External gills

External gills are the feathery, branch-like gills that stick out from the sides of the head on neotenic salamanders like the axolotl, letting them breathe underwater for life.

Full, fluffy gills are a good sign in an axolotl; gills that curl forward can signal stress (strong filter flow is one known cause), and gills that shrink or fray can be an early sign of illness. A true axolotl keeps its gills — an animal losing them may actually be a metamorphosing salamander larva.