Freshwater snails aregastropodmollusks that live infresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs to major rivers. The great majority of freshwater gastropods have ashell, with very few exceptions. Some groups of snails that live in freshwaterrespire usinggills, whereasother groups need to reach the surface to breathe air. In addition, some are amphibious and have both gills and alung (e.g.Ampullariidae). Most feed on algae, but many aredetritivores and some arefilter feeders.

Freshwater snails are indirectly among the deadliest animals to humans, as they carry parasitic worms that causeschistosomiasis, a disease estimated to kill between 10,000 and 200,000 people annually.^[1][2]

There are thousands of known species, and at least 33–38 independentlineages of gastropods have successfully colonized freshwater environments.^[3] It is not possible to quantify the exact number of these lineages yet, because they have yet to be clarified within theCerithioidea.^[3] From six to eight of these independent lineages occur inNorth America.^[4]

According to a 2008 review of the taxonomy, there are about 4,000 species of freshwater gastropods (3,795–3,972).^[5] As of 2023, there are 5182 known species of fossil freshwater gastropods.^[6]

The followingcladogram is an overview of the main clades of gastropods based on thetaxonomy of Bouchet & Rocroi (2005),^[7] modified after Jörger et al. (2010)^[8] and simplified with families that contain freshwater species marked inboldface:^[5] (Marine gastropods (Siphonarioidea, Sacoglossa, Amphiboloidea, Pyramidelloidea) are not depicted within Panpulmonata for simplification. Some of these highlighted families consist entirely of freshwater species, but some of them also contain, or even mainly consist of, marine species.)

TheNeritimorpha are a group of primitive "prosobranch" gilled snails which have a shellyoperculum.

• Neritiliidae - 5 extant freshwater species^[5]
• Neritidae - largely confined to the tropics, also the rivers of Europe, family includes the marine "nerites".^[9] There are about 110 extant freshwater species.^[5]

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  FamilyNeritidae, shells ofTheodoxus fluviatilis.
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  FamilyNeritidae,Vittina natalensis
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  FamilyNeritidae,Vittina waigiensis
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  FamilyNeritidae,Clithon corona

TheCaenogastropoda are a large group of gilled operculate snails, which are largely marine. In freshwater habitats there are ten major families of caenogastropods, as well as several other families of lesser importance:

Architaenioglossa

• Ampullariidae - an exclusively freshwater family that is largely tropical and includes the large "apple snails" kept in aquaria.^[9] About 105–170 species.^[5]
• Viviparidae - medium to large snails, live-bearing, commonly referred to as "mystery snails". Worldwide except South America, and everywhere confined to fresh waters.^[9] About 125–150 species.^[5]

•  
  FamilyAmpullariidae,Pomacea bridgesii.
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  FamilyViviparidae,Viviparus viviparus.

Sorbeoconcha

• Melanopsidae - family native to rivers draining to the Mediterranean, also Middle East, and some South Pacific islands.^[9] About 25–50 species.^[5]
• Pachychilidae - 165–225 species.^[5] native to South and Central America. Formerly included with the Pleuroceridae by many authors.
• Paludomidae - about 100 species in south Asia, diverse in African Lakes, and Sri Lanka.^[5] Formerly classified with the Pleuroceridae by some authors.
• Pleuroceridae - abundant and diverse in eastern North America, largely high-spired snails of small to large size.^[9] About 150 species.^[3]
• Semisulcospiridae - primarily eastern Asia, Japan, also theJuga snails of northwestern North America. Formerly included with the Pleuroceridae. About 50 species.^[3]
• Thiaridae - high-spired parthenogenic snails of the tropics, includes those referred to as "trumpet snails" in aquaria.^[9] About 110 species.^[3]

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  FamilyMelanopsidae,Melanopsis praemorsa
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  FamilyPleuroceridae,Io fluvialis.
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  FamilySemisulcospiridae,Semisulcospira kurodai.
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  FamilyThiaridae,Melanoides tuberculata.

Littorinimorpha

• Littorinidae - 9 species in the genusCremnoconchus are freshwater living in streams and waterfalls.^[10] Other species are marine.
• Amnicolidae - about 200 species.^[5]
• Assimineidae - about 20 freshwater species,^[5] other are marine
• Bithyniidae - small snails, native to Eastern Hemisphere.^[9] About 130 species.^[5]
• Cochliopidae - about 246 species.^[5]
• Helicostoidae - the only speciesHelicostoa sinensis lives in China.^[5]
• Hydrobiidae - small to very small snails found worldwide.^[9] About 1250 freshwater species^[5] other are marine.
• Lithoglyphidae - about 100 species.^[5]
• Moitessieriidae - about 55 species.^[5]
• Pomatiopsidae - small amphibious snails scattered worldwide, most diverse in eastern and Southeast Asia.^[9] About 170 species.^[5]
• Stenothyridae - about 60 freshwater species,^[5] others are marine.

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  FamilyBithyniidae,Bithynia tentaculata.
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  FamilyCochliopidae,Antrobia culveri.
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  FamilyHelicostoidae,Helicostoa sinensis shells.
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  FamilyHydrobiidae,Sadleriana fluminensis
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  FamilyLithoglyphidae,Lithoglyphus naticoides.
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  FamilyPomatiopsidae,Oncomelania hupensis.

Neogastropoda

• Nassariidae - 8–10 freshwater species in the genusAnentome andClea,^[5] native to Southeast Asia. Other Nassariidae are marine.
• Marginellidae - 2 freshwater species in the genusRivomarginella,^[5] native to Southeast Asia. Other Marginellidae are marine.

