do mexican salamanders never need any water to survive at anytime in their whole lifetime

No, Mexican salamanders, like all amphibians, require water at various points in their life cycles, especially for reproduction and the development of their eggs and larvae. Although adult salamanders can live in moist environments with less water than aquatic stages, they are still dependent on water to some extent.

For example:

1. Reproduction: Salamanders usually lay their eggs in water or moist environments like damp soil or leaf litter. The eggs need moisture to develop.

2. Larval stage: The larvae (tadpoles) typically live in water. They have gills and breathe through them, requiring an aquatic environment to survive.

3. Adult stage: While adult salamanders can live in moist terrestrial environments, they still depend on water to some extent for drinking, dispersing excess salts, and maintaining their skin's moisture levels.

4. Habitat: Salamanders are often found in damp environments like forests, grasslands, or near water sources. They prefer areas with high humidity.

So, Mexican salamanders do not survive their entire lives without any water. Water plays a crucial role in their life cycle, particularly during reproduction and the early stages of development. While they may be adapted to drier environments than some other amphibians, they still rely on water to some extent for survival and well-being.