Planorbidae, common name the ramshorn snails or ram's horn snails, is a

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

of air-breathing freshwater snails, aquatic pulmonate gastropod

molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...

. Unlike most molluscs, the blood of ram's horn snails contains iron-based

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

instead of copper-based

hemocyanin Hemocyanins (also spelled haemocyanins and abbreviated Hc) are proteins that transport oxygen throughout the bodies of some invertebrate animals. These metalloproteins contain two copper atoms that reversibly bind a single oxygen molecule (O2) ...

. As a result, planorbids are able to breathe

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

more efficiently than other molluscs. The presence of hemoglobin gives the body a reddish colour. This is especially apparent in

albino Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and pink or blue eyes. Individuals with the condition are referred to as albino. Varied use and interpretation of the term ...

animals. Being air breathers like other ''

Panpulmonata Panpulmonata is a taxonomic clade of snails and slugs in the clade Heterobranchia within the clade Euthyneura. Panpulmonata was established as a new taxon by Jörger et al. in October 2010. The older name "Pulmonata" referred to a group of gas ...

'', planorbids do not have

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, but instead have a

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

. The foot and head of planorbids are rather small, while their thread-like tentacles are relatively long. Many of the species in this family have coiled shells that are planispiral, in other words, the shells are more or less coiled flat, rather than having an elevated

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires a ...

as is the case in most

gastropod shell The gastropod shell is part of the body of a gastropod or snail, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium storage. Some ...

s. Although they carry their shell in a way that makes it appear to be dextral, the shell of coiled planorbids is in fact sinistral in coiling, but is carried upside down, which makes it appear to be dextral.

General taxonomic context

For several taxa, no consensus exists as to whether the taxa should even be assigned to the

Planorbidae. This is certainly the case with the freshwater

limpets Limpets are a group of aquatic snails that exhibit a conical shell shape (patelliform) and a strong, muscular foot. Limpets are members of the class Gastropoda, but are polyphyletic, meaning the various groups called "limpets" descended indep ...

Ferrissia ''Ferrissia'' is a genus of small, air-breathing freshwater limpets, aquatic gastropod mollusks in the family Planorbidae, the ram's horn snails and their allies. Species Species within the genus ''Ferrissia'' include: * '' Ferrissia baconi'' ...

'', and ''

Ancylus ''Ancylus'' is a genus of very small, freshwater, air-breathing limpets. They are aquatic pulmonate gastropod mollusks in the tribe Ancylini within the family Planorbidae, the ram's horn snails and their allies.Bouchet, P.; Rosenberg, G. (2 ...

''. Both of these genera have sometimes been assigned to the family

Lymnaeidae Lymnaeidae, common name the pond snails, is a taxonomic family of small to large air-breathing freshwater snails, aquatic pulmonate gastropod mollusks, that belong to the clade Hygrophila. Lymnaeidae is the only family within the superf ...

. Alternatively sometimes each one of them is raised to the level of a family. However, according to the

taxonomy of the Gastropoda (Bouchet & Rocroi, 2005) The taxonomy of the Gastropoda as it was revised in 2005 by Philippe Bouchet and Jean-Pierre Rocroi is a system for the scientific classification of gastropod mollusks. (Gastropods are a taxonomic class of animals which consists of snails and s ...

, these genera are currently placed in the tribe Ancylini within the family Planorbidae, and that is the taxonomic system that is followed here.

