{{Short description|Family of crustaceans}} {{Redirect|Branchiura|the genus of annelids|Branchiura (annelid)}} {{distinguish|text=Brachyura, the infraorder comprising true crabs}} {{Automatic taxobox | fossil_range = | image = Argulus.jpg | image_caption = ''Argulus'' sp. on a stickleback | grandparent_authority = Thorell, 1864 | parent_authority = Yamaguti, 1963 | taxon = Argulidae | authority = Leach, 1819 | subdivision = * ''Argulus'' <small>Müller O.F., 1785</small> * ''Chonopeltis'' <small>Thiele, 1900</small> * ''Dipteropeltis'' <small>Calman, 1912</small> * ''Dolops'' <small>Audouin, 1837</small> }}
The family '''Argulidae''', whose members are commonly known as '''carp lice''' or '''fish lice''', (not to be confused with Caligidae, also commonly referred to as sea lice) are parasitic crustaceans in the class Ichthyostraca. It is the only family in the monotypic subclass '''Branchiura''' and the order '''Arguloida''', although a second family, Dipteropeltidae, has been proposed.<ref>{{cite web |url=http://animaldiversity.ummz.umich.edu/site/accounts/classification/Arguloidea.html#Arguloidea |title=Animal Diversity Web: Arguloidea |publisher=University of Michigan |author1=P. Myers |author2=R. Espinosa |author3=C. S. Parr |author4=T. Jones |author5=G. S. Hammond |author6=T. A. Dewey |year=2006 |access-date=2007-05-06 |archive-url=https://web.archive.org/web/20071201134840/http://animaldiversity.ummz.umich.edu/site/accounts/classification/Arguloidea.html#Arguloidea |archive-date=2007-12-01 |url-status=dead }}</ref><ref>{{Cite web |title=WoRMS - World Register of Marine Species - Argulidae Leach, 1819 |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=104070 |access-date=2022-12-10 |website=www.marinespecies.org}}</ref>
== Taxonomy == {{See also|List of Argulidae species}} Branchiurans were once thought to be copepods but are now recognised as a separate subclass in the superclass Oligostraca due to their distinct morphological characteristics.<ref name=":1">Alan P. Covich, ... D. Christopher Rogers, in Ecology and Classification of North American Freshwater Invertebrates (Third Edition), 2010</ref> There are approximately 170 species in four genera recognised in the family Branchiura.<ref>{{cite web |author=Geoff Boxshall |title=Argulidae |editor1=T. Chad Walter |editor2=Geoff Boxshall |work=World Copepoda database |publisher=World Register of Marine Species |url=http://www.marinespecies.org/aphia.php?p=taxdetails&id=104070 |access-date=December 31, 2009 |date=September 5, 2009}}</ref> The centres of diversity are the Afrotropical and Neotropical realms.<ref name="Poly">{{cite book |author=William J. Poly |year=2008 |chapter=Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater |series=Developments in Hydrobiology|editor1=Estelle V. Balian |editor2=Christian Lévêque |editor3=Hendrik Segers|editor4=Koen Martens|title=Freshwater Animal Diversity Assessment |isbn=978-1-4020-8258-0 |publisher=Springer |orig-date=Originally published 2008 in volume 595 of ''Hydrobiologia''|volume=198|pages=209–212 |doi=10.1007/s10750-007-9015-3 |s2cid=26179318 |chapter-url=https://books.google.com/books?id=Dw4H6DBHnAgC&pg=PA209}}</ref>
==Description== Branchiurans have a flattened, oval body, which is almost entirely covered by a broad, oval carapace, four thoracic segments each with a pair of swimming legs, a pair of anterior compound eyes, and an unsegmented abdomen without appendages which ends in paired abdominal lobes separated by the medial anal cleft.<ref name=":0" /><ref>[https://books.google.com/books?id=oZXxlwT3v7oC&dq=branchiurans+thorax+4+segments+abdomen+reduced+appendages+absent&pg=RA1-PA402 Encyclopedia of Biodiversity]</ref><ref>[https://books.google.com/books?id=ktTOf3l66QQC&dq=branchiura+abdominal+lobes&pg=PT139 Marine Parasitology]</ref> They are compressed dorsoventrally and can vary in size from just a few millimetres to over {{convert|30|mm|abbr=on}} long, with females usually somewhat larger than the males.<ref name="Poly"/>
