Basommatophora

Horn snail

The water snails ( Basommatophora ), more water snails in the broader sense ( Pulmonata ) apply traditional subordination of the lung worm. They are found in freshwater and in the marine environment. You have trained a lung, but partly used either air or water for respiration.

Several recent studies have shown that water snails in the broader sense not a natural taxon are, but represent a paraphyletic group because they do not contain all the descendants of their last common ancestor. They are therefore referred to as a group or systematic representations written in quotation marks (" Basommatophora ", " water snails in the broader sense "). However, all genuine indigenous representatives belong to a monophyletic subgroup, the Hygrophila (water snails in the narrow sense or freshwater snails; see scheme ).

Features

This subordination of predominantly air-breathing snails, is characterized by a pair of sensors, the eyes are at their base. Hence the name Basommatophora, from Greek βάσις ( base ) = basis, ὄμμα ( omma ) = eye and φέρω ( phero ) = I wear. Some forms take the oxygen on the surface of the body on or over the body surface and " lungs ". They have no family except the Amphibolidae dish lid (operculum ). The cases vary from trocho - up planispiral. Also cup-shaped housing come before ( Siphonariidae, Teichnapfschnecken, some dish snails).

Habitat and Distribution

The water snails i.w.S. occur worldwide. On the one hand live in fresh water (especially the Hygrophila ), on the other hand, in the littoral of the seas. In Central Europe, four families are found, all of which are also among the Hygrophila: mud snails ( Lymnaeidae ) Teichnapfschnecken ( Acroloxidae ), plate screw ( Planorbidae ) and bladder snails ( Physidae ). Those species that were previously managed as an independent family " Ancylidae ", are now found predominantly to the plate screws.

The representatives of the Siphonariidae have secondarily colonized the sea. Amphibola crenata ( Gmelin, 1791) lives in the splash area of the intertidal zone or in the march area; they can be described as semi terrestrial living species and can even during long dry periods buried in mud to survive.

System

The systematic allocation of the individual families and genera is still in flux and stabilizes slowly. The following list follows Jeffrey (2001) and in particular that of Bouchet & Rocroi (2005) made ​​subdivision of the " water snails in a broader sense " in six superfamilies and nine families, of which a family is only described fossil. This provisional wholesale division is also largely consistent with recent molecular genetic findings.

This clear separation and classification of the superfamily of " Amphiboloidea " and the " Siphonarioidea " in monophyletic taxa is not yet possible, which is why they are placed temporarily from the Hygrophila. Recently a division into three families is proposed for the family of Amphibolidae that Amphibolidae that Phallomedusidae and Maningrididae. However, this must be regarded as provisional, as not all genera and species could be assigned, therefore, the following compilation of this splitting apart.

The Classification of the † Acroreiidae will probably remain inherently insecure due to the characteristic poverty of preserved fossils, as long as not much better fossils are known.

• Group " Basommatophora " ( " water snails in the broader sense " )

A) the following two superfamilies are provisionally classified here and possibly paraphyletic or polyphyletic groups represent

• 1 superfamily Amphiboloidea Gray, 1840 Family Amphibolidae Gray, 1840; spiral shells, brackish water of the southern hemisphere

• Family Siphonariidae Gray, 1840; cup-shaped, intertidal zone of warm seas
• † family Acroreiidae Cossmann, 1893; cup-shaped, only fossil ( Cretaceous and Paleogene )

B) The following four superfamilies form the monophyletic taxon Hygrophila

• Hygrophila A. Ferussac, 1822 ( water snails in the narrow sense, freshwater snails ) 3 superfamily Chilinoidea Dall, 1870 Family Chilinidae Dall, 1870; only South America
• Family Latiidae Hutton, 1882; only New Zealand

• Family Acroloxidae Thiele, 1931; cup-

• Family Lymnaeidae Rafinesque, 1815

• Family Planorbidae Rafinesque; z.T. cup-shaped ( formerly known as " Ancylidae " summarized )
• Family Physidae Fitzinger, 1833

Bouchet & Rocroi (2005) refrain in their classification on category labels at the top of the superfamily and leave open how the Hygrophila are classified. The Hygrophila are but according to taxonomic usage most likely a partial order ( Infraordo ) equated. In the English literature, the Hygrophila are also referred to as "Higher Basommatophora ".