''Ariunculus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of air-breathing land

slug Slug, or land slug, is a common name for any apparently shell-less Terrestrial mollusc, terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced ...

s in the family

Arionidae Arionidae, common name the "roundback slugs" or "round back slugs" are a taxonomic family of air-breathing land slugs, terrestrial pulmonate gastropod mollusks in the superfamily Arionoidea. Distribution The distribution of this family of s ...

, the roundback slugs. Sometimes it has been considered as a subgenus of ''

Arion Arion (; ) was a kitharode in ancient Greece, a Dionysiac poet credited with inventing the dithyramb. The islanders of Lesbos claimed him as their native son, but Arion found a patron in Periander, tyrant of Corinth. Although notable for his mu ...

'', and sometimes the subgenus ''Ichnusarion'' has been raised to generic rank.

Etymology

The stem of ''

'' plus the suffix -unculus, which is a diminutive in Latin. Hence "little ''Arion''". Pollonera justifies why "Ariunculus" is appropriate rather than "Arionculus" (cf. "homo" and "homunculus"). The subgenus name ''Ichnusarion'' is also based on "''

''", to which has been added "Ichnusa", a Latin name of

Sardinia Sardinia ( ; ; ) is the Mediterranean islands#By area, second-largest island in the Mediterranean Sea, after Sicily, and one of the Regions of Italy, twenty regions of Italy. It is located west of the Italian Peninsula, north of Tunisia an ...

, where the single species of this subgenus is endemic.

Species

Only two species are currently recognised: subgenus ''Ariuncululus'' * '' Ariunculus speziae''

Lessona Lessona is a ''comune'' (municipality) in the Province of Biella in the Italy, Italian region Piedmont, located about northeast of Turin and about east of Biella. As of 31 December 2004, it had a population of 2,487 and an area of .All demograph ...

, 1881 – type species of the genus; Italian Alps with one record in Switzerland subgenus ''Ichnusarion'' Pollonera, 1890 * '' Ariunculus isselii''

& Pollonera, 1882 –

Other species have been discounted as distinct members of the genus: * ''A. mortilleti'' and ''A. camerani'' are considered synonyms of ''A. speziae'' (all three were originally described in the same article, but differ only in size and coloration, not genitalia); * ''A. moreleti'' is considered a species of '' Letourneuxia''; * ''A. pallaryi'' matches ''Letourneuxia numidica'' in its description; * ''A. austriacus'' has been synonymised with ''

Arion subfuscus ''Arion subfuscus'' is a species of land slug. It forms a species complex with '' Arion fuscus''. It is native to Eurasia, and has been introduced to eastern North America North America is a continent in the Northern Hemisphere, North ...

''; * ''A. tricolor'' and ''A. nigratus'' are thought to have been misidentified juveniles of a large ''Arion''; * ''A. ischii'' was apparently a misprint for ''A. isselii''.

Diagnostic characters

Genital characters that have been proposed as diagnostic of the genus are: * the genital pore is very anterior, anterior to the

pneumostome The pneumostome or breathing pore is a respiratory opening of the external body anatomy of a pulmonate land slug or land snail. It is a part of the respiratory system of gastropods. It is an opening in the right side of the mantle of a st ...

; * the atrium is large; * the duct of the bursa copulatrix opens near the end of the epiphallus; * the oviduct is long with two bends; * the epiphallus blends imperceptibly with the vas deferens; At least in one species of ''Ariunculus'', this last character reflects that sperm is transferred naked rather than in a spermatophore formed in the epiphallus; this is a fundamental contrast with ''

'' and '' Geomalacus''. ''Ariunculus'' differs from '' Geomalacus'', and is similar to ''

'', in that the caudal gland is prominent and the mantle contains only calcareous granules rather than a shell plate.

References

{{DEFAULTSORT:Ariunculus (Genus) Arionidae Gastropod genera