2005 taxonomy

According to the

, this family consists of the following subfamilies: * subfamily Planorbinae Rafinesque, 1815 ** tribe Planorbini Rafinesque, 1815 - synonyms: Choanomphalinae Fisher & Crosse, 1880; Orygoceratidae Brusina, 1882 ** tribe Ancylini Rafinesque, 1815 - synonym: Pseudancylinae Walker, 1923 (inv.) ** tribe Biomphalariini Watson, 1954 - synonyms: Acrorbini Starobogatov, 1958; Drepanothrematini Zilch, 1959; Taphiinae Harry & Hubendick, 1964 ** tribe Planorbulini Pilsbry, 1934 ** tribe Segmentinini Baker, 1945 * subfamily Bulininae Fischer & Crosse, 1880 ** tribe Bulinini Fischer & Crosse, 1880 - synonyms: Laevapicinae Hannibal, 1912; Isidorinae Annandale, 1922; Gundlachiinae Starobogatov, 1967 ** tribe Coretini Gray, 1847 - synonyms: Pompholicinae Dall, 1866 (inv.); Camptoceratinae Dall, 1870; Megasystrophinae Tryon, 1871 (inv.); Pompholycodeinae Lindholm, 1927; Helisomatinae Baker, 1928; Bayardellini Starobogatov & Prozorova, 1990; Planorbariini Starobogatov, 1990 ** tribe Miratestini Sararsin & Sarasin, 1897 - synonyms: Ferrissiinae Walker, 1917; Ancylastrinae Walker, 1923; Protancylinae Walker, 1923; Physastrinae Starobogatov, 1958; Ameriannini Zilch, 1959; Patelloplanorbidae Franc, 1968 ** tribe Plesiophysini Bequaert & Clench, 1939 * subfamily Neoplanorbinae Hannibal, 1912 - synonym: Payettiinae Dall, 1924 * subfamily Rhodacmeinae Walker, 1917

2007 taxonomy for part of the family

Albrecht ''et al.'' (2007)Albrecht C., Kuhn K. & Streit B. (2007). "A molecular phylogeny of Planorboidea (Gastropoda, Pulmonata): insights from enhanced taxon sampling". ''

Zoologica Scripta ''Zoologica Scripta'' is a bimonthly peer-reviewed scientific journal on systematic zoology, published by Wiley-Blackwell on behalf of the Norwegian Academy of Science and Letters and the Royal Swedish Academy of Sciences. It was established in 197 ...

'' 36: 27-39.. analyzed a limited number of genera of Planorbidae, based on sequences of mitochondrial 18S ribosomal DNA and cytochrome-c oxidase I (COI) genes, and on the basis of the results, they rearranged the taxonomy like this: "A-clade" sensu Albrecht ''et al.'' (2007) * '' Burnupia'' Walker, 1912 Tribus Bulinini * ''

Bulinus ''Bulinus'' is a genus of small tropical freshwater snails, aquatic gastropod mollusks in the family Bulinidae, the ramshorn snails and their allies. MolluscaBase eds. (2020). MolluscaBase. Bulinus O. F. Müller, 1781. Accessed through: World ...

'' Müller, 1781 * ''

Indoplanorbis ''Indoplanorbis'' is a genus of air-breathing freshwater snail. Its only member species is ''Indoplanorbis exustus'', an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails. The species is widely distributed ac ...

'' Annandale, 1921 Tribus Ancylini Rafinesque-Schmaltz, 1815 * ''

'' Müller, 1774 * ''

'' Walker, 1903 * '' Gundlachia'' Pfeiffer, 1849 * '' Laevapex'' Walker, 1903 * '' Hebetancylus'' Pilsbry, 1914 "B-clade" sensu Albrecht ''et al.'' (2007) * '' Glyptophysa'' Crosse, 1872 * '' Protancylus'' Sarasin, 1897 * '' Kessneria'' Walker & Ponder, 2001 * '' Leichhardtia'' Walker, 1988 Tribus Camptoceratini * '' Planorbarius'' Duméril 1806 Tribus Planorbini * '' Anisus'' Studer, 1820 * '' Bathyomphalus'' Charpentier, 1837 * ''

Gyraulus ''Gyraulus'' is a genus of small, mostly air-breathing, freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails. The genus ''Gyraulus'' is known from the Early Cretaceous to the present. Fossi ...

'' Charpentier, 1837 * '' Hovorbis'' Brown & Mandahl-Barth, 1973 * '' Choanomphalus'' Gerstfeldt, 1859 * ''

Planorbis ''Planorbis'' is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids. All species in this genus have sinistral or left-coiling shells.Bouchet, P.; Rosen ...

'' Müller 1774 Tribus Segmentinini * ''

Segmentina ''Segmentina'' is a genus of very small, air-breathing, freshwater snails, aquatic gastropod mollusks or micromollusks in the family Planorbidae, the ramshorn snails. Albrecht et al. (2007)Albrecht C., Kuhn K. & Streit B. (2007). "A molecul ...

'' Fleming, 1818 * '' Hippeutis'' Charpentier, 1837 * '' Polypylis'' Pilsbry, 1906 "C-Clade" sensu Albrecht ''et al.'' (2007) * ''

Biomphalaria ''Biomphalaria'' is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails and their allies.MolluscaBase (2018). Biomphalaria Preston, 1910. Accessed through: World Regi ...

