Editing Gastropoda

{{Short description|Class of molluscs}}
{{redirect|Gastropod|the podcast about the science and history of food|Gastropod (podcast){{!}}''Gastropod'' (podcast)}}
{{Automatic taxobox
| fossil_range = {{fossil range|earliest=511|Cambrian|Present|ref=<ref name="GastropodaPonder&Lindberg2008">{{cite book |last1=Aktipis |first1=S.W. |last2=Giribet |first2=G. |last3=Lindberg |first3=D.R. |last4=W.F. |first4=Ponder |editor1-last=Ponder |editor1-first=W. |editor2-last=Lindberg |editor2-first=D.R. |title=Phylogeny and evolution of the Mollusca |date=2008 |publisher=University of California Press |isbn=978-0-520-25092-5 |pages=201–238 |chapter=Gastropoda}}</ref>}}
| image = Gastropod collage.jpg
| image_upright = 1.2
| image_caption = Various gastropods from different types: [[black slug]] (a slug), ''[[Haliotis asinina]]'' (an abalone), ''[[Cornu aspersum]]'' (a land snail), ''[[Notarchus|Notarchus indicus]]'' (a seahare), ''[[Patella vulgata]]'' (a limpet), and ''[[Polycera aurantiomarginata]]'' (a nudibranch).
| taxon = Gastropoda
| authority = [[Georges Cuvier|Cuvier]], 1795<ref name="Cuvier 1795"/>
| subdivision_ranks = Subclasses
| subdivision = * [[Caenogastropoda]]
* [[Heterobranchia]]
* [[Neomphaliones]]
* [[Neritimorpha]]
* [[Patellogastropoda]]
* [[Vetigastropoda]]
| synonyms_ref = <ref name="WoRMS" />
| synonyms = * Angiogastropoda - represented as Gastropoda
* Apogastropoda - alternate representation of Gastropoda
* Psilogastropoda - represented as Gastropoda
| diversity = [[#Diversity|65,000 to 80,000 species]]
| diversity_ref = <ref name="Bouchet"/><ref name="Solem"/>
}}

'''Gastropods''' ({{IPAc-en|ˈ|g|æ|s|t|r|ə|p|ɒ|d|z}}), commonly known as '''slugs and snails''', belong to a large [[Taxonomy (biology)|taxonomic]] class of [[invertebrate]]s within the phylum [[Mollusca]] called '''Gastropoda''' ({{IPAc-en|g|æ|s|ˈ|t|r|ɒ|p|ə|d|ə}}).<ref name="WoRMS">{{cite WoRMS |author= |year=2020 |title=Gastropoda |db=Marine Mollusca |id=101 |access-date=2020-09-29}}</ref>

This class comprises [[snail]]s and [[slug]]s from saltwater, freshwater, and from the land. There are many thousands of species of [[sea snail]]s and [[sea slug|slugs]], as well as [[freshwater snail]]s, freshwater [[limpet]]s, [[land snail]]s and [[slug]]s.

The class Gastropoda is a diverse and highly successful class of mollusks within the phylum Mollusca. It contains a vast total of named species, second only to the [[insect]]s in overall number. The fossil history of this class goes back to the [[Furongian|Late Cambrian]]. {{as of|2017}}, 721 [[family (taxonomy)|families]] of gastropods are known, of which 245 are [[extinct]] and appear only in the [[fossil]] record, while 476 are currently [[neontology|extant]] [[living fossil|with]] or without a fossil record.<ref name="Bouchet 2017">{{Cite journal|title=Revised Classification, Nomenclator and Typification of Gastropod and Monoplacophoran Families|first1=Ellen E.|last1=Strong|first2=Michael|last2=Schrödl|first3=Pavel|last3=Parkhaev|first4=Alexander|last4=Nützel|first5=Yasunori|last5=Kano|first6=Andrzej|last6=Kaim|first7=Bernhard|last7=Hausdorf|first8=Jean-Pierre|last8=Rocroi|first9=Philippe|last9=Bouchet|date=December 31, 2017|journal=Malacologia|volume=61|issue=1–2|pages=1–526|doi=10.4002/040.061.0201|s2cid=91051256}}</ref>

Gastropoda (previously known as '''univalves''' and sometimes spelled "Gasteropoda") are a major part of the phylum Mollusca, and are the most highly diversified [[class (biology)|class]] in the [[phylum]], with 65,000 to 80,000<ref name="Bouchet"/><ref name="Solem">{{cite web|last1=Solem|first1=A.G.|title=Gastropod|url=https://global.britannica.com/animal/gastropod|archive-url=https://archive.today/20160308013014/http://global.britannica.com/animal/gastropod|url-status=dead|archive-date=8 March 2016|website=Encyclopaedia Britannica|publisher=Encyclopaedia Britannica Inc.|access-date=6 March 2017}}</ref> living snail and slug [[species]]. The [[anatomy]], behavior, feeding, and reproductive adaptations of gastropods vary significantly from one [[clade]] or group to another, so stating many generalities for all gastropods is difficult.

The class Gastropoda has an extraordinary diversification of [[habitat]]s. Representatives live in gardens, woodland, deserts, and on mountains; in small ditches, great rivers, and lakes; in [[estuaries]], [[mudflat]]s, the rocky [[intertidal]], the sandy subtidal, the [[Abyssal zone|abyssal]] depths of the oceans, including the [[hydrothermal vent]]s, and numerous other ecological niches, including [[parasitic]] ones.

Although the name "snail" can be, and often is, applied to all the members of this class, commonly this word means only those species with an external [[Gastropod shell|shell]] big enough that the soft parts can withdraw completely into it. Slugs are gastropods that have no shell or a very small, internal shell; semislugs are gastropods that have a shell that they can partially retreat into but not entirely.

The marine shelled species of gastropods include species such as [[abalone]], [[conch]]es, [[Common periwinkle|periwinkle]]s, [[whelk]]s, and numerous other sea snails that produce [[seashell]]s that are coiled in the adult stage—though in some, the coiling may not be very visible, for example in [[cowries]]. In a number of [[Family (biology)|families]] of species, such as all the various [[limpet]]s, the shell is coiled only in the [[larval]] stage, and is a simple conical structure after that.

==Etymology==
In the scientific literature, gastropods were described as "gasteropodes" by {{lang|fr|[[Georges Cuvier]]|italics=unset}} in 1795.<ref name="Cuvier 1795">{{cite journal |language=fr |last=Cuvier |first=G |authorlink=Georges Cuvier |year=1795 |title=Second mémoire sur l'organisation et les rapports des animaux à sang blanc, dans lequel on traite de la structure des Mollusques et de leur division en ordres, lu à la Société d'histoire naturelle de Paris, le 11 Prairial, an III |journal=Magazin Encyclopédique, ou Journal des Sciences, des Lettres et des Arts |volume=2 |pages=433–449 |url=https://archive.org/stream/magazinencyclop12pari#page/448/mode/1up |archiveurl=https://web.archive.org/web/20170725031628/https://archive.org/stream/magazinencyclop12pari#page/448/mode/1up |archivedate=2017-07-25}}</ref> The word ''gastropod'' comes from Greek {{wikt-lang|grc|γαστήρ}} ({{Transliteration|grc|gastḗr}} 'stomach') and {{wikt-lang|grc|πούς}} ({{Transliteration|grc|poús}} 'foot'), a reference to the fact that the animal's "foot" is positioned below its guts.<ref>{{cite web |title=Gastropod |url=https://www.etymonline.com/search?q=gastropod |website=Online Etymology Dictionary |access-date=3 September 2019 |archive-url=https://web.archive.org/web/20181006082612/https://www.etymonline.com/search?q=gastropod |archive-date=6 October 2018 |url-status=live }}</ref>

The earlier name "univalve" means one [[Valve (mollusc)|valve]] (or shell), in contrast to [[bivalve]]s, such as clams, which have two valves or shells.

