Gill Teeth of Atlantic salmon
Species: S. salar
fish exchange gases using gills on either side of the pharynx. Gills are tissues which consist of threadlike protein structures called filaments. These filaments have many functions including the transfer of ions and water, as well as the exchange of oxygen, carbon dioxide, acids and ammonia. Each filament contains a capillary network that provides a large surface area for exchanging oxygen and carbon dioxide. Fish exchange gases by pulling oxygen-rich water through their mouths and pumping it over their gills. Atlantic salmon have four sets of gills which take the oxygen it needs to breath from the water as it flows over the gills. The gills have specialized cells that allow the salmon to migrate between salt and fresh water. The four sets also allow for efficient dissolving of oxygen. During development from larva to juvenile in Atlantic salmon, there is a change in the anatomical potential for gas exchange among gills, body skin and yolk sac as the larvae resorb yolk, grow and develop gills. Newly hatched Atlantic salmon have poorly developed gills.