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Trochidae
Trochidae

The Trochidae, common name top-snails or top-shells, are a taxonomic family of very small to large sea snails, marine gastropod molluscs in the clade Vetigastropoda (according to the taxonomy of the Gastropoda by Bouchet & Rocroi from 2005).

This family is commonly known as the "top-snails" because in many species the shell resembles a toy spinning top.

Anatomy


The animal is similar in general form to the Turbinidae. The top snails are characterized by some primitive traits: a heart with two atria. They have retained only one kidney and the second osphradium has been lost in the course of evolution. The mantle cavity contains a single gill.

Along the side of the foot are three or more pairs of sensory epipodial tentacles. The head has a short, broad rostrum. The intertentacular lobes are simple or digitated, separate or united across the front, sometimes obsolete. The jaws are developed or absent.[2]

The radula is rhipidoglossate. The rhachidian teeth are always present and well-developed. The lateral teeth generally number 5 on each side, sometimes more numerous. The marginal teeth are narrow and very numerous.

Description


The length of an adult shell varies between 5 mm and 130 mm. There is also a wide variation in the shape of the shell. This goes from low auriform (ear-shaped) with a wide aperture to the long, slender conical forms of typical top shells. The shape may also be subglobose, turbinate or helicoid. Their height may vary between 3 mm and 152 mm. The shell contains only a few whorls. These have a highly variable exterior, ranging from smooth or glossy to sculptured.

The internal shell is nacreous. They have a brown, entirely corneous, circular, multispiral operculum which fits the aperture snugly. The operculum is formed of numerous gradually increasing whorls with a central nucleus. The aperture may be entire, tetragonal or rounded and has no reflected lip. The peristome is generally not continuous.

These shells are often brightly colored and adorned with darker bands.

The Trochidae differ from the Turbinidae in having a corneous, never calcareous, operculum, which is always multispiral.[2]

Habitat


Most species in the family live either in the intertidal zone or in the shallow subtidal zone, but some live in deeper water. They are usually abundant on solid, suitable substrates, like rocky shores and reefs.[3]

Distribution


This family has a worldwide distribution in tropical, temperate and arctic waters. Members of this family are among the most common marine snails along the rocky shores of Europe.

Ecology


The Trochidae are dioecious, and the fertilization occurs externally by the release of eggs and sperm.[3] Top snail eggs are laid individually or in gelatinous egg masses in the water. Individuals may hatch as free-swimming planktonic larvae or juvenile crawlers with a short swimming stage.[3]

This family of snails consists of herbivores, grazing with their radulae on rocky surfaces, feeding on algae and vegetable detritus, and more rarely by filter-feeding, as observed in the genus Umbonium.[3]

Taxonomy


This family consists of six following subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005):

  • Trochinae Rafinesque, 1815 tribe Trochini Rafinesque, 1815 - synonym: Pyramidinae Gray, 1847 tribe Cantharidini Gray, 1857 tribe Monodontini Gray, 1857 - synonym: Gibbulinae Stoliczka, 1868
  • Halistilynae Keen, 1958
  • Lirulariinae Hickman & McLean, 1990
  • Margaritinae Thiele, 1924 tribe Margaritini Thiele, 1924 - synonym: Margaritinae Stoliczka, 1868 (inv.) tribe Gazini Hickman & McLean, 1990 tribe Kaiparathinini Marshall, 1993
  • Stomatellinae Gray, 1840 - synonyms: Stomatiidae Carpenter, 1861, Stomatellidae Gray, 1840
  • Umboniinae H. Adams & A. Adams, 1854 (1840) tribe Umboniini H. Adams & A. Adams, 1854 (1840) - synonym: Rotellinae Swainson, 1840 tribe Bankiviini Hickman & McLean, 1990 tribe Isandini Hickman, 2003 tribe Talopiini Finlay, 1928 - synonym: Monileini Hickman & McLean, 1990

The family Trochidae was redefined according to Williams et al. (2008).[4] The tribes from Trochinae were raised to subfamilies,[4] Margaritinae was moved to the family Turbinidae,[4] and Halistylinae provisionally stays in Trochidae.[4]

  • Trochinae Rafinesque, 1815
  • Cantharidinae Gray, 1857
  • Monodontinae Gray, 1857
  • Halistylinae Keen, 1958
  • Lirulariinae Hickman & McLean, 1990
  • Stomatellinae Gray, 1840
  • Umboniinae H. Adams & A. Adams, 1854 (1840) - tribes of Umboniinae are retained the same as in taxonomy of the Gastropoda by Bouchet & Rocroi (2005) tribe Umboniini H. Adams & A. Adams, 1854 (1840) - synonym: Rotellinae Swainson, 1840 tribe Bankiviini Hickman & McLean, 1990 tribe Isandini Hickman, 2003 tribe Talopiini Finlay, 1928 - synonym: Monileini Hickman & McLean, 1990

Williams et al. (2010)[1] added three new subfamilies to Trochidae : Alcyninae, Fossarininae and Chrysostomatinae. The subfamily Lirulariinae is now incorporated within the subfamily Umboniinae. In this study was also shown that the subfamily Margaritinae is not monophyletic. Here is also shown, which genera were placed into these three new subfamilies:[1]

