Branchiura

(invertebrate zoology) The fish lice, a subclass of fish ectoparasites in the class Crustacea.

(Fish lice)

Phylum: Anthropoda

Subphylum: Crustacea

Class: Maxillopoda

Subclass: Branchiura

Number of families: 1

Thumbnail description
Branchiurans are ectoparasites of fishes, mainly living in freshwater habitats; they have flattened bodies comprised of five limb-bearing segments; the head has well-developed carapace lobes

Evolution and systematics

The subclass Branchiura comprises just four genera placed in a single family, the Argulidae, and about 175 species.

Physical characteristics

Branchiuran fish lice have flattened bodies, which have a low profile when attached to their hosts. The body comprises a head of five limb-bearing segments and a short trunk divided into a thoracic region, carrying four pairs of strong swimming legs and a short, unsegmented abdomen. The head has well-developed carapace lobes, which are posterior extensions of the dorsal head shield that mostly cover the legs on both sides of the body and may extend further to cover the abdomen. These carapace lobes contain the highly branched gut caecae and have two specialized areas ventrally, which are traditionally referred to as "respiratory areas," but appear to be involved in regulating the internal body fluids. Anteriorly, on the ventral surface of the head lie the short antennules and antennae. Both are provided with claws and are important organs of attachment to the host. The distal segments of the antennules are sensory and carry arrays of short setae.

Branchiurans have a tubular sucking mouth equipped with rasping mandibles located at the tip of the mouth tube. In Argulus there is a retractable poison stylet located just in front of the mouth. This stylet is absent in Chonopeltis and Dipteropeltis. The maxillules are developed into powerful muscular suckers in the adults of all genera, except Dolops, which retains long clawed maxillules into the adult phase. The maxillae are uniramous (one branched) limbs with spinous (spine-like) processes on the basal segments and small claws at the tip. The four pairs of thoracic swimming legs are biramous and directed laterally. The first and second legs commonly carry an additional process, the flagellum, originating near the base of the exopod. The third and fourth legs are usually modified in the male and are used for transferring sperm to the female during mating. The abdomen contains the paired testes in the male and, in the female, the paired seminal receptacles, where sperm are stored until needed to fertilize eggs. The abdomen terminates in paired abdominal lobes separated by the median anal cleft, in which lies the anus and the minute paired caudal rami.

Distribution

Argulus species occur in freshwater habitats on all continental land masses. Species of Dolops exhibit a southern distribution, occurring in freshwater in southern Africa, South America, and Australasia (Tasmania). Chonopeltis species occur only in African freshwaters, while the sole species of Dipteropeltis is restricted to South America.

Habitat

Branchiurans are ectoparasites of fishes, but are occasionally reported from the tadpoles of amphibians. They live mainly in freshwater habitats, both running and static water, and may occur at high density in artificial water bodies such as reservoirs, ornamental fishponds, and fish farms. A few species of Argulus infest estuarine and coastal marine fishes, but they do not occur in oceanic waters.

Behavior

Only the behavior of Argulus is well known; little is known of the other genera. After taking a meal, a mature female Argulus will leave its host and begin to lay eggs in rows on any hard, submerged surface. The eggs are cemented to the substrate and abandoned. These eggs hatch into free-swimming larvae equipped with setose (bristly) swimming antennae and mandibles and rudiments of the maxillules, maxillae, and first two pairs of swimming legs. These larvae function as a dispersal phase and molt into the second stage, in which strong claws have replaced the setae on the antenna and the setose palp of the mandible is lost. Branchiurans are parasitic from the second stage onwards, but appear to leave the host and then find a new host at intervals throughout development. Changes during the larval phase are gradual, mainly involving the development of the thoracic legs and reproductive organs, except for the maxillule, which undergoes a metamorphosis around stage five, changing from a long limb bearing a powerful distal claw to a powerful circular sucker. This is one of the most remarkable transformations known for any arthropod limb.

Feeding ecology and diet

Branchiurans attach to the skin of their fish host and feed on its blood and external tissues. They have rasping mandibles, which scrape tissues into the opening at the tip of the tubular sucking mouth. In Argulus, the poison stylet is used to inject a secretion into the host. The secretion may contain digestive enzymes to begin to break up host tissues before ingestion. Paired labial stylets, lying within the opening of the mouth tube, are also secretory and may produce secretions with a similar pre-digestive function. Host blood is also taken and is digested within paired, lobate gut caecae that lie within the carapace lobes.

Reproductive biology

The sexes are separate and, in most branchiurans, males transfer sperm directly to the females using a variety of structures on the third and fourth thoracic legs. In Dolops, however, sperm are transferred in chitinous packages called spermatophores.

Conservation status

No species are listed by the IUCN.

