Planorbidae

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Planorbidae
Indoplanorbis exustus.jpg
A live individual of Indoplanorbis exustus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Superorder: Hygrophila
Superfamily: Lymnaeoidea
Family: Planorbidae
Rafinesque, 1815 [1]
Genera

See text

Diversity [2]
About 250 freshwater species

Planorbidae, common name the ramshorn snails or ram's horn snails, is a family of air-breathing freshwater snails, aquatic pulmonate gastropod molluscs. Unlike most molluscs, the blood of ram's horn snails contains iron-based hemoglobin instead of copper-based hemocyanin. [3] As a result, planorbids are able to breathe oxygen more efficiently than other molluscs. The presence of hemoglobin gives the body a reddish colour. This is especially apparent in albino animals.

Being air breathers like other Panpulmonata , planorbids do not have gills, but instead, have a lung. 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 as is the case in most gastropod shells. 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 family Planorbidae. This is certainly the case with the freshwater limpets Ferrissia , and Ancylus . Both of these genera have sometimes been assigned to the family Lymnaeidae. 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), 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

Albino planorbid clearly shows the reddish-colored body tissues due to the pigment hemoglobin Lymnea-snail.JPG
Albino planorbid clearly shows the reddish-colored body tissues due to the pigment hemoglobin

According to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), this family consists of the following subfamilies:

2007 taxonomy for part of the family

Albrecht et al. (2007) [4] 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) [4]

Tribus Bulinini

Tribus Ancylini Rafinesque-Schmaltz, 1815

"B-clade" sensu Albrecht et al., (2007) [4]

Tribus Camptoceratini

Tribus Planorbini

Tribus Segmentinini

"C-Clade" sensu Albrecht et al., (2007) [4]

Cladogram

The following is a cladogram that shows the phylogenic relationships within the Planorbidae according to Albrecht 2007: [4]

Genera

The type genus 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): [5]

View of the sunken spire of the shell of Anisus septemgyratus Anisus septegyrus1pl.jpg
View of the sunken spire of the shell of Anisus septemgyratus

Subfamily = ? (other genera that are not yet sorted are listed here)

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 Biomphalaria . [6]

Shell description

Apical, apertural and umbilical view of the shell of Biomphalaria tenagophila. Scale bar is 3 mm. Biomphalaria tenagophila shell.png
Apical, apertural and umbilical view of the shell of Biomphalaria tenagophila . Scale bar is 3 mm.

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 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 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.

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

Planorbarius corneus. View of the sunken spire (held facing downwards in life) Planorbarius corneus top.jpg
Planorbarius corneus . View of the sunken spire (held facing downwards in life)
Planorbarius corneus. View of the umbilicus (held uppermost in life) Planorbarius corneus bottom.jpg
Planorbarius corneus . View of the umbilicus (held uppermost in life)

Flat-coiled planorbid gastropod shells 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 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:

However, once it is understood that the planorbid shell is sinistral, if the shell is held with the aperture 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 aperture 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.[ citation needed ]

Geological history

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

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.[ citation needed ]

Related Research Articles

<i>Biomphalaria</i> Genus of freshwater snails

Biomphalaria is a genus of air-breathing freshwater snails, aquatic pulmonates belonging to the family Planorbidae, the ram's horn snails and their allies.

<span class="mw-page-title-main">Volutidae</span> Family of sea snails

Volutidae, common name volutes, are a taxonomic family of predatory sea snails that range in size from 9 mm to over 500 mm. They are marine gastropod mollusks. Most of the species have no operculum.

<span class="mw-page-title-main">Buccinidae</span> Family of large sea snails

The Buccinidae are a very large and diverse taxonomic family of large sea snails, often known as whelks or true whelks.

<span class="mw-page-title-main">Gastropod shell</span> Part of the body of a gastropod or snail

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 gastropods appear shell-less (slugs) but may have a remnant within the mantle, or in some cases the shell is reduced such that the body cannot be retracted within it (semi-slug). Some snails also possess an operculum that seals the opening of the shell, known as the aperture, which provides further protection. The study of mollusc shells is known as conchology. The biological study of gastropods, and other molluscs in general, is malacology. Shell morphology terms vary by species group.

<span class="mw-page-title-main">Physidae</span> Family of molluscs

Physidae, commonly called the bladder snails, is a family of small air-breathing freshwater snails, aquatic pulmonate gastropod molluscs in the superfamily Lymnaeoidea.

<i>Euhadra</i> Genus of gastropods

Euhadra is a genus of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the subfamily Bradybaeninae of the family Camaenidae.

<span class="mw-page-title-main">Ancylini</span> Tribe of gastropods

Ancylini is a tribe of small, freshwater, air-breathing limpets, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails and their allies. This tribe used to be treated as a family; the current taxonomic placement within Planorbidae is according to the taxonomy of the Gastropoda.

Africanogyrus is a genus of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails and their allies.

<i>Lanistes</i> Genus of gastropods

Lanistes is a genus of freshwater snails which have a gill and an operculum, aquatic gastropod mollusks in the family Ampullariidae, the apple snails.

