 Several genera of teleosts have independently developed air @-@ breathing capabilities , and some have become amphibious . Some combtooth blennies emerge to feed on land , and freshwater eels are able to absorb oxygen through damp skin . Mudskippers can remain out of water for considerable periods , exchanging gases through skin and mucous membranes in the mouth and pharynx . Swamp eels have similar well @-@ vascularised mouth @-@ linings , and can remain out of water for days and go into a resting state ( aestivation ) in mud . The <unk> have developed an accessory breathing structure known as the labyrinth organ on the first gill arch and this is used for respiration in air , and <unk> catfish have a similar <unk> organ . Certain other catfish , such as the Loricariidae , are able to respire through air held in their digestive tracts . 