'' Preston, 1910 * '' Menetus'' Adams & Adams, 1855 * '' Planorbella'' Haldeman, 1843 * '' Planorbula'' Haldeman, 1843

Cladogram

The following is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

that shows the phylogenic relationships within the Planorbidae according to Albrecht 2007:

Genera

The

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal ...

of this family is ''Planorbis'' Müller. The following list of genera is organized according to the 2005 taxonomy, because Albrecht's 2007 taxonomy is not available for all genera of Planorbidae. Genera in the family Planorbidae include (subgenera listed according to Glöer (2002): * subfamily Planorbinae Rafinesque, 1815 Anisus septegyrus1pl

*** '' Anisus'' S. Studer, 1820 **** subgenus '' Disculifer'' Boettger, 1944 *** '' Bathyomphalus'' Charpentier, 1837 *** ''

'' Charpentier, 1837 **** subgenus '' Torquis'' Dall, 1905 **** subgenus '' Lamorbis'' Starobogatov, 1967 **** subgenus ''

Armiger In heraldry, an armiger is a person entitled to use a heraldic achievement (e.g., bear arms, an "armour-bearer") either by hereditary right, grant, matriculation, or assumption of arms. Such a person is said to be armigerous. A family or a cl ...

'' Hartmann, 1843 *** '' Hippeutis'' Charpentier, 1837 ** tribe Ancylini Rafinesque, 1815 *** ''

'' Müller, 1773 - type genus of tribe Ancylini ** tribe Biomphalariini Watson, 1954 *** ''

'' Preston, 1910 - type genus of tribe Biomphalariini *** '' Drepanotrema'' Crosse & Fischer, 1880 ** tribe Planorbini Rafinesque, 1815 *** '' Afrogyrorbis'' Starobogatov, 1967Starobogatov, Y. I. (1967). On the systematization of freshwater pulmonate molluscs. ''Trudy Zoologicheskogo Instituta, Leningrad'', 42, 280–304. *** ''

'' Müller, 1773 ** tribe Planorbulini Pilsbry, 1934 *** '' Planorbula'' Haldeman, 1840 - type genus of tribe Planorbulini ** tribe Segmentinini Baker, 1945 *** ''

'' Fleming, 1818 - type genus of tribe Segmentinini * subfamily Bulininae Fischer & Crosse, 1880 *** ''

'' Annandale & Prashad, 1920 - contains one species ''

Indoplanorbis exustus ''Indoplanorbis'' is a genus of air-breathing freshwater snail. Its Monotypic taxon, only member species is ''Indoplanorbis exustus'', an aquatic animal, aquatic pulmonate gastropod mollusk in the family (biology), family Planorbidae, the sheep, ...

''Liu L et al. (2010) "The phylogeography of ''Indoplanorbis exustus'' (Gastropoda: Planorbidae) in Asia". ''

Parasites & Vectors ''Parasites & Vectors'' is a peer-reviewed open-access medical journal published by BioMed Central. The journal publishes articles on the biology of parasites, parasitic diseases, intermediate hosts, vectors and vector-borne pathogens. ''Paras ...

'' 3: 57. . *** '' Planorbarius'' Duméril, 1806 *** '' Planorbella'' Haldeman, 1842 *** '' Menetus'' Adams & Adams, 1855 **** subgenus '' Dilatata'' Clessin, 1885 ** tribe Bulinini Fischer & Crosse, 1880 *** ''

'' Müller, 1781 - type genus of subfamily Bulininae *** '' Gundlachia'' Pfeiffer, 1849 ** tribe Coretini Gray, 1847 *** '' Coretus'' Gray, 1847 - type genus of tribe Coretini ** tribe Miratestini Sarasin & Sarasin, 1897 *** '' Miratesta'' Sarasin & Sarasin, 1897 - type genus of tribe Miratestini *** '' Amerianna'' Strand, 1928 *** ''

