In fishes gas exchange is done by direct contact of water with the branchiae (gills). Gases gain and exit the circulation through the gills.

In adult amphibians gas exchange is done through the moist and permeable skin (cutaneous respiration) and also through the lungs, a set of tiny airway terminations associated to a highly vascularized tissue specialized in gas exchange.

The axolotl is an exotic amphibian found in Mexico that lives in water and “breathes” through gills even as an adult.   _{Your Comment}