Editing Lancelet (section)

{{Short description|Subphylum of chordates}}
{{Distinguish|Lancet (disambiguation){{!}}Lancet|Lancelot}}
{{Automatic taxobox
| name = Lancelet
| fossil_range = {{Fossil range|Recent|earliest=518}} Possible [[Cambrian]] and [[Permian]] records
| image = Branchiostoma_lanceolatum.jpg
| image_caption = ''[[Branchiostoma lanceolatum]]''
| display_parents = 4
| grandparent_authority =
| parent_authority = [[Ernst Haeckel|Haeckel]], 1866<ref name="Nielsen2012">{{cite journal
  | author=Nielsen, C.
  | date=July 2012
  | title=The authorship of higher chordate taxa
  | journal=Zoologica Scripta
  | volume=41 | issue=4 | pages=435–436
  | doi=10.1111/j.1463-6409.2012.00536.x
  | s2cid=83266247
 }}
</ref>
| taxon = Leptocardii
| authority = [[Johannes Peter Müller|Müller]], 1845<ref name="Müller1845" />
| synonyms = *Subphylum or class
** Acrania Haeckel, 1866
* Order
** Amphioxi Bonaparte, 1846<ref name="Bonaparte1846" />
** Amphioxiformes Berg, 1937<ref name="Fowler1965" />
** Branchiostomiformes Fowler, 1947<ref name="Fowler1947" />
* Family
** Amphioxidae Gray, 1842<ref>{{cite book | last1 = Anonymous | year = 1842 | url = https://www.biodiversitylibrary.org/item/244322 | publisher = G. Woodfall and son | location = British Museum Catalogue | pages = 308 | title = Synopsis of the Contents of the British Museum. Forty-fourth Edition| volume = 44th Ed. }}</ref>
** Asymmetrontidae Whitley, 1932<ref>{{cite journal | last1 = Whitley | first1 = Gilbert P. | year = 1932 | url = http://biostor.org/reference/102060 | pages = 256–264 | title = The lancelets and lampreys of Australia | journal = Australian Zoologist | volume = 7}}</ref>
** Epigonichthyidae Hubbs, 1922<ref>{{cite journal | last1 = Hubbs | first1 = Carl L. | year = 1922 | pages = 1–16 | title = A list of the lancelets of the world with diagnoses of five new species of ''Branchiostoma'' | journal = Occasional Papers of the Museum of Zoology, University of Michigan | volume = 105}}</ref>
| subdivision_ranks = Genera
| subdivision = *{{extinct}}''[[Cathaymyrus]]''?
* {{extinct}}''[[Palaeobranchiostoma]]''?
* '''Branchiostomatidae''' <small>[[Charles Lucien Bonaparte|Bonaparte]], 1846</small><ref name="Bonaparte1846" />
** ''[[Asymmetron]]''
** ''[[Branchiostoma]]''
** ''[[Epigonichthys]]''
}}

The '''lancelets''' ({{IPAc-en|ˈ|l|æ|n|s|l|ᵻ|t|s|,_|ˈ|l|ɑː|n|-}} {{respell|LA(H)N|slits}}), also known as '''amphioxi''' ({{singular}}: '''amphioxus''' {{IPAc-en|ˌ|æ|m|f|i|ˈ|ɒ|k|s|ə|s}} {{respell|AM|fee|OK|səs}}), consist of 32 described species of "fish-like" benthic [[filter feeding]] [[chordate]]s<ref>{{Cite journal|last1=Poss|first1=Stuart G.|last2=Boschung|first2=Herbert T.|date=1996-01-01|title=Lancelets (cephalochordata: Branchiostomattdae): How Many Species Are Valid?|url=https://www.tandfonline.com/doi/abs/10.1080/00212210.1996.10688872|journal=Israel Journal of Zoology|volume=42|issue=sup1|pages=S13–S66|doi=10.1080/00212210.1996.10688872|issn=0021-2210|doi-broken-date=1 November 2024}}</ref> in the subphylum '''Cephalochordata''', class '''Leptocardii''', and family '''Branchiostomatidae'''.<ref>{{Cite book |last=Freeborn |first=Michelle |url=https://www.wikidata.org/wiki/Q58012425 |title=The fishes of New Zealand |date=2015-01-01 |publisher=Te Papa Press |isbn=978-0-9941041-6-8 |editor-last=Roberts |editor-first=Clive Douglas |volume=Two |pages=6 |editor-last2=Stewart |editor-first2=Andrew L. |editor-last3=Struthers |editor-first3=Carl D.}}</ref>

