Pharyngeal slit
Pharyngeal slits are
ontogeny recapitulates phylogeny"; this hypothesis, while false, contains elements of truth, as explored by Stephen Jay Gould in Ontogeny and Phylogeny.[3] However, it is now accepted[who?] that it is the vertebrate pharyngeal pouches and not the neck slits that are homologous to the pharyngeal slits of invertebrate chordates.[citation needed] Pharyngeal arches, pouches, and clefts are, at some stage of life, found in all chordates. One theory of their origin is the fusion of nephridia which opened both on the outside and the gut, creating openings between the gut and the environment.[4]
Pharyngeal arches in vertebrates
In vertebrates, the pharyngeal arches are derived from all three
pharyngeal jaws, which develop using the same genetic pathways involved in oral jaw formation.[9]
Evolution of pharyngeal slits
The presence of pharyngeal slits in hemichordates led to debates of whether this structure was homologous to the slits found in chordates or a result of
extant echinoderms lack pharyngeal structures, but fossil records reveal that ancestral forms of echinoderms had gill-like structures.[12]
Comparative developmental and genetic studies of these pharyngeal structures between hemichordates and molecular
sense.
References
- )
- PMID 15964754.
- ISBN 0-674-63941-3(paperback)
- ^ The Nephridial Hypothesis of the Gill Slit Origin
- ^ S2CID 28318053.
- S2CID 10792335.
- ^ Kardong KV (2003). "Vertebrates: Comparative Anatomy, Function, Evolution". Third Edition. New York (McGraw Hill).
- S2CID 10274300.
- PMID 19215146.
- ^ Gee H (1996). "Before the backbone. Views on the origin of vertebrates". London (Chapman & hall).
{{cite journal}}: Cite journal requires|journal=(help) - PMID 11961109.
- S2CID 45702564.
- S2CID 5766664.
- PMID 10226012.
- PMID 8674422.
