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Helicidae

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Title: Helicidae  
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Subject: Chilostoma crombezi, Leptaxis simia, Helicigona lapicida, Helicigona trizona, Helix aperta
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Helicidae

Helicidae
Helix pomatia
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia

clade Euthyneura
clade Panpulmonata
clade Eupulmonata
clade Stylommatophora
informal group Sigmurethra

Superfamily: Helicoidea
Family: Helicidae
Rafinesque, 1815
Type genus
Helix
Subfamilies

Ariantinae
Helicinae

The Helicidae, sometimes known as the typical snails, are a taxonomic family of small to large, air-breathing, land snails. In other words, they are terrestrial pulmonate gastropod mollusks.

A number of species in this family are valued as food items, including Cornu aspersum (formerly Helix aspersa) the garden snail, and Helix pomatia the "escargot".[1] The biology of these two species in particular has been much studied.

Contents

  • Shell description 1
  • Anatomy 2
  • Distribution 3
  • Genera 4
  • References 5
  • External links 6

Shell description

The shells of these snails are mostly rather globular in shape. In some genera, such as Cepaea, the shells are brightly colored and patterned.

Anatomy

The animal is capable of complete retraction within the shell. The tail is without a mucous gland or projection.[2]

The mouth is always provided with a jaw, which is striate, ribbed, sulcate or plicate, sometimes composed of several imbricating pieces. The radula is composed of many transverse horizontal series of teeth, the centrals tricuspidate, about the size of the laterals, laterals bicuspid, or tricuspid with the interior cusp obsolete, marginals usually wider than high, short with two or three small cusps.[2]

In the soft parts the most obvious distinction is the lack of a caudal mucous pit, and their possessing a sculptured jaw. Typically, there is a distinction in the dentition, although in some species the lateral teeth take on a pseudozonitoid appearance; even in such cases the extreme marginals in Helix remain short and very obtuse.[2]

This family of snails is defined by the anatomical presence of a diverticulum. Some genera within this family create and use love darts as part of their mating behavior. These snails have one dart apparatus. The dart sac has no accessory sac, and contains two tubular glands, inserted at the base of the dart sac.

In this family, the number of haploid chromosomes lies between 21 and 30 (according to the values in this table).[3]

Helicid snails for sale as food in Italy; on the left Cepaea hortensis.

Distribution

The family is native to Eurasia and belongs the Western Palearctic group.

However some species, notably Cornu aspersum, have been introduced and become established in numerous different areas worldwide.

Many accidental introductions happen because the eggs of most Helicidae are laid in the soil, and they may thus easily travel unnoticed along with landscaping plants.

Genera

The family Helicidae contains 2 subfamilies (according taxonomy of the Gastropoda by Bouchet & Rocroi, 2005) and genera within the family Helicidae include (after Fauna Europaea[4] and Taxonomy Browser[5]):

Subfamily Helicinae Rafinesque, 1815 - In this subfamily the glands are divided. The love dart has four blades or vanes. There are two penial papillae.

  • Tribe Thebini Wenz, 1923 - The synonym Euparyphinae Perrot, 1939 has been declared an invalid name.
Theba Risso, 1826
Allognathus
Assyriella
Cantareus Risso, 1826
Cepaea Held, 1838
Codringtonia
Cornu Born, 1778
Eobania P. Hesse, 1913
Helix Linnaeus, 1758 - type genus
Hemicycla
Iberus
Idiomela T. Cockerell, 1921
Lampadia
Leptaxis
Levantina
Otala Schumacher, 1817
Pseudotachea
Tyrrhenaria
Macularia
Marmorana W. Hartmann, 1844 - This genus might actually belong to the subfamily Ariantinae and not to the subfamily Helicinae, as has been assumed until now.[6]
Tacheocampylaea
Tyrrheniberus

Subfamily Ariantinae Mörch, 1864 - in this subfamily the glands are divided or undivided. The love darts contain two to four blades. There is only one penial papilla.

Arianta Turton, 1831
Causa
Chilostoma Fitzinger, 1833
Cylindrus Fitzinger, 1833
Drobacia
Faustina
Helicigona A. Férussac, 1821
Isognomostoma Fitzinger, 1833
Vidovicia

References

  1. ^ M.P. Kerney & R.A.D. Cameron. 1979. A field guide to the land snails of Britain and northwestern Europe. Collins, London.
  2. ^ a b c Tryon G. W. 1887 Manual of conchology; structural and systematic. With illustrations of the species. Second series: Pulmonata. Volume 3. Helicidae - Volume I. page 3-4.
  3. ^ Barker G. M.: Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology. in Barker G. M. (ed.): The biology of terrestrial molluscs. CABI Publishing, Oxon, UK, 2001, ISBN 0-85199-318-4. 1-146, cited pages: 139 and 142.
  4. ^ Fauna Europaea
  5. ^ Taxonomy Browser
  6. ^ Nordsieck H. (2006). Higher classification of Helicoidea and the molecular analyses of their phylogeny. hnords.de, Accessed 20/06/12

External links

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