== Diversity ==
At all [[Taxonomy (biology)|taxonomic]] levels, gastropods are second only to insects in terms of their [[Biodiversity|diversity]].<ref>{{cite book|chapter=Molecular systematics of the major lineages of the Gastropoda. |pages =140–160 |title= Molecular Systematics and Phylogeography of Mollusks|author=McArthur, A.G. |author2=M.G. Harasewych|year=2003|editor1=C. Lydeard |editor2= D.R. Lindberg|location= Washington|publisher= Smithsonian Books}}</ref>

Gastropods have the greatest numbers of named [[Mollusca|mollusk]] species. However, estimates of the total number of gastropod species vary widely, depending on cited sources. The number of gastropod species can be ascertained from estimates of the number of described species of Mollusca with accepted names: about 85,000 (minimum 50,000, maximum 120,000).<ref name="Chapman 2009">Chapman, A.D. (2009). [http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/2009/04-02-groups-invertebrates.html#mollusca Numbers of Living Species in Australia and the World, 2nd edition] {{Webarchive|url=https://web.archive.org/web/20101206050101/http://www.environment.gov.au/biodiversity/abrs/publications/other/species-numbers/2009/04-02-groups-invertebrates.html#mollusca |date=2010-12-06 }}. Australian Biological Resources Study, Canberra. Accessed 12 January 2010. {{ISBN|978-0-642-56860-1}} (printed); {{ISBN|978-0-642-56861-8}} (online).</ref> But an estimate of the total number of Mollusca, including undescribed species, is about 240,000 species.<ref>Appeltans W., Bouchet P., Boxshall G.A., Fauchald K., Gordon D.P., Hoeksema B.W., Poore G.C.B., van Soest R.W.M., Stöhr S., Walter T.C., Costello M.J. (eds) (2011). World Register of Marine Species. Accessed at [http://www.marinespecies.org marinespecies.org] {{Webarchive|url=https://archive.today/20151003132733/http://www.marinespecies.org/ |date=2015-10-03 }} on 2011-03-07.</ref> The estimate of 85,000 mollusks includes 24,000 described species of terrestrial gastropods.<ref name="Chapman 2009"/>

Different estimates for aquatic gastropods (based on different sources) give about 30,000 species of marine gastropods, and about 5,000 species of freshwater and [[Brackish water|brackish]] gastropods. Many deep-sea species remain to be discovered, as only 0.0001% of the deep-sea floor has been studied biologically.<ref>{{Cite web|url=http://www.comlsecretariat.org/wp-content/uploads/2010/06/SYNDEEP-Towards-a-first-global-synthesis-of-biodiversity-biogeography-and-ecosystem-function-in-the-deep-sea-Eva-Ramirez-Llodra-et-al..pdf|title=Census of Marine Life (2012). SYNDEEP: Towards a first global synthesis of biodiversity, biogeography and ecosystem function in the deep sea. Unpublished data (datasetID: 59)|access-date=2019-04-25|archive-url=https://web.archive.org/web/20190630235926/https://www.comlsecretariat.org/wp-content/uploads/2010/06/SYNDEEP-Towards-a-first-global-synthesis-of-biodiversity-biogeography-and-ecosystem-function-in-the-deep-sea-Eva-Ramirez-Llodra-et-al..pdf|archive-date=2019-06-30|url-status=usurped}}</ref><ref name="britannica 2010">[https://www.britannica.com/EBchecked/topic/226777/gastropod "gastropod"] {{Webarchive|url=https://web.archive.org/web/20081013064413/https://www.britannica.com/EBchecked/topic/226777/gastropod |date=2008-10-13 }}. (2010). In Encyclopædia Britannica. Retrieved March 05, 2010, from Encyclopædia Britannica Online.</ref> The total number of living species of freshwater snails is about 4,000.<ref name="Strong 2008">{{cite journal|hdl=10088/7390|doi=10.1007/s10750-007-9012-6|title=Global diversity of gastropods (Gastropoda; Mollusca) in freshwater|date=January 2008 |last1=Strong|first1=Ellen E.|last2=Gargominy|first2=Olivier|last3=Ponder|first3=Winston F.|last4=Bouchet|first4=Philippe|journal=Hydrobiologia|volume=595|issue=1 |pages=149–166|bibcode=2008HyBio.595..149S |s2cid=44234861}}</ref>

Recently [[extinct]] species of gastropods (extinct since 1500) number 444, 18 species are now [[extinct in the wild]] (but still exist in captivity), and 69 species are "possibly extinct".<ref name="Régnier 2009">{{Cite journal
| last1 = Régnier | first1 = C.
| last2 = Fontaine | first2 = B. T.
| last3 = Bouchet | first3 = P.
| s2cid = 8021609
| doi = 10.1111/j.1523-1739.2009.01245.x
| title = Not Knowing, Not Recording, Not Listing: Numerous Unnoticed Mollusk Extinctions
| journal = Conservation Biology
| volume = 23
| issue = 5
| pages = 1214–1221
| date = October 2009
| pmid = 19459894
| bibcode = 2009ConBi..23.1214R
}}</ref>

The number of prehistoric (fossil) species of gastropods is at least 15,000 species.<ref>{{in lang|es}} Nájera J. M. (1996). "Moluscos del suelo como plagas agrícolas y cuarentenarias". ''X Congreso Nacional Agronómico / II Congreso de Suelos 1996'' 51-56. [http://www.bio-nica.info/biblioteca/Monje1996.pdf PDF] {{Webarchive|url=https://web.archive.org/web/20110721191146/http://www.bio-nica.info/biblioteca/Monje1996.pdf |date=2011-07-21 }}</ref>

In marine habitats, the [[continental slope]] and the [[continental rise]] are home to the highest diversity, while the continental shelf and abyssal depths have a low diversity of marine gastropods.<ref>{{Cite journal|last=Rex|first=Michael A.|date=1973-09-14|title=Deep-Sea Species Diversity: Decreased Gastropod Diversity at Abyssal Depths|journal=Science|language=en|volume=181|issue=4104|pages=1051–1053|doi=10.1126/science.181.4104.1051|issn=0036-8075|pmid=17731267|bibcode=1973Sci...181.1051R|s2cid=43572097}}</ref>

== Habitat ==
[[File:Slimaczek.jpg|thumb|''[[Cepaea nemoralis]]'': a European pulmonate land snail, which has been introduced to many other countries]]
{{main|sea snail|sea slug|Terrestrial animal#Gastropods|land snail|semi-slug|slug}}
Gastropods are found in a wide range of aquatic and terrestrial habitats, from deep ocean trenches to deserts.{{citation needed|date=February 2025}}

Some of the more familiar and better-known gastropods are [[Terrestrial animal#Gastropods|terrestrial gastropods]] (the land snails and slugs). Some live in fresh water, but most named species of gastropods live in a marine environment. {{citation needed|date=February 2025}}

Gastropods have a worldwide distribution, from the near [[Arctic]] and [[Antarctic]] zones to the tropics. They have become adapted to almost every kind of existence on earth, having colonized nearly every available medium.{{citation needed|date=February 2025}}

In habitats where not enough [[calcium carbonate]] is available to build a really solid shell, such as on some acidic soils on land, various species of slugs occur, and also some snails with thin, translucent shells, mostly or entirely composed of the protein [[conchiolin]].{{citation needed|date=February 2025}}

Snails such as ''[[Sphincterochila boissieri]]'' and ''[[Xerocrassa seetzeni]]''<!-- syn. Trochoidea seetzeni--> have adapted to desert conditions. Other snails have adapted to an existence in ditches, near deepwater [[hydrothermal vents]], in [[oceanic trench]]es 10,000 meters (6 miles) below the surface,<ref>{{Cite journal |last1=Fukumori |first1=Hiroaki |last2=Takano |first2=Tsuyoshi |last3=Hasegawa |first3=Kazunori |last4=Kano |first4=Yasunori |date=2019 |title=Deepest known gastropod fauna: Species composition and distribution in the Kuril–Kamchatka Trench |url=https://linkinghub.elsevier.com/retrieve/pii/S0079661119302307 |journal=Progress in Oceanography |language=en |volume=178 |pages=102176 |doi=10.1016/j.pocean.2019.102176|bibcode=2019PrOce.17802176F }}</ref> the pounding surf of [[rocky shore]]s, [[cave]]s, and many other diverse areas.

