''Calliostoma'' is a genus of small to medium-sized

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

s with gills and an operculum,

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s within the family Calliostomatidae, the Calliostoma top snails. Previously this genus was placed within the family Trochidae. ''Calliostoma'' is the type genus of the family Calliostomatidae.

Taxonomy

The name of this genus is derived from the Greek words ''kallos'' (beautiful) and ''stoma'' (mouth), referring to the pearly aperture of the shell. The genus ''Calliostoma'' is known in fossil records from the Upper Cretaceous onwards. As of 2022, ''Calliostoma'' is treated as a very broad genus of about 300 accepted species. While current information is too fragmentary to assign all species in a revised genus, it is expected to be broken up and (some) subgenera will be elevated to the status of genus. A complete listing can be found at the list of ''Calliostoma'' species.

Description

The rather thin, acute, coeloconoid (=approaching conical shape but with concave sides) shell is imperforate or rarely umbilicate. The whorls are smooth, often polished and spirally ridged or granular. The

body whorl The body whorl is part of the morphology of the shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the b ...

is angulated at the periphery. The aperture is quadrangular, sinuated at the base and slightly oblique. The columella is simple, usually ending anteriorly in a slight tooth. The nucleus appears to be either dextral or sinistral indifferently.

Distribution and habitat

The distribution of this genus is worldwide, found mainly on hard substrates, although Japanese species have been found on sandy bottoms. These snails occur from shallow waters to

bathyal The bathypelagic zone or bathyal zone (from Greek βαθύς (bathýs), deep) is the part of the open ocean that extends from a depth of below the ocean surface. It lies between the mesopelagic above, and the abyssopelagic below. The bathypelagic ...

depths.

Behaviour and ecology

The species in this genus are mainly herbivorous or feed on

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

, although a few have been observed to be omnivorous (Keen, 1975) or even carnivorous, feeding on a wide range of

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

and on animals belonging to various other invertebrate

phyla Phyla, the plural of ''phylum'', may refer to: * Phylum, a biological taxon between Kingdom and Class * by analogy, in linguistics, a large division of possibly related languages, or a major language family which is not subordinate to another Phyl ...

. The North Atlantic topshell ''

Calliostoma occidentale ''Calliostoma occidentale'', common name the boreal topsnail, is a species of sea snail, a marine gastropod mollusk in the family Calliostomatidae. Description The size of the shell varies between 6 mm and 17 mm. The shell is rather ...

'' has been reported to feed on coelenterates. Contrary to what is the case in most other top shells, species of the genus ''Calliostoma'' deposits their eggs in gelatinous ribbons that are only fertilized ''after'' being deposited. The young emerge as small snails (Lebour, 1936) without passing through a free-living planktonic stage as a veliger larva.

Gallery

File:Calliostoma bairdii drawing.jpg, Drawing of a dorsal view of a living animal of ''

Calliostoma bairdii ''Calliostoma bairdii'', common name the Baird's top shell, is a species of sea snail with an operculum, a marine gastropod mollusk in the family Calliostomatidae, the calliostoma top snails.Rosenberg, G. (2010). ''Calliostoma bairdii'' Verril ...

'' dredged in the Atlantic Ocean at a depth of from 100 m to 1170 m Calliostoma supragranosum.jpg, Rare purple beaded specimen of ''Calliostoma supragranosum'' found subtidally in Southern California

References