Helicodonta obvoluta
Encyclopedia
Helicodonta obvoluta is a species
of air-breathing land snail
, a terrestrial
pulmonate gastropod mollusk in the family Helicodontidae
.
The distribution of this species is spread over large parts of Europe, where it inhabits deciduous and mixed forests.
This species is sometimes called the "cheese snail" because the shape of the shell resembles that of a wheel of cheese
.
and a wide umbilicus. The peristome is flattened above and below. The white everted lip is slightly thickened centrally to form a callus
in the palatal and parietal region, therefore the mouth seems to be separated into three embayments in some specimens. The shell diameter ranges from 10-15mm; the shell height from 5-7mm. The weight of the adult living snail is about 414.2±6.7 mg. In contrast to many other snail species within the superfamily Helicoidea, this species has no love dart
s.
The eggs are laid in clusters of 9-27 per clutch in rotten wood and are covered with a mucus layer for protection. Juveniles hatch after 14–31 days of incubation time, and reach maturity after 140–624 days. The spring generation may reach maturity in the same year, while the autumn generation has to overwinter as immature snails. Helicodonta obvoluta spends most of its lifespan near and in fallen tree trunks, which provide places for egg-laying, feeding, shelter in daytime and hibernation sites in winter. In the case of populations that live in milder, oceanic climates such as Great Britain
, snails can also hibernate within leaf litter.
across France
, Switzerland
, Liechtenstein
, Belgium
, Luxembourg
, the Netherlands
, southern and central Germany
, Austria
, Czech Republic
, Slovakia
, Poland
, Hungary
, Slovenia
, Croatia
, Italy
, Bosnia and Herzegovina
and Serbia
. There are also isolated populations in southeastern England
and northern Germany, which may be remnants of an earlier, more extensive, distribution range. The distribution in Albania
, Macedonia
and Greece
is unclear, as the populations there belong to Helicodonta albanica, which is assigned as separate species by many authors, while others treat it as subspecies of Helicodonta obvoluta.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
pulmonate gastropod mollusk in the family Helicodontidae
Helicodontidae
Helicodontidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks in the clade Eupulmonata .- Taxonomy :...
.
The distribution of this species is spread over large parts of Europe, where it inhabits deciduous and mixed forests.
This species is sometimes called the "cheese snail" because the shape of the shell resembles that of a wheel of cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....
.
Description
Shells of juveniles and young adults of this snail are typically covered with hairs 1mm in length. The hair may be absent in older specimens. The dark-brown shell is characterized by a flat upper side with a very slightly sunken spireSpire (mollusc)
A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...
and a wide umbilicus. The peristome is flattened above and below. The white everted lip is slightly thickened centrally to form a callus
Callus (mollusc)
A callus is an anatomical feature that exists in some mollusk shells, a thickened area of shell material that can partly or completely covers the umbilicus, or can be located on the body whorl near the aperture of the shell A callus is an anatomical feature that exists in some mollusk shells, a...
in the palatal and parietal region, therefore the mouth seems to be separated into three embayments in some specimens. The shell diameter ranges from 10-15mm; the shell height from 5-7mm. The weight of the adult living snail is about 414.2±6.7 mg. In contrast to many other snail species within the superfamily Helicoidea, this species has no love dart
Love dart
A love dart is a hard, long, sharp, calcareous or chitinous dart which some hermaphroditic land snails and slugs create. Love darts are made in sexually mature animals only, and are used as part of the sequence of events during courtship, before actual mating takes place...
s.
Life cycle
The average life span of Helicodonta obvoluta is 2 years, with a maximum of 3 years. The activity period stretches from April to November; daily activity is concentrated in the early morning and at night time. Mating can last for 2-3 hours. There are two periods of reproduction, the first one in spring (April–June), the second in autumn (August–October).The eggs are laid in clusters of 9-27 per clutch in rotten wood and are covered with a mucus layer for protection. Juveniles hatch after 14–31 days of incubation time, and reach maturity after 140–624 days. The spring generation may reach maturity in the same year, while the autumn generation has to overwinter as immature snails. Helicodonta obvoluta spends most of its lifespan near and in fallen tree trunks, which provide places for egg-laying, feeding, shelter in daytime and hibernation sites in winter. In the case of populations that live in milder, oceanic climates such as Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
, snails can also hibernate within leaf litter.
Distribution
The main distribution zone of this species extends from north western SpainSpain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
across France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, Liechtenstein
Liechtenstein
The Principality of Liechtenstein is a doubly landlocked alpine country in Central Europe, bordered by Switzerland to the west and south and by Austria to the east. Its area is just over , and it has an estimated population of 35,000. Its capital is Vaduz. The biggest town is Schaan...
, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, Luxembourg
Luxembourg
Luxembourg , officially the Grand Duchy of Luxembourg , is a landlocked country in western Europe, bordered by Belgium, France, and Germany. It has two principal regions: the Oesling in the North as part of the Ardennes massif, and the Gutland in the south...
, the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, southern and central Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
, Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....
, Slovakia
Slovakia
The Slovak Republic is a landlocked state in Central Europe. It has a population of over five million and an area of about . Slovakia is bordered by the Czech Republic and Austria to the west, Poland to the north, Ukraine to the east and Hungary to the south...
, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
, Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
, Croatia
Croatia
Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, Bosnia and Herzegovina
Bosnia and Herzegovina
Bosnia and Herzegovina , sometimes called Bosnia-Herzegovina or simply Bosnia, is a country in Southern Europe, on the Balkan Peninsula. Bordered by Croatia to the north, west and south, Serbia to the east, and Montenegro to the southeast, Bosnia and Herzegovina is almost landlocked, except for the...
and Serbia
Serbia
Serbia , officially the Republic of Serbia , is a landlocked country located at the crossroads of Central and Southeast Europe, covering the southern part of the Carpathian basin and the central part of the Balkans...
. There are also isolated populations in southeastern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
and northern Germany, which may be remnants of an earlier, more extensive, distribution range. The distribution in Albania
Albania
Albania , officially known as the Republic of Albania , is a country in Southeastern Europe, in the Balkans region. It is bordered by Montenegro to the northwest, Kosovo to the northeast, the Republic of Macedonia to the east and Greece to the south and southeast. It has a coast on the Adriatic Sea...
, Macedonia
Republic of Macedonia
Macedonia , officially the Republic of Macedonia , is a country located in the central Balkan peninsula in Southeast Europe. It is one of the successor states of the former Yugoslavia, from which it declared independence in 1991...
and Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
is unclear, as the populations there belong to Helicodonta albanica, which is assigned as separate species by many authors, while others treat it as subspecies of Helicodonta obvoluta.