Gastropods can be accidentally transferred from one habitat to another by other animals, e.g. by [[bird]]s.<ref>RUSIECKI S. & RUSIECKA A. 2013. [http://www.foliamalacologica.com/index.php?option=com_content&view=article&id=402&catid=114&Itemid=146 Hairy snail ''Trochulus hispidus'' (Linnaeus, 1758) in flight - a note on avian dispersal of snails.] {{Webarchive|url=https://web.archive.org/web/20130916075630/http://foliamalacologica.com/index.php?option=com_content&view=article&id=402&catid=114&Itemid=146 |date=2013-09-16 }} ''Folia Malacologica'' 21(2):111-112.</ref>

== Anatomy ==
[[File:Snail diagram-en edit1.svg|thumb|The anatomy of a common air-breathing land snail: much of this anatomy does not apply to gastropods in other [[clade]]s or groups.]]

Snails are distinguished by an anatomical process known as [[Torsion (gastropod)|torsion]], where the visceral mass of the animal rotates 180° to one side during development, such that the [[anus]] is situated more or less above the head. This process is unrelated to the coiling of the shell, which is a separate phenomenon. Torsion is present in all gastropods, but the [[Opisthobranchia|opisthobranch gastropods]] are secondarily untorted to various degrees.<ref name="Southern Synthesis">{{cite book|last=Kay|first=A.|title=Mollusca: The Southern Synthesis. Fauna of Australia|year=1998|publisher=CSIRO Publishing|isbn=978-0-643-05756-2|pages=565–604|author2=Wells, F. E. |author3=Poder, W. F. |editor=Beesley, P. L. |editor2=Ross, G. J. B. |editor3=Wells, A.|chapter=Class Gastropoda}}</ref><ref name="Brusca&Brusca">{{cite book|last=Brusca|first=R. C.|title=Invertebrates|year=2003|publisher=Sinauer Associates, Inc.|isbn=978-0-87893-097-5|pages=701–769|author2=Brusca, G. J.|chapter=Phylum Mollusca}}</ref>

Torsion occurs in two stages. The first, mechanistic stage is muscular, and the second is [[:wiktionary:mutagenetic|mutagenetic]]. The effects of torsion are primarily physiological. The organism develops by asymmetrical growth, with the majority of growth occurring on the left side. This leads to the loss of right-side anatomy that in most bilaterians is a duplicate of the left side anatomy. The essential feature of this asymmetry is that the anus generally lies to one side of the median plane. The [[Ctenidium (mollusc)|gill-combs]], the [[osphradium|olfactory organs]], the [[hypobranchial gland|foot slime-gland]], [[Nephridium|nephridia]], and the [[Atrium (heart)|auricle]] of the heart are single or at least are more developed on one side of the body than the other. Furthermore, there is only one [[genital]] orifice, which lies on the same side of the body as the anus.<ref>{{Cite book|url=https://www.biodiversitylibrary.org/item/16786|title=Manual of the New Zealand mollusca /|first=Henry|last=Suter|publisher=J. Mackay, govt. printer|access-date=2018-01-14|archive-url=https://web.archive.org/web/20170926235652/http://www.biodiversitylibrary.org/item/16786|archive-date=2017-09-26|url-status=live}}</ref> Furthermore, the anus becomes redirected to the same space as the head. This is speculated to have some evolutionary function, as prior to torsion, when retracting into the shell, first the posterior end would get pulled in, and then the anterior. Now, the front can be retracted more easily, perhaps suggesting a defensive purpose.{{citation needed|date=February 2025}}

Gastropods typically have a well-defined [[head (anatomy)|head]] with two or four sensory [[tentacle]]s with eyes, and a ventral foot. The foremost division of the foot is called the propodium. Its function is to push away sediment as the snail crawls. The larval shell of a gastropod is called a [[protoconch]].{{citation needed|date=February 2025}}

=== Shell ===
[[File:Zonitoides nitidus shell (cropped).jpg|thumb|The shell of ''[[Zonitoides nitidus]]'', a small land snail, has [[Gastropod shell#Chirality|dextral coiling]], which is typical (but not universal) of [[gastropod shell]]s.]]
[[File:Physella_acuta_01.JPG|thumb|The shell of ''[[Physella acuta]]'', a freshwater snail, which is left-coiling ([[Gastropod shell#Chirality|sinistral]]).]]
{{main|Gastropod shell}}

Most shelled gastropods have a one piece [[Gastropod shell|shell]] (with exceptional [[Juliidae|bivalved gastropods]]), typically coiled or spiraled, at least in the larval stage. This coiled shell usually opens on the right-hand side (as viewed with the shell [[apex (mollusc)|apex]] pointing upward). Numerous species have an [[operculum (gastropod)|operculum]], which in many species acts as a trapdoor to close the shell. This is usually made of a horn-like material, but in some molluscs it is calcareous. In the land slugs, the shell is reduced or absent, and the body is streamlined.

Some gastropods have adult shells which are bottom heavy due to the presence of a thick, often broad, convex ventral callus deposit on the inner lip and adapical to the aperture which may be important for gravitational stability.<ref>{{cite journal|author1=Geerat J. Vermeij|title=The balanced life: evolution of ventral shell weighting in gastropods|journal=Zoological Journal of the Linnean Society|volume=194|issue=1|year=2022|pages=256–275|url=https://doi.org/10.1093/zoolinnean/zlab019|doi=10.1093/zoolinnean/zlab019|access-date=2022-01-04|archive-date=2023-08-23|archive-url=https://web.archive.org/web/20230823114009/https://academic.oup.com/zoolinnean/article/194/1/256/6261015|url-status=live}}</ref>

=== Body wall ===
Some [[Opisthobranchia|sea slugs]] are very brightly colored. This serves either as a [[Aposematism|warning]], when they are [[poisonous]] or contain [[stinging cell]]s, or to [[camouflage]] them on the brightly colored [[hydroids]], [[sponge]]s, and seaweeds on which many of the species are found.{{citation needed|date=February 2025}}

Lateral outgrowths on the body of [[nudibranch]]s are called [[cerata]]. These contain an outpocketing of [[digestive gland]]s called the [[Diverticula (mollusc)|diverticula]].{{citation needed|date=February 2025}}

=== Sensory organs and nervous system ===
[[File:Vinogradski puz glava.jpg|thumb|The upper pair of [[tentacle]]s on the head of ''Helix pomatia'' have eye spots, but the main sensory organs of the snail are sensory receptors for [[olfaction]], situated in the [[epithelium]] of the tentacles.]]
{{main|Sensory organs of gastropods|Nervous system of gastropods}}

The [[sense|sensory organs]] of gastropods include [[olfaction|olfactory organs]], eyes, [[statocyst]]s and [[mechanoreceptor]]s.<ref name="sensory"/> Gastropods have no hearing.<ref name="sensory">Chase R.: ''Sensory Organs and the Nervous System''. in Barker G. M. (ed.): ''The biology of terrestrial molluscs''. CABI Publishing, Oxon, UK, 2001, {{ISBN|0-85199-318-4}}. 1-146, cited pages: 179–211.</ref>

In terrestrial gastropods (land snails and slugs), the olfactory organs, located on the tips of the four [[tentacle]]s, are the most important sensory organ.<ref name="sensory"/> The chemosensory organs of [[opisthobranch]] marine gastropods are called [[rhinophore]]s.

