Semi-slugs, also spelled semislugs, are land

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 ...

s whose shells are too small for them to retract into, but not quite

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

. The shell of some semi-slugs may not be easily visible on casual inspection, because the shell may be covered over with the mantle. This is a type of gastropod that is intermediate between a

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 ...

(without an external shell) and a

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial molluscs, terrestrial gastropod mollusks that have gastropod shell, shel ...

(with a large enough shell to retract completely into). There exist a number of gastropod families that have semi-slug species.Breure A. S. H. (2010). "The rediscovery of a semi-slug: ''Coloniconcha prima'' Pilsbry, 1933 (Gastropoda, Pleurodontidae) from Hispaniola". ''

Basteria ''Basteria'' is a bimonthly peer-reviewed scientific journal published by the Netherlands Malacological Society, covering research on molluscs. It was established in 1936 and is now published mostly in English. The editor-in-chief is Ruud Bank. A ...

'' 74(4-6): 78-86. There exist about 1,000 species of semi-slugs in comparison to about only 500 species of slugs.Burton D. W. (1982). "How to be sluggish". ''

Tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

'' 25(2): 48-63
HTM

Examples

Semi-slugs have a worldwide distribution and have evolved in several families; genera include: *

Palearctic The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa. Th ...

and

Nearctic The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...

** family

Parmacellidae Parmacellidae is a family (biology), family of air-breathing land slugs, terrestrial molluscs, terrestrial pulmonate gastropod mollusks within the superfamily Parmacelloidea (according to the Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), t ...

: '' Cryptella'' ** family Vitrinidae: '' Eucobresia, Semilimax, Vitrina, Vitrinobrachium'' * Asia - Pacific ** family

Ariophantidae Ariophantidae is a Taxonomy (biology), taxonomic family (biology), family of air-breathing land snails and semi-slugs, terrestrial molluscs, terrestrial pulmonate gastropod mollusks in the superfamily Helicarionoidea (according to the Taxonomy of ...

: '' Parmarion'', '' Ratnadvipia, Varadia'' ** family

Helicarionidae Helicarionidae is a family of air-breathing land snails or semi-slugs, terrestrial pulmonate gastropod mollusks in the superfamily Helicarionoidea. Distribution The distribution of Helicarionidae includes the eastern Palearctic, Malagasy, ...

: '' Attenborougharion'', '' Helicarion'', '' Howearion'', ''

Ibycus Ibycus (; ; ) was an Greek lyric, Ancient Greek lyric poet, a citizen of Rhegium in Magna Graecia, probably active at Samos during the reign of the tyrant Polycrates and numbered by the scholars of Hellenistic Alexandria in the canon (fiction), ca ...

'', '' Parmellops'', '' Ubiquitarion'' ** Semi-slugs also exist but are exceptional in the

Camaenidae Camaenidae is a Family (biology), family of air-breathing land snails, terrestrial molluscs, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea, the typical snails and their allies. This is one of the most diverse families i ...

. *

Neotropics The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeog ...

** family Amphibulimidae: '' Amphibulima'', '' Gaeotis'' ** family Xanthonychidae: '' Cryptostrakon'', '' Semiconchula,'' '' Xanthonyx'' ** family Pleurodontidae: '' Coloniconcha prima'' *

Tropical Africa The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean. It was formerly known as the Ethiopi ...

** family Urocyclidae: '' Gymnarion''

References

{{reflist Gastropod anatomy

Examples

See also

References