External gills

External gills are special breathing organs found in some animals, especially young amphibians like salamanders and their relatives. Unlike fish, which have gills hidden inside their bodies, animals with external gills have these organs right on the outside, sticking out from their heads on little stalks. These gills help the animals get oxygen from the water.

Many salamander babies, called larvae, have external gills that look like feathery branches. These gills are used until the salamander grows up and can breathe air directly. Some salamanders, like the olm and mudpuppies, keep their external gills their whole lives because they never change into land-breathing adults. Even the embryos of frogs and other amphibians develop external gills for a short time before they hatch.

The gills are made of thin, delicate parts that allow for the exchange of gases—taking in oxygen and getting rid of carbon dioxide. These gills can move to stir the water around them, helping the animal get more oxygen. Studying external gills helps scientists understand how animals breathe and evolve.