The majority of gastropods have simple visual organs, eye spots either at the tip or [[Leptopoma|base]] of the tentacles. However, "eyes" in gastropods range from simple [[ocelli]] that only distinguish light and dark, to more complex [[Eye#Pit eyes|pit eyes]], and even to [[Eye#Spherical lens eye|lens eyes]].<ref>{{cite book | last=Götting | first=Klaus-Jürgen | title= Lexikon der Biologie | chapter=Schnecken | editor=Becker, U. |editor2=Ganter, S. |editor3=Just, C. |editor4=Sauermost, R. | year=1994 | publisher=Spektrum Akademischer Verlag | location=Heidelberg | isbn=978-3-86025-156-0}}</ref> In land snails and slugs, vision is not the most important sense, because they are mainly [[Nocturnality|nocturnal]] animals.<ref name="sensory"/>

The nervous system of gastropods includes the [[peripheral nervous system]] and the [[central nervous system]]. The central nervous system consists of [[ganglia]] connected by nerve cells. It includes paired ganglia: the cerebral ganglia, pedal ganglia, [[Osphradium|osphradial]] ganglia, pleural ganglia, parietal ganglia and the visceral ganglia. There are sometimes also buccal ganglia.<ref name="sensory"/>

=== Digestive system ===
{{main|Digestive system of gastropods|Radula}}
The [[radula]] of a gastropod is usually adapted to the food that a species eats. The simplest gastropods are the [[limpet]]s and [[abalone]], herbivores that use their hard [[radula]] to rasp at [[seaweed]]s on rocks.{{citation needed|date=February 2025}}

Many marine gastropods are burrowers, and have a [[siphon (mollusc)|siphon]] that extends out from the [[Mantle (mollusc)|mantle]] edge. Sometimes the shell has a [[siphonal canal]] to accommodate this structure. A siphon enables the animal to draw water into their [[mantle cavity]] and over the gill. They use the siphon primarily to "taste" the water to detect prey from a distance. Gastropods with siphons tend to be either predators or scavengers.{{citation needed|date=February 2025}}

=== Respiratory system ===
{{main|Respiratory system of gastropods|Respiratory system#Anatomy of respiratory system in invertebrates}}
Almost all marine gastropods breathe with a [[gill]], but many freshwater species, and the majority of terrestrial species, have a pallial [[lung]]. The respiratory protein in almost all gastropods is [[hemocyanin]], but one freshwater [[Pulmonata|pulmonate]] family, the [[Planorbidae]], have [[hemoglobin]] as the respiratory protein.{{citation needed|date=February 2025}}

In one large group of sea slugs, the gills are arranged as a rosette of feathery plumes on their backs, which gives rise to their other name, [[nudibranch]]s. Some nudibranchs have smooth or [[wart]]y backs with no visible gill mechanism, such that respiration may likely take place directly through the skin.

=== Circulatory system ===
{{main|Circulatory system of gastropods}}
Gastropods have [[Circulatory system#Open circulatory system|open circulatory system]] and the transport fluid is [[hemolymph]]. [[Hemocyanin]] is present in the [[hemolymph]] as the respiratory pigment.{{citation needed|date=February 2025}}

===Excretory system===
{{main|Excretory system of gastropods}}
The primary organs of excretion in gastropods are [[nephridium|nephridia]], which produce either [[ammonia]] or [[uric acid]] as a waste product. The nephridium also plays an important role in maintaining water balance in freshwater and terrestrial species. Additional organs of excretion, at least in some species, include pericardial glands in the body cavity, and digestive glands opening into the [[stomach]].{{citation needed|date=February 2025}}

=== Reproductive system ===
[[File:Elysia timida mating.jpg|thumb|Mating behaviour of ''[[Elysia timida]]'']]
{{main|Reproductive system of gastropods}}
[[Mating of gastropods#Courtship|Courtship]] is a part of [[mating of gastropods|mating]] behavior in some gastropods, including some of the [[Helicidae]]. Again, in some land snails, an unusual feature of the [[reproductive system of gastropods]] is the presence and utilization of [[love dart]]s.{{citation needed|date=February 2025}}

In many marine gastropods other than the [[opisthobranch]]s, there are separate sexes ([[dioecious]]/[[Gonochorism|gonochoric]]); most land gastropods, however, are [[hermaphrodite]]s.{{citation needed|date=February 2025}}

==Life cycle==
[[File:Naturalis Biodiversity Center - RMNH.MOL.233518 - Aplysia spec. - Aplysiidae - Mollusc shell.jpeg|thumb|Egg strings of an Aplysia species.]]
{{main|Reproductive system of gastropods}}
{{see also|Mating of gastropods}}

[[Mating of gastropods#Courtship|Courtship]] is a part of the behavior of [[mating]] gastropods with some [[pulmonate]] families of land snails creating and utilizing [[love dart]]s, the throwing of which have been identified as a form of [[sexual selection]].<ref>{{Cite journal|url=https://academic.oup.com/icb/article/46/4/419/633995|title=Tales of two snails: sexual selection and sexual conflict in Lymnaea stagnalis and Helix aspersa|first=Joris M.|last=Koene|date=August 1, 2006|journal=Integrative and Comparative Biology|volume=46|issue=4|pages=419–429|via=academic.oup.com|doi=10.1093/icb/icj040|pmid=21672754|access-date=August 31, 2019|archive-url=https://web.archive.org/web/20190901225823/https://academic.oup.com/icb/article/46/4/419/633995|archive-date=September 1, 2019|url-status=live|doi-access=free}}</ref>

The main aspects of the life cycle of gastropods include:
* Egg laying and the eggs of gastropods
* The [[embryonic development]] of gastropods
* The larvae or larval stadium: some gastropods may be [[trochophore]] and/or [[veliger]]
* [[Estivation]] and [[hibernation]] (each of these are present in some gastropods only)
* The growth of gastropods
* Courtship and mating in gastropods: [[fertilization]] is internal or external according to the species. External fertilization is common in marine gastropods.

== Feeding behavior ==
[[file:Pomacea maculata.jpg|thumb|An [[apple snail]], ''[[Pomacea maculata]]'', floating and eating a piece of carrot]]
The diet of gastropods differs according to the group considered. Marine gastropods include some that are [[herbivore]]s, [[detritus]] feeders, [[predatory]] [[carnivore]]s, [[scavenger]]s, [[parasite]]s, and also a few ciliary feeders, in which the [[radula]] is reduced or absent. Land-dwelling species can chew up leaves, bark, fruit, fungi, and decomposing animals while marine species can scrape algae off the rocks on the seafloor. Certain species such as the [https://www.britannica.com/animal/gastropod/Food-and-feeding Archaeogastropoda] maintain horizontal rows of slender marginal teeth. In some species that have evolved into endoparasites, such as the [[Eulimidae|eulimid]] ''[[Thyonicola dogieli|Thyonicola doglieli]]'', many of the standard gastropod features are strongly reduced or absent.{{citation needed|date=February 2025}}

A few [[sea slug]]s are herbivores and some are carnivores. The carnivorous habit is due to specialisation. Many gastropods have distinct dietary preferences and regularly occur in close association with their food species.

Some predatory carnivorous gastropods include: [[cone shell]]s, ''[[Testacella]]'', ''[[Daudebardia]]'', [[turrid]]s, [[ghost slug]]s and others.

===Terrestrial gastropods===
Studies based on direct observations, [[fecal]] and [[Gastrointestinal tract|gut]] analyses, as well as food-choice experiments, have revealed that snails and slugs consume a wide variety of food resources.<ref name="Potapov2022"/> Their diet spans from living plants at various developmental stages such as [[pollen]], seeds, [[seedling]]s, and wood, to decaying plant material like leaf litter. Additionally, they feed on fungi, [[lichens]], [[algae]], soil, and even other animals, both living and dead, including their feces. Given this diverse diet, terrestrial gastropods can be classified as [[herbivores]], [[omnivores]], [[carnivores]], and [[detritivores]].<ref name="Potapov2022">{{cite journal |last1=Potapov |first1=Anton M. |last2=Beaulieu |first2=Frédéric |last3=Birkhofer |first3=Klaus |last4=Bluhm |first4=Sarah L. |last5=Degtyarev |first5=Maxim I. |last6=Devetter |first6=Miloslav |last7=Goncharov |first7=Anton A. |last8=Gongalsky |first8=Konstantin B. |last9=Klarner |first9=Bernhard |last10=Korobushkin |first10=Daniil I. |last11=Liebke |first11=Dana F. |last12=Maraun |first12=Mark |last13=Mc Donnell |first13=Rory J. |last14=Pollierer |first14=Melanie M. |last15=Schaefer |first15=Ina |last16=Shrubovych |first16=Julia |last17=Semenyuk |first17=Irina I. |last18=Sendra |first18=Alberto |last19=Tuma |first19=Jiri |last20=Tůmová |first20=Michala |last21=Vassilieva |first21=Anna B. |last22=Chen |first22=Ting-Wen |last23=Geisen |first23=Stefan |last24=Schmidt |first24=Olaf |last25=Tiunov |first25=Alexei V. |last26=Scheu |first26=Stefan |title=Feeding habits and multifunctional classification of soil-associated consumers from protists to vertebrates |journal=Biological Reviews |date=2022 |volume=97 |issue=3 |pages=1057–1117 |doi=10.1111/brv.12832|pmid=35060265 |doi-access=free }}</ref> However, the majority are [[microbivores]], primarily consuming [[microbe]]s associated with decaying organic material.<ref name="Speiser2001">{{cite journal |last1=Speiser |first1=B. |title=Food and feeding behaviour. |journal=The Biology of Terrestrial Molluscs |date=2001 |pages=259–288 |doi=10.1079/9780851993188.0259|isbn=978-0-85199-318-8 }}</ref> Despite their [[ecological]] importance, there is a notable lack of research exploring the specific roles that terrestrial gastropods play within soil food webs.<ref name="Potapov2022"/>

