How Fish Can Breathe Under Water

Bay of Plenty Times, Volume LXVI, Issue 12332, 22 April 1938, Page 5 (Supplement)

How Fish Can Breathe Under Water

Oxygen and the other gases which combine to make up the air we breathe are dissolved in the water in which fish live. Lungs are designed to utilise air in its free state, hence we cannot get the oxygen we need by breathing under water.

Strictly speaking, fish do not breathe under water, either. They have nostrils, but these nose openings lead only to closed passages—not to lungs, in most kinds of fish. Fish obtain the necessary amount of oxygen by taking in w v ater through their mouths and then forcing it out again through their gills..

Gills are a special part of the fish’s body, consisting of a number of delicate feather-like ribbons of membrane, richly supplied with blood vessels. The gills, located on either side of the fish’s "neck,” have the property if extracting oxygen from the water which is is forced through them, at the same time giving off carbon dioxide to the water.

Fish do not require as much oxygen, even in proportion to their size, as we do. They do not burn up any of their supply of oxygen in keeping their bodies warm, for fish are coldblooded creatures: that is, their blood and bodies are about the same temperature as the water in which they live. All fish have gills, but not all kinds of fish are lungless. The African mudfish, the South American lolaeh and the barramunda of Australia are three varieties of fish which have'both gills and lungs. The posses sion of lungs enables them to exist through periods when the swamps and mudflats which they inhabit dry up, or the mud gets too thick for gills to function.