spiracle (sensu Vertebrata)Go to external page http://purl.obolibrary.org/obo/UBERON_0010019
A small hole behind each eye that opens to the mouth in some fish. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar to the other gill openings. [ https://www.worldcat.org/search?q=bn%3A0073040584 http://en.wikipedia.org/wiki/Spiracle#Vertebrates ]
Synonyms: vertebrate spiracle
GO term spiracle morphogenesis, open tracheal system - does not refer to this structure
The spiracle is still found in all cartilaginous fish except chimaeras, and in bony fishes in the coelacanth, sturgeon, paddlefish and bichirs. It is also seen as an otic notch in the skull of the extinct labyrinthodonts, and is thought to be associated with the ear opening in amniotes and frogs
In elasmobranchs (sharks and rays), a spiracle is found behind each eye, and is often used to pump water through the gills while the animal is at rest (Fouts, 2003). A spiracle is also found in primitive bony fishes as the chirrups.