====Fungivory====
[[File:Amanita amerimuscaria 126174.jpg|thumb|A [[banana slug]], ''[[Ariolimax]]'', feeding on an ''[[Amanita]]'' [[mushroom]]]]
Many terrestrial gastropod mollusks are known to consume fungi, a behavior observed in various species of snails and slugs across distinct families.<ref name="Santamaria2023">{{cite journal |last1=Santamaria |first1=Brianna |last2=Verbeken |first2=Annemieke |last3=Haelewaters |first3=Danny |title=Mycophagy: A Global Review of Interactions between Invertebrates and Fungi |journal=Journal of Fungi |date=26 January 2023 |volume=9 |issue=2 |pages=163 |doi=10.3390/jof9020163|doi-access=free |pmid=36836278 |pmc=9968043 }}</ref><ref name=Mycologia2002>{{cite journal|last=Keller|first=H. W.|author2=Snell, K. L.|title=Feeding activities of slugs on Myxomycetes and macrofungi|journal=Mycologia|year=2002|volume=94|issue=5|pages=757–760|url=http://www.mycologia.org/content/94/5/757.full|doi=10.2307/3761690|pmid=21156549|jstor=3761690}}</ref> Notable examples of [[fungivore]] slugs include members of the family [[Philomycidae]], which feed on [[slime molds]] (myxomycetes), and the [[Ariolimacidae]], which primarily consume mushrooms ([[basidiomycetes]]).<ref name=Mycologia2002/> Snail families that contain fungivore species include [[Clausiliidae]],<ref name="Welter-Schultes2012">{{cite book |last1=Welter-Schultes |first1=F. W. |title=European non-marine molluscs: a guide for species identification = Bestimmungsbuch für europäische Land- und Süsswassermollusken |date=2012 |publisher=Planet Poster Ed |location=Göttingen |isbn=978-3-933922-75-5 |edition=1.}}</ref> [[Macrocyclidae]],<ref name="Barahona-Segovia2024">{{cite journal |last1=Barahona-Segovia |first1=Rodrigo M. |last2=Gallardo-Pillancari |first2=Esteban |last3=Orrego |first3=Gabriel |last4=Osorio |first4=Felipe |title=Mycophagy and feeding on other native land snails by the black snail Macrocyclis peruvianus (Gastropoda, Macrocyclidae) |journal=Austral Ecology |date=2024 |volume=49 |issue=2 |doi=10.1111/aec.13491|bibcode=2024AusEc..49E3491B }}</ref> and [[Polygyridae]].<ref name="Wolf&Wolf1939">{{cite journal |last1=Wolf |first1=F. T. |last2=Wolf |first2=F. A. |title=The snail ''Polygyra thyroidus'' as a mycophagist |journal=Bulletin of the Torrey Botanical Club |date=1939 |volume=66 |issue=1 |pages=1–5|doi=10.2307/2481011 |jstor=2481011 }}</ref>

Mushroom-producing fungi used as a food source by snails and slugs include species from several genera. Some examples are [[milk-cap]]s (''[[Lactarius]]'' spp.), the [[oyster mushroom]] (''Pleurotus ostreatus''), and the [[Boletus|penny bun]]. Additionally, slugs feed on fungi from other genera, such as ''[[Agaricus]]'', ''[[Pleurocybella]]'', and ''[[Russula]]''.<ref name=Mycologia2002/> Snails have also been reported to feed on [[Boletus|penny buns]] as well as ''[[Coprinellus]]'',<ref name="Putra2021">{{cite journal |last1=Putra |first1=Ivan Permana |last2=Thamrin |first2=Juan Alvares Dagtonan |title=''Coprinellus'' sect. ''Disseminati'': Source of Gastropod Mycophagy in Bogor-Indonesia |journal=Biota Jurnal Ilmiah Ilmu-Ilmu Hayati |date=2021 |pages=147–154 |doi=10.24002/biota.v6i3.3316|doi-access=free }}</ref> ''[[Aleurodiscus]]'', ''[[Armillaria]]'', ''[[Grifola ]]'', ''[[Marasmiellus]]'', ''[[Mycena]]'', ''[[Pholiota]]'', and ''[[Ramaria]]''.<ref name="Barahona-Segovia2024" />  As for slime molds, commonly consumed species include ''[[Stemonitis axifera]]'' and ''[[Symphytocarpus flaccidus]]''.<ref name=Mycologia2002/>

Feeding behaviors in slugs exhibit considerable variation. Some species display selectivity, consuming specific parts or developmental stages of fungi. For instance, certain slugs may target fungi only at particular stages of maturity, such as immature fruiting bodies or spore-producing structures.<ref name=Mycologia2002/> Conversely, other species show little to no selectivity, consuming entire mushrooms regardless of developmental stage. This variability stresses the diverse dietary adaptations among slug species and their ecological roles in fungal consumption.<ref name=Mycologia2002/> Moreover, by consuming fungi, snails and slugs can also indirectly help in their [[Biological dispersal|dispersal]] by carrying along some of their [[spore]]s<ref name=Mycologia2002/><ref name="Lilelskov2005">{{cite journal |last1=Lilleskov |first1=E. A. |last2=Bruns |first2=T. D. |title=Spore dispersal of a resupinate ectomycorrhizal fungus, Tomentella sublilacina, via soil food webs |journal=Mycologia |date=2005 |volume=97 |issue=4 |pages=762–769 |doi=10.3852/mycologia.97.4.762|pmid=16457345 }}</ref> or the fungi themselves.<ref name="Vašutová2019">{{cite journal |last1=Vašutová |first1=Martina |last2=Mleczko |first2=Piotr |last3=López-García |first3=Alvaro |last4=Maček |first4=Irena |last5=Boros |first5=Gergely |last6=Ševčík |first6=Jan |last7=Fujii |first7=Saori |last8=Hackenberger |first8=Davorka |last9=Tuf |first9=Ivan H. |last10=Hornung |first10=Elisabeth |last11=Páll-Gergely |first11=Barna |last12=Kjøller |first12=Rasmus |title=Taxi drivers: the role of animals in transporting mycorrhizal fungi |journal=Mycorrhiza |date=2019 |volume=29 |issue=5 |pages=413–434 |doi=10.1007/s00572-019-00906-1|pmid=31292712 |bibcode=2019Mycor..29..413V }}</ref>

== Genetics ==
Gastropods exhibit an important degree of variation in [[mitochondrial gene]] organization when compared to other animals.<ref name="Cunha 2009">{{Cite journal |last1=Cunha |first1=R. L. |last2=Grande |first2=C. |last3=Zardoya |first3=R. |year=2009 |title=Neogastropod phylogenetic relationships based on entire mitochondrial genomes |journal=BMC Evolutionary Biology |volume=9 |issue=1 |pages=210 |doi=10.1186/1471-2148-9-210 |pmc=2741453 |pmid=19698157 |doi-access=free|bibcode=2009BMCEE...9..210C }}</ref> Main events of [[Mutation|gene rearrangement]] occurred at the origin of [[Patellogastropoda]] and [[Heterobranchia]], whereas fewer changes occurred between the ancestors of [[Vetigastropoda]] (only [[tRNA]]s D, C and N) and [[Caenogastropoda]] (a large single [[Chromosomal inversion|inversion]], and [[Chromosomal translocation|translocation]]s of the tRNAs D and N).<ref name="Cunha 2009"/> Within Heterobranchia, gene order seems relatively conserved, and gene rearrangements are mostly related with [[Transposon|transposition]] of tRNA genes.<ref name="Cunha 2009"/>

== Geological history and evolution ==
{{See also|List of marine gastropod genera in the fossil record}}
[[File:Trochonema.jpg|thumb|''[[Trochonema]]'' sp., an early gastropod from the Middle Ordovician of the [[Galena Group]] of [[Minnesota]].]]
[[File:JurassicMarineIsrael.JPG|thumb|Fossil gastropod and attached mytilid [[bivalve]]s on a Jurassic limestone bedding plane of the [[Matmor Formation]] in southern [[Israel]].]]

