Q. How different is the fish epidermis from the amphibian epidermis?

The fish epidermis is very contains and thin mucus-secreting cells the fish skin doesn't present keratin, the mucus has a protective function and it also helps the sliding of the animal under water, the fish scales originate from the dermis and not from the epidermis.

In amphibians there is already a slight keratinization of the skin probably an additional adaptation to the terrestrial environment. Amphibians have wet and smooth epidermis without scales, these features facilitates their cutaneous respiration.