Lower Heterobranchia

• Glacidorbidae - 20 species.^[5]
• Valvatidae - small low-spired snails referred to as "valve snails". 71 species.^[5]

Acochlidiacea

• Acochlidiidae (including synonym Strubelliidae) - 5 shell-less species:^[5]Acochlidium amboinense,Acochlidium bayerfehlmanni,Acochlidium fijiiensis,Palliohedyle sutteri andStrubellia paradoxa^[11]
• Tantulidae - there is only one species^[5] which is shell-lessTantulum elegans.

Pulmonata, Basommatophora

Basommatophorans are pulmonate or air-breathing aquatic snails, characterized by having their eyes located at the base of their tentacles, rather than at the tips, as in the true land snailsStylommatophora. The majority of basommatophorans have shells that are thin, translucent, and relatively colorless, and all five freshwater basommatophoran families lack an operculum.

• Chilinidae - small to medium-sized snails confined to temperate and cold South America.^[9] About 15 species.^[5]
• Latiidae - small limpet-like snails confined to New Zealand.^[9] One^[5] or three species.
• Acroloxidae - about 40 species.^[5]
• Lymnaeidae - found worldwide, but are most numerous in temperate and northern regions.^[9] These are the dextral (right-handed) pond snails. About 100 species.
• Planorbidae - "rams horn" snails, with a worldwide distribution.^[9] About 250 species.^[5]
• Physidae - left-handed (sinistral) "pouch snails", native to Europe, Asia, North America.^[9] About 80 species.^[5]

•  
  FamilyAcroloxidae,Acroloxus lacustris.
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  FamilyLymnaeidae,Lymnaea stagnalis.
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  FamilyPhysidae,Physella acuta.
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  FamilyPlanorbidae,Planorbarius corneus.

The freshwater snailPhysa acuta is in the subclass Heterobranchia and the family Physidae.P. acuta is aself-fertile snail that can undergo either sexual reproduction or self-fertilization. Noel et al.^[12] experimentally tested whether accumulation of deleteriousmutations is avoided either byinbreeding populations of the snail (undergoing self-fertilization), or inoutbreeding populations undergoingsexual reproduction. Inbreeding promotes thehomozygous expression of deleterious recessive mutations in progeny that then exposes these mutations to selective elimination because of their deleterious affects on progeny. Outbreeding sexual reproduction allows females to choose male mating partners with smaller mutation loads that then also leads to a reduction of deleterious mutations in progeny. On the basis of their findings, Noel et al.^[12] concluded that both outbred and inbred populations ofP. acuta can efficiently eliminate deleterious mutations.

Several different freshwater snail species are eaten inAsian cuisine.

Archaeological investigations inGuatemala have revealed that the diet of theMaya of theClassic Period (AD 250–900) included freshwater snails.^[13]

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  A dish of cooked freshwater snails,ampullariids andviviparids fromPoipet, Cambodia
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  A Bengali dish of stir-fried freshwater snails with onion and garlic paste and other spices, fromKolkata,West Bengal, India

Freshwater snails are commonly found in aquaria along with tropical fish. Species available vary in different parts of the world. In the United States, commonly available species includeramshorn snails such asPlanorbella duryi,bladder snails such asPhysella acuta,apple snails such asPomacea bridgesii, the high-spired thiaridMalaysian trumpet snail,Melanoides tuberculata, and severalNeritina species.

Freshwater snails are widely known to be hosts in the lifecycles of a variety of human and animalparasites, particularlytrematodes (or "flukes"). Some of these relations for prosobranch snails includeOncomelania in the familyPomatiopsidae as hosts ofSchistosoma, andBithynia,Parafossarulus andAmnicola as hosts ofOpisthorchis.^[14]Thiara andSemisulcospira may hostParagonimus.^[14]Juga plicifera may hostNanophyetus salmincola.^[15] Basommatophoran snails are even more widely infected, with manyBiomphalaria (Planorbidae) serving as hosts forSchistosoma mansoni,Fasciolopsis and other parasitic groups.^[14] The tinyBulinus snails are hosts forSchistosoma haematobium.^[14] Lymnaeid snails (Lymnaeidae) serve as hosts forFasciola and the cerceriae causingswimmer's itch.^[14] The term "neglected tropical diseases" applies to all snail-borne infections, includingschistosomiasis,fascioliasis,fasciolopsiasis,paragonimiasis,opisthorchiasis,clonorchiasis, andangiostrongyliasis.^[16]

• Terrestrial molluscs
• Land snail
• Land slug
• Sea snail
• Sea slug

This article incorporates CC-BY-2.5 text from the reference^[16]

• J. Mouthon,Typology of molluscs of flowing water; biotypological organisations; socioecological groupings; Annls Limnol. Volume 17, Number 2, 1981
• Haynes A. (2000). "The distribution of freshwater gastropods on four Vanuatu islands: Espiritu Santo, Pentecost, Éfate and Tanna (South Pacific)".Annales de Limnologie36(2): 101–111.doi:10.1051/limn/2000006,PDF.
• Vermeij J. & Wesselingh F. P. (2002). "Neogastropod molluscs from the Miocene of western Amazonia, with comments on marine to freshwater transitions in molluscs".Journal of Paleontology76(2): 265–270.doi:10.1666/0022-3360(2002)076<0265:NMFTMO>2.0.CO;2.
• J.B. Burch,Freshwater snails of North America; 1982 - nepis.epa.gov.