The reason is that the adult's lungs, which replace the tadpole's gills, are not very well developed, so its skin must be kept moist by glandular secretions to help it breathe.
因為山椒魚也是由卵孵化成蝌蚪，再發育為成體；呼吸器官由鰓變成肺的過程中，發育較差，皮膚上於是分佈了許多黏液腺、分泌黏液，使皮膚保持濕潤、幫助呼吸。