Miratesta celebensis is a species of freshwater air-breathing snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids. Like all other planorbids it has a sinistral or left-coiling shell.

Miratesta is a genus of freshwater air-breathing 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.

†Neoplanorbis carinatus was a species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails.

<i>Neoplanorbis</i> Genus of gastropods

Neoplanorbis is a genus of small, freshwater, air-breathing snails. They are aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails.

†Neoplanorbis smithi was a species of small freshwater snail, an aquatic gastropod mollusk in the family Planorbidae, the ramshorn snails. This species was endemic to the United States; it is now extinct. The shells of this species appear to be dextral in coiling, but as is the case in all planorbids, the shell is actually sinistral. In life the shell was carried upside down with the aperture on the right, and this makes it appear to be dextral.

<i>Neoplanorbis tantillus</i> Species of gastropod

Neoplanorbis tantillus is a species of very small air-breathing freshwater snail, an aquatic gastropod mollusk in the family Planorbidae, the ram's horn snails. This species is endemic to the United States. In 2012, it has been declared extinct by the IUCN Red List of Threatened Species.

<i>Planorbarius</i> Genus of gastropods

Planorbarius is a genus of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Planorbidae, the ram's horn snails, or planorbids, which all have sinistral or left-coiling shells.

<i>Biomphalaria tenagophila</i> Species of gastropod

Biomphalaria tenagophila is a species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails.

<i>Biomphalaria peregrina</i> Species of gastropod

Biomphalaria peregrina is a species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusk in the family Planorbidae, the ram's horn snails.

<i>Choanomphalus</i> Genus of molluscs

Choanomphalus 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.

<span class="mw-page-title-main">Lymnaeoidea</span> Superfamily of gastropods

Lymnaeoidea, commonly known as pond snails, is a taxonomic superfamily of air-breathing freshwater snails that belong to the superorder Hygrophila.

References

  1. ↑ Rafinesque C. S. 1815. Analyse de la Nature ou tableau de l'univers et des corps organisés. Palermo, 223 pp., page 143.
  2. ↑ Strong E. E., Gargominy O., Ponder W. F. & Bouchet P. (2008). "Global Diversity of Gastropods (Gastropoda; Mollusca) in Freshwater". Hydrobiologia 595: 149-166. hdl: 10088/7390 doi:10.1007/s10750-007-9012-6.
  3. ↑ Lieb, Bernhard; et al. (8 August 2006). "Red blood with blue-blood ancestry: Intriguing structure of a snail hemoglobin". Proceedings of the National Academy of Sciences of the United States of America . 103 (32): 12011–12016. Bibcode:2006PNAS..10312011L. doi: 10.1073/pnas.0601861103 . PMC   1567689 . PMID   16877545. We present here the complete cDNA and predicted amino acid sequence of two hemoglobin polypeptides from the planorbid Biomphalaria glabrata...Moreover, we identified a previously undescribed rosette-like hemolymph protein that has been mistaken for hemoglobin. We also detected expression of an incomplete hemocyanin as trace component. The combined data show that B. glabrata hemoglobin evolved from pulmonate myoglobin, possibly to replace a less-efficient hemocyanin, and reveals a surprisingly simple evolutionary mechanism to create a high molecular mass respiratory protein from 78 similar globin domains.
  4. 1 2 3 4 5 Albrecht C., Kuhn K. & Streit B. (2007). "A molecular phylogeny of Planorboidea (Gastropoda, Pulmonata): insights from enhanced taxon sampling". Zoologica Scripta 36: 27-39. doi : 10.1111/j.1463-6409.2006.00258.x.
  5. ↑ (in German) Glöer P. 2002. Die Süßwassergastropoden Nord- und Mitteleuropas. Die Tierwelt Deutschlands, ConchBooks, Hackenheim, 326 pp., ISBN   3-925919-60-0, page 19-20.
  6. 1 2 3 4 5 6 7 8 9 10 11 12 13 Bouchet, Philippe; Rocroi, Jean-Pierre; Frýda, Jiri; Hausdorf, Bernard; Ponder, Winston; Valdés, Ángel & Warén, Anders (2005). "Classification and nomenclator of gastropod families". Malacologia . 47 (1–2). Hackenheim, Germany: ConchBooks: 1–397. ISBN   3-925919-72-4. ISSN   0076-2997.
  7. ↑ Starobogatov, Y. I. (1967). On the systematization of freshwater pulmonate molluscs. Trudy Zoologicheskogo Instituta, Leningrad, 42, 280–304.
  8. ↑ Liu L et al. (2010) "The phylogeography of Indoplanorbis exustus (Gastropoda: Planorbidae) in Asia". Parasites & Vectors 3: 57. doi : 10.1186/1756-3305-3-57.
  9. ↑ Mollusc Specialist Group (1996). Culmenella rezvoji. In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. <www.iucnredlist.org>. Downloaded on 08 March 2011.
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