{{Short description|Species of annelid worm}} {{Speciesbox | image = Nereis diversicolor 1.jpg | image_caption = | genus = Hediste | species = diversicolor | authority = ([[Otto Friedrich Müller|O.F. Müller]], 1776)<ref name=WoRMS>{{cite WoRMS |author=Fauchald, Kristian |year=2013 |title=''Hediste diversicolor'' (O.F. Müller, 1776) |id=152302 |accessdate=2013-05-17 }}</ref> | synonyms = *''Neanthes diversicolor'' (Müller, 1776) *''Nereis (Hediste) diversicolor'' O.F. Müller, 1776 *''Nereis brevimanus'' Johnston, 1840 *''Nereis depressa'' Frey & Leuckart, 1847 *''Nereis diversicolor'' (Müller, 1776) *''Nereis sarsii'' Rathke, 1843 *''Nereis versicolor'' Müller *''Nereis viridis'' Johnston, 1840 | synonyms_ref =<ref name=WoRMS/> }}
'''''Hediste diversicolor''''', commonly known as a '''ragworm''', is a [[Polychaeta|polychaete worm]] in the family [[Nereididae]]. It lives in a burrow in the sand or mud of beaches and [[Estuary|estuaries]] in intertidal zones in the north Atlantic. This species is used in research, but its classification is in dispute; in the literature, it is often classified as ''Nereis diversicolor'' (O.F. Müller, 1776).<ref name=MarLIN>{{cite web |url=http://www.marlin.ac.uk/speciesfullreview.php?speciesID=3470 |title=Ragworm: ''Hediste diversicolor'' |author=Budd, Georgina |date=2008 |work=[[Marine Life Information Network]] |accessdate=2013-05-18}}</ref> Its specific name "diversicolor" refers to the fact that its colour changes from brown to green as the breeding season approaches.
==Description== ''Hediste diversicolor'' can grow up to {{convert|10|cm|0|abbr=on}} in length and may have from ninety to one hundred twenty segments when mature. The head has a pair of palps, two pairs of antennae, four pairs of tentacles and four eyes. Each body segment has a pair of bristly appendages known as parapodia which are used for swimming. There is a prominent blood vessel running along the dorsal surface of the animal. This ragworm is pale brown but changes to green as the [[gonad]]s mature and the breeding season approaches.<ref name=MarLIN/><ref name=BBC>{{cite web |url=https://www.bbc.co.uk/nature/blueplanet/factfiles/segmented_worms/ragworm_bg.shtml |title=Ragworm (''Nereis diversicolor'') |work=Science and Nature: Animals |publisher=BBC |accessdate=2013-05-17}}</ref>
==Distribution and habitat== ''Hediste diversicolor'' is native to the north-east Atlantic. Its range extends from the [[Baltic Sea]] and [[North Sea]] southwards to the [[Azores]] and [[Mediterranean Sea]]. It has been introduced to the north-west Atlantic in the areas of [[Cobscook Bay]], the [[Gulf of Maine]] and the [[Gulf of St Lawrence]].<ref name=Introduced>{{cite journal |author= A. L. Einfeldt, J. R. Doucet, J. A. Addison |title=Phylogeography and cryptic introduction of the ragworm ''Hediste diversicolor'' (Annelida, Nereididae) in the Northwest Atlantic |journal=Invertebrate Biology |volume=133 |issue=3 |pages=232–241 |doi=10.1111/ivb.12060|year=2014 }}</ref> It is plentiful on beaches of sand, muddy sand and mud, including areas of low [[salinity]], where it lives in a semi-permanent J-shaped or U-shaped burrow and under adjoining stones in the [[intertidal zone]].<ref name=MarLIN/><ref name=BBC/>
==Biology== Examination of the contents of the gut shows that ''Hediste diversicolor'' is a [[Predation|predator]] and generalist [[scavenger]], able to adapt its diet to whatever is currently available. It spins a mucus net at the entrance of its burrow in which it traps [[phytoplankton]], [[zooplankton]], [[diatom]]s, [[bacteria]] and other small particles. It creates a water current through its tube by writhing about inside to draw particles through the net. Periodically it rolls the net up and swallows it before spinning another. When the availability of suitably-sized food particles is low it emerges from its burrow and hunts for small invertebrates, seizing them with its strong jaws. It also eats [[detritus]] and even animal [[faeces]].<ref>{{cite journal |author1=Costa, Pedro Fidalgo E. |author2=Oliveira, Rui F. |author3=Cancela da Fonseca, Luis |year=2006 |title=Feeding Ecology of'' Nereis diversicolor'' (O.F. Müller) (Annelida, Polychaeta) on Estuarine and Lagoon Environments in the Southwest Coast of Portugal |journal=Pan-American Journal of Aquatic Sciences |volume=1 |issue=2 |pages=114–126 |url=http://www.panamjas.org/pdf_artigos/PANAMJAS_1%282%29_114-126.pdf |access-date=2013-05-18 |archive-date=2014-02-11 |archive-url=https://web.archive.org/web/20140211022116/http://www.panamjas.org/pdf_artigos/PANAMJAS_1(2)_114-126.pdf |url-status=dead }}</ref> They also draw, otherwise not edible, [[cordgrass]] seeds into their burrows and let them sprout to produce high-quality food, one of the rare examples of “gardening” by animals.<ref>Zhu, Z., J. van Belzen, T. Hong, T. Kunihiro, T. Ysebaert, P. M. J. Herman, et al. (2016). Sprouting as a gardening strategy to obtain superior supplementary food: evidence from a seed-caching marine worm. Ecology. doi: 10.1002/ecy.1613</ref>
