Editing Copepod (section)

==Ecology==
[[File:Lernaeolophus sultanus on Pristipomoides filamentosus New Caledonia.tif|thumb|''Lernaeolophus sultanus'' (Pennellidae), parasite of the fish ''[[Pristipomoides filamentosus]]'', scale: each division = 1 mm <ref>{{Cite journal  | last1 = Justine | first1 = JL. | last2 = Beveridge | first2 = I. | last3 = Boxshall | first3 = GA. | last4 = Bray | first4 = RA. | last5 = Miller | first5 = TL. | last6 = Moravec | first6 = F. | last7 = Trilles | first7 = JP. | last8 = Whittington | first8 = ID. | title = An annotated list of fish parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda, Nematoda) collected from Snappers and Bream (Lutjanidae, Nemipteridae, Caesionidae) in New Caledonia confirms high parasite biodiversity on coral reef fish | journal = Aquat Biosyst | volume = 8 | issue = 1 | pages = 22 | date = 4 September 2012 | doi = 10.1186/2046-9063-8-22 | pmid = 22947621 | pmc = 3507714 | bibcode = 2012AqBio...8...22J | doi-access = free }}</ref>]]

Planktonic copepods are important to global [[ecology]] and the [[carbon cycle]]. They are usually the dominant members of the [[zooplankton]], and are major food organisms for small [[fish]] such as the [[dragonet]], [[banded killifish]], [[Alaska pollock]], and other crustaceans such as [[krill]] in the ocean and in fresh water. Some scientists say they form the largest animal [[biomass]] on earth.<ref>{{cite web |author1=Johannes Dürbaum |author2=Thorsten Künnemann |date=November 5, 1997 |title=Biology of Copepods: An Introduction |url=http://www.uni-oldenburg.de/zoomorphology/Biologyintro.html |publisher=[[Carl von Ossietzky University of Oldenburg]] |access-date=December 8, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20100526164720/http://www.uni-oldenburg.de/zoomorphology/Biologyintro.html |archive-date=May 26, 2010 }}</ref> Copepods compete for this title with [[Antarctic krill]] (''Euphausia superba''). ''C. glacialis'' inhabits the edge of the Arctic icepack, especially in [[polynya]]s where light (and photosynthesis) is present, in which they alone comprise up to 80% of zooplankton biomass. They bloom as the ice recedes each spring. The ongoing large reduction in the annual ice pack minimum may force them to compete in the open ocean with the much less nourishing ''C. finmarchicus'', which is spreading from the North Sea and the Norwegian Sea into the Barents Sea.<ref name=pity>{{cite news |url=http://www.economist.com/node/21556804 |title=Biodiversity: Pity the copepod |date=June 16, 2012 |publisher=The Economist |pages=8–9 |access-date=2012-06-19 |archive-url=https://web.archive.org/web/20120618000653/http://www.economist.com/node/21556804 |archive-date=June 18, 2012 |url-status=live }}</ref>

[[File:Acanthochondria cornuta on flounder.jpg|thumb|''[[Acanthochondria cornuta]]'', an ectoparasite on [[flounder]] in the [[North Sea]]]]

Because of their smaller size and relatively faster growth rates, and because they are more evenly distributed throughout more of the world's oceans, copepods almost certainly contribute far more to the [[secondary productivity]] of the world's oceans, and to the global ocean [[carbon sink]] than krill, and perhaps more than all other groups of organisms together. The surface layers of the oceans are believed to be the world's largest carbon sink, absorbing about 2 billion tons of carbon a year, the equivalent to perhaps a third of [[greenhouse gas|human carbon emissions]], thus reducing their impact. Many planktonic copepods feed near the surface at night, then sink (by changing oils into more [[density|dense]] fats)<ref>{{cite journal |author1=David W. Pond |author2=Geraint A. Tarling |year=2011 |title=Phase transitions of wax esters adjust buoyancy in diapausing ''Calanoides acutus'' |journal=[[Limnology and Oceanography]] |volume=56 |issue=4 |pages=1310–1318 |doi=10.4319/lo.2011.56.4.1310|bibcode=2011LimOc..56.1310P |doi-access=free }}</ref><ref>{{Cite news |author1=David W. Pond |author2=Geraint A. Tarling |title=Copepods share "diver's weight belt" technique with whales |publisher=[[British Antarctic Survey]] |url=http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=1511 |date=13 June 2011 |access-date=November 20, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130105192201/http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=1511 |archive-date=5 January 2013 }}</ref> into deeper water during the day to avoid visual predators. Their moulted [[exoskeleton]]s, [[feces|faecal]] pellets, and [[Respiration (physiology)|respiration]] at depth all bring [[carbon]] to the deep sea.