The first gastropods were exclusively marine, with the earliest known representatives appearing in the [[Furongian|Late Cambrian]] (e.g., ''[[Chippewaella]]'', ''[[Strepsodiscus]]'').<ref>{{Cite journal|title=Strepsodiscus (Gastropoda) in the Late Cambrian of Missouri |journal=Journal of Paleontology|volume=59|issue=3|pages=733–740|jstor=1304993|last1=Yochelson|first1=Ellis L.|last2=Nuelle|first2=Laurence M.|year=1985}}</ref> However, their only definitive gastropod feature is a [[coiled shell]], which raises the possibility that they may belong to the stem lineage of gastropods, or might not be gastropods at all.<ref>Budd, G. E., and S. Jensen. 2000: A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews 75:253–295.</ref> Early Cambrian species such as ''[[Helcionella]]'', ''[[Barskovia]]'', and ''[[Scenella]]'' are no longer considered gastropods, and the small coiled ''[[Aldanella]]'' from the same period is probably not even a mollusk.{{citation needed|date=December 2024}}

It is not until the [[Ordovician]] that true [[crown-group]] gastropods appear.<ref name=":0">{{Cite journal |author=Be'Norr, K., and J. FnÍon |title=Notes on the evolution and higher classification of the subclass Neritimorpha (Gastropoda) with the description of some new taxa |journal=Geol. Et Palaeont 33 |year=1999 |pages=219–235 |url=http://www.paleoliste.de/bandel/bandel_1999d.pdf |access-date=2017-12-13 |archive-url=https://web.archive.org/web/20171213201725/http://www.paleoliste.de/bandel/bandel_1999d.pdf |archive-date=2017-12-13 |url-status=live }}</ref> By this time, gastropods had diversified into a variety of forms and inhabited a range of [[aquatic environment]]s. Fossil gastropods from the early [[Paleozoic]] are often poorly preserved, making identification difficult. However, the [[Silurian]] genus ''[[Poleumita]]'' contains at least 15 identified species. Overall, gastropods were less common in the [[Paleozoic]] than [[bivalves]].<ref name=":0" />

Most Paleozoic gastropods belong to primitive groups, some of which still exist today. By the [[Carboniferous]] period, many gastropod shell shapes found in fossils resemble those of modern species, though most of these early forms are not directly related to living gastropods. It was during the [[Mesozoic]] era that the ancestors of many extant gastropods evolved.<ref name=":0" /> One of the earliest known terrestrial gastropods is ''[[Anthracopupa]]'' (or ''[[Maturipupa]]''), found in the [[Carboniferous]] [[Coal Measure]]s of Europe.<ref>{{Cite journal |last1=Jochum |first1=Adrienne |last2=Yu |first2=Tingting |last3=Neubauer |first3=Thomas A. |date=2020 |title=First record of the Paleozoic land snail family Anthracopupidae in the Lower Jurassic of China and the origin of Stylommatophora |url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/first-record-of-the-paleozoic-land-snail-family-anthracopupidae-in-the-lower-jurassic-of-china-and-the-origin-of-stylommatophora/294B5CB18D294A34BF7D814D1FD68701 |journal=Journal of Paleontology |language=en |volume=94 |issue=2 |pages=266–272 |doi=10.1017/jpa.2019.68 |bibcode=2020JPal...94..266J |s2cid=204269735 |issn=0022-3360 |access-date=2022-07-29 |archive-date=2023-08-23 |archive-url=https://web.archive.org/web/20230823114010/https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/first-record-of-the-paleozoic-land-snail-family-anthracopupidae-in-the-lower-jurassic-of-china-and-the-origin-of-stylommatophora/294B5CB18D294A34BF7D814D1FD68701 |url-status=live }}</ref> However, land snails and their relatives were rare before the [[Cretaceous]] period.<ref name=":0" />

In Mesozoic rocks, gastropods become more common in the fossil record, with well-preserved shells. Fossils are found in ancient beds from both freshwater and marine environments. Notable examples include the [[Purbeck Marble]] of the [[Jurassic]] and the [[Sussex Marble]] of the early Cretaceous, both from [[southern England]]. These limestones contain abundant remains of the pond snail ''[[Viviparus]]''.<ref name=":0" /> [[Cenozoic]] rocks yield vast numbers of gastropod fossils, many of which are closely related to modern species. The diversity of gastropods increased significantly at the start of this era, alongside that of bivalves.<ref name=":0" />

Certain trail-like markings preserved in ancient sedimentary rocks are thought to have been made by gastropods crawling over the soft mud and sand. Although these [[trace fossil]]s are of debatable origin, some of them do resemble the trails made by living gastropods today.<ref name=":0" />

Gastropod fossils may sometimes be confused with [[ammonite]]s or other shelled [[cephalopod]]s. An example of this is ''[[Bellerophon (genus)|Bellerophon]]'' from the limestones of the [[Carboniferous]] period in Europe, the shell of which is planispirally coiled and can be mistaken for the shell of a cephalopod.{{Citation needed|date=December 2024}}

Gastropods also provide important evidence of faunal changes during the [[Pleistocene]] epoch, reflecting the impacts of advancing and retreating [[ice sheets]].{{Citation needed|date=December 2024}}

[[File:Cretaceous_Gastropod_Fossils_Lebanon.jpg|thumb|Cretaceous_Gastropod_Fossils_Lebanon]]

===Phylogeny===
A [[cladogram]] showing the phylogenic relationships of Gastropoda with example species:<ref>{{Cite journal| doi = 10.1186/s12879-016-1944-x| pmid = 27793108| pmc = 5084317| issn = 1471-2334| volume = 16| issue = 1| pages = 618| last1 = Kenny| first1 = Nathan J.| last2 = Truchado-García| first2 = Marta| last3 = Grande| first3 = Cristina| title = Deep, multi-stage transcriptome of the schistosomiasis vector ''Biomphalaria glabrata'' provides platform for understanding molluscan disease-related pathways| journal = BMC Infectious Diseases| date = 2016| doi-access = free}}</ref>
{{Clear}}
{{clade
|label1=Gastropoda
|1={{clade
   |1={{clade
      |1={{clade
         |1={{clade
            |1={{clade
               |1={{clade
                  |1=[[Panpulmonata]] [[Panpulmonata#Cladogram|►]] [[File:False Limpet Shell Macro Digon3.jpg|100x100px]][[File:Ancylus fluviatilis O.F.Müller, 1774 (4206383684).jpg||100x100px]][[File:Grapevinesnail 01a.jpg|100x100px]][[File:Biomphalaria glabrata.jpg|100x100px]]
                  |2=[[Euopisthobranchia]] [[Euopisthobranchia#Cladogram|►]] [[File:Aplysia californica NHGRI-79108.jpg|100x100px]]
                  }}
               |2=[[Nudipleura]] [[Nudipleura#2010 taxonomy|►]] [[File:Glaucus atlanticus 1 cropped.jpg|100x100px]]
               }}
            |2=[[Caenogastropoda]][[File:Ampullaria ampullacea (Linné) (2999358117).jpg|100x100px]][[File:Acicula lineata (Draparnaud, 1801) (4309322782).jpg|100x100px]][[File:Epitonium-scalare--Trp-6.png|100x100px]][[File:Charonia tritonis.png|100x100px]][[File:Acanthina brevidentata (Wood, 1828) (3063441884).jpg|100x100px]][[File:Neverita didyma.jpg|100x100px]][[File:Oncomelania hupensis.jpg|100x100px]]
            }}
         |2=[[Neritimorpha]][[File:Theodoxus anatolicus (Récluz, 1841) (3000195752).jpg|100x100px]]
         }}
      |2=[[Vetigastropoda]][[File:Angaria Delphinus Shell Macro.JPG|100x100px]][[File:Oxystele variegata - ZooKeys-365-337-g004A.jpg|100x100px]][[File:Lucapina suffusa (Reeve, 1850) (4947706383).jpg|100x100px]][[File:Fissurella nimbosa Linné, 1758 (4426866577).jpg|100x100px]]
      }}
   |2=[[Patellogastropoda]] [[Patellogastropoda#2007 taxonomy|►]][[File:Patelloida pustulata (Helbling, 1779) (4631972937).jpg||100x100px]]
   }}
}}

[[Neomphaliones]] and [[Lower Heterobranchia]] are not included in the above cladogram.