Lancelets diverged from other chordates during or prior to the [[Cambrian]] period. A number of fossil chordates have been suggested to be closely related to lancelets, including ''[[Pikaia]]'' and ''[[Cathaymyrus]]'' from the Cambrian and ''[[Palaeobranchiostoma]]'' from the [[Permian]], but their close relationship to lancelets has been doubted by other authors.<ref>{{Cite journal |last1=Briggs |first1=Derek E.G. |last2=Kear |first2=Amanda J. |date=1993 |title=Decay of Branchiostoma: implications for soft-tissue preservation in conodonts and other primitive chordates |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.1993.tb01532.x |journal=Lethaia |language=en |volume=26 |issue=4 |pages=275–287 |doi=10.1111/j.1502-3931.1993.tb01532.x |bibcode=1993Letha..26..275B |issn=0024-1164|url-access=subscription }}</ref><ref>{{Cite journal |last1=Nanglu |first1=Karma |last2=Cole |first2=Selina R. |last3=Wright |first3=David F. |last4=Souto |first4=Camilla |date=February 2023 |title=Worms and gills, plates and spines: the evolutionary origins and incredible disparity of deuterostomes revealed by fossils, genes, and development |url=https://onlinelibrary.wiley.com/doi/10.1111/brv.12908 |journal=Biological Reviews |language=en |volume=98 |issue=1 |pages=316–351 |doi=10.1111/brv.12908 |pmid=36257784 |s2cid=252995259 |issn=1464-7931|url-access=subscription }}</ref> [[Molecular clock]] analysis suggests that modern lancelets probably diversified much more recently, during the [[Cretaceous]] or [[Cenozoic]].<ref name=":4">{{Cite journal |last1=Zhang |first1=Qi-Lin |last2=Zhang |first2=Guan-Ling |last3=Yuan |first3=Ming-Long |last4=Dong |first4=Zhi-Xiang |last5=Li |first5=Hong-Wei |last6=Guo |first6=Jun |last7=Wang |first7=Feng |last8=Deng |first8=Xian-Yu |last9=Chen |first9=Jun-Yuan |last10=Lin |first10=Lian-Bing |date=2018-12-18 |title=A Phylogenomic Framework and Divergence History of Cephalochordata Amphioxus |journal=Frontiers in Physiology |volume=9 |page=1833 |doi=10.3389/fphys.2018.01833 |doi-access=free |issn=1664-042X |pmc=6305399 |pmid=30618839}}</ref><ref name="Igawa2017" />

[[List of authors of names published under the ICZN|Zoologists]] are interested in them because they provide evolutionary insight into the origins of [[vertebrate]]s. Lancelets contain many organs and organ systems that are [[Homology (biology)|homologous]] to those of modern fish, but in a more primitive form. Therefore, they provide a number of examples of possible evolutionary [[exaptation]]. For example, the gill-slits of lancelets are used for feeding only, and not for respiration. The circulatory system carries food throughout their body, but does not have red blood cells or hemoglobin for transporting oxygen.

