''Polydora ciliata'' is a species of annelid worm in the family Spionidae, commonly known as a bristleworm. It is a burrowing worm and is found in the northeastern Atlantic Ocean and some other parts of the world.

Taxonomy

''Polydora ciliata'' was first described in 1838 by the Scottish physician and naturalist George Johnston as ''Leucodore ciliatus'', but was later placed in the genus ''

Polydora Polydora (; grc, Πολυδώρᾱ in Attic and in Ionic, means 'many-gifts' or 'the shapely') was the name of several characters in Greek mythology: *Polydora, the 'handsome' Oceanid, one of the 3,000 water-nymph daughters of the Titans Oce ...

''. A planktonic organism was described as ''Metadasydytes quadrimaculatus'' in 1971 by Roch Roszczak, who placed it in the phylum

Gastrotrich The gastrotrichs (phylum Gastrotricha), commonly referred to as hairybellies or hairybacks, are a group of microscopic (0.06-3.0 mm), worm-like, acoelomate animals, and are widely distributed and abundant in freshwater and marine environmen ...

a; it was later established that the animal he was describing was in fact the larval stage of a spionid worm, probably ''Polydora ciliata''.

Description

The species can grow to a length of about with around 180 segments. The front of the

prostomium The prostomium (From Ancient Greek, meaning "before the mouth"; plural: prostomia; sometimes also called the "acron") is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not include) t ...

(head) has no eyes or antennae, but the hind part has a pair of long palps and up to four eyes. The multi-segmented body is broadest fairly near the front and then tapers gradually to the

pygidium The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compo ...

(terminal segment) which bears a funnel. Each segment bears

parapodia In invertebrates, the term parapodium ( Gr. ''para'', beyond or beside + ''podia'', feet; plural: parapodia) refers to lateral outgrowths or protrusions from the body. Parapodia are predominantly found in annelids, where they are paired, unjointed ...

(outgrowths) and

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 such ...

e (bristles), the ventral branches of the parapodia being triangular or finger-like, and these structures reducing in size towards the rear of the animal. On segment five, the bristles are specially modified for burrowing.

Gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s are present on all the segments beyond 7 except for the last 10 to 20 segments.

Distribution and habitat

''P. ciliata'' has a widespread distribution round the coasts of northwestern Europe. As a burrowing species, it tunnels into limestone; chalk and clay, calcareous algae, the holdfasts of seaweeds, wood, muddy sediment and

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is est ...

shells, including those of

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not ...

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which ...

s and periwinkles. It is also known from the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on ...

, the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

, the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Rom ...

, the Indo-Pacific and Antarctica.

Ecology

The burrow of ''P. ciliata'' is U-shaped, and the presence of these worms can be recognised by the sets of small, double perforations they make. The worm is believed to burrow by abrading the substrate with its bristly chaetae, but there may also be some chemical action involved in burrowing. The tube is lined with

mucus Mucus ( ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both serous and mucous cells. It ...

and fine grains of sediment and extends slightly above the surrounding material. When feeding, the worm extends its head out of the tube and uses its two long palps to feed on

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts comm ...

. It has been observed feeding on dead

barnacle A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...

s and other small dead

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s, and can also

filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

plankton from the water. The worms are either male or female; sperm is liberated into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

and drawn into the burrow of the female by means of the respiratory current. Up to 60 eggs are enclosed in a capsule, and several capsules are suspended by threads inside the female's tube. The eggs hatch in about one week and are

plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a cruc ...

ic for up to six weeks before settling. When the worms bore into the shells of oysters, mussels and periwinkles, they do not feed on the mollusc's soft parts, but they weaken the shell and make the mollusc more vulnerable to attack by

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all th ...

s and other predators.

References

{{Taxonbar, from=Q2102804 Polychaetes Animals described in 1838 Taxa named by George Johnston (naturalist)