About half of the estimated 14,000 described species of copepods are [[parasite|parasitic]]<ref>{{cite journal|last1=Bernot|first1=J.|last2=Boxshall|first2=G.|last3=Crandall|first3=L.|title=A synthesis tree of the Copepoda: integrating phylogenetic and taxonomic data reveals multiple origins of parasitism|journal=PeerJ|date=August 18, 2021|volume=9|pages=e12034 |doi=10.7717/peerj.12034|pmid=34466296 |pmc=8380027|doi-access=free }}</ref>
<ref>See photograph at {{cite web |url=http://censeam.niwa.co.nz/__data/assets/pdf_file/0011/60986/blobfish.pdf |title=Blobfish / ''Psychrolutes microporos'' |access-date=December 9, 2007 |publisher=[[Census of Marine Life]] / [[National Institute of Water and Atmospheric Research|NIWA]] |archive-url=https://web.archive.org/web/20081016041437/http://censeam.niwa.co.nz/__data/assets/pdf_file/0011/60986/blobfish.pdf |archive-date=October 16, 2008 |url-status=dead }} Photograph taken by Kerryn Parkinson and Robin McPhee in June 2003.</ref> and many have adapted extremely modified bodies for their parasitic lifestyles.<ref>{{cite journal|last1=Bernot|first1=J.|last2=Boxshall|first2=G.|last3=Crandall|first3=L.|title=A synthesis tree of the Copepoda: integrating phylogenetic and taxonomic data reveals multiple origins of parasitism|journal=PeerJ|date=August 18, 2021|volume=9|pages=e12034 |doi=10.7717/peerj.12034|pmid=34466296 | pmc=8380027|doi-access=free }}</ref>
They attach themselves to bony fish, sharks, marine mammals, and many kinds of invertebrates such as corals, other crustaceans, molluscs, sponges, and tunicates. They also live as ectoparasites on some freshwater fish.<ref>{{cite journal|last1=Boxshall|first1=G.|last2=Defaye|first2=D.|title=Global diversity of copepods (Crustacea: Copepoda) in freshwater|journal=Hydrobiologia|date=2008|volume=595|pages = 195–207|doi=10.1007/s10750-007-9014-4|bibcode=2008HyBio.595..195B |s2cid=31727589 |url=https://link.springer.com/article/10.1007/s10750-007-9014-4|url-access=subscription}}</ref>

===Copepods as parasitic hosts===
In addition to being parasites themselves, copepods are subject to parasitic infection. The most common parasites are marine [[dinoflagellate]]s of the genus ''[[Blastodinium]]'', which are gut parasites of many copepod species.<ref name="name">{{cite web |author1=Edouard Chatton |title=Les Péridiniens parasites. Morphologie, reproduction, éthologie |url=http://www.im.microbios.org/0903/0903173.pdf |location=Arch. Zool. Exp. Gén. |pages=59, 1–475. plates I–XVIII |year=1920 |access-date=2014-10-22 |archive-url=https://web.archive.org/web/20140504204852/http://www.im.microbios.org/0903/0903173.pdf |archive-date=2014-05-04 |url-status=live}}</ref><ref name="name1">{{cite journal |last1=Skovgaard |first1=Alf |last2=Karpov |first2=Sergey A. |last3=Guillou |first3=Laure |title=The Parasitic Dinoflagellates Blastodinium spp. Inhabiting the Gut of Marine, Planktonic Copepods: Morphology, Ecology, and Unrecognized Species Diversity |journal=Front. Microbiol. |date=2012 |volume=3 |issue=305 |pages=305 |doi=10.3389/fmicb.2012.00305 |pmid=22973263 |pmc=3428600 |doi-access=free }}</ref> Twelve species of ''Blastodinium'' are described, the majority of which were discovered in the [[Mediterranean Sea]].<ref name="name"/> Most ''Blastodinium'' species infect several different hosts, but species-specific infection of copepods does occur. Generally, adult copepod females and juveniles are infected.

During the naupliar stage, the copepod host ingests the unicellular [[dinospore]] of the parasite. The dinospore is not digested and continues to grow inside the intestinal lumen of the copepod. Eventually, the parasite divides into a multicellular arrangement called a trophont.<ref name="name2">{{cite journal |last1=Fields |first1=D.M. |last2=Runge |first2=J.A. |last3=Thompson |first3=C. |last4=Shema |first4=S.D. |last5=Bjelland |first5=R.M. |last6=Durif |first6=C.M.F. |last7=Skiftesvik |first7=A.B. |last8=Browman |first8=H.I. |title=Infection of the planktonic copepod Calanus finmarchicus by the parasitic dinoflagellate, Blastodinium spp.: effects on grazing, respiration, fecundity and fecal pellet production |journal=J. Plankton Res. |date=2014 |volume=37 |pages=211–220 |doi=10.1093/plankt/fbu084|doi-access=free}}</ref> This trophont is considered parasitic, contains thousands of cells, and can be several hundred micrometers in length.<ref name="name1"/> The trophont is greenish to brownish in color as a result of well-defined [[chloroplast]]s. At maturity, the trophont ruptures and ''Blastodinium'' spp. are released from the copepod anus as free dinospore cells. Not much is known about the dinospore stage of ''Blastodinium'' and its ability to persist outside of the copepod host in relatively high abundances.<ref>{{cite journal |last1=Alves-de-Souza |first1=Catharina |last2=Cornet |first2=C |last3=Nowaczyk |first3=A |last4=Gasparini |first4=Stéphane |last5=Skovgaard |first5=Alf |last6=Guillou |first6=Laure |title=Blastodinium spp. infect copepods in the ultra-oligotrophic marine waters of the Mediterranean Sea |journal=Biogeosciences |date=2011 |volume=8 |issue=2 |pages=2125–2136 |doi=10.5194/bgd-8-2563-2011 |bibcode=2011BGeo....8.2125A |url=https://archimer.ifremer.fr/doc/00133/24387/22424.pdf |doi-access=free}}</ref>

