''Trochulus biconicus'' 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

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

Hygromiidae Hygromiidae is a taxonomic family of small to medium-sized air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Helicoidea.Helicellidae Ihering, 1909 Anatomy Some snails in genera within this family create and ...

, the hairy snails and their allies. It was first described by the Swiss malacologist Leo Eder in 1917. This species is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Switzerland Switzerland, officially the Swiss Confederation, is a landlocked country located in west-central Europe. It is bordered by Italy to the south, France to the west, Germany to the north, and Austria and Liechtenstein to the east. Switzerland ...

, where it grows on rock

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s and grassy limestone

scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. The term ''scree'' is ap ...

s with sparse vegetation. Since its original discovery in Bannalper Schonegg, it has since been documented in various

cantons A canton is a type of administrative division of a country. In general, cantons are relatively small in terms of area and population when compared with other administrative divisions such as counties, departments, or provinces. Internationally, th ...

Uri Uri may refer to: Places * Canton of Uri, a canton in Switzerland * Úri, a village and commune in Hungary * Uri, Iran, a village in East Azerbaijan Province * Uri, Jammu and Kashmir, a town in India * Uri (island), off Malakula Island in V ...

Obwalden Canton of Obwalden or Obwald ( ; ; ; ) is one of the Canton of Switzerland, 26 cantons forming the Switzerland, Swiss Confederation. It is composed of seven municipalities and the seat of the government and parliament is in Sarnen. It is traditio ...

, and

Nidwalden Canton of Nidwalden or Nidwald ( ; ; ; ) is one of the 26 cantons forming the Swiss Confederation. It is composed of eleven municipalities and the seat of the government and parliament is in Stans. It is traditionally considered a " half-canto ...

Species summary

Description

''Trochulus biconicus'' is a species of small terrestrial snail characterised by its flattened shell with a low

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spire ...

. The shell consists of 5 to 6.5 tightly coiled

whorls 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 diagram ...

that increase slowly but regularly in size, with the body whorl (the final and largest whorl) about twice the width of the first whorl. The shell measures 2.5 to 3.5 mm in height and 5.0 to 7.0 mm in width, giving it a height-to-width ratio of 0.48 to 0.57. The body whorl has a height of 2.5 to 2.8 mm, which is 78% to 90% of the total shell height. 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 ...

(the opening of the shell) is narrow and crescent-shaped with a whitish lip. Both the basal and palatal (outer) margins of the aperture are slightly turned outward. The umbilicus (the central cavity on the underside of the shell) is deep and permanently open, with major and minor diameters of 0.9 to 1.3 mm and 0.8 to 1.1 mm respectively, comprising 16% to 19% of the overall shell diameter. Adult specimens lack hairs on their shells, which are pale brown in colour and display irregular growth lines that are more pronounced on the upper surface than on the underside. The reproductive system of ''Trochulus biconicus'' features four elongated

mucous gland Mucous glands, also known as muciparous glands, are found in several different parts of the body, and they typically stain lighter than serous glands during standard histological preparation. Most are multicellular, but goblet cells are single-c ...

s and inner dart sacs that are slightly longer than the outer ones. The vagina is long and cylindrical. The

flagellum A flagellum (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

(a whip-like structure) exceeds the length of the epiphallus (the tube connecting the

vas deferens The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male reproductive system of many vertebrates. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididyma ...

to the penis), which in turn is longer than the

fusiform Fusiform (from Latin ''fusus'' ‘spindle’) means having a spindle (textiles), spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon (geometry), lemon-shape, but often implies a focal broadening of a ...

(spindle-shaped) penis. The spermatheca

duct The word duct is derived from the Latin word for ''led/leading''. It may refer to: * Duct (anatomy), various ducts in anatomy and physiology ** Tear duct, which carry tears to the eyes * Duct (HVAC), for transfer of air between spaces in a struct ...

is straight, leading to an oval

spermatheca The spermatheca (pronounced : spermathecae ), also called ''receptaculum seminis'' (: ''receptacula seminis''), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, Oligochaeta worms and certain other in ...

that does not extend as far as the

albumen Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens, it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms aro ...

gland.

References

''Trochulus biconicus''
at AnimalBase {{Taxonbar, from=Q5504500 Hygromiidae Endemic fauna of Switzerland Gastropods described in 1917 Taxonomy articles created by Polbot