The Trochidae,

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 ...

top-snails or top-shells, are 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 various sized

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

s, marine

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 ...

mollusc 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 ...

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

Taxonomy

The family Trochidae consists of the following subfamilies: * Alcyninae Williams, Donald, Spencer & Nakano, 2010 *

Cantharidinae The Cantharidinae are a Taxonomy (biology), taxonomic subfamily (biology), subfamily of very small to large sea snails, Marine (ocean), marine gastropod molluscs in the family Trochidae, common name top snails.Bouchet, P.; Gofas, S. (2011). Canth ...

Gray, 1857 * Carinotrochinae S.-Q. Zhang, J. Zhang & S.-P. Zhang, 2020 * Chrysostomatinae Williams, Donald, Spencer & Nakano, 2010 * Fossarininae Bandel, 2009 * Halistylinae Keen, 1958 * Kaiparathininae B. A. Marshall, 1993 * Monodontinae Gray, 1857 * Stomatellinae Gray, 1840 * Trochinae Rafinesque, 1815 *

Umboniinae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. This family is commonly known as the top-snails because in many species the shell resembles ...

H. Adams & A. Adams, 1854 (1840) Additionally, the following genera have not yet been placed in any subfamily: * '' Callumbonella'' Thiele, 1924 * †'' Coeloconulus'' Nützel, 2012 * ''

Enida ''Enida'' is a genus of sea snails, marine gastropod mollusks in the family Trochidae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. T ...

'' A. Adams, 1860 * †'' Eocalliostoma'' O. Haas, 1953 * †'' Fagnastesia'' S. N. Nielsen, Frassinetti & Bandel, 2004 * †'' Falsotectus'' Gründel, Keupp & Lang, 2017 * †'' Guidonia'' De Stefani, 1880 * †'' Lithotrochus'' Conrad, 1855 * †'' Tylotrochus'' Koken, 1896

Description

Shell

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

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

d. 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. Species of the family Trochidae differ from those in the family Turbinidae in having a corneous, never calcareous, operculum, which is always multispiral.Tryon (1889), Manual of Conchology XI, Academy of Natural Sciences, Philadelphia
/ref>

Internal 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 In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...

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. 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.

Distribution and habitat

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. 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.Poutiers, J. M. (1998). Gastropods in: FAO Species Identification Guide for Fishery Purposes: The living marine resources of the Western Central Pacific Volume 1. Seaweeds, corals, bivalves and gastropods. Rome, FAO, 1998. page 399.

Ecology

Life cycle

Species of the family Trochidae are dioecious, and the

fertilization Fertilisation or fertilization (see American and British English spelling differences#-ise, -ize (-isation, -ization), spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give ...

occurs externally by the release of eggs and sperm. 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.

Feeding behavior

This family of snails consists of

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s, grazing with their radulae on rocky surfaces, feeding on

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and vegetable detritus, and more rarely by filter-feeding, as observed in the genus '' Umbonium''.

References

* Williams S.T., Donald K.M., Spencer H.G. & Nakano T. (2010) ''Molecular systematics of the marine gastropod families Trochidae and Calliostomatidae (Mollusca: Superfamily Trochoidea)''. Molecular Phylogenetics and Evolution 54:783-809

External links

Miocene Gastropods and Biostratigraphy of the Kern River Area, California; United States Geological Survey Professional Paper 642
{{Authority control Trochoidea (superfamily) Taxa named by Constantine Samuel Rafinesque