External gills are the gills of an animal, most typically an amphibian, that are exposed to the environment, rather than set inside the pharynx and covered by gill slits, as they are in most fishes. Instead, the respiratory organs are set on a frill of stalks protruding from the sides of an animals head. In aquatic organisms, gills are a respiratory organ for the extraction of oxygen from water and for the excretion of carbon dioxide. ... The pharynx (plural: pharynges) is the part of the neck and throat situated immediately posterior to the mouth and nasal cavity, and cranial to the esophagus, larynx, and trachea. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world, Photo by Uwe Kils This page is about the animals which live in water. ...

The external gills of this adult Alabama waterdog are clearly visible

This type of gill is most commonly observed on the aquatic larva of most species of salamanders, as well as on neotenic adults. They are also present on salamander species such as the mudpuppy, axolotl, as well as most members of the Proteidae family, which naturally never metamorphose into an air-breathing form. Families Salamander is the common name applied to approximately 500 amphibian vertebrates with slender bodies, short legs, and long tails (order Caudata or Urodela). ... Neoteny is a term in developmental biology that describes the retention of juvenile characteristics in the adults of a species and is similar to but not the same as progenesis, which is the attainment of sexual maturity by an organism still in its larval stage, as is found among certain... Genera Necturus Proteus The Mudpuppies or Waterdogs are a family of aquatic salamanders. ... This article or section does not cite its references or sources. ... Genera Necturus Proteus The Mudpuppies or Waterdogs are a family of aquatic salamanders. ...