Significance to humans

Branchiurans are important pests in fish culture facilities, mainly in freshwater facilities, but occasionally in marine fish farms.

Species accounts

Resources

Overstreet, R. M., I. Dyková, and W. E. Hawkins. "Branchiura." In Microscopic Anatomy of Invertebrates. Vol. IX, Crustacea, edited by F. W. Harrison. New York: J. Wiley and Sons, 1992.

Gresty, K. A., G. A. Boxshall, and K. Nagasawa. "The Fine Structure and Function of the Cephalic Appendages of the Branchiuran Parasite, Argulus japonicus Thiele." Philosophical Transactions of the Royal Society of London B339 (1993): 119–135.

[Article by: Geoffrey Allan Boxshall, PhD]

A subclass of the Crustacea known as the fish lice. They are ectoparasites of fresh-water and marine fish. Argulus is a common genus. They are a small homogeneous group, less than 100 species, with worldwide distribution, and very much alike in appearance. The disklike head and thorax (cephalothorax) is strongly flattened and bears a small unsegmented abdomen bilobed at its distal end. Larger species may exceed 1 in. (25 mm) in length.

The appendages, all on the cephalothorax, consist of two pairs of antennae, the mouthparts which are one pair of mandibles and two pairs of maxillae, and four pairs of swimming legs. The wafer-thin cephalothorax with its appendages appressed to the underside permits fish lice to flatten themselves against a fish's skin. The resulting highly streamlined contour serves to minimize the considerable force of frictional drag found in a dense medium like water.

Other adaptations for holding fast to a mucus-covered swimming fish include numerous spinules and strategically placed hooks on the underside of the body and utilization of specialized portions of the body as suction cups. Despite these elaborate specializations, fish lice never lose the ability to abandon a host and swim. At least some of this activity is associated with mating and spawning.

Branchiurans feed on tissue fluids, especially blood. The mouth, located at the end of a movable proboscis, is applied to the host's skin and the rasping mandibles make the necessary wound. Fish lice usually are no threat to fish populations. In restricted areas such as hatchery ponds, however, an infestation can increase to levels that bring about high fish mortality. Treatment may require such drastic measures as drainage and cleaning before restocking can be successful. See also Crustacea.

The noun has one meaning:

Meaning #1: copepods with suctorial mouthparts; parasitic on fishes
  Synonym: order Branchiura

Branchiura
Argulus sp. on a fish
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Crustacea
Class:	Maxillopoda
Subclass:	Branchiura Thorell, 1864
Order:	Arguloida Yamaguti, 1963
Family:	Argulidae Leach, 1819

Branchiura, commonly called carp lice or fish lice are a group of parasitic crustaceans of uncertain position within the Maxillopoda. Although they are thought to be primitive forms, they have no fossil record. Almost all are ectoparasites on fish, a few on amphibians ^[1].

Branchiurans have a flattened, oval body, which is almost entirely covered by a wide carapace. The 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 two pairs of thoracic appendages, which they can use to swim between different hosts. They leave their hosts for up to three weeks in order to mate and lay eggs, and reattach afterwards behind the fish's operculum, where they feed on mucus and sloughed-off scales, or pierce the skin and feed on the internal fluids.^[1] The eggs hatch into parasitic postnauplius larvae.

The subclass contains a single order, Arguloida (occasionally "Arguloidea"), which contains a single family, Argulidae ^[2], with around 200 species ^[3], although a second family, Dipteropeltidae has been proposed.^[4].

List of species

This is a list of species names that have been applied to species described in the Order Arguloida; however, many of the names are now considered to be invalid, or are synonyms of other species names. Only the genera Argulus, Chonopeltis and Dolops are recognised today^{[citation needed]}. The taxonomy of several species, especially in the genus Argulus, continues to be studied ^[3]:

Agenor purpureus Risso, 1826 Argulus africanus Thiele, 1900 Argulus alexandrensis WilsonCB, 1923 Argulus alosae Gould, 1841 Argulus amazonicus Malta & Santos-Silva, 1986 Argulus ambloplites WilsonCB, 1920 Argulus americanus WilsonCB, 1902 Argulus angusticeps Cunnington, 1913 Argulus annae Schuurmans StekhovenJHJr, 1951 Argulus appendiculosus WilsonCB, 1907 Argulus arcassonensis Cuénot, 1912 Argulus argulus Leach, 1814 Argulus armiger MüllerOF, 1785 Argulus australiensis Byrnes, 1985 Argulus belones Kampen, 1909 Argulus bengalensis Ramakrishna, 1951 Argulus bicolor Bere, 1936 Argulus biramosus Bere, 1931 Argulus boli Tripathi, 1975 Argulus borealis WilsonCB, 1912 Argulus brachypeltis Fryer, 1959 Argulus caecus WilsonCB, 1922 Argulus canadensis WilsonCB, 1916 Argulus capensis Barnard, 1955 Argulus carteri Cunnington, 1931 Argulus catostomi Dana & Herrick, 1837 Argulus cauveriensis Thomas & Devaraj, 1975 Argulus charon MüllerOF, 1785 Argulus chesapeakensis Cressey, 1971 Argulus chicomendesi Malta & Varella, 2000 Argulus chilensis Martinez, 1952 Argulus chinensis Ku & Yang, 1955 Argulus chromidis Kroyer, 1863 Argulus confuscus Rushton-Mellor, 1994 Argulus coregoni Thorell, 1865 Argulus cubensis WilsonCB, 1936 Argulus dactylopteri Thorell, 1865 Argulus dageti Dollfus, 1960 Argulus dartevellei Brian, 1940 Argulus delphinus MüllerOF, 1785 Argulus diversicolor Byrnes, 1985 Argulus diversus WilsonCB, 1944 Argulus ellipticaudatus WangKN, 1960 Argulus elongatus Heller, 1857 Argulus ernsti Weibezahn & Cobo, 1964 Argulus exiguus Cunnington, 1913 Argulus flavescens WilsonCB, 1916 Argulus floridensis Meehan, 1940 Argulus fluviatilis Thomas & Devaraj, 1975 Argulus foliaceus (Linnaeus), 1758 Argulus fryeri Rushton-Mellor, 1994 Argulus funduli Kroyer, 1863 Argulus fuscus Bere, 1936 Argulus giganteus Lucas, 1845 Argulus giordanii Brian, 1959 Argulus gracilis Rushton-Mellor, 1994 Argulus hylae Lemos de Castro & Gomes-Correa, 1985 Argulus ichesi Bouvier, 1910 Argulus incisus Cunnington, 1913 Argulus indicus Weber, 1892 Argulus ingens WilsonCB, 1912 Argulus intectus WilsonCB, 1944 Argulus izintwala Van AsJG & Van AsLL, 2001 Argulus japonicus Thiele, 1900 Argulus jollymani Fryer, 1956 Argulus juparanensis Lemos de Castro, 1950

Argulus kosus Avenant-Oldewage, 1994 Argulus kunmingensis Shen, 1948 Argulus kusafugu Yamaguti & Yamasu, 1959 Argulus laticauda SmithSI, 1874 Argulus latus SmithSI, 1874 Argulus lepidostei Kellicott, 1877 Argulus longicaudatus WilsonCB, 1944 Argulus lunatus WilsonCB, 1944 Argulus macropterus Heegaard, 1962 Argulus maculosus WilsonCB, 1902 Argulus major WangKN, 1960 Argulus mangalorensis Natarajan, 1982 Argulus matritensis Arevalo, 1921 Argulus matuii Sikama, 1938 Argulus meehani Cressey, 1971 Argulus megalops SmithSI, 1874 Argulus megalops spinosus WilsonCB, 1944 Argulus melanostictus WilsonCB, 1935 Argulus melita Beneden, 1891 Argulus mexicanus Pineda, Paramo & del Rio, 1995 Argulus mississippiensis WilsonCB, 1916 Argulus mongolianus Tokioka, 1939 Argulus monodi Fryer, 1959 Argulus multicolor Schuurmans StekhovenJHJr, 1937 Argulus multipocula Barnard, 1955 Argulus nativus Kirtisinghe, 1959 Argulus natterei Heller, 1857 Argulus niger WilsonCB, 1902 Argulus nobilis Thiele, 1904 Argulus onodai Tokioka, 1936 Argulus otolithi Brian, 1927 Argulus papuensis Rushton-Mellor, 1994 Argulus paranensis Ringuelet, 1943 Argulus parsi Tripathi, 1975 Argulus paulensis WilsonCB, 1924 Argulus pelucidus Wagler, 1935 Argulus personatus Cunnington, 1913 Argulus pestifer Ringuelet, 1948 Argulus petagonicus Ringuelet, 1943 Argulus phoxini Leydig, 1871 Argulus piperatus WilsonCB, 1920 Argulus pugettensis Dana, 1852 Argulus purpureus (Risso), 1826 Argulus puthenveliensis Ramakrishna, 1959 Argulus quadristriatus Devaraj & Ameer Hamsa, 1977 Argulus reticulatus WilsonCB, 1920 Argulus rhamdiae WilsonCB, 1936 Argulus rhipidiophorus Monod, 1931 Argulus rijckmansii Brian, 1940 Argulus rothschildi Leigh-Sharpe, 1933 Argulus rotundus WilsonCB, 1944 Argulus rubescens Cunnington, 1913 Argulus rubropunctatus Cunnington, 1913 Argulus salminei Kroyer, 1863 Argulus salminei argentinensis Brian, 1947 Argulus scutiformis Thiele, 1900 Argulus shoutedeni Monod, 1928 Argulus siamensis WilsonCB, 1926 Argulus silvestrii Lahille, 1926 Argulus smalei Avenant-Oldewage & Oldewage, 1995 Argulus spinulosus Silva, 1980 Argulus stizostethii Kellicott, 1880 Argulus striatus Cunnington, 1913 Argulus taliensis Shen, 1948 Argulus tientsinensis Ku & Wang, 1956 Argulus trachynoti Brian, 1927