'' Walker, 1903 **** '' Pettancyclus'' Iredale, 1943 ** tribe Plesiophysini Bequaert & Clench, 1939 *** '' Plesiophysa'' Fischer, 1883 - type genus of tribe Plesiophysini * subfamily Neoplanorbinae Hannibal, 1912 *** '' Neoplanorbis'' Pilsbry, 1906 - type genus of subfamily Neoplanorbinae * subfamily Rhodacmeinae Walker, 1917 *** '' Rhodacmea'' Walker, 1917 - type genus of subfamily Rhodacmeinae Subfamily = ? (other genera that are not yet sorted are listed here) * '' Acrorbis'' Odhner, 1937 * '' Africanogyrus'' Özdikmen & Darilmaz, 2007
- synonym: '' Afrogyrus'' Brown & Mandahl-Barth, 1973 * '' Afroplanorbis'' Thiele, 1931 * '' Amphigyra'' Pilsbry, 1906 * '' Anisopsis'' Sandberger, 1875 * '' Antillorbis'' Harry & Hubendick, 1964 * '' Armigerus'' Clessin, 1884 * '' Australorbis'' Pilsbry, 1934 * '' Bayardella'' Burch, 1977 * '' Berellaia'' Laubrière & Carez, 1880 * '' Camptoceras'' Benson, 1843 * '' Camptoceratops'' Wenz, 1923 * '' Carinifex'' Binney, 1865 * '' Carinogyraulis'' Polinski, 1929 * '' Ceratophallus'' Brown & Mandahl-Barth, 1973 * '' Choanomphalus'' Gerstfeldt, 1859 * '' Culmenella'' Clench, 1927Mollusc Specialist Group (1996)
''Culmenella rezvoji''
In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. . Downloaded on 08 March 2011. * '' Fossulorbis'' Pilsbry, 1934 * '' Glyptophysa'' Crosse, 1872 * '' Helicorbis'' Benson, 1855 * '' Helisoma'' Swainson, 1840 * '' Intha'' Annandale, 1922 * '' Isidorella'' Tate, 1896 * '' Kessneria'' Walker & Ponder, 2001 * '' Leichhardtia'' Walker, 1988 * '' Lentorbis'' Mandahl-Barth, 1954 * '' Macrophysa'' (Meek) Dall, 1870 * '' Paraplanorbis'' Hanna, 1922 * '' Patelloplanorbis'' Hubendick, 1957 * '' Pecosorbis'' Taylor, 1985 * '' Pentagoniostoma'' Branson, 1935 * '' Perrinilla'' Hannibal, 1912 * '' Physastra'' Tapparone-Canefri, 1883 * '' Physopsis'' Krauss, 1848 * '' Pingiella'' Baker, 1945 * '' Pitharella'' Edwards, 1860 * '' Planorbifex'' Pilsbry, 1935 * '' Planorbina'' Haldeman, 1842 * '' Platyphysa'' Fischer, 1883 * '' Platytaphius'' Pilsbry, 1924 * '' Polypylis'' Pilsbry, 1906 * '' Promenetus'' Baker, 1935 * '' Protancylus'' Sarasin & Sarasin, 1897 * '' Pygmanisus'' Iredale, 1943 * '' Segmentorbis'' Mandahl-Barth, 1954 * '' Sineancylus'' Gutiérrez Gregoric, 2014 * '' Syrioplanorbis'' Baker, 1945 * '' Trochorbis'' Benson, 1855 * '' Vorticifex'' Meek in Dall, 1870 The genus '' Camptoceratops'' Wenz, 1923 is no longer considered to be a planorbid. It was recognised by Curry (1965, p. 360) as a euthecosomatous pteropod (Heterobranchia) (note by Arie W. Janssen, 092507). The generic name ''Taphius'' Adams & Adams, 1855 is a synonym for ''

''.

Shell description

The shells of most species in this family are disk-like or button-like, being coiled in one plane, although several groups have shells that are more higher-spired, and some are limpet-like. All coiled shell Planorbidae are

sinistral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

in their shell coiling, as is proved by their internal anatomy (the respiratory and the genital orifice are situated on the left side), however the animals carry their shells with what would normally be the ventral (i.e. umbilical) surface uppermost, and because of this, the shells appear to be dextral. Indeed, formerly planorbids were thought to have dextral shells, and so species of this family were figured as if they had dextral shells. Although it is now understood that these species are sinistral in shell coiling, disk-like Planorbid shells are often still shown in illustrations oriented as if they were dextral. Most species of coiled planorbids have a rather thin and moderately smooth shell, although more distinct sculpture such as a keel occurs in, and is diagnostic of, certain species. In the flat, keeled species, the whorls tend to overlap. The

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An ...

has a sharp outer lip. A peristome can be present, but often the lip is not thickened nor reflected. Those planorbid species which have a high-spired shell may have a narrow Umbilicus (mollusc), umbilicus, but frequently this is covered by parietal callus, callus. In height most species vary between 6 mm and 6 cm, however, disk-like shells are usually less than about 2 cm in maximum dimension. Like all pulmonate aquatic snails, ramshorn shells do not have an Operculum (gastropod), operculum to close the shell aperture.

