do almost all salamanders only have terrestrial life stage

No, not all salamanders have only terrestrial life stages. Salamanders exhibit a diversity of life cycle patterns, including aquatic, terrestrial, and dual-life cycle stages. Here are some specifics:

1. Aquatic Larvae: Many salamander species begin life as aquatic larvae in water environments such as ponds, lakes, or streams. The larvae typically have external gills for breathing underwater.

2. Metamorphosis: Some species undergo metamorphosis from an aquatic larval stage to a terrestrial adult stage. During this transition, they develop lungs, lose their gills, and adapt to life on land. Examples of such species include the various newts and some members of the Salamandridae family.

3. Semi-Aquatic or Fully Aquatic Adults: Some salamander species retain an aquatic lifestyle even as adults. For example, the axolotl (Ambystoma mexicanum) lives its entire life in water and never undergoes metamorphosis to become terrestrial.

4. Terrestrial Adults: Many salamander species, especially in the family Plethodontidae (lungless salamanders), are fully terrestrial as adults. They live in moist environments like forests, under rocks, or in leaf litter, and can breathe through their skin as well as, in some cases, small lungs.

5. Lifelong Aquatic Species: A few salamander species spend their entire lives in water, such as the neotenic axolotl and the olm (Proteus anguinus), which lives in underground waters in Europe.

6. Aquatic-Terrestrial Transitions: Adult salamanders, even those that are primarily terrestrial, often return to water to breed. Females lay eggs in water, and the larvae hatch and grow in an aquatic environment before transitioning to land.

7. Adaptations: Salamander species have evolved various adaptations to suit their life stage requirements, such as the development of lungs for terrestrial life or the maintenance of gills for persistent aquatic life.

In summary, salamanders exhibit a wide range of life stages and habitats, from those that are entirely aquatic to those that are primarily terrestrial, with many undergoing a transition between these environments during their life cycle.