do mexican salamanders completely never live in water during everytime in their whole lifetime

No, Mexican axolotls (Ambystoma mexicanum), while being unique among salamanders for their neotenic characteristics, are not completely terrestrial and do live in water throughout their entire lives. Axolotls are fully aquatic animals and require water for their survival. Here are several reasons why they cannot live without water:

1. Respiration: Even though axolotls have rudimentary lungs, they primarily rely on their gills and skin for gas exchange. Their gills are well-adapted for extracting oxygen from water, while their skin is permeable and assists in breathing when submerged. Without water, they would not be able to respire efficiently.

2. Skin Hydration: Axolotls have moist, permeable skin that requires hydration to function properly. Dry conditions can lead to skin damage and dehydration, which may prove fatal for them. They need a moist environment to maintain their skin’s integrity.

3. Feeding: Axolotls feed on aquatic prey such as small fish, worms, and crustaceans. They are not adapted to capture terrestrial prey and rely on their watery environment for sustenance.

4. Reproduction: Axolotls reproduce in water, laying clutches of eggs in a gelatinous mass that is adhered to underwater surfaces. The larvae develop in an aquatic environment before eventually metamorphosing into adult axolotls.

5. Behavior: Axolotls are active swimmers and are well-adapted for life in water. Their limb structure and flattened tails are suited for maneuvering in aquatic environments.

In summary, Mexican axolotls are obligate aquatic animals that require water for respiration, skin hydration, feeding, reproduction, and general behavior. They cannot complete their life cycle outside of water, contrary to some misconceptions about their neotenic traits. It is essential to provide them with a suitable aquatic habitat that supports their specific needs and promotes their health and well-being.