Why must amphibian skin remain moist?

Amphibian skin must remain moist primarily because it serves as a vital respiratory organ, a process known as cutaneous respiration.123

In most amphibian species, the skin is thin and highly vascular, containing a rich network of capillaries that facilitates the exchange of oxygen and carbon dioxide between the animal and its environment. For this gas exchange to occur effectively, the skin must be permeable; moisture is essential to keep the surface gas-permeable and to allow for the diffusion of respiratory gases.123

Beyond respiration, the skin plays a critical role in maintaining water balance and the diffusion of ions. Because the skin is not protected by thick, horny scales like those of many other vertebrates, it is susceptible to drying out, which would inhibit these essential physiological functions. Consequently, amphibians rely on mucus-secreting glands within their skin to maintain the necessary moisture levels for survival.2134