Most salamanders have gills during their larval stage.
They live in water and, like fish, breathe underwater. As they reach maturity, which can take years in some species, they lose the gills, develop lungs, and leave the water.
But some types of salamanders never mature and live their entire lives in the larval stage. They keep their gills, stay in water, and breed there, without ever physically taking on adult characteristics like tougher skin and lungs.
Some of these salamanders, like the axolotl, stay in their larval stage because important growth chemicals like iodine are missing from their watery environments.
However, some cave-dwelling salamanders remain in their young forms regardless of outside influences.
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