Sinistral shells

Flat-coiled planorbid

s are hard to understand in terms of their coiling and orientation. Many of the shells of species in this family are almost planispiral in coiling such that one side of the shell often looks rather like the other side, but it is important to bear in mind that nonetheless there is an Umbilicus (mollusc), umbilical side and a spire (mollusc), spire side of the shell. In addition these are in fact sinistral shells, despite the fact that the snail carries its shell as if it were a normal dextral shell. To make sense of the shell coiling, the following facts are useful: * In life, these pond snails hold their shells ''upside down'' compared to the normal gastropod shell orientation, with the umbilicus (mollusk), umbilicus facing upwards. * The spire (mollusc), spire of the shell is quite sunken in many species. In addition, it is carried facing downwards. * The umbilicus of the shell is very wide and shallow. * In some species the umbilicus is not as deeply "dished" as the sunken spire is, so superficially it can be hard to tell one from the other. However, once it is understood that the planorbid shell is sinistral, if the shell is held with the

on the left and facing the observer, then the sunken spire side of the shell is uppermost. This is a convenience for understanding the shell, but is the opposite of the way the shell is actually carried in life. The side of the shell which is in fact the spire (a sunken spire) faces ''down'' in the living animal, contrary to what is the case in almost all other shelled gastropods. Because the shell is carried "upside down" like this, the

of the shell is angled to face downwards also, so the aperture faces a little towards the spire, not away from it, as is usually the case in other shelled gastropods.

Habitat

Most species of planorbids live only in fresh water, such as ponds, lakes, and slow moving rivers. A minority of species are able to survive in brackish water.

Geological history

Ancestors of ramshorn snails are known with certainty since the Jurassic period. Modern taxa developed in the Jurassic.

Geographical distribution

Species in this family occur worldwide. In Northwest Europe about 20 species are known (including non-indigenous species). In this region, various extinct taxa are known to have occurred, starting in the Jurassic period.

References

* Gittenberger, E., Janssen, A.W., Kuijper, W.J., Kuiper, J.G.J., Meijer, T., Velde, G. van der & Vries, J.N. de (1998) ''De Nederlandse zoetwatermollusken. Recente en fossiele weekdieren uit zoet en brak water'' Nederlandse Fauna 2. Nationaal Natuurhistorisch Museum Naturalis, KNNV Uitgeverij & EIS-Nederland, Leiden, 288 pp. * Fischer, P.H. (1880-1887) ''Manuel de Conchyliologie et de Paléontologie conchyliologique ou histoire naturelle des Mollusques vivants et fossiles suivi d'un appendice sur les Brachiopodes par D. Oehlert.'' – XXIV + 1369 pp. * (German) Thiele, J. (1929-1935) ''Handbuch der Systematischen Weichtierkunde.'' Jena, (1), 1-376, 1929; (2), 377-778, 1931; 779-1022, 1934; 1023-1134, 1935. * Vaught, K.C. (1989) ''A classification of living mollusca.'' American Malacologists Inc., Melbourne USA, & 0-915826-22-6, 195 pp. * (German) Wenz, W. (1923-1930) ''Gastropoda extramarina tertiaria.'' Fossilium Catalogus I. (4 vols.), 3387 pp. * (German) Zilch, A. (1959-1960) ''Euthyneura.'' In: H. Schindewolf (ed.), Handbuch der Paläozoologie, 6(2): pp. I-XII + 1-834.

External links

*
NCBI Taxonomy Browser: Planorbidae
*
Systema naturae 2000 (classification) - Taxon: Planorbidae
*
ITIS: Planorbidae
* http://mkohl1.net/Planorbidae.html
Frank Collins Baker, ''The Molluscan Family Planorbidae'', The University of Illinois press, Urbana, 1945
{{taxonbar, from=Q1475666 Planorbidae, Gastropod families Taxa named by Constantine Samuel Rafinesque