''Amphidromus inversus'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of air-breathing

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 ...

, a terrestrial

pulmonate Pulmonata or pulmonates is an informal group (previously an order, and before that, a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group inclu ...

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 ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the family

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 ...

. MolluscaBase eds. (2020). MolluscaBase. Amphidromus inversus (O. F. Müller, 1774). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1245795 on 2020-05-17 Like most members of the subgenus ''Amphidromus'', it is chirally dimorphic: within the same populations, both dextral (clockwise-coiled) and sinistral (anticlockwise-coiled) individuals co-exist. This is one of the very few cases of genetic

antisymmetry In linguistics, antisymmetry, is a theory of syntax described in Richard S. Kayne's 1994 book ''The Antisymmetry of Syntax''. Building upon X-bar theory, it proposes a universal, fundamental word order for phrases (Branching (linguistics), branchin ...

known in nature. Among the subgenus ''Amphidromus'', ''A. inversus'' stands out because since c. 2004, it has been the focus of studies aimed at understanding the evolution of chiral dimorphism. Most of these studies have taken place on the Malaysian island of Kapas.

Subspecies

* ''Amphidromus inversus albulus'' Sutcharit & Panha, 2006 * ''Amphidromus inversus andamensis'' (L. Pfeiffer, 1871) * ''Amphidromus inversus annamiticus'' (Crosse & P. Fischer, 1863) :: (Described as ''Amphidromus annamiticus'') The shell is dextral and imperforate, featuring a thick, slightly convexly conic spire that appears pink above, with a purple suprasutural band near the apex. Comprising seven to seven and a half whorls, the earlier two are convex, with several succeeding whorls being almost flat and slightly marginate above the sutures. The last two whorls are more convex and pale brown with some oblique chestnut streaks, the last whorl abruptly darkening to chestnut beneath. One varix may be present, or none. The aperture is white within, with the recurved edge of the peristome being dark. The parietal callus is white, gradually becoming thin and revealing the chestnut color of the base within. * ''Amphidromus inversus fureyi'' Thach & F. Huber, 2021 * ''Amphidromus inversus inversus'' (O. F. Müller, 1774) * ''Amphidromus inversus koperbergi'' Laidlaw & Solem, 1961

Distribution

Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...

, Peninsular Malaysia, Thailand

Description

(Original description of ''Helix inversa'' in Latin) This

Helix A helix (; ) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is for ...

possesses a conico-acuminate shell that is sinistral and whitish, displaying reddish streaks and a band, and features a reflected lip. This is a somewhat larger

(land snail) and it exhibits a dextral coiling, sharing similarities in shape and size with ''Helix recta'', but differing in color and the coiling direction of its

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

s. The

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

of this shell is acute. Its eight whorls coil sinistrally and are marked with reddish streaks drawn obliquely along their length; a broad pale reddish band encircles the shell near the base. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

is ovate and white. The outer

lip The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Mammal lips are soft, movable and serve to facilitate the ingestion of food (e.g. sucklin ...

appears pure white and reflected; the inner lip (labium incumbens) presents the same color, while the whorl penetrating the aperture is brown. (Description by Reeve) The shell is oblong-ovate and rather thick, most frequently coiling sinistrally. It comprises seven convex, smooth whorls with a reflected lip. Its base color is whitish, overlaid with stains and irregularly longitudinal streaks of burnt brown. The lip appears white, while the columella and outer edge of the lip exhibit a purplish-brown hue.

Ecology

Schilthuizen et al. (2005) described spatial structure of population of ''Amphidromus inversus'' in Malaysia.

References

* Maassen, W. J. M. (2001). A preliminary checklist of the non-marine molluscs of West-Malaysia: "a Hand List". De Kreukel, Extra Editie 2001. 1–155 * Yamane, S. & Tomiyama, K. (1986). A small collection of land snails from the Krakatau Islands, Indonesia. Venus, 45 (1): 61-64. Tokyo.

External links