Gyraulus crista
Encyclopedia
Gyraulus crista, commonly called the Nautilus ramshorn, is a minute species
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 freshwater snail
Freshwater snail
A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....

, an aquatic
Aquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...

 pulmonate gastropod mollusk in the family Planorbidae
Planorbidae
Planorbidae, common name the ramshorn snails or ram's horn snails, is a family of air-breathing freshwater snails, aquatic pulmonate gastropod mollusks....

, the ram's horn snails.

Synonyms:
  • Armiger crista
  • Planorbis crista


Subspecies:
  • Gyraulus crista cristatus Draparnaud, 1805
  • Gyraulus crista nautileus Linnaeus, 1767
  • Gyraulus crista spinulosus Clessin

Distribution

The distribution of this species is Holarctic
Holarctic
The Holarctic ecozone refers to the habitats found throughout the northern continents of the world as a whole. This region is divided into the Palearctic, consisting of Northern Africa and all of Eurasia, with the exception of Southeast Asia and the Indian subcontinent, and the Nearctic,...

, and includes:
  • Not listed in IUCN red list
    IUCN Red List
    The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

     - not evaluated (NE)
  • The Czech Republic - least concern (LC)
  • Germany
  • Netherlands
  • Slovakia
  • Sweden
  • The British Isles, Great Britain, Ireland

Shell description

The minute shell is nearly planispiral in its coiling, but the spire
Spire (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...

is actually considerably sunken rather than raised (which is usually the case with gastropods).

The shell has regular transverse ridges which form points extending beyond the main curve of the periphery of the shell.

The shell color is a translucent yellowy-brown. The maximum shell dimension is about 3 mm.

Life habits

This minute species, although technically a pulmonate gastropod, does not use air for respiration but instead absorbs oxygen through its mantle cavity which is full of water.
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