== Taxonomy ==
{{Further|Changes in the taxonomy of gastropods since 2005}}{{See also|Taxonomy of the Gastropoda (Ponder & Lindberg, 1997)}}

=== Current classification ===
The present backbone classification of gastropods relies on the results of phylogenomic analyses. Consensus has not been reached yet considering the relationships at the very base of the gastropod tree of life, but otherwise the major groups are known with confidence.<ref name=":1">{{Cite journal |last1=Cunha |first1=Tauana Junqueira |last2=Giribet |first2=Gonzalo |date=2019-03-13 |title=A congruent topology for deep gastropod relationships |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=286 |issue=1898 |pages=20182776 |doi=10.1098/rspb.2018.2776 |issn=0962-8452 |pmc=6458328 |pmid=30862305}}</ref><ref name=":2">{{Cite journal |last1=Uribe |first1=Juan E |last2=González |first2=Vanessa L |last3=Irisarri |first3=Iker |last4=Kano |first4=Yasunori |last5=Herbert |first5=David G |last6=Strong |first6=Ellen E |last7=Harasewych |first7=M G |date=2022-10-12 |editor-last=Oaks |editor-first=Jamie |title=A Phylogenomic Backbone for Gastropod Molluscs |url=https://academic.oup.com/sysbio/article/71/6/1271/6619577 |journal=Systematic Biology |language=en |volume=71 |issue=6 |pages=1271–1280 |doi=10.1093/sysbio/syac045 |pmid=35766870 |issn=1063-5157 |access-date=2023-08-10 |archive-date=2023-08-23 |archive-url=https://web.archive.org/web/20230823114119/https://academic.oup.com/sysbio/article-abstract/71/6/1271/6619577?redirectedFrom=fulltext |url-status=live |hdl=10261/279410 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Chen |first1=Zeyuan |last2=Schrödl |first2=Michael |date=2022-04-18 |title=How many single-copy orthologous genes from whole genomes reveal deep gastropod relationships? |journal=PeerJ |language=en |volume=10 |pages=e13285 |doi=10.7717/peerj.13285 |pmid=35497189 |issn=2167-8359|pmc=9048639 |doi-access=free }}</ref>

* Gastropoda
** Adenogonogastropoda<ref name=":2" /> (Angiogastropoda<ref name=":1" />)
*** [[Apogastropoda]]
**** [[Caenogastropoda]]
**** [[Heterobranchia]]
*** [[Neritimorpha]]
** [[Patellogastropoda]]
** [[Vetigastropoda]] (including [[Neomphaliones]])

[[File:Turritellatricarinata.jpg|thumb|A group of fossil shells of ''[[Turritella cingulifera]]'' from the [[Pliocene]] of [[Cyprus]]]]
[[File:Fulguropsis radula 01.JPG|thumb|right|220px|Five views of a shell of a ''[[Fulguropsis]]'' species]]
[[File:Gastropoda sp.JPG|thumb|220px|Microphoto (35x) of Gastropoda sp. from Holocene sediments of Amuq Plain SSE Turkey]]

=== History ===
Since [[Charles Darwin|Darwin]], biological taxonomy has attempted to reflect the [[phylogeny]] of organisms, i.e., the [[tree of life]]. The classifications used in taxonomy attempt to represent the precise interrelatedness of the various taxa. However, the taxonomy of the Gastropoda is constantly being revised and so the versions shown in various texts can differ in major ways.

In the older classification of the gastropods, there were four subclasses:<ref>Paul Jeffery.''Suprageneric classification of class Gastropoda''. The Natural History Museum, London, 2001.</ref>
* [[Opisthobranchia]] (gills to the right and behind the heart).
* [[Gymnomorpha]] (no shell)
* [[Prosobranchia]] (gills in front of the heart).
* [[Pulmonata]] (with a lung instead of gills)

The [[Taxonomy (biology)|taxonomy]] of the Gastropoda is still under revision, and more and more of the old taxonomy is being abandoned, as the results of [[DNA]] studies slowly become clearer. Nevertheless, a few of the older terms such as "opisthobranch" and "prosobranch" are still sometimes used in a descriptive way.

New insights based on DNA sequencing of gastropods have produced some revolutionary new taxonomic insights. In the case of the Gastropoda, the taxonomy is now gradually being rewritten to embody strictly [[monophyletic]] groups (only one lineage of gastropods in each group). Integrating new findings into a working [[Taxonomy (biology)|taxonomy]] remain challenging. Consistent ranks within the taxonomy at the level of subclass, superorder, order, and suborder have already been abandoned as unworkable. Ongoing revisions of the higher taxonomic levels are expected in the near future.{{when|date=September 2024}}

[[Convergent evolution]], which appears to exist at especially high frequency in gastropods, may account for the observed differences between the older phylogenies, which were based on morphological data, and more recent gene-sequencing studies.

In 2004, Brian Simison and [[David R. Lindberg]] showed possible [[Paraphyly|diphyletic]] origins of the Gastropoda based on [[mitochondrial]] gene order and [[amino acid sequence]] analyses of complete genes.<ref>{{Cite web |title=Unitas malacologica, Newsletter number 21 december 2004 - a .pdf file |url=http://www.ucd.ie/cobid/unitas/newsletter/UMNewsletter_21.pdf |url-status=live |archive-url=https://web.archive.org/web/20110615172727/http://www.ucd.ie/cobid/unitas/newsletter/UMNewsletter_21.pdf |archive-date=15 June 2011 |access-date=9 March 2009}}</ref>

In 2005, [[Philippe Bouchet]] and [[Jean-Pierre Rocroi]] made sweeping changes in the [[systematics]], resulting in the [[Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)|Bouchet & Rocroi taxonomy]], which is a step closer to the evolutionary history of the [[phylum]].<ref name="Bouchet">Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. {{ISBN|3-925919-72-4}}. 397 pp. [http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278 vliz.be] {{Webarchive|url=https://web.archive.org/web/20200714234835/http://www.vliz.be/en/imis?module=ref&refid=78278 |date=2020-07-14 }}</ref><ref>Poppe G.T. & Tagaro S.P. 2006. The new classification of Gastropods according to Bouchet & Rocroi, 2005. Visaya, février 2006: 10 pp. [http://www.journal-malaco.fr/bouchet&rocroi_2005_Visaya.pdf journal-malaco.fr] {{webarchive|url=https://web.archive.org/web/20070927101354/http://www.journal-malaco.fr/bouchet%26rocroi_2005_Visaya.pdf |date=2007-09-27 }}</ref> The Bouchet & Rocroi classification system is based partly on the older systems of classification, and partly on new [[cladistic]] research. In the past, the taxonomy of gastropods was largely based on [[phenetic]] morphological characters of the taxa. The recent advances are more based on molecular characters from [[DNA]]<ref>{{cite journal| author1=Elpidio A. Remigio| author2=Paul D.N. Hebert| name-list-style=amp| title=Testing the utility of partial COI sequences for phylogenetic (full text on line)| journal=Molecular Phylogenetics and Evolution| year=2003| volume=29| url=http://www.bolinfonet.org/pdf/MPEVsnailpaper.pdf| pages=641–647| doi=10.1016/S1055-7903(03)00140-4| pmid=14615199| issue=3| url-status=dead| archive-url=https://web.archive.org/web/20070927101355/http://www.bolinfonet.org/pdf/MPEVsnailpaper.pdf| archive-date=2007-09-27}}</ref> and [[RNA]] research. This has made the taxonomical ranks and their hierarchy controversial.