Lancelet [[genome]]s hold clues about the early [[evolution]] of vertebrates: by comparing genes from lancelets with the same genes in vertebrates, changes in gene expression, function and  number as vertebrates evolved can be discovered.<ref>[http://newswise.com/articles/view/541865/ Worm-like Marine Animal Providing Fresh Clues About Human Evolution] Newswise, Retrieved on July 8, 2008.</ref><ref>{{Cite journal|last=Holland|first=PWH|date=1992|title=An amphioxus homeobox gene: sequence conservation, spatial expression during development and insights into vertebrate evolution|url=http://dx.doi.org/10.1016/0168-9525(93)90180-p|journal=Development|volume=116|issue=2|pages=653–661|doi=10.1016/0168-9525(93)90180-p|s2cid=7298022 |issn=0168-9525|url-access=subscription}}</ref> The genome of a few species in the genus ''[[Branchiostoma]]'' have been sequenced: ''B. floridae,''<ref>{{Cite journal|last1=Rokhsar|first1=Daniel S.|last2=Satoh|first2=Nori|last3=Holland|first3=Peter W. H.|last4=Holland|first4=Linda Z.|author-link4=Linda Holland|last5=Fujiyama|first5=Asao|last6=Bronner-Fraser|first6=Marianne|last7=Toyoda|first7=Atsushi|last8=Shin-I|first8=Tadasu|last9=Schmutz|first9=Jeremy|year=2008|title=The amphioxus genome and the evolution of the chordate karyotype|journal=Nature|language=en|volume=453|issue=7198|pages=1064–1071|doi=10.1038/nature06967|pmid=18563158|issn=1476-4687|bibcode=2008Natur.453.1064P|s2cid=4418548|doi-access=free}}</ref> ''B. belcheri'',<ref name=":5">{{Cite journal|last1=Xu|first1=Anlong|last2=Chen|first2=Shangwu|last3=Dong|first3=Meiling|last4=Wu|first4=Fenfang|last5=Fu|first5=Yonggui|last6=Yuan|first6=Shaochun|last7=You|first7=Leiming|last8=Zhou|first8=Sisi|last9=Qiujin Zhang|date=2014-12-19|title=Decelerated genome evolution in modern vertebrates revealed by analysis of multiple lancelet genomes|journal=Nature Communications|language=en|volume=5|pages=5896|doi=10.1038/ncomms6896|issn=2041-1723|pmc=4284660|pmid=25523484|bibcode=2014NatCo...5.5896H}}</ref> and ''B. lanceolatum''.<ref>{{Cite journal|last1=Marlétaz|first1=Ferdinand|last2=Firbas|first2=Panos N.|last3=Maeso|first3=Ignacio|last4=Tena|first4=Juan J.|last5=Bogdanovic|first5=Ozren|last6=Perry|first6=Malcolm|last7=Wyatt|first7=Christopher D. R.|last8=de la Calle-Mustienes|first8=Elisa|last9=Bertrand|first9=Stephanie|last10=Burguera|first10=Demian|last11=Acemel|first11=Rafael D.|date=December 2018|title=Amphioxus functional genomics and the origins of vertebrate gene regulation|url= |journal=Nature|language=en|volume=564|issue=7734|pages=64–70|doi=10.1038/s41586-018-0734-6|issn=1476-4687|pmc=6292497|pmid=30464347|bibcode=2018Natur.564...64M}}</ref>

In Asia, lancelets are harvested commercially as food for humans. In Japan, amphioxus (''B. belcheri'') has been listed in the registry of "Endangered Animals of Japanese Marine and Fresh Water Organisms".<ref>{{Cite journal|last1=Tomiyama|first1=Minoru|last2=Azuma|first2=Nobuyuki|last3=Kubokawa|first3=Kaoru|date=1998|title=A New Population of the Amphioxus (Branchiostoma belcheri) in the Enshu-Nada Sea in Japan|journal=Zoological Science|volume=15|issue=5|pages=799–803|doi=10.2108/zsj.15.799|s2cid=85834803|issn=0289-0003|doi-access=free}}</ref>