''Amphitrite ornata'' or ornate worm, is a

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

of marine

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

worm in the family

Terebellidae The Terebellidae is a marine family of polychaete worms, of which the type taxon is '' Terebella'', described by Carl Linnaeus in his 1767 12th edition of ''Systema Naturae''. Characteristics Most terebellids live in burrows or crevices and a ...

. Polychaetes, or marine bristle worms, have elongated bodies divided into many segments. Each segment may bear

setae In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

(bristles) and

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 ...

(paddle-like appendages). Some species live freely, either swimming, crawling or burrowing, and these are known as "errant". Others live permanently in tubes, either calcareous or parchment-like, and these are known as "sedentary".

Distribution

This species is found in

Cobscook Bay Cobscook Bay is located in Washington County in the state of Maine. It opens into Passamaquoddy Bay, within the Bay of Fundy. Cobscook Bay is immediately south of the island city of Eastport, the main island of which (Moose Island) straddles the ...

, the

Gulf of Maine , image = , alt = , caption = , image_bathymetry = GulfofMaine2.jpg , alt_bathymetry = , caption_bathymetry = Major features of the Gulf of Maine , location = Northeast coast of the ...

and the north west

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

at a depth of up to 200 metres.

Description

The ornate worm can grow to up to forty centimetres long and lives in a firm, sand-encrusted tube. All that is visible are the three bright red bushy

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 and a spread of long, peach-coloured

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s above them. The tentacles can extend to forty centimetres and are constantly in motion, searching for food particles.Life in Chesapeake Bay
/ref> The rest of the worm's segmented, tapering body remains concealed in the tube.

Biology

This worm lives in a tough U-shaped tube in the mud

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

. The sexes are separate and the females can be distinguished by their darker abdominal segments. Spawning takes place in June to August, peaking in July, especially around the periods of new and full moon and the subsequent increase in tidal flows. The eggs and sperm develop and float freely in the body cavity of the worm but by some little understood process, only the ripe products are released. The eggs are fertilized externally and the rate of development of the

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...

e is rapid. Swimming forms are present four to five hours after fertilization, and well-formed

trochophore A trochophore (; also spelled trocophore) is a type of free-swimming planktonic marine larva with several bands of cilia. By moving their cilia rapidly, they make a water eddy, to control their movement, and to bring their food closer, to captur ...

s within 20 hours. Larval segmentation begins at 36 hours and metamorphosis starts at about the fifth day, when five trunk segments are already present. At this stage, the larvae cease to swim about freely and sink to the sea floor. Metamorphosis is complete by the eleventh day.

Ecology

This worm is often found associated with the fringe worm, '' Cirratulus cirriformia'', in the

littoral The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal areas ...

and sublittoral zones, in soft mud and under stones. The tiny pea crab ''

Pinnixa chaetopterana ''Pinnixa chaetopterana'', the tube pea crab, is a small decapod crustacean that lives harmlessly within the tube of the polychaete worm, ''Chaetopterus variopedatus''. Description ''P. chaetopterana'' is a tiny, soft-bodied crab. The bodies o ...

'' is sometimes found living as a

commensal Commensalism is a long-term biological interaction ( symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fr ...

inside the tube behind the worm. The ornate worm is often found in marine environments also inhabited by '' Notomastus lobatus'' (

Polychaeta Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ...

) and '' Saccoglossus kowalewskyi'' ( Hemichordata), which produce and contaminate sediments with

bromophenols A bromophenol is any organobromide of phenol that contains one or more covalently bonded bromine atoms. There are five basic types of bromophenols (mono- to pentabromophenol) and 19 different bromophenols in total when positional isomerism is tak ...

and bromopyrroles. These organic halogen metabolites are toxic and it has been found that ''A. ornata'' produces a novel dehaloperoxidase that detoxifies haloaromatic compounds. The

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s responsible have been identified.

References

{{Taxonbar, from=Q2559519 Terebellida Fauna of the Atlantic Ocean Animals described in 1855