The eastern mudsnail, ''Ilyanassa obsoleta'', 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), ...

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

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 Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Nassariidae The Nassariidae, Nassa mud snails (US), or dog whelks (UK) are a taxonomic family of small to medium-sized snails, mostly marine gastropod mollusks in the clade Neogastropoda. These snails have rounded shells with a high spire, an oval ap ...

, the nassa mud snails.MolluscaBase eds. (2021). MolluscaBase. Ilyanassa obsoleta (Say, 1822). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=467490 on 2021-09-04

Shell description

This species has a small

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

with a slightly rough exterior, because the surface has intersecting weak spiral and axial ribs. The shell has an oval

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 ...

with a small notch or

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water i ...

at the anterior end. The aperture has a smooth inner lip with a partial shield, and the outer lip is thin and smooth. The exterior of the shell is chalky white, but it is covered by a very dark brown, closely adhering

periostracum The periostracum ( ) is a thin, organic coating (or "skin") that is the outermost layer of the shell of many shelled animals, including molluscs and brachiopods. Among molluscs, it is primarily seen in snails and clams, i.e. in gastropods an ...

, except in areas of the shell where the periostracum has been eroded. 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 the shell is almost always eroded, and the shell is often quite damaged by the acidic properties of the mud in which the animal lives. The maximum shell length is a little more than one inch, or about 28 mm.

Distribution

The indigenous distribution of this western

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

species is from

Nova Scotia Nova Scotia is a Provinces and territories of Canada, province of Canada, located on its east coast. It is one of the three Maritime Canada, Maritime provinces and Population of Canada by province and territory, most populous province in Atlan ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. The nonindigenous distribution includes the West Coast of the United States.

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

. 2008. Nassarius obsoletus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Accessed 29 October 2008.

Ecology

Habitat

This snail is very common on mud flats in the intertidal and shallow subtidal zones, in sounds and inlets.

Feeding habits

This species is a

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

feeder, eating whatever is found in the film on top of the mud where it lives, including many microscopic marine plants.

References

;Notes * Cernohorsky W. O. (1984). Systematics of the family Nassariidae (Mollusca: Gastropoda). Bulletin of the Auckland Institute and Museum 14: 1-356. * Brunel, P., L. Bosse, & G. Lamarche. (1998). Catalogue of the marine invertebrates of the estuary and Gulf of St. Lawrence. Canadian Special Publication of Fisheries and Aquatic Sciences, 126. 405 p.

External links

* Goulding MQ. 2009
''Cell Lineage of the Ilyanassa Embryo: Evolutionary Acceleration of Regional Differentiation during Early Development''
PLoS ONE 4(5): e5506.
Blakeman Smith, Journal of Molluscan Studies

Kelaher et al., J Experimental Marine Biology and Ecology
*
Yang, Y.; Abalde, S.; Afonso, C. L.; Tenorio, M. J.; Puillandre, N.; Templado, J.; Zardoya, R. (2021). Mitogenomic phylogeny of mud snails of the mostly Atlantic/Mediterranean genus Tritia (Gastropoda: Nassariidae). Zoologica Scripta
{{Taxonbar, from1=Q3142539, from2=Q61697812 Ilyanassa Gastropods described in 1822