''Echiurus echiurus'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of spoon worm in the family

Echiuridae Echiuridae is a family of spoon worms in the suborder Echiurida. It is a monotypic family, the only genus being ''Echiurus''. These worms burrow into soft sediment on the seabed. Species The World Register of Marine Species recognises the fol ...

. It is found in the North Atlantic Ocean and a

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

is found in Alaska. It burrows into soft sediment and under boulders and stones in muddy places.

Description

This spoon worm has a roughly cylindrical trunk between long. At the anterior end of the trunk, just beside the mouth, a scoop-shaped

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

about long extends forward. The trunk has about 22 rings of papillae, a ring of larger papillae alternating with several rings of smaller papillae. A pair of hooked

chaeta A chaeta or cheta (from Greek χαίτη “crest, mane, flowing hair"; plural: chaetae) is a chitinous bristle or seta found in annelid worms, (although the term is also frequently used to describe similar structures in other invertebrates suc ...

e (chitinous bristles) is borne just behind the mouth on the underside of the worm and there are two rings of chaetae on the posterior end of the trunk, near the anus. Internally, the rectum is partially obscured by two long anal

diverticula In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...

with ciliated funnels. Externally, the trunk is greyish-brown while the proboscis is orange with brownish streaks.

Distribution

''Echiurus echiurus'' has a

holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region ...

distribution, extending southwards in the Atlantic Ocean as far as the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian S ...

and the

Kattegat The Kattegat (; sv, Kattegatt ) is a sea area bounded by the Jutlandic peninsula in the west, the Danish Straits islands of Denmark and the Baltic Sea to the south and the provinces of Bohuslän, Västergötland, Halland and Skåne in Sweden ...

, burrowing into soft sediment, often at considerable depths. A subspecies ''Echiurus echiurus alaskanus'' occurs in southeastern Alaska, its range extending from

Point Barrow Point Barrow or Nuvuk is a headland on the Arctic coast in the U.S. state of Alaska, northeast of Utqiaġvik (formerly Barrow). It is the northernmost point of all the territory of the United States, at , south of the North Pole. (The northe ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

Puget Sound Puget Sound ( ) is a sound of the Pacific Northwest, an inlet of the Pacific Ocean, and part of the Salish Sea. It is located along the northwestern coast of the U.S. state of Washington. It is a complex estuarine system of interconnected ma ...

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered o ...

. This subspecies inhabits muddy deposits that accumulate around boulders and pebbles in the lower

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

and the shallow

subtidal zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

Ecology

When burrowing, the proboscis is raised and folded backwards and plays no part in the digging process. The front of the trunk is shaped into a wedge and pushed forward, with the two anterior chaetae being driven into the sediment. Next the rear end of the trunk is drawn forward and the posterior chaetae anchor it in place. These manoeuvres are repeated and the worm slowly digs its way forwards and downwards. It takes about forty minutes for the worm to disappear from view. The burrow descends diagonally and then flattens out, and it may be a metre or so long before ascending vertically to the surface. Here, the worm unfolds its proboscis and extends it along the surface of the sediment to feed, retreating into its burrow when the tide goes out.

References

{{Taxonbar, from=Q2338159 Echiurans Fauna of the Atlantic Ocean Fauna of the Pacific Ocean Animals described in 1766 Taxa named by Peter Simon Pallas