The sexes are separate in ''Hediste diversicolor'', and females heavily outnumber the males. As the breeding season approaches, the males, which were previously indistinguishable from the females, turn bright green. At the same time, the females turn a duller dark green on the dorsal surface with their earlier orange-brown pigmentation still showing through. Eggs develop within the female's body cavity. [[Histolysis]] then occurs and the body wall becomes brittle and eventually bursts, liberating the eggs into the burrow.<ref name=MarLIN/>
Synchronized spawning takes place in early spring, usually at the time of the new or [[full moon]] when the water has warmed up after the winter and attained a temperature above {{convert|6|°C}}. The timing of this event varies throughout the worm's range and more southern populations mature at a year of age while more northerly ones may be three years old before they breed. The male seems to be attracted to a burrow occupied by a female by the release of a [[pheromone]] into the water. He crawls across the seabed and liberates [[sperm]] into the water just outside the entrance of the female's burrow. The sperm is drawn into the tube by the water current that the female creates by undulating her body. Here fertilisation takes place and the [[larva]]e are brooded for ten to fourteen days. Both males and females die after spawning.<ref name=MarLIN/><ref>{{cite journal |author1=Bartels-Hardege, H. D. |author2=Zeeck, E. |year=1990 |title= Reproductive behaviour of ''Nereis diversicolor'' (Annelida: Polychaeta) |journal=Marine Biology |volume=106 |pages=409–412 |doi=10.1007/BF01344320 |issue=3 |s2cid=86682968 }}</ref>
==Ecology== ''Hediste diversicolor'' is widespread and common and is eaten by many species of birds and fish. It is the main food item for the [[pied avocet]] (''Recurvirostra avosetta''), the [[grey plover]] (''Pluvialis squatarola''), the [[curlew sandpiper]] (''Calidris ferruginea''), the [[bar-tailed godwit]] (''Limosa lapponica'') and the [[Eurasian curlew|curlew]] (''Numenius arquata'').<ref>{{cite journal |author1=Goss-Custard, J. D. |author2=Jones, R. E. |author3=Newberry, P. E. |year=1989 |title=The ecology of the Wash. 1. Distribution and diet of wading birds |journal=Journal of Applied Ecology |volume=14 |pages=681–700 |doi=10.2307/2402803 |issue=3|jstor=2402803 }}</ref> Several [[flatfish]] which live on intertidal mudflats feed on the ragworm. These include the [[common dab]] (''Limanda limanda''), the [[common sole]] (''Solea solea''), the [[European flounder]] (''Platichthys flesus'') and the [[European plaice]] (''Pleuronectes platessa'').<ref name=MarLIN/>
''Hediste diversicolor'' has been found to have a deleterious effect on the establishment of [[saltmarsh]]es. When tests were undertaken in southern England on establishing the seagrass ''[[Zostera noltei]]'', it was found that efforts were more successful when the ragworm was excluded from the area of transplanted material. In another planting trial, the pioneering [[cordgrass]] ''[[Spartina anglica]]'', used to prevent coastal erosion, was similarly adversely affected. In the laboratory, ragworms were seen to pull leaves of the grasses into their burrows where they fed on them, and the disturbance to the substrate caused by their burrowing activities was also thought to contribute to the reduced establishment rates.<ref>{{cite journal |author=Emmerson, M. |year=2000 |title=Remedial habitat creation: does ''Nereis diversicolor'' play a confounding role in the colonisation and establishment of the pioneering saltmarsh plant, ''Spartina anglica''? |journal=Helgoland Marine Research |volume=54 |pages=110–116 |doi=10.1007/s101520050009 |issue=2–3 |doi-access=free }}</ref>
==Uses== ''Hediste diversicolor'' is used as a [[Model organism|model laboratory animal]] for research. It has also been used to evaluate the quality of marine sediment because it [[Bioaccumulation|bioaccumulates]] certain heavy metals such as [[lead]], [[cadmium]], [[chromium]] and [[arsenic]].<ref>{{cite journal |vauthors=Gaion A, Sartori D, Scuderi A, Fattorini D |date=2014 |title=Bioaccumulation and biotransformation of arsenic compounds in Hediste diversicolor (Muller 1776) after exposure to spiked sediments|url=https://link.springer.com/article/10.1007/s11356-014-2538-z|journal=Environmental Science and Pollution Research |volume=21 |issue=9 |pages=5952–5959|doi=10.1007/s11356-014-2538-z|pmid=24458939 |s2cid=12568097 |url-access=subscription }}</ref><ref>{{cite book |author1=Septier, François |author2=Dhainaut, Nicole |year=1992 |title=Etude de la bioconcentration de métaux lourds chez une annélide polychète estuarienne endobenthique (''Nereis diversicolor''). Utilisation des plans factoriels pour une meilleure évaluation des risques écotoxicologiques liés aux interactions métalliques|trans-title=Study of the uptake of heavy metal by a burrowing annelid polychete (''Nereis diversicolor''). Use of experimental designs for a better evaluation of the ecotoxicological risks related to metal interactions |publisher=Doctoral thesis, Université de Lille 1, France |url=http://cat.inist.fr/?aModele=afficheN&cpsidt=153311 }}</ref> Anglers use it for [[Fishing bait|bait]] when sea fishing, digging it out of the [[Substrate (biology)|substrate]] with a large fork. It is also available commercially.<ref name=MarLIN/>
==References== {{Reflist}}
{{Taxonbar|from=Q488741}}
[[Category:Phyllodocida]] [[Category:Animals described in 1776]] [[Category:Taxa named by Otto Friedrich Müller]]