Editing Snail (section)

==Overview==
Snails that [[respiration (physiology)|respire]] using a [[lung]] belong to the group [[Pulmonata]]. As traditionally defined, the Pulmonata were found to be [[polyphyletic]] in a molecular study per Jörger ''et al.'', dating from 2010.<ref name="Jörger 2010">{{cite journal|last=Jörger|first=Katharina M|author2=Stöger, Isabella |author3=Kano, Yasunori |author4=Fukuda, Hiroshi |author5=Knebelsberger, Thomas |author6= Schrödl, Michael |title=On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia|journal=BMC Evolutionary Biology|year=2010|volume=10|issue=1|pages=323|doi=10.1186/1471-2148-10-323|pmid=20973994|pmc=3087543 |doi-access=free |bibcode=2010BMCEE..10..323J }}</ref> But snails with [[gill]]s also form a [[polyphyletic]] group; in other words, snails with lungs and snails with gills form a number of [[Taxonomy (biology)|taxonomic]] groups that are not necessarily more closely related to each other than they are related to some other groups.

Both snails that have lungs and snails that have gills have diversified so widely over geological time that a few species with gills can be found on land and numerous species with lungs can be found in freshwater. Even a few marine species have lungs.

Snails can be found in a very wide range of environments, including [[ditch]]es, [[desert]]s, and the [[abyssal zone|abyssal]] depths of the sea. Although [[terrestrial ecoregion|land]] snails may be more familiar to laymen, [[marine biology|marine]] snails constitute the majority of snail species, and have much greater diversity and a greater [[biomass (ecology)|biomass]]. Numerous kinds of snail can also be found in [[freshwater snail|fresh water]].

Most snails have thousands of microscopic tooth-like structures located on a banded ribbon-like tongue called a [[radula]]. The radula works like a file, ripping food into small pieces. Many snails are [[herbivore|herbivorous]], eating plants or rasping algae from surfaces with their radulae, though a few land species and many marine species are [[omnivore]]s or [[predation|predatory]] [[carnivore]]s. Snails cannot absorb colored pigments when eating paper or cardboard so their feces are also colored.<ref>{{cite web|url=https://www.dezeen.com/2013/11/26/tiles-made-from-snail-poo-by-lieske-schreuder/|title=Floor tiles made of coloured snail poo by Lieske Schreuder - design|date=26 November 2013|access-date=29 March 2018}}</ref>

Several species of the genus ''[[Achatina]]'' and related genera are known as giant African land snails; some grow to {{Convert|38|cm|in|abbr=on}} from snout to tail, and weigh {{convert|1|kg|0|abbr=on}}.<ref name="Fredericks2010">{{cite book |last=Fredericks |first=Anthony D. |year=2010 |title=How Long Things Live & How They Live As Long As They Do |publisher=Stackpole Books |isbn=9780811736220 |page=[https://archive.org/details/howlongthingsliv0000fred/page/73 73] |url=https://archive.org/details/howlongthingsliv0000fred |url-access=registration |access-date=19 June 2012}}</ref> The largest living species of sea snail is ''[[Syrinx aruanus]]''; its shell can measure up to {{convert|90|cm|abbr=on}} in length, and the whole animal with the shell can weigh up to {{convert|18|kg|abbr=on}}. The smallest land snail, ''[[Angustopila psammion]],'' was discovered in 2022 and measures 0.6 mm in diameter.<ref>{{Cite web |date=2 Feb 2022 |title=New snail species are world's smallest, tinier than grains of sand |url=https://www.nationalgeographic.com/animals/article/smallest-snails-on-earth-discovered?linkId=150748492 |url-status=live |archive-url=https://web.archive.org/web/20220830205208/https://www.nationalgeographic.com/animals/article/smallest-snails-on-earth-discovered?linkId=150748492 |archive-date=30 Aug 2022 |access-date=16 Oct 2024 |website=National Geographic}}</ref>

The largest known land gastropod is the African giant snail ''[[Achatina achatina]]'', the largest recorded specimen of which measured {{Convert|39.3|cm|in}} from snout to tail when fully extended, with a shell length of {{Convert|27.3|cm|in|abbr=on}} in December 1978. It weighed exactly 900 g (about 2 lb). Named Gee Geronimo, this snail was owned by Christopher Hudson (1955–79) of Hove, East Sussex, UK, and was collected in Sierra Leone in June 1976.<ref>{{Cite web|website=Guinness World Records|title=Largest Snail|url=http://www.guinnessworldrecords.com/explore-records/animals?page=2|access-date=17 December 2016}}</ref>

Snails are [[Protostome|protostomes]]. That means during development, in the [[gastrulation]] phase, the blastopore forms the mouth first. Cleavage in snails is spiral holoblastic patterning. In spiral holoblastic cleavage, the cleavage plane rotates each division and the cell divisions are complete. Snails do not undergo metamorphosis after hatching. Snails hatch in the form of small adults. The only additional development they will undergo is to consume calcium to strengthen their shell. Snails can be male, female, [[Hermaphrodite|hermaphroditic]], or [[Parthenogenesis|parthenogenetic]] so there are many different systems of sexual determination.