  • subfamily Alcyninae Williams, Donald, Spencer & Nakano, 2010 - only one genus Alcyna
  • subfamily Trochinae Rafinesque, 1815
  • subfamily Monodontinae Gray, 1857
  • subfamily Fossarininae Bandel, 2009
  • subfamily Chrysostomatinae Williams, Donald, Spencer & Nakano, 2010 genus Chrysostoma genus Chlorodiloma
  • subfamily Umboniinae H. Adams & A. Adams, 1854 (1840) - synonym: Lirulariinae Hickman & McLean, 1990
  • subfamily Stomatellinae Gray, 1840
  • subfamily Cantharidinae Gray, 1857
  • subfamily Halistylinae Keen, 1958

Genera


Genera within the family Trochidae include:

  • Alcyna A. Adams, 1860 - type genus of the subfamily Alcyninae, it is also the only genus in this subfamily
  • Aphanotrochus Martens, 1880: synonym of Priotrochus P. Fischer, 1879
  • Caragolus Monterosato, 1884: synonym of Phorcus Risso, 1826
  • Elenchus Swainson, 1840: synonym of Cantharidus Montfort, 1810
  • Gibbulastra Monterosato, 1884: synonym of Gibbula Risso, 1826
  • Korenia Friele, 1877: synonym of Gibbula Risso, 1826
  • Limax Martyn, 1784: synonym of Cantharidus Montfort, 1810
  • Mawhero Marshall, 1998: synonym of Cantharidus Montfort, 1810
  • Micrelenchus Finlay, 1926: synonym of Cantharidus Montfort, 1810
  • Osilinus Philippi, 1847:[15] synonym of Phorcus Risso, 1826
  • Phorculus Cossmann, 1888: synonym of Gibbula Risso, 1826
  • Plumbelenchus Finlay, 1926: synonym of Cantharidus Montfort, 1810
  • Scrobiculinus Monterosato, 1889: synonym of Gibbula Risso, 1826
  • Steromphala Gray, 1847: synonym of Gibbula Risso, 1826
  • Strigosella Sacco, 1896: synonym of Gibbula Risso, 1826
  • Trochocochlea Mörch, 1852: synonym of Phorcus Risso, 1826
  • Latona Hutton, 1884: synonym of Chlorodiloma Pilsbry, 1889
  • Minos Hutton, 1884: synonym of Fossarina A. Adams & Angas, 1864
  • Botellus Iredale, 1924: synonym of Botelloides Strand, 1928
  • Anisodiloma Finlay, 1926: synonym of Diloma Philippi, 1845
  • Cavodiloma Finlay, 1926: synonym of Diloma Philippi, 1845
  • Fractarmilla Finlay, 1926: synonym of Diloma Philippi, 1845
  • Melagraphia Gray, 1847: synonym of Diloma Philippi, 1845
  • Neodiloma P. Fischer, 1885: synonym of Diloma Philippi, 1845
  • Neomonodonta Kuroda & Habe, 1971: synonym of Monodonta Lamarck, 1799
  • Zediloma Finlay, 1926: synonym of Diloma Philippi, 1845
  • Gena Gray, 1840:[22] synonym of Stomatella Lamarck, 1816
  • Plocamotis P. Fischer, 1885: synonym of Stomatella Lamarck, 1816
  • Stomax Montfort, 1810: synonym of Stomatia Helbling, 1779
  • Camelotrochus B. A. Marshall, 1998: synonym of Trochus (Camelotrochus) B. A. Marshall, 1998 represented as Trochus Linnaeus, 1758
  • Carinidea Swainson, 1840: synonym of Infundibulum Montfort, 1810
  • Clangulus Blainville, 1817: synonym of Clanculus Montfort, 1810
  • Colliculus Monterosato, 1888: synonym of Gibbula Risso, 1826
  • Fragella Swainson, 1840: synonym of Clanculus Montfort, 1810
  • Infundibulops Pilsbry, 1889: synonym of Trochus (Infundibulops) Pilsbry, 1889 represented as Trochus Linnaeus, 1758
  • Lamprostoma Swainson, 1840: synonym of Trochus Linnaeus, 1758
  • Otavia Risso, 1826: synonym of Clanculus Montfort, 1810
  • Polydonta Schumacher, 1817: synonym of Trochus Linnaeus, 1758
  • Thorista Iredale, 1915: synonym of Coelotrochus P. Fischer, 1879
  • Thoristella Iredale, 1915: synonym of Coelotrochus P. Fischer, 1879

Umboniinae H. Adams & A. Adams, 1854 - synonyms: Lirulariinae, tribe Bankiviini, tribe Isandini, tribe Talopiini and tribe Umboniini.

Main characteristics: eyes pedunculate; left tentacle attached to a frontal appendage; mantle reflected over the edge of the aperture; radula: six lateral teeth on each side; the shel is polished; the peristome is incomplete; the umbilicus is generally closed by a callosity [24]

  • Globulus Schumacher, 1817: synonym of Umbonium Link, 1807
  • Liotrochus Fischer, 1878: synonym of Ethalia H. Adams & A. Adams, 1854
  • Monilia: synonym of Monilea Swainson, 1840
  • Rotella Lamarck, 1822: synonym of Umbonium Link, 1807
  • Solanderia P. Fischer, 1879: synonym of Rossiteria Brazier, 1895
  • Suchium Makiyama, 1924: synonym of Umbonium Link, 1807

Other genera within the family Trochidae include:[35][36][37]

Unassigned


  • Intortia Egorova, 1972: synonym of Lissotesta Iredale, 1915
  • Umbotrochus Thiele, 1924: synonym of Callumbonella Thiele, 1924
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