The copepod ''Calanus finmarchicus'', which dominates the northeastern [[Atlantic Ocean|Atlantic coast]], has been shown to be greatly infected by this parasite. A 2014 study in this region found up to 58% of collected ''C. finmarchicus'' females to be infected. In this study, ''Blastodinium''-infected females had no measurable feeding rate over a 24-hour period. This is compared to uninfected females which, on average, ate 2.93 × 10<sup>4</sup> cells per day.<ref name="name2"/> ''Blastodinium''-infected females of  ''C. finmarchicus'' exhibited characteristic signs of starvation, including decreased [[Respiration (physiology)|respiration]], fecundity, and fecal pellet production. Though [[photosynthetic]], ''Blastodinium'' spp. procure most of their energy from organic material in the copepod gut, thus contributing to host starvation.<ref name="name1"/> Underdeveloped or disintegrated [[ovary|ovaries]] and decreased fecal pellet size are a direct result of starvation in female copepods.<ref>{{cite journal|last1=Niehoff|first1=Barbara|title=Effect of starvation on the reproductive potential of Calanus finmarchicus|journal=ICES Journal of Marine Science|date=2000|volume=57 |issue=6|pages=1764–1772|doi=10.1006/jmsc.2000.0971|bibcode=2000ICJMS..57.1764N |doi-access=free}}</ref> Parasitic infection by ''Blastodinium'' spp. could have serious ramifications on the success of copepod species and the function of entire [[marine ecosystems]]. ''Blastodinium'' parasitism is not lethal, but has negative impacts on copepod physiology, which in turn may alter [[marine biogeochemical cycles]].

Freshwater copepods of the [[cyclops (genus)|''Cyclops'']] genus are the intermediate host of the [[Guinea worm]] (''[[Dracunculus medinensis]]''), the [[nematode]] that causes [[dracunculiasis]] disease in humans. This disease may be close to being eradicated through efforts by the U.S. [[Centers for Disease Control and Prevention]] and the [[World Health Organization]].<ref>{{cite magazine | url=https://time.com/3680439/guinea-worm-almost-extinct/ | magazine=Time | title=This Species is Close to Extinction and That's a Good Thing | date=January 23, 2015 | access-date=May 31, 2015 | archive-url=https://web.archive.org/web/20150524160212/http://time.com/3680439/guinea-worm-almost-extinct/ | archive-date=May 24, 2015 | url-status=live }}</ref>

Copepods are known hosts of ''[[Vibrio]]'' bacteria, including pathogenic species. The ''Vibrio'' attach to the copepod's chitinous carapace, wearing it away to create a niche to stay. They are more protected from ecological stressors when attached to copepods and have an easy dispersal method. ''Vibrio'' are not known to infect copepods, but the degradation of the carapace is presumably detrimental to the copepod.<ref>{{Cite journal |last=Erken |first=Martina |date=May 29, 2015 |title=Interactions of Vibrio spp. with Zooplankton |url=https://journals.asm.org/doi/pdf/10.1128/microbiolspec.ve-0003-2014 |journal=Microbiology Spectrum|volume=3 |issue=3 |doi=10.1128/microbiolspec.ve-0003-2014 |pmid=26185068 |hdl=10220/46401 }}</ref><ref>{{Cite journal |last=Huq |first=Anwarul |display-authors=etal |date=July 15, 1982 |title=Ecological Relationships Between Vibrio cholerae and Planktonic Crustacean Copepods |journal=Applied and Environmental Microbiology|volume=45 |issue=1 |pages=275–283 |doi=10.1128/aem.45.1.275-283.1983 |pmid=6337551 |pmc=242265 }}</ref>

Copepods are infected by a variety of [[marine fungi]] including ''[[Metschnikowia]]'' species, and this can be lethal. They are also parasitized by [[Cestoda|tapeworms]], [[Isopoda|isopods]], and many kinds of protist, including Ellobiopsidae, [[Ciliate|Ciliates]], and [[Apicomplexa|Sporozoans]].<ref>{{Cite journal |last1=Ho |first1=Ju-shey |last2=Perkins |first2=Penny |date=1985 |title=Symbionts of Marine Copepoda: an Overview |url=https://www.ingentaconnect.com/content/umrsmas/bullmar/1985/00000037/00000002/art00020# |journal=Bulletin of Marine Science|volume=37 |issue=2 |pages=586–598 }}</ref>