The mandibles are generally toothed hooks in Branchiurans. The maxillules provide sucking capability, and in the genera ''Argulus, Chonopeltis,'' and ''Dipteropeltis'', the adults have a pair of suction cups that are from modified first maxillae.<ref name=":0" /> The genus ''Dolops,'' keeps the larval stages claw-like appendages into adulthood.<ref name=":0" /> It is still unknown whether the ancestral state of these organisms had suction discs or the hooked condition seen in ''Dolops'', although it is thought that the specialized suctions discs are a later product of evolution.<ref name=":3" /> Also, females tend to be larger than the males.<ref name=":0" /> Between the genera there are multiple distinction between the sexes.<ref name=":0" /> For example, males in ''Argulus'' and ''Chonopeltis'' possess secondary sexual modifications on legs 2–4.<ref name=":0" /> The sexes both have their own sexual reproductive organs on their abdomens.<ref name=":0" /> The females have a spermathecae, while the males have a pair of testes.<ref name=":0" />
Their compound eyes are prominent, and the mouthparts and the first pair of antennae are modified to form a hooked, spiny proboscis armed with suckers, as an adaptation to parasitic life. They have four pairs of thoracic appendages, which are used to swim when not attached to the host.<ref name="Poly"/>
Not much research has been done on the respiratory system, which lacks gills, but respiratory areas on the carapace and gas exchange through the fleshy abdomen has been suggested.<ref>[https://books.google.com/books?id=QQEtDwAAQBAJ&dq=Respiratory+system+fleshy+abdomen+areas+carapace+lobes&pg=PA129 Branchiura: A Compendium of the Geographical Distribution and a Summary of Their Biology]</ref><ref>[https://www.paleo.pan.pl/people/Dzik/Publications/Opolanka.pdf Gill Structure and Relationships of the Triassic Cycloid Crustaceans]</ref>
== Distribution and habitat == Branchiurans are widely distributed throughout the world. Most species are found in Africa and South America, and none are found in Antarctica.<ref name=":2">{{cite journal |last1=Moller |first1=Ole Sten |last2=Olesen |first2=Jorgen |title=The little-known Dipteropeltis hirundo Calman, 1912 (Crustacea, Branchiura): SEM investigations of paratype material in light of recent phylogenetic analyses |journal=Experimental Parasitology |date=May 2010 |volume=125 |issue=1 |pages=30–41 |doi=10.1016/j.exppara.2009.09.008 |pmid=19747916 }}</ref> In North America, the genus ''Argulus'' is the only one known to be found in freshwater ecosystems.
==Behaviour and ecology== === Parasitism === Branchiurans are obligate ectoparasites that are found primarily on marine and freshwater fish (only the genus Argulus occurs in marine environments),<ref>{{Cite journal |last1=May-Tec |first1=Ana Luisa |last2=Baños-Ojeda |first2=Carlos |last3=Mendoza-Franco |first3=Edgar F. |date=2022 |title=Parasitic crustaceans (Branchiura and Copepoda) parasitizing the gills of puffer fish species (Tetraodontidae) from the coast of Campeche, Gulf of Mexico |url=https://archive.org/details/parasiticcrusta1089mayt |journal=ZooKeys |issue=1089 |pages=[https://archive.org/details/parasiticcrusta1089mayt/page/76 73]–92 |doi=10.3897/zookeys.1089.79999 |doi-access=free |pmc=8942962 |pmid=35586605|bibcode=2022ZooK.1089...73M }}</ref> but can also be found on other aquatic organisms such as invertebrates, salamanders, tadpoles and alligators.<ref name=":0">{{Cite journal|last=Poly|first=William J.|date=January 2008|title=Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater|journal=Hydrobiologia|volume=595|issue=1|pages=209–212|doi=10.1007/s10750-007-9015-3|s2cid=26179318 |issn=0018-8158}}</ref><ref>{{Cite book |title=Parasitic Crustacea |date=2019 |pmc=7124122 |last1=Williams Jr |first1=E. H. |last2=Bunkley-Williams |first2=L. |chapter=Life Cycle and Life History Strategies of Parasitic Crustacea |series=Zoological Monographs |volume=3 |pages=179–266 |doi=10.1007/978-3-030-17385-2_5 |isbn=978-3-030-17383-8 }}</ref><ref name=":1" /> Some species feed on the blood of their host, while others feed on mucus and extracellular material.