Odostomiinae


Odostomiinae, Odostomia snails and their allies, is a taxonomic subfamily of minute parasitic sea snails. These are marine heterobranch gastropod mollusks, or micromollusks, in the family Pyramidellidae.

Taxonomy

The subfamily Odostomiinae has been recognized as monophyletic.
It includes the tribe Liostomini, a name given to those genera which have an intorted protoconch. The rest of the genera however do not form a single monophyletic taxon.
Subfamily Odostomiinae has been classified as one of eleven recognised subfamilies of the very voluminous gastropod family Pyramidellidae : Odostomiinae, Turbonillinae, Chrysallidinae, Cingulininae, Cyclostremellinae, Sayellinae, Syrnolinae, Eulimellinae, Pyramidellinae, Odostomellinae and Tiberiinae.
In the taxonomy of Bouchet & Rocroi, this subfamily also comprises the subfamilies Chrysallidinae, Cyclostremellinae and Odostomellinae, that they have downgraded to the rank of tribe.
subfamily Odostomiinae Pelseneer, 1928
According to Schander, Van Aartsen and Corgan there are 33 genera in Odostominae with four possible additional genera of uncertain status.

Genera

Genera in the subfamily Odostomiinae include:
tribe OdostomiiniOdostomia Fleming, 1813 - type genusAartsenia Warén, 1991Auristomia Monterosato, 1884BooneaBrachystomia Monterosato, 1884Colpostomia Cossmann, 1921Creanatodostomia Nomura, 1937Cyclodostomia Sacco, 1892Doliella Monterosato, 1880Eulimastoma Bartsch, 1916Eustomia Cossmann, 1921Evalea A. Adams, 1860Gumina Finlay, 1928Heida Dall, 1903Jordaniella Chaster, 1898Kunopia Laseron, 1959Liostomia G. O. Sars, 1878Macrodostomia Sacco, 1892Marginodostomia Nomura, 1936possible synonyme of Cyclodostomia fide Saurin Megastomia Monterosato, 1884Nesiodostomia Pilsbry, 1918Nisostomia Cossmann, 1921Noemiamea De Folin in Hoyle, 1886- have been shown to be a part of Odostomia sensu stricta by Schander and co-workers Obexomia Laws, 1941Odetta De Folin, 1870Ondina De Folin, 1870Pyramistomia Cossmann, 1921Sinuatodostomia Nomura, 1937Sinustomia Cossmann, 1921Striodostomia Laws, 1940Turridostomia Habe, 1961Villia Dall, & Bartsch, 1904Volutaxiella Strebel, 1908
tribe Chrysallidini
tribe Cyclostremellini
tribe Odostomellini

Additional genera

Some additional genera which may belong in the subfamily Odostomiinae are:Angustispira Pelseneer, 1912Helodiamea Peñas & Rolán, 2017 Myxa Hedley, 1903Pseudorissoina Tate & May, 1900Ugartea Bartsch, 1917

Distribution

This family is found worldwide, from the tropics to the poles.

Shell description

The shell of these snails has a blunt, heterostrophic protoconch, which is often pointed sideways or wrapped up. Most species in the subfamily have shells which are smaller than 13 mm. The texture of these shells is most often smooth but sometimes sculptured in various forms such as ribs and spirals. Their color is mostly white, cream or yellowish, sometimes with red or brown lines. The teleoconch is dextrally coiled, but the larval shells are sinistral. This results in a sinistrally coiled protoconch. The columella has usually one, but sometimes several, spiral folds. The aperture is closed by an operculum.

Life habits

The Odostomiinae are ectoparasites, feeding mainly on other molluscs and on annelid worms, but some are known to feed on peanut worms and crustaceans.
They do not have a radula. Instead their long proboscis is used to pierce the skin of its prey and suck up its fluids and soft tissues. The eyes on the grooved tentacles are situated toward the base of the tentacles. Between the head and the foot, a lobed process called the mentum is visible. These molluscs are hermaphrodites.