Argulus trilineatus WilsonCB, 1904 Argulus varians Bere, 1936 Argulus versicolor WilsonCB, 1902 Argulus vierai Pereira-Fonseca, 1939 Argulus violaceus Thomsen, 1925 Argulus viridis Nettovich, 1900 Argulus vittatus (Rafinesque-Schmaltz), 1814 Argulus wilsoni Brian, 1940 Argulus yucatanus Poly, 2004 Argulus yucatanus Poly, 2005 Argulus yuii WangKN, 1958 Argulus yunnanensis Shen, 1948 Argulus zei Brian, 1924 Binoculus bicornutus Risso, 1816 Binoculus caudatus Say, 1818 Binoculus gasterostei Geoffroy, 1762 Binoculus haemisphericus Geoffroy, 1762 Binoculus palustris MüllerOF, 1776 Binoculus piscinus MüllerOF, 1776 Binoculus productus Nordmann, 1832 Binoculus salmoneus MüllerOF, 1785 Binoculus sexsetaceus Nordmann, 1832 Chonopeltis australis Boxshall, 1976 Chonopeltis australissumus Fryer, 1977 Chonopeltis brevis Fryer, 1961 Chonopeltis congicus Fryer, 1959 Chonopeltis elongatus Fryer, 1974 Chonopeltis flaccifrons Fryer, 1960 Chonopeltis fryeri Van As, 1986 Chonopeltis inermis Thiele, 1900 Chonopeltis inermis schoutedeni Brian, 1940 Chonopeltis koki Van As, 1992 Chonopeltis lisikili Van AsJG & Van AsLL, 1996 Chonopeltis meridionalis Fryer, 1964 Chonopeltis minutus Fryer, 1977 Chonopeltis schoutedeni Brian, 1940 Chonopeltis victori Avenant-Oldewage, 1991 Diprosia vittata Rafinsque, 1814 Dipteropeltis hirundo Calman, 1912 Dolops bidentata (Bouvier), 1899 Dolops carvalhoi Lemos de Castro, 1949 Dolops discoidalis Bouvier, 1899 Dolops doradis (Cornalia), 1860 Dolops geayi (Bouvier), 1897 Dolops intermedia da Silva, 1978 Dolops kollari (Heller), 1857 Dolops lacordairei Audouin, 1837 Dolops longicauda (Heller), 1857 Dolops nana Lemos de Castro, 1950 Dolops ranarum (Stuhlmann), 1891 Dolops reperta (Bouvier), 1899 Dolops striata (Bouvier), 1899 Dolops tasmanicus Fryer, 1969 Gyropeltis bidentata Bouvier, 1899 Gyropeltis doradis Cornalia, 1860 Gyropeltis geayi Bouvier, 1897 Gyropeltis kollari Heller, 1857 Gyropeltis lacordairei Audouin, 1837 Gyropeltis longicauda Heller, 1857 Gyropeltis ranarum Stuhlmann, 1891 Gyropeltis reperta Bouvier, 1899 Gyropeltis striata Bouvier, 1899 Huargulus chinensis Yü, 1938 Moreiriella ribeiroi (Moreira), 1913 Ozolus gasterostei Latreille, 1802 Talaus ribeiroi Moreira, 1913

References

1. ^ ^{a b} Ben Waggoner. "Introduction to the Branchiura". University of California Museum of Paleontology. http://www.ucmp.berkeley.edu/arthropoda/crustacea/maxillopoda/branchiura.html. Retrieved 2007-05-06. 
2. ^ Joel W. Martin & George E. Davis (2001) (PDF). An Updated Classification of the Recent Crustacea. Natural History Museum of Los Angeles County. pp. 132 pp. http://atiniui.nhm.org/pdfs/3839/3839.pdf. 
3. ^ ^{a b} "The World of Copepods - Species Taxonomy Results". Smithsonian Institution. http://ravenel.si.edu/iz/copepod/species/list_all_by_order.cfm. 
4. ^ P. Myers, R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond & T. A. Dewey (2006). "Animal Diversity Web: Arguloidea". University of Michigan. http://animaldiversity.ummz.umich.edu/site/accounts/classification/Arguloidea.html#Arguloidea. 

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