<ref name=":1" /> Feeding is facilitated by distinct morphological adaptations (see Anatomy). Branchiura are able to attach to hosts through two mechanisms, hooked maxillae (as seen in ''Dolops'') or suction disks.<ref name=":3">{{cite journal |last1=Moller |first1=O.S. |last2=Olesen |first2=J. |last3=Avenant-Oldewage |first3=A. |last4=Thomsen |first4=P.F. |last5=Glenner |first5=H. |title=First maxillae suction discs in Branchiura (Crustacea): Development and evolution in light of the first molecular phylogeny of Branchiura, Pentastomida, and other "Maxillopoda" |journal=Arthropod Structure & Development |date=July 2008 |volume=37 |issue=4 |pages=333–346 |doi=10.1016/j.asd.2007.12.002|pmid=18394959 |bibcode=2008ArtSD..37..333M }}</ref> After engorging themselves, the parasites typically wait two to three weeks before feeding again.<ref name=":1" /> Mitigation of these parasites has been studied through the use of a treatment containing plant parts.<ref name=":4">{{cite journal |last1=Banerjee |first1=Anirban |title=Saha |journal=Samar Kumar |date=15 November 2013 |volume=414-415 |pages=202–209 |doi=10.1016/j.aquaculture.2013.07.044}}</ref> From this study, it is thought that Tobacco leaf dust (containing nicotine) can safely and effectively eliminate adult Branchiurans from fish, although this may be specific to only ''Argulus bengalensis''.<ref name=":4" />
=== Reproduction === Only the life cycle of freshwater forms of the genus ''Argulus'' is well known.<ref>[https://books.google.com/books?id=ap-eBgAAQBAJ&dq=Argulus+Branchiura+life+cycle+hard+eggs+dispersal&pg=PA177 Lifestyles and Feeding Biology]</ref> Branchiurans are not permanently attached to their hosts, and leave them for up to three weeks to mate and lay eggs, and reattach behind the fish's operculum, where they feed on mucus and sloughed-off scales, or pierce the skin and feed on the internal fluids.<ref name="UCMP">{{cite web |url=http://www.ucmp.berkeley.edu/arthropoda/crustacea/maxillopoda/branchiura.html |title=Introduction to the Branchiura |author=Ben Waggoner |access-date=May 6, 2007 |publisher=University of California Museum of Paleontology| archive-url= https://web.archive.org/web/20070504091801/http://www.ucmp.berkeley.edu/arthropoda/crustacea/maxillopoda/branchiura.html| archive-date= 4 May 2007 | url-status= live}}</ref> The eggs hatch into parasitic postnauplius larvae. While on their host, Branchiurans mate.<ref name=":0" /> The female holds the eggs in the thorax and in some species the eggs can be found inside the lobes of the carapace.<ref name=":0" /> The spermathecae on the female stores the sperm.<ref name=":0" /> In the genus ''Dolops,'' the males deposit a spermatophore onto the females.<ref name=":0" /> Once the eggs are fertilized the females leave the host organism to lay their eggs in rows on surfaces of plants, rocks, etc.<ref name=":0" /> Like the adults, the larvae are parasites on fish. They are opportunistic in selecting host species of fish, and females are motile in their pursuit of locality of egg-laying. ''Chonopeltis'' larvae appear to be less developed than those of the other genera. Members of one group of ''Argulus'' hatch as metanauplius-larvae, followed by a juvenile stage. Another ''Argulus'' group, and all known species of ''Dolops'', hatch as juveniles.<ref>[https://books.google.com/books?id=PPnZAwAAQBAJ&dq=Argulus+Non-Swimming+Larvae+juveniles&pg=PA130 Atlas of Crustacean Larvae]</ref>
===Impact=== Fish lice occasionally reach high enough densities to cause fish kills in aquaculture operations, or more rarely in wild populations of fish. They can also become abundant in aquaria, sometimes resulting in the death of ornamental fish.<ref name="Poly"/>
==References== {{Reflist|32em}}
==External links== * {{Commons category-inline}} *{{Wikispecies-inline}}
{{Arthropods}} {{fish disease topics}} {{Portalbar|Crustaceans}} {{Taxonbar|from1=Q18196331|from2=Q18196332|from3=Q841641}} {{Authority control}}
Category:Crustacean families Category:Carboniferous first appearances Category:Arthropod subclasses