larvae. The larvae are ferocious zooplankton hunters that undergo metamorphosis prior to leaving the aquatic milieu and becoming terrestrial juveniles (termed efts), which seasonally return to water to breed after they reach sexual maturity. Many salamander species are entirely land living without an aquatic larval stage.