Planorbidae,

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

the ramshorn snails or ram's horn snails, is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of air-breathing

freshwater snail Freshwater snails are gastropod mollusks that live in fresh 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 t ...

s, aquatic

pulmonate Pulmonata or pulmonates is an informal group (previously an order, and before that, a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group inclu ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

molluscs Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

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

hemoglobin Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transportation of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the sole exception of the fish family Channichthyidae. Hemoglobin ...

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 a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

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 reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of ...

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 euth ...

, planorbids do not have

gill A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

s, but instead, have a

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

. 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. Spire ...

as is the case in most

gastropod shell The gastropod shell is part of the body of many gastropods, including snails, 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 ...

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.

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 Limpets are a group of aquatic snails with a conical gastropod shell, shell shape (patelliform) and a strong, muscular foot. This general category of conical shell is known as "patelliform" (dish-shaped). Existing within the class Gastropoda, ...

-like. All coiled shell Planorbidae are sinistral 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. Planorbids were once 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. Nearly all shells are composed of growth lines. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

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, but frequently this is covered by

callus A callus (: calluses) is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, b ...

. 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 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 umbilical side and a

side of the shell. The shells of planorbids are sinistral on close inspection, despite the fact that most species carry the shell as if it were a normal dextral shell. 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 towards the spire, not away from it. and the umbilicus faces upwards. The

of the shell is quite sunken in many species. The umbilicus of the shell is very wide and shallow, and faces upwards. In some species the umbilicus is not as deeply "dished" as the sunken spire, so it may be hard to tell one from the other without close inspection.

Distribution and habitat

Species in this family occur worldwide. Most species of planorbids live only in fresh water, such as ponds, lakes, and slow moving rivers. However, some species are known to tolerate conditions such as brackish water or sewage.

Geological history

Ancestors of ramshorn snails are known with certainty since the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

period, but there are a few possible earlier occurrences starting in the Late

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Taxonomy

The following genera are recognised in the family Planorbidae: * Subfamily Ancylinae Rafinesque, 1815 ** Genus †'' Ancylina'' Bandel & F. Riedel, 1994 ** ''Genus'' †'' Palaeancylus'' Yen, 1948 ** Tribe Ancylini Rafinesque, 1815 *** Genus '' Ancylus'' O. F. Müller, 1773 *** Genus '' Ferrissia'' B. Walker, 1903 *** Genus '' Pettancylus'' Iredale, 1943 *** Genus '' Rhodacmea'' B. Walker, 1917 *** Genus '' Stimulator'' Iredale, 1944 **Tribe Laevapicini Hannibal, 1912 *** Genus '' Anisancylus'' Pilsbry, 1924 *** Genus '' Gundlachia'' L. Pfeiffer, 1849 *** Genus '' Hebetancylus'' Pilsbry, 1914 *** Genus '' Laevapex'' B. Walker, 1903 *** Genus '' Sineancylus'' Gutiérrez Gregoric, 2014 *** Genus '' Uncancylus'' Pilsbry, 1914 * Subfamily Miratestinae P. Sarasin & F. Sarasin, 1897 ** Genus '' Amerianna'' Strand, 1928 ** Genus '' Ancylastrum'' Bourguignat, 1853 ** Genus '' Bayardella'' J. B. Burch, 1977 ** Genus '' Glyptophysa'' Crosse, 1872 ** Genus '' Isidorella'' Tate, 1896 ** Genus '' Kessneria'' J. C. Walker & Ponder, 2001 ** Genus '' Leichhardtia'' J. C. Walker, 1988 ** Genus '' Miratesta'' P. Sarasin & F. Sarasin, 1897 ** Genus '' Patelloplanorbis'' Hubendick, 1957 ** Genus '' Protancylus'' P. Sarasin & F. Sarasin, 1897 * Subfamily Planorbinae Rafinesque, 1815 ** Tribe Camptoceratini Dall, 1870 *** Genus '' Camptoceras'' W. H. Benson, 1843 *** Genus '' Culmenella'' Clench, 1927 ** Tribe Coretini J. E. Gray, 1847 *** Genus '' Planorbarius'' Duméril, 1805 ** Tribe Drepanotrematini Zilch, 1959 *** Genus '' Antillorbis'' H. W. Harry & Hubendick, 1964 *** Genus '' Drepanotrema'' P. Fischer & Crosse, 1880 ** Tribe Helisomatini F. C. Baker, 1928 *** Genus '' Acrorbis'' Odhner, 1937 *** Genus '' Biomphalaria'' Preston, 1910 *** Genus '' Dilatata'' Clessin, 1884 *** Genus '' Helisoma'' Swainson, 1840 *** Genus '' Menetus'' H. Adams & A. Adams, 1855 *** Genus '' Pecosorbis'' D. W. Taylor, 1985 *** Genus '' Planorbella'' Haldeman, 1843 *** Genus '' Planorbula'' Haldeman, 1840 *** Genus '' Promenetus'' F. C. Baker, 1935 *** Genus '' Vorticifex'' Meek, 1870 ** Tribe Neoplanorbini Hannibal, 1912 *** Genus '' Amphigyra'' Pilsbry, 1906 *** Genus '' Neoplanorbis'' Pilsbry, 1906 *** Genus †'' Payettia'' Dall, 1924 ** Tribe Planorbini Rafinesque, 1815 *** Genus '' Afrogyrorbis'' Starobogatov, 1967 *** Genus '' Anisus'' S. Studer, 1820 *** Genus ''

