Menetus dilatatus is a 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 small air-breathing 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.

Shell description

The shell

Gastropod shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

 is small, of a yellowish green-color, minutely wrinkled by the lines of growth. 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 flat, composed of 2.5-3 whorls

Whorl (mollusc)

A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...

, separated by a well-defined suture. The outer whorl has a sharp margin on a level with the spire, diminishing near, but still modifying, the aperture

Aperture (mollusc)

The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....

. Below this line the whorl is very convexly rounded so as to encircle a small, deep, abruptly formed umbilicus. This whorl rapidly enlarges, and terminates in a very large, not very oblique aperture, with the lip expanded so as to make it trumpet-shaped.

The width of the shell is 2-3 mm. The height of the shell is 0.9 mm.

Distribution

The species is native to North America. The type locality is Nantucket island

Nantucket, Massachusetts

Nantucket is an island south of Cape Cod, Massachusetts, in the United States. Together with the small islands of Tuckernuck and Muskeget, it constitutes the town of Nantucket, Massachusetts, and the coterminous Nantucket County, which are consolidated. Part of the town is designated the Nantucket...

 and Hingham, Massachusetts

Hingham, Massachusetts

Hingham is a town in northern Plymouth County on the South Shore of the U.S. state of Massachusetts and suburb in Greater Boston. The United States Census Bureau 2008 estimated population was 22,561...

, USA.

Its non-native distribution includes:

• Czech Republic - non-indigenous, in Bohemia around Elber river and in Southern Bohemia
• Germany
• Netherlands
• Poland
• Great Britain

External links

• Goodchild C. G. & Fried B. (1963). "Experimental Infection of the Planorbid Snail Menetus dilatatus buchanensis (Lea) with Spirorchis sp. (Trematoda)". The Journal of Parasitology 49(4): 588-592. JSTOR.
• http://spinner.cofc.edu/~fwgna/species/planorbidae/m_dilatatus.html