''Polydora ciliata'' is a species of annelid worm in the family

Spionidae Spionidae is a family of marine worms within the Polychaeta. Spionids are selective deposit feeders that use their two grooved palps to locate prey. However, some spionids are capable of interface feeding, i.e. switching between deposit and sus ...

, 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''. 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), cylindrical, acoelomate animals, and are widely distributed and abundant in freshwater and marine en ...

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"; : prostomia; sometimes also called the "acron") is the Cephalization, cephalized first body segment in an annelid worm's body at the anterior end. It is in front of (but does not in ...

(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 (: 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 compos ...

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

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

(outgrowths) and

chaeta A chaeta or cheta (; ) is a chitinous bristle or seta found on annelid worms, although the term is also frequently used to describe similar structures in other invertebrates such as arthropods. Polychaete annelids (''polychaeta'' literally me ...

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 respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...

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

holdfast Holdfast most often refers to: *Holdfast (biology), a root-like structure that anchors aquatic sessile organisms to their substrate *Holdfast (tool), a tool used to secure a workpiece to a workbench or anvil Holdfast or hold fast may also refer t ...

s of seaweeds, wood, muddy sediment and

mollusc Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

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 no ...

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

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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

, the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

, the

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea 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 bound ...

, 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 fluid, serous and muc ...

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 ( 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 ...

. It has been observed feeding on dead

barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...

s and other small dead

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

s, and can also filter plankton from the water. The worms are either male or female; sperm is liberated into the

water column The (oceanic) water column is a concept used in oceanography to describe the physical (temperature, salinity, light penetration) and chemical ( pH, dissolved oxygen, nutrient salts) characteristics of seawater at different depths for a defined ...

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 that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

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 (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

s and other

predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

References

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