Armiger In heraldry, an armiger is a (natural or juridical) 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 armig ...

'' Hartmann, 1843 *** Genus '' Bathyomphalus'' Charpentier, 1837 *** Genus '' Choanomphalus'' Gerstfeldt, 1859 *** Genus '' Gyraulus'' Charpentier, 1837 *** Genus '' Hovorbis'' D. S. Brown & Mandahl-Barth, 1973 *** Genus †'' Orygoceras'' Brusina, 1882 *** Genus '' Planorbis'' O. F. Müller, 1773 ** Tribe Segmentinini F. C. Baker, 1945 *** Genus '' Helicorbis'' W. H. Benson, 1855 *** Genus '' Hippeutis'' Charpentier, 1837 *** Genus '' Intha'' Annandale, 1922 *** Genus '' Kolhymorbis'' Starobogatov & Streletzkaja, 1967 *** Genus '' Lentorbis'' Mandahl-Barth, 1954 *** Genus '' Polypylis'' Pilsbry, 1906 *** Genus '' Segmentina'' J. Fleming, 1818 *** Genus '' Segmentorbis'' Mandahl-Barth, 1954 *** Genus '' Trochorbis'' W. H. Benson, 1855 Planorbidae ''incertae sedis'': * Genus †'' Ampullariella'' Raspail, 1909 * Genus †'' Archaeoplanorbis'' W. Yu, 1982 * Genus †'' Atopippeutis'' Kadolsky, 2015 * Genus †'' Bicarinopsis'' H.-Z. Pan, 1979 * Genus †'' Brannerillus'' Hannibal, 1912 * Genus †'' Fuchsogyra'' Bandel, 2010 * Genus †'' Graptophysa'' Yen & Reeside, 1946 * Genus †'' Headonia'' Harzhauser & Neubauer, 2020 * Genus †'' Idahoella'' Yen, 1948 * Genus †'' Jiangyouspira'' H.-Z. Pan, 1984 * Genus †'' Liangulorbis'' Wenz, 1947 * Genus †'' Marinescugyra'' Bandel, 2010 * Genus †'' Mioplatytaphius'' Čtyroký, 1972 * Genus †'' Nihewanspira'' S.-Y. Guo, 1983 * Genus †'' Omalodiscus'' W. H. Benson, 1855 * Genus †'' Paraplanorbis'' G. D. Hanna, 1922 * Genus †'' Pentagoniostoma'' C. C. Branson, 1935 * Genus †'' Physoides'' H.-Z. Pan, 1982 * Genus †'' Planorbifex'' Pilsbry, 1935 * Genus †'' Pompholopsis'' Call, 1888 * Genus †'' Proplanorbarius'' Bandel, 1991 * Genus †'' Proplanorbis'' Starobogatov, 1967 * Genus †'' Pseudophysa'' Yen, 1938 * Genus †'' Rostroapertura'' Firby, 1963 * Genus †'' Sinoplanorbis'' W. Yü, 1965 * Genus †'' Sinosegmentina'' Y.-T. Li, 1986 * Genus †'' Steklovidiscus'' Gozhik & Prysjazhnjuk, 1980

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
{{Authority control Gastropod families Taxa named by Constantine Samuel Rafinesque