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Argulidae; Temporal range: Carboniferous–Recent PreꞒ Ꞓ O S D C P T J K Pg N [citation needed]
	Argulus sp. on a stickleback
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Ichthyostraca
Subclass:	Branchiura; Thorell, 1864
Order:	Arguloida; Yamaguti, 1963
Family:	Argulidae; Leach, 1819
Genera
	Argulus Müller O.F., 1785; Chonopeltis Thiele, 1900; Dipteropeltis Calman, 1912; Dolops Audouin, 1837;

The family Argulidae, whose members are commonly known as carp lice or fish 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.^[1]^[2] Although they are thought to be primitive forms, they have no fossil record.^{[citation needed]}

Taxonomy

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.^[3] There are approximately 170 species in four genera recognised in the family Branchiura.^[4] The centres of diversity are the Afrotropical and Neotropical realms.^[5]

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.^[6]^[7]^[8] They are compressed dorsoventrally and can vary in size from just a few millimetres to over 30 mm (1.2 in) long, with females usually somewhat larger than the males.^[5]

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.^[6] The genus Dolops, keeps the larval stages claw-like appendages into adulthood.^[6] 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.^[9] Also, females tend to be larger than the males.^[6] Between the genera there are multiple distinction between the sexes.^[6] For example, males in Argulus and Chonopeltis possess secondary sexual modifications on legs 2-4.^[6] The sexes both have their own sexual reproductive organs on their abdomens.^[6] The females have a spermathecae, while the males have a pair of testes.^[6]

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.^[5]

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.^[10]^[11]

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.^[12] 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),^[13] but can also be found on other aquatic organisms such as invertebrates, salamanders, tadpoles and alligators.^[6]^[14]^[3] Some species feed on the blood of their host, while others feed on mucus and extracellular material.^[3] 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.^[9] After engorging themselves, the parasites typically wait two to three weeks before feeding again.^[3] Mitigation of these parasites has been studied through the use of a treatment containing plant parts.^[15] 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.^[15]

Reproduction

Only the life cycle of freshwater forms of the genus Argulus is well known.^[16] 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.^[17] The eggs hatch into parasitic postnauplius larvae. While on their host, Branchiurans mate.^[6] The female holds the eggs in the thorax and in some species the eggs can be found inside the lobes of the carapace.^[6] The spermathecae on the female stores the sperm.^[6] In the genus Dolops, the males deposit a spermatophore onto the females.^[6] Once the eggs are fertilized the females leave the host organism to lay their eggs in rows on surfaces of plants, rocks, etc.^[6] 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.^[18]

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.^[5]

References

^ P. Myers; R. Espinosa; C. S. Parr; T. Jones; G. S. Hammond; T. A. Dewey (2006). "Animal Diversity Web: Arguloidea". University of Michigan. Archived from the original on 2007-12-01. Retrieved 2007-05-06.
^ "WoRMS - World Register of Marine Species - Argulidae Leach, 1819". www.marinespecies.org. Retrieved 2022-12-10.
^ ^a ^b ^c ^d Alan P. Covich, ... D. Christopher Rogers, in Ecology and Classification of North American Freshwater Invertebrates (Third Edition), 2010
^ Geoff Boxshall (September 5, 2009). T. Chad Walter; Geoff Boxshall (eds.). "Argulidae". World Copepoda database. World Register of Marine Species. Retrieved December 31, 2009.
^ ^a ^b ^c ^d William J. Poly (2008) [Originally published 2008 in volume 595 of Hydrobiologia]. "Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater". In Estelle V. Balian; Christian Lévêque; Hendrik Segers; Koen Martens (eds.). Freshwater Animal Diversity Assessment. Developments in Hydrobiology. Vol. 198. Springer. pp. 209–212. doi:10.1007/s10750-007-9015-3. ISBN 978-1-4020-8258-0. S2CID 26179318.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Poly, William J. (January 2008). "Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater". Hydrobiologia. 595 (1): 209–212. doi:10.1007/s10750-007-9015-3. ISSN 0018-8158. S2CID 26179318.
^ Encyclopedia of Biodiversity
^ Marine Parasitology
^ ^a ^b Moller, O.S.; Olesen, J.; Avenant-Oldewage, A.; Thomsen, P.F.; Glenner, H. (July 2008). "First maxillae suction discs in Branchiura (Crustacea): Development and evolution in light of the first molecular phylogeny of Branchiura, Pentastomida, and other "Maxillopoda"". Arthropod Structure & Development. 37 (4): 333–346. Bibcode:2008ArtSD..37..333M. doi:10.1016/j.asd.2007.12.002. PMID 18394959.
^ Branchiura: A Compendium of the Geographical Distribution and a Summary of Their Biology
^ Gill Structure and Relationships of the Triassic Cycloid Crustaceans
^ Moller, Ole Sten; Olesen, Jorgen (May 2010). "The little-known Dipteropeltis hirundo Calman, 1912 (Crustacea, Branchiura): SEM investigations of paratype material in light of recent phylogenetic analyses". Experimental Parasitology. 125 (1): 30–41. doi:10.1016/j.exppara.2009.09.008. PMID 19747916.
^ May-Tec, Ana Luisa; Baños-Ojeda, Carlos; Mendoza-Franco, Edgar F. (2022). "Parasitic crustaceans (Branchiura and Copepoda) parasitizing the gills of puffer fish species (Tetraodontidae) from the coast of Campeche, Gulf of Mexico". ZooKeys (1089): 73–92. Bibcode:2022ZooK.1089...73M. doi:10.3897/zookeys.1089.79999. PMC 8942962. PMID 35586605.
^ Williams Jr, E. H.; Bunkley-Williams, L. (2019). "Life Cycle and Life History Strategies of Parasitic Crustacea". Parasitic Crustacea. Zoological Monographs. Vol. 3. pp. 179–266. doi:10.1007/978-3-030-17385-2_5. ISBN 978-3-030-17383-8. PMC 7124122.
^ ^a ^b Banerjee, Anirban (15 November 2013). "Saha". Samar Kumar. 414–415: 202–209. doi:10.1016/j.aquaculture.2013.07.044.
^ Lifestyles and Feeding Biology
^ Ben Waggoner. "Introduction to the Branchiura". University of California Museum of Paleontology. Archived from the original on 4 May 2007. Retrieved May 6, 2007.
^ Atlas of Crustacean Larvae