In 2017, Bouchet, Rocroi, and other collaborators published a significantly updated version of the 2005 taxonomy.<ref name="Bouchet2">Philippe Bouchet, Jean-Pierre Rocroi, Bernhard Hausdorf, Andrzej Kaim, Yasunori Kano, Alexander Nützel, Pavel Parkhaev, Michael Schrödl and Ellen E. Strong. 2017. ''[http://www.bioone.org/doi/abs/10.4002/040.061.0201?journalCode=mala Revised Classification, Nomenclator and Typification of Gastropod and Monoplacophoran Families] {{Webarchive|url=https://web.archive.org/web/20230823114015/https://bioone.org/journals/malacologia/volume-61/issue-1-2/040.061.0201/Revised-Classification-Nomenclator-and-Typification-of-Gastropod-and-Monoplacophoran-Families/10.4002/040.061.0201.short|date=2023-08-23}}''. [[Malacologia]], 61(1-2): 1-526.</ref> In the [[Taxonomy of the Gastropoda (Bouchet et al., 2017)|Bouchet et al. taxonomy]], the authors used unranked [[clade]]s for taxa above the rank of superfamily (replacing the ranks suborder, order, superorder and subclass), while using the traditional [[Linnaean taxonomy|Linnaean approach]] for all taxa below the rank of superfamily. Whenever [[monophyly]] has not been tested, or is known to be paraphyletic or polyphyletic, the term "group" or "informal group" has been used. The classification of families into subfamilies is often not well resolved.{{Citation needed|date=September 2023}}

Fixed ranks like family, genus, and species however remain useful for practical classification and remain used in the [[World Register of Marine Species]] (WoRMS). Also many researchers continue to use traditional ranks because they are entrenched in the literature and familiar to specialists and non-specialists alike.

==Ecology and conservation==
Many gastropod species face threats from habitat destruction, pollution, and climate change. Some species are endangered or have become extinct due to these factors. Conservation efforts often focus on protecting their habitats, especially in freshwater and terrestrial ecosystems.

===Predators===
Gastropods are [[prey]] to a wide range of organisms depending on the environment. In marine habitats, gastropods are preyed upon by  [[fish]], [[marine birds]], [[marine mammal]]s,  [[crustacean]]s, and other mollusks such as [[cephalopod]]s. In terrestrial environments, gastropod predators include [[insect]]s, [[arachnid]]s ([[spider]]s, [[harvestmen]]),<ref name="Nyffeler2001">{{cite journal |last1=Nyffeler |first1=M. |last2=Symondson |first2=W. O. C. |title=Spiders and harvestmen as gastropod predators |journal=Ecological Entomology |date=2001 |volume=26 |issue=6 |pages=617–628|doi=10.1046/j.1365-2311.2001.00365.x |bibcode=2001EcoEn..26..617N }}</ref> [[bird]]s, and [[mammal]]s, among others.

== Gallery ==
<gallery>
File:Caucasotachea atrolabiata.jpg|''[[Caucasotachea atrolabiata]]'' ([[Heterobranchia]])
File:Cypraea Tigris.jpg|alt=Cypraea_Tigris|''[[Cypraea tigris]]'' ([[Caenogastropoda]])
File:Mauritia mauritiana,.jpg|''[[Mauritia mauritiana]]'' ([[Caenogastropoda]])
File:Amblychilepas compressa 001.jpg|alt=Amblychilepas_compressa_001|''[[Amblychilepas compressa]]'' ([[Vetigastropoda]])
File:Conus rosiae 002.jpg|alt=|''[[Conus rosiae]]'' ([[Caenogastropoda]])
File:Marisa cornuarietis ,.jpg|''[[Marisa cornuarietis]]'' ([[Caenogastropoda]])
File:Pomacea canaliculata.jpg|''[[Pomacea canaliculata]]'' ([[Caenogastropoda]])
File:Helicella macedonica.jpg|''[[Helicella macedonica]]'' ([[Heterobranchia]])
File:Geophorus romblonensis.jpg|''[[Geophorus romblonensis]]'' ([[Neritimorpha]])
File:Architectonica perspectiva S4-01.jpg|''[[Architectonica perspectiva]]'' ([[Heterobranchia]])
File:Cypraea onyx S2-21 37mm.jpg|''[[Erronea onyx]]'' ([[Caenogastropoda]])
File:Lyncina lynx S2-22 46mm.jpg|''[[Lyncina lynx]]''  ([[Caenogastropoda]])
</gallery>

== References ==
{{Reflist}}

== Sources ==
* This article incorporates [[CC-BY 2.0|CC-BY-2.0]] text from the following source: Cunha, R. L.; Grande, C.; Zardoya, R. (2009). "Neogastropod phylogenetic relationships based on entire mitochondrial genomes". ''BMC Evolutionary Biology''. '''9''': 210. [[Doi (identifier)|doi]]:10.1186/1471-2148-9-210. [[PMC (identifier)|PMC]]&nbsp;2741453. [[PMID (identifier)|PMID]]&nbsp;19698157.
* Abbott, R. T. (1989): ''Compendium of Landshells. A color guide to more than 2,000 of the World's Terrestrial Shells.'' 240 S., American Malacologists. Melbourne, Fl, Burlington, Ma. {{ISBN|0-915826-23-2}}
* Abbott, R. T. & Dance, S. P. (1998): ''Compendium of Seashells. A full-color guide to more than 4,200 of the world's marine shells.'' 413 S., Odyssey Publishing. El Cajon, Calif. {{ISBN|0-9661720-0-0}}
* Parkinson, B., Hemmen, J. & Groh, K. (1987): ''Tropical Landshells of the World.'' 279 S., Verlag Christa Hemmen. Wiesbaden. {{ISBN|3-925919-00-7}}
* Ponder, W. F. & Lindberg, D. R. (1997): ''Towards a phylogeny of gastropod molluscs: an analysis using morphological characters''. ''Zoological Journal of the Linnean Society'', '''119''' 83–265.
* Robin, A. (2008): ''Encyclopedia of Marine Gastropods.'' 480 S., Verlag ConchBooks. Hackenheim. {{ISBN|978-3-939767-09-1}}

== External links ==
{{Wiktionary|gastropod|univalve}}
{{Wikispecies}}
{{Commons category}}
* [http://www.scholarpedia.org/article/Gastropod_reproductive_behavior Gastropod reproductive behavior]
* [http://www.manandmollusc.net/advanced_introduction/gastropod_taxonomy_1.html 2004 Linnean taxonomy of gastropods]
* {{Cite journal | last1 = Webster | first1 = S. | last2 = Fiorito | first2 = G. | doi = 10.1007/s100710100108 | title = Socially guided behaviour in non-insect invertebrates | journal = Animal Cognition | volume = 4 | issue = 2 | pages = 69 | year = 2001 | s2cid = 25373798 }} – Article about [[Social learning (social pedagogy)|social learning]] also in gastropods.
* [https://www.flickr.com/photos/jsjgeology/sets/72157647577987145 Gastropod photo gallery], mostly fossils, a few modern shells
* [https://www.youtube.com/watch?v=LKD5DZ4f6z0 A video of a crawling Garden Snail] (''[[Cornu aspersum]]''), [[YouTube]]
* [https://molluscsoftasmania.org.au/ Grove, S.J. (2018). A Guide to the Seashells and other Marine Molluscs of Tasmania: Molluscs of Tasmania with images]

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[[Category:Gastropods| ]]
[[Category:Mollusc classes]]
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[[Category:Articles containing video clips]]
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[[Category:Taxa named by Georges Cuvier]]