Editing Lung (section)

=== Invertebrates ===
{{further|Respiratory system of gastropods}}
[[File:Spider internal anatomy-en.svg|thumb|[[Book lung]]s of a female spider (shown in pink)]]
A number of [[invertebrate]]s have lung-like structures that serve a similar respiratory purpose to true vertebrate lungs, but are not evolutionarily related and only arise out of [[convergent evolution]]. Some [[arachnid]]s, such as [[spider]]s and [[scorpion]]s, have structures called [[book lung]]s used for atmospheric gas exchange. Some species of spider have four pairs of book lungs but most have two pairs.<ref>{{Cite web
| url = https://www.britannica.com/science/book-lung
| title = book lung {{!}} anatomy
| website = Encyclopædia Britannica
| access-date = 2016-02-24
}}</ref> Scorpions have [[Spiracle (arthropods)|spiracle]]s on their body for the entrance of air to the book lungs.<ref>{{Cite web
| url = https://www.britannica.com/science/spiracle
| title = spiracle {{!}} anatomy
| website = Encyclopædia Britannica
| access-date = 2016-02-24
}}</ref>

The [[coconut crab]] is terrestrial and uses structures called [[branchiostegal lung]]s to breathe air.<ref name="Farrelly2005">{{cite journal|vauthors=Farrelly CA, Greenaway P|year=2005|title=The morphology and vasculature of the respiratory organs of terrestrial hermit crabs (''Coenobita'' and ''Birgus''): gills, branchiostegal lungs and abdominal lungs |journal=Arthropod Structure & Development|volume=34 |issue=1 |pages=63–87 |doi=10.1016/j.asd.2004.11.002|bibcode=2005ArtSD..34...63F }}</ref> Juveniles are released into the ocean, however adults cannot swim and possess an only rudimentary set of gills. The adult crabs can breathe on land and hold their breath underwater.<ref>{{Cite book
| url = https://books.google.com/books?id=RR09AAAAIAAJ
| title = Biology of the Land Crabs
| last1 = Burggren
| first1 = Warren W.
| last2 = McMahon
| first2 = Brian R.
| year = 1988
| publisher = Cambridge University Press
| isbn = 978-0-521-30690-4
| page = 25
| language = en
}}</ref> The branchiostegal lungs are seen as a developmental adaptive stage from water-living to enable land-living, or from fish to amphibian.<ref>{{Cite book
| url = https://books.google.com/books?id=RR09AAAAIAAJ
| title = Biology of the Land Crabs
| last1 = Burggren
| first1 = Warren W.
| last2 = McMahon
| first2 = Brian R.
| year = 1988
| publisher = Cambridge University Press
| isbn = 978-0-521-30690-4
| page = 331
| language = en
}}</ref>

[[Pulmonates]] are mostly [[land snail]]s and [[slug]]s that have developed a simple lung from the [[mantle cavity]]. An externally located opening called the [[pneumostome]] allows air to be taken into the mantle cavity lung.<ref>Land Snails (& other Air-Breathers in Pulmonata Subclass & Sorbeconcha Clade).
at Washington State University Tri-Cities Natural History Museum. Accessed 25 February 2016. http://shells.tricity.wsu.edu/ArcherdShellCollection/Gastropoda/Pulmonates.html {{Webarchive|url=https://web.archive.org/web/20181109010506/http://shells.tricity.wsu.edu/ArcherdShellCollection/Gastropoda/Pulmonates.html |date=2018-11-09 }}</ref><ref>{{Cite book
| url = https://books.google.com/books?id=7UyeBQAAQBAJ
| title = Mollusca: Metabolic Biochemistry and Molecular Biomechanics
| last = Hochachka
| first = Peter W.
| year = 2014
| publisher = Academic Press
| isbn = 978-1-